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Valve ports, engine rpm & their effective limits?
Posted by: Garry Hunsaker (IP Logged)
Date: March 20, 2002 04:45AM
<HTML>
I am wondering if there is anything remotely like a rule of thumb as to how short a stroke, and therefore a limit to how short a duration a steam engine’s ports can remain open and still properly ‘charge’ the cylinder. The steam engine has enough problems with out adding windage restrictions. (Or is this what engineers refer to as ‘shock’?) What has brought me to this question is looking at the three cylinder engine in my old Subaru Justy. It’s 3.27” stroke is almost liveable. (To be honest, I think I need to check out the crankshaft on the Chevy Geo. There are a heck of a lot more of them around to choose from)
The only thing in the way of data I have had in the past to work with was J. N. Walton’s book on Doble. I have been hunting around today for the numbers I ran several years ago, that Doble outlined for his triple expansion engine, but I still haven’t come up with the place I put them to make sure I didn’t lose them... (So what else is new.)
Shooting from memory, I believe I was aiming at 50 to 60 hp. Any way, the one thing I do remember is measuring my old 1970 VW van. The best I remember I came to the conclusion that by running the engine at roughly twice the speed of the differential gear I would have the effective torque of the standard VW van about half way between first and second gear. (The acceleration should be interesting to say the least)
For those that might be curious, I had intended to lay the resulting engine on its side on the left side of engine compartment. By adding a splined stub shaft to the end of the crank, and running that into a gear box, I would have to create using the side plates, bearings, and third member from the VW, I thought I could make this work.
I was still scratching my head on how, or if I needed to, set the gear box up for backlash adjustment on the deferential gears I would have to come up with. The thought did occur to me to create new side plates so the outer bolt circle, and its corresponding surface would be slightly eccentric in relation to the third member support bearings. I figured throwing the axles a few thousandths out of their original position wouldn’t bother those CV joints too much. Though making exactly matching eccentric side plates in relation to a set of perfectly divided and aligned bolt circles still had me wondering on the how the heck am I going to do that???
The advantage of placing the engine to one side was it would leave better than three quarters of the engine compartment open for a steam generator. Using the info I was beginning to pick up from the SACA back then, I figured by using extended surface tubing in the pre-boil sections of a monotube boiler, I could keep the size down to where the whole package could be hung on a square tube frame and attached to beefed up versions of the original engine and transmission mounts. There should even be room for a water tank forward of the differential, and enough room to place most of the auxiliaries above the engine and out of the road grit and grime. The exception being the water pumps, I hoped to get those below the level of the bottom of the water tank. The only thing I didn’t envision attaching to this package was the condenser. That I planned placing on the left side of the body with lovers cut in the body to shove the heat out with an electric fan-s.
I was still finding myself with too many questions. A few of which I have had answered thanks to this form and the SACA discussion list. Before I started hacking out metal, melting down old Cummins diesel pistons, making patterns, and all the other fun stuff that goes with experimental prototypes built on no budget, I thought I had better have a bit more understanding of what is going on, and if such a short stroke engine could ‘breath’ properly under steam at the RPM I envisioned. I believe that may have been around 800 foot per minute piston speed at 70 mph and 2100 rpm, which is considerably faster than I care to drive one of those old vans. Though mainly, I didn’t want to end up spending a few years creating such a monstrosity and discover later it would have a top speed of twenty two miles and hour.
I have several other questions, but they can wait till later. And don’t get too freaked on my original tipple expansion thoughts. As far as piston engines go, I am now convinced the uniflow is the only way to go. And the use of a constant volume steam exaust motor to drive the water pumps and cylinder oil injection in relationship to engine load seems wise.., and will probably lead me to even more questions.
So if you are still reading this...
You must be as addicted to steam as I am..
Garry
PS: I envisioned this menagerie at around 800 psi and 800F of steam, though at the moment, I don't remember the lbs per hour I came up with. It does seem like I was going to end up with about half the surface area in tubing of the engine Doble had outlined in Walton's book. (This was before I had heard of extended surface tubing, and about that time the universe put my life on hold)</HTML>
I am wondering if there is anything remotely like a rule of thumb as to how short a stroke, and therefore a limit to how short a duration a steam engine’s ports can remain open and still properly ‘charge’ the cylinder. The steam engine has enough problems with out adding windage restrictions. (Or is this what engineers refer to as ‘shock’?) What has brought me to this question is looking at the three cylinder engine in my old Subaru Justy. It’s 3.27” stroke is almost liveable. (To be honest, I think I need to check out the crankshaft on the Chevy Geo. There are a heck of a lot more of them around to choose from)
The only thing in the way of data I have had in the past to work with was J. N. Walton’s book on Doble. I have been hunting around today for the numbers I ran several years ago, that Doble outlined for his triple expansion engine, but I still haven’t come up with the place I put them to make sure I didn’t lose them... (So what else is new.)
Shooting from memory, I believe I was aiming at 50 to 60 hp. Any way, the one thing I do remember is measuring my old 1970 VW van. The best I remember I came to the conclusion that by running the engine at roughly twice the speed of the differential gear I would have the effective torque of the standard VW van about half way between first and second gear. (The acceleration should be interesting to say the least)
For those that might be curious, I had intended to lay the resulting engine on its side on the left side of engine compartment. By adding a splined stub shaft to the end of the crank, and running that into a gear box, I would have to create using the side plates, bearings, and third member from the VW, I thought I could make this work.
I was still scratching my head on how, or if I needed to, set the gear box up for backlash adjustment on the deferential gears I would have to come up with. The thought did occur to me to create new side plates so the outer bolt circle, and its corresponding surface would be slightly eccentric in relation to the third member support bearings. I figured throwing the axles a few thousandths out of their original position wouldn’t bother those CV joints too much. Though making exactly matching eccentric side plates in relation to a set of perfectly divided and aligned bolt circles still had me wondering on the how the heck am I going to do that???
The advantage of placing the engine to one side was it would leave better than three quarters of the engine compartment open for a steam generator. Using the info I was beginning to pick up from the SACA back then, I figured by using extended surface tubing in the pre-boil sections of a monotube boiler, I could keep the size down to where the whole package could be hung on a square tube frame and attached to beefed up versions of the original engine and transmission mounts. There should even be room for a water tank forward of the differential, and enough room to place most of the auxiliaries above the engine and out of the road grit and grime. The exception being the water pumps, I hoped to get those below the level of the bottom of the water tank. The only thing I didn’t envision attaching to this package was the condenser. That I planned placing on the left side of the body with lovers cut in the body to shove the heat out with an electric fan-s.
I was still finding myself with too many questions. A few of which I have had answered thanks to this form and the SACA discussion list. Before I started hacking out metal, melting down old Cummins diesel pistons, making patterns, and all the other fun stuff that goes with experimental prototypes built on no budget, I thought I had better have a bit more understanding of what is going on, and if such a short stroke engine could ‘breath’ properly under steam at the RPM I envisioned. I believe that may have been around 800 foot per minute piston speed at 70 mph and 2100 rpm, which is considerably faster than I care to drive one of those old vans. Though mainly, I didn’t want to end up spending a few years creating such a monstrosity and discover later it would have a top speed of twenty two miles and hour.
I have several other questions, but they can wait till later. And don’t get too freaked on my original tipple expansion thoughts. As far as piston engines go, I am now convinced the uniflow is the only way to go. And the use of a constant volume steam exaust motor to drive the water pumps and cylinder oil injection in relationship to engine load seems wise.., and will probably lead me to even more questions.
So if you are still reading this...
You must be as addicted to steam as I am..
Garry
PS: I envisioned this menagerie at around 800 psi and 800F of steam, though at the moment, I don't remember the lbs per hour I came up with. It does seem like I was going to end up with about half the surface area in tubing of the engine Doble had outlined in Walton's book. (This was before I had heard of extended surface tubing, and about that time the universe put my life on hold)</HTML>
Re: Valve ports, engine rpm & their effective limits?
Posted by: Jim Crank (IP Logged)
Date: March 20, 2002 01:25PM
<HTML>Garry,
The data on Doble's triple expansion engine with reheat is in that multipart article Abner wrote and Walton copied. It is not a Sentinel engine; but for the Blakeborough company and was a proposed car engine.
Be careful about thinking about running the feedwater pump and everything else off some constant volume exhaust motor, like a Roots blower. Too much backpressure will ruin things.
Use the Roots for the condenser fan, vacuum pump and maybe for a draft booster and let the engine run the feed pump. They take too much power to be run off some exhaust turbine/motor.
A three cylinder unaflow with poppet valves and very short cutoff at high speed will do the job as well as a compound or triple. Don't forget, Abner was always looking for extreme engine efficiency, no matter what the cost as far as practical usage is concerned.
Jim</HTML>
The data on Doble's triple expansion engine with reheat is in that multipart article Abner wrote and Walton copied. It is not a Sentinel engine; but for the Blakeborough company and was a proposed car engine.
Be careful about thinking about running the feedwater pump and everything else off some constant volume exhaust motor, like a Roots blower. Too much backpressure will ruin things.
Use the Roots for the condenser fan, vacuum pump and maybe for a draft booster and let the engine run the feed pump. They take too much power to be run off some exhaust turbine/motor.
A three cylinder unaflow with poppet valves and very short cutoff at high speed will do the job as well as a compound or triple. Don't forget, Abner was always looking for extreme engine efficiency, no matter what the cost as far as practical usage is concerned.
Jim</HTML>
Re: Valve ports, engine rpm & their effective limits?
Posted by: Garry Hunsaker (IP Logged)
Date: March 20, 2002 04:34PM
<HTML>Thanks for the advice Jim
Your answer mentioning the ‘Blakeborough company’ has me chomping at the bit for the release of your book on Bessler - Doble. From what I have picked up from your posts, you have more first hand knowledge of this work than perhaps any one else still kicking around on this planet.
I have taken your input on the exhaust motor concept to heart. To be honest, I haven’t set down to plow my way through the basic horse ponys required to drive the pumps. Until I can get this micro shop of mine in some kind of usable order, I am still in the head scratching phase. Which considering my current changes of direction, is probably not a bad place to be.
I appreciate your advice on Doble as well. Though I do admit, if I ever get anything running that becomes reliable enough I start getting bored with it, I will probably turn right around and build a couple of scaled down versions of his designs just to see what they might have done.
As far as ‘balanced poppet valves’ could anyone point me in the direction of well drawn plans, or perhaps photo’s and articles, of a successful application of this design. I am a tinkerer, I am not an engineer, and my gut instinct is concerned about sealing what I guess you would call the valve stem area. I understand Pritchard used a ‘labyrinth’ seal apparently to good effect. Though I am having trouble getting my mind wrapped around that idea as well.
The piston valve is easy for me to understand. My major head scratcher with the poppet valve is what are the ways in which one can handle the change in valve timing. I am of the way-old school, in which a sliding eccentric is high tech. Personally, I think the idea of sliding specially machined cam shafts around, as was done on the Paxton Phoenix, is a bit beyond the average home work shopper’s patience and most certainly mine. I am also wondering about the mass such valves would represent in trying to get them 'gently' reseated at higher engine rpm’s.
Well, I guess that is way more than enough for now..
Again Jim thank you for you time
I am honored to have you and those others with such incredible back grounds in steam listen to my ramblings and point me in new and interesting directions. (well, new for me anyway :)
Garry</HTML>
Your answer mentioning the ‘Blakeborough company’ has me chomping at the bit for the release of your book on Bessler - Doble. From what I have picked up from your posts, you have more first hand knowledge of this work than perhaps any one else still kicking around on this planet.
I have taken your input on the exhaust motor concept to heart. To be honest, I haven’t set down to plow my way through the basic horse ponys required to drive the pumps. Until I can get this micro shop of mine in some kind of usable order, I am still in the head scratching phase. Which considering my current changes of direction, is probably not a bad place to be.
I appreciate your advice on Doble as well. Though I do admit, if I ever get anything running that becomes reliable enough I start getting bored with it, I will probably turn right around and build a couple of scaled down versions of his designs just to see what they might have done.
As far as ‘balanced poppet valves’ could anyone point me in the direction of well drawn plans, or perhaps photo’s and articles, of a successful application of this design. I am a tinkerer, I am not an engineer, and my gut instinct is concerned about sealing what I guess you would call the valve stem area. I understand Pritchard used a ‘labyrinth’ seal apparently to good effect. Though I am having trouble getting my mind wrapped around that idea as well.
The piston valve is easy for me to understand. My major head scratcher with the poppet valve is what are the ways in which one can handle the change in valve timing. I am of the way-old school, in which a sliding eccentric is high tech. Personally, I think the idea of sliding specially machined cam shafts around, as was done on the Paxton Phoenix, is a bit beyond the average home work shopper’s patience and most certainly mine. I am also wondering about the mass such valves would represent in trying to get them 'gently' reseated at higher engine rpm’s.
Well, I guess that is way more than enough for now..
Again Jim thank you for you time
I am honored to have you and those others with such incredible back grounds in steam listen to my ramblings and point me in new and interesting directions. (well, new for me anyway :)
Garry</HTML>
Re: Valve ports, engine rpm & their effective limits?
Posted by: Jim Crank (IP Logged)
Date: March 20, 2002 07:06PM
<HTML>Garry,
Balanced poppet valves are an arrangement of two poppet valves on the same stem, the steam pushes one open as hard as the other one is pushed close. Then the valve spring holds the valve closed. The problem is that one has to be resiliant or spring loaded, so differential expansion of the cylinder block or valve chamber, won't let one leak while the other one is down on the seat. Hard to do.
The best book ever written on these poppet valves is "The Una-Flow Steam Engine" by Stumpf,Van Nostrand Co, N.Y., 1912. Hard book to find; but maybe the university library has a copy. Took me twenty years to get my copy.
Sliding camshafts are something I wouldn't know how to make in my shop either! I would have to have professional help getting one made, expensive!! They don't gently seat unless the cam has a slow closing ramp on it.
Nothing wrong with an inside admission piston valve as long as it it about half as big as the piston it is serving, and the ports at each end are as short as possible, right straight in, no bends. Exhaust around the ends, then the packing gland doesn't see high pressure. At least three rings on each end of the valve.
A shifting eccentric type of valve gear is easy to make in a home shop on the Bridgeport.
Besler only used piston valves on any of his engines. Nothing else; but they were BIG ones for good breathing an low flow losses.
What the heck, Garry, steamers are fun and a super challange for the engineer, and why not pass on the information. We all started from ground zero. Keep thinking.
Jim</HTML>
Balanced poppet valves are an arrangement of two poppet valves on the same stem, the steam pushes one open as hard as the other one is pushed close. Then the valve spring holds the valve closed. The problem is that one has to be resiliant or spring loaded, so differential expansion of the cylinder block or valve chamber, won't let one leak while the other one is down on the seat. Hard to do.
The best book ever written on these poppet valves is "The Una-Flow Steam Engine" by Stumpf,Van Nostrand Co, N.Y., 1912. Hard book to find; but maybe the university library has a copy. Took me twenty years to get my copy.
Sliding camshafts are something I wouldn't know how to make in my shop either! I would have to have professional help getting one made, expensive!! They don't gently seat unless the cam has a slow closing ramp on it.
Nothing wrong with an inside admission piston valve as long as it it about half as big as the piston it is serving, and the ports at each end are as short as possible, right straight in, no bends. Exhaust around the ends, then the packing gland doesn't see high pressure. At least three rings on each end of the valve.
A shifting eccentric type of valve gear is easy to make in a home shop on the Bridgeport.
Besler only used piston valves on any of his engines. Nothing else; but they were BIG ones for good breathing an low flow losses.
What the heck, Garry, steamers are fun and a super challange for the engineer, and why not pass on the information. We all started from ground zero. Keep thinking.
Jim</HTML>
Re: Valve ports, engine rpm & their effective limits?
Posted by: David K. Nergaard (IP Logged)
Date: March 20, 2002 07:58PM
<HTML>I see no reason for "double beat" poppet valves in an automotive engine. At the speeds that even a Stanley runs, the acceleration forces needed to lift the valve are huge compared to the steam pressure forces. And with a uniflow engine, the steam pressure is very near the boiler pressure when the valve opens, anyway.
Sliding cam shafts may be tricky to design, but I think it is the easiest way to go if you want to use really hot steam. If you can make the desired cam in wood, plaster or what have you, a good modern machine shop can copy it in essentially any metal you want. Hooray for computor controlled goodies!
There was a second edition of Prof. Stumpf's book issued in 1922. I have both on microfilm.</HTML>
Sliding cam shafts may be tricky to design, but I think it is the easiest way to go if you want to use really hot steam. If you can make the desired cam in wood, plaster or what have you, a good modern machine shop can copy it in essentially any metal you want. Hooray for computor controlled goodies!
There was a second edition of Prof. Stumpf's book issued in 1922. I have both on microfilm.</HTML>
Re: Valve ports, engine rpm & their effective limits?
Posted by: Tim Senior (IP Logged)
Date: March 20, 2002 08:13PM
<HTML>One Mr. Bugatti designed a double beat (balanced) poppet valve with one of the poppets machined with a deep groove that made the contact face thin and flexible, the other left thick and rigid, so allowing for any slight variation in seat dimentions. These valves don't look too difficult to produce, however I think that the seats may be a trifle more demanding.
Regards Tim.</HTML>
Regards Tim.</HTML>
Re: Valve ports, engine rpm & their effective limits?
Posted by: Peter Brow (IP Logged)
Date: March 21, 2002 07:07AM
<HTML>Hi Garry,
Lube pump should be run by engine, as oil requirement is proportional to engine rpm. Water pumps can eat several hp in a steam car system at top speed, so an exhaust motor is definitely out for that when you figure the low pressures available to run it.
Peter Pellandine once noted that he had to put a tremendous amount of work into cam profiling to get his poppet/cam engine running well. And as I recall, that was for single cams, or a few shiftable cams. A continuously variable sliding cam would be quite a design/development project!
The Graham Baker pages at Karl Peterson's website have an idea for sealing poppet valve stems. He used a PTFE-packed stuffing box, whose cap/packing were compressed by the valve spring, and claimed that this ran for years in daily workhorse use with no leaks or problems. As I recall, his inlet steam temp was 600°F.
I have read that classic valve gear (like Stephenson) recovers most of the kinetic energy put into accelerating the valve, while decelerating it, whereas cam/follower valve drives turn valve-acceleration energy (briefly stored in valve spring) almost entirely into friction heat (& noise) while easing the valve back onto its seat. In IC engines, the poppet valvetrain alone gobbles a large portion of the hp developed at the pistons, especially at part load. At the website for the "Coates rotary valve", the makers compare their valve system's low hp usage to the high friction losses in poppet-valve systems, and they give some numbers on poppet valvetrain friction losses in the process.
Kent says that classic valves in typical steam engines account for 8% of the total friction loss.
The Coates valve is interesting, BTW; quite different from the troublesome experimental disk or barrel rotary valves familiar in steam literature. The Coates valve has a ported sphere rotating on a pressure-compensated self-adjusting seal ring, to eliminate the expansion/contraction/leakage/seizure problems of older rotary valve types in high- and variable-temperature applications. Coates valves work as both inlet and exhaust valves in IC engines. Nice use of advanced materials, too. Costly as built, but perhaps simplifiable for steam use?
One thing I look out for is "Savings A" (eg, reduced steam leakage/increased expansion) being more than offset by "Increased Loss B" (eg, increased friction). Depending on expander efficiency, one BTU worth of extra friction will negate 5-10 BTU worth of steam savings, whether the savings achieved at the cost of the extra friction are from increased expansion or reduced heat loss/leakage. Increasing velocity, mass, or cyclic rate of components increases friction losses of driving them.
I don't have the Coates or Graham Baker URLs handy, but a quick search on Yahoo or other search engine should turn them up. Intriguing designs.
Peter</HTML>
Lube pump should be run by engine, as oil requirement is proportional to engine rpm. Water pumps can eat several hp in a steam car system at top speed, so an exhaust motor is definitely out for that when you figure the low pressures available to run it.
Peter Pellandine once noted that he had to put a tremendous amount of work into cam profiling to get his poppet/cam engine running well. And as I recall, that was for single cams, or a few shiftable cams. A continuously variable sliding cam would be quite a design/development project!
The Graham Baker pages at Karl Peterson's website have an idea for sealing poppet valve stems. He used a PTFE-packed stuffing box, whose cap/packing were compressed by the valve spring, and claimed that this ran for years in daily workhorse use with no leaks or problems. As I recall, his inlet steam temp was 600°F.
I have read that classic valve gear (like Stephenson) recovers most of the kinetic energy put into accelerating the valve, while decelerating it, whereas cam/follower valve drives turn valve-acceleration energy (briefly stored in valve spring) almost entirely into friction heat (& noise) while easing the valve back onto its seat. In IC engines, the poppet valvetrain alone gobbles a large portion of the hp developed at the pistons, especially at part load. At the website for the "Coates rotary valve", the makers compare their valve system's low hp usage to the high friction losses in poppet-valve systems, and they give some numbers on poppet valvetrain friction losses in the process.
Kent says that classic valves in typical steam engines account for 8% of the total friction loss.
The Coates valve is interesting, BTW; quite different from the troublesome experimental disk or barrel rotary valves familiar in steam literature. The Coates valve has a ported sphere rotating on a pressure-compensated self-adjusting seal ring, to eliminate the expansion/contraction/leakage/seizure problems of older rotary valve types in high- and variable-temperature applications. Coates valves work as both inlet and exhaust valves in IC engines. Nice use of advanced materials, too. Costly as built, but perhaps simplifiable for steam use?
One thing I look out for is "Savings A" (eg, reduced steam leakage/increased expansion) being more than offset by "Increased Loss B" (eg, increased friction). Depending on expander efficiency, one BTU worth of extra friction will negate 5-10 BTU worth of steam savings, whether the savings achieved at the cost of the extra friction are from increased expansion or reduced heat loss/leakage. Increasing velocity, mass, or cyclic rate of components increases friction losses of driving them.
I don't have the Coates or Graham Baker URLs handy, but a quick search on Yahoo or other search engine should turn them up. Intriguing designs.
Peter</HTML>
Re: Valve ports, engine rpm & their effective limits?
Posted by: Peter Heid (IP Logged)
Date: March 21, 2002 02:14PM
<HTML>Teflon and other very high temperature valve stem seals have been available in the performance automotive aftermarket for many years. I don't know but they may be useable or adaptable to steam valve use. Some rubber IC valve stem seals use a teflon insert that can easily be removed for use as a packing or such. They come in a few sizes.
Peter Heid</HTML>
Peter Heid</HTML>
Re: Valve ports, engine rpm & their effective limits?
Posted by: Jim Crank (IP Logged)
Date: March 21, 2002 02:49PM
<HTML>Peter,
Tried to find the Coats and Graham Baker on Goggle; but nothing worth anything came up.
If you can find the actual web/e-mail sites do let me know. I am frantic for a poppet valve gear that can work at 4-5,000 rpm with the Wankel. They can; but other valves are a little more acceptable.
After all, the NASCAR types get to about 4750 on their cams and they are flat tappets.
Jim</HTML>
Tried to find the Coats and Graham Baker on Goggle; but nothing worth anything came up.
If you can find the actual web/e-mail sites do let me know. I am frantic for a poppet valve gear that can work at 4-5,000 rpm with the Wankel. They can; but other valves are a little more acceptable.
After all, the NASCAR types get to about 4750 on their cams and they are flat tappets.
Jim</HTML>
Re: Valve ports, engine rpm & their effective limits?
Posted by: Peter Heid (IP Logged)
Date: March 21, 2002 04:04PM
<HTML>Jim,
Try www.coatesengines.com, I don't know about the Graham Baker though.
Peter Heid</HTML>
Try www.coatesengines.com, I don't know about the Graham Baker though.
Peter Heid</HTML>
Re: Valve ports, engine rpm & Coates valvetheir effective limits?
Posted by: Jim Crank (IP Logged)
Date: March 21, 2002 06:39PM
<HTML>Peter,
Found it and thanks. Not enough to really tell just how he is doing this, though.
I have a book on rotary valve engines, mostly motorcycle stuff, Cross, Aspin, etc. dug it out and started reading it again.
Felix Wankel also did a disk type rotary valve that the Germans used in a, now get this, V-8 torpedo engine. NSU also used this balanced Wankel valve.
That new book on Wankel and his engine describes it quite well.
Every one I ever saw leaked like a sieve with 750° Steam after about one hour, even with being flooded with oil. I am really suspicious of rotary valves; but will sure stop and listen if a good one ever turns up.
Onward.
Jim</HTML>
Found it and thanks. Not enough to really tell just how he is doing this, though.
I have a book on rotary valve engines, mostly motorcycle stuff, Cross, Aspin, etc. dug it out and started reading it again.
Felix Wankel also did a disk type rotary valve that the Germans used in a, now get this, V-8 torpedo engine. NSU also used this balanced Wankel valve.
That new book on Wankel and his engine describes it quite well.
Every one I ever saw leaked like a sieve with 750° Steam after about one hour, even with being flooded with oil. I am really suspicious of rotary valves; but will sure stop and listen if a good one ever turns up.
Onward.
Jim</HTML>
Re: Valve ports, engine rpm & Coates valvetheir effective limits?
Posted by: Peter Heid (IP Logged)
Date: March 21, 2002 08:04PM
<HTML>Jim,
Have you looked at the norton rotary motorcycle (NVT) prototyped a few years ago. They ran something like 11,000 rpm with an iron rotor and were talking of titanium next. They were trying to race and develop the bike but I believe money troubles and unclear race classifications finalized the project. I don't have any tech info but I may be able to dig up a couple of names to research if your interested.
Are outboard wankels built to the same designs as all the others, the snowmobile wankels are a bit on the crude side and of no technical value.
The disc type of rotary valve is in common use in base inducted 2 stroke cycle engines and the design they use is very much limited to the intake pressures that the engines operate at. These valves may be 5 or more inches in diameter and have about 0.001-0.002 clearance, plenty of space to leak.
I must wonder about a V8 torpedo engine, It must be a compact engine or big torpedos. Where do you fit the exhaust headers ?
Peter Heid</HTML>
Have you looked at the norton rotary motorcycle (NVT) prototyped a few years ago. They ran something like 11,000 rpm with an iron rotor and were talking of titanium next. They were trying to race and develop the bike but I believe money troubles and unclear race classifications finalized the project. I don't have any tech info but I may be able to dig up a couple of names to research if your interested.
Are outboard wankels built to the same designs as all the others, the snowmobile wankels are a bit on the crude side and of no technical value.
The disc type of rotary valve is in common use in base inducted 2 stroke cycle engines and the design they use is very much limited to the intake pressures that the engines operate at. These valves may be 5 or more inches in diameter and have about 0.001-0.002 clearance, plenty of space to leak.
I must wonder about a V8 torpedo engine, It must be a compact engine or big torpedos. Where do you fit the exhaust headers ?
Peter Heid</HTML>
Re: Valve ports, engine rpm & Coates valvetheir effective limits?
Posted by: Peter Brow (IP Logged)
Date: March 21, 2002 09:11PM
<HTML>Hi Jim,
Yeah, disk and barrel valves are worthless except in low pressure low temp apps, like hydraulic or saturated steam. Been there, done that, not going back. The Coates is a different species. Maybe they changed the website; at one time there were excellent illustrations which explained the whole valve perfectly. Maybe try the patent servers for the original (or later) Coates valve patents. A search for "Coates" under inventor name, in the patent servers, should do it.
I'm thinking, a Coates inlet valve whose port enters the curved outer surface of a Wankel chamber at a point which the apex seal passes over just after cutoff. Another idea: 2 Coates valves in tandem, with one adjustable as to phase, for ultra-short-cutoff tandem inlet valves with no tappeta-tappeta noise. Do the same for exhaust valves, and you've got completely continuously variable cutoff and compression, a la Andy Patterson's advanced engine control concept. A compression for every cutoff, and vice versa, perfectly tailored for clearance volume, for no-throttling control & max expansion over a large portion of the engine's load/speed range. Maybe give the fabled Williams Cycle a test, just by adjusting the valve timing.
Peter</HTML>
Yeah, disk and barrel valves are worthless except in low pressure low temp apps, like hydraulic or saturated steam. Been there, done that, not going back. The Coates is a different species. Maybe they changed the website; at one time there were excellent illustrations which explained the whole valve perfectly. Maybe try the patent servers for the original (or later) Coates valve patents. A search for "Coates" under inventor name, in the patent servers, should do it.
I'm thinking, a Coates inlet valve whose port enters the curved outer surface of a Wankel chamber at a point which the apex seal passes over just after cutoff. Another idea: 2 Coates valves in tandem, with one adjustable as to phase, for ultra-short-cutoff tandem inlet valves with no tappeta-tappeta noise. Do the same for exhaust valves, and you've got completely continuously variable cutoff and compression, a la Andy Patterson's advanced engine control concept. A compression for every cutoff, and vice versa, perfectly tailored for clearance volume, for no-throttling control & max expansion over a large portion of the engine's load/speed range. Maybe give the fabled Williams Cycle a test, just by adjusting the valve timing.
Peter</HTML>
Re: Valve ports, engine rpm & Coates valvetheir effective limits?
Posted by: Jim Crank (IP Logged)
Date: March 22, 2002 01:44PM
<HTML>Peter and Peter,
I would guess the V-8 was used in the standard German Navy torpedo, maybe 21" like ours.
The exhaust was out the tail. Read the new Wankel history book, it is well explained in there with drawings too. Amazon.com and then under books, then put in "Wankel Engines." Well worth reading.
I haven't seen any production Wankel outboard engine. Who makes one? I am directing all my Wankle attention to the Mazda 20-B three rotor. Fortunately the housings and rotors are identical to the standard 13-B, so my junkyard engine provides real information as to port locations and diminsions.
I have seen many rotary valve steam engines and so far have seen not one that worked and didn't leak like mad and have to be flooded with oil to even work at all!!
I will go back to the Coates site and prowl around and see if some link shows his valve operating principals. If it is for real with 1200 psi and 750° steam, then it sure is worth a good analysis.
What I am presently waiting for is a letter from a proposed consulting engineer at M.I.T. who wrote one of the best books on turbine design and I had correspondence with some years ago. There is one turbine design that shows promise for REALLY widening that awful narrow efficiency peak and will deliver good water rates at half or quarter speed. If he agrees and can give me hard data, then I will build that for the steamer.
If turbines are all the same and just won't give any real part load efficiency, then it is the Wankel, with a really super oil separator in the exhaust steam line.
If that Coates valve really will work, then it is worth a try for sure; but please pardon my hesitation for now, just too many failures in the past to take any rotary valve on face value.
What patent site lets me see the patent? I have looked for this many times; but never got the right place.
Jim</HTML>
I would guess the V-8 was used in the standard German Navy torpedo, maybe 21" like ours.
The exhaust was out the tail. Read the new Wankel history book, it is well explained in there with drawings too. Amazon.com and then under books, then put in "Wankel Engines." Well worth reading.
I haven't seen any production Wankel outboard engine. Who makes one? I am directing all my Wankle attention to the Mazda 20-B three rotor. Fortunately the housings and rotors are identical to the standard 13-B, so my junkyard engine provides real information as to port locations and diminsions.
I have seen many rotary valve steam engines and so far have seen not one that worked and didn't leak like mad and have to be flooded with oil to even work at all!!
I will go back to the Coates site and prowl around and see if some link shows his valve operating principals. If it is for real with 1200 psi and 750° steam, then it sure is worth a good analysis.
What I am presently waiting for is a letter from a proposed consulting engineer at M.I.T. who wrote one of the best books on turbine design and I had correspondence with some years ago. There is one turbine design that shows promise for REALLY widening that awful narrow efficiency peak and will deliver good water rates at half or quarter speed. If he agrees and can give me hard data, then I will build that for the steamer.
If turbines are all the same and just won't give any real part load efficiency, then it is the Wankel, with a really super oil separator in the exhaust steam line.
If that Coates valve really will work, then it is worth a try for sure; but please pardon my hesitation for now, just too many failures in the past to take any rotary valve on face value.
What patent site lets me see the patent? I have looked for this many times; but never got the right place.
Jim</HTML>
Re: Valve ports, engine rpm & Coates valvetheir effective limits?
Posted by: Peter Heid (IP Logged)
Date: March 22, 2002 02:44PM
<HTML>Jim,
I think it was OMC that had a 300 hp wankel, I can dig for a bit more info if you would like. I don't know if their design was anything different from most other wankels, may just be another dead end.
I find it funny you mentioned the NSU (never starts up), I have a 1960 600cc, rear engine, rear drive Prinz that I have thought of steam powering. It looks like the front is the same as the rear, you can't tell which way it is going. The original power plant is 24 HP 2 cylinder air cooled. So light and small that I brought it home on a snowmobile trailer.
Peter heid</HTML>
I think it was OMC that had a 300 hp wankel, I can dig for a bit more info if you would like. I don't know if their design was anything different from most other wankels, may just be another dead end.
I find it funny you mentioned the NSU (never starts up), I have a 1960 600cc, rear engine, rear drive Prinz that I have thought of steam powering. It looks like the front is the same as the rear, you can't tell which way it is going. The original power plant is 24 HP 2 cylinder air cooled. So light and small that I brought it home on a snowmobile trailer.
Peter heid</HTML>
Re: Valve ports, engine rpm & their effective limits?
Posted by: George K. Nutz (IP Logged)
Date: March 22, 2002 03:08PM
<HTML>Peter,
I may be wrong but believe the 8-10% friction loss of valves was for slide valves, that is about what a Stanley uses.
In actuality the Williams simple poppet intake valve was a "balanced" valve as the clearance volume was so low that the balancing valve in the compression phase made the pressure equal on the top and bottom of the simple poppet valve almost equal and removed all the valve loading due to pressure differential many degrees before the inlet valve cam came into contact with the valve lifter.
Hal Fuller, last steam engineer at Skinner Engine Company, has developed, over the years, a completely hydraulic valve lifter of constant lead and infinitely variable cutoff
using diesel fuel injector technology. He has made a 60HP test engine and driven a 60 cycle generator as the dyno, his speed/frequency control is obtained by changing the percentage of admission and is so very fast in cutoff change that he can unload the AC generator and the AC frequency may go from 60Hz to 61+Hz, this is without changing inlet pressure. Hal was formerly a research engineer with SES in the old days. Lots of good stuff out there,
George</HTML>
I may be wrong but believe the 8-10% friction loss of valves was for slide valves, that is about what a Stanley uses.
In actuality the Williams simple poppet intake valve was a "balanced" valve as the clearance volume was so low that the balancing valve in the compression phase made the pressure equal on the top and bottom of the simple poppet valve almost equal and removed all the valve loading due to pressure differential many degrees before the inlet valve cam came into contact with the valve lifter.
Hal Fuller, last steam engineer at Skinner Engine Company, has developed, over the years, a completely hydraulic valve lifter of constant lead and infinitely variable cutoff
using diesel fuel injector technology. He has made a 60HP test engine and driven a 60 cycle generator as the dyno, his speed/frequency control is obtained by changing the percentage of admission and is so very fast in cutoff change that he can unload the AC generator and the AC frequency may go from 60Hz to 61+Hz, this is without changing inlet pressure. Hal was formerly a research engineer with SES in the old days. Lots of good stuff out there,
George</HTML>
Re: Valve ports, engine rpm & Coates valvetheir effective limits?
Posted by: Jim Crank (IP Logged)
Date: March 22, 2002 03:18PM
<HTML>Peter,
Yes, OMC did do an experimental Wankel. If I recall correctly, the actual engine came from Curtis-Wright when they were wallowing in the area.
An NSU Prinz? My God, I forgot about that one.
A friend of mine used to race the Wankel roadster version of it. A few laps and the engine broke it's seals. Loudest car on the track too!! He put a megaphone on it, absolutely ear shattering.
Well, it's a nice little and light car and why not do a plant for it? 20HP would make it run like it never did before.
I saw a car yesterday that bought back many memories of Besler's proposed conversion kit idea. A beautiful Chevy Corvair convertible. Still a nice car and certainly available and for sure there is room for a well done steam plant in it. Boiler in front and engine in the back. Condensers on the front, under the front hood and in the back. Ought to work well.
Jim</HTML>
Yes, OMC did do an experimental Wankel. If I recall correctly, the actual engine came from Curtis-Wright when they were wallowing in the area.
An NSU Prinz? My God, I forgot about that one.
A friend of mine used to race the Wankel roadster version of it. A few laps and the engine broke it's seals. Loudest car on the track too!! He put a megaphone on it, absolutely ear shattering.
Well, it's a nice little and light car and why not do a plant for it? 20HP would make it run like it never did before.
I saw a car yesterday that bought back many memories of Besler's proposed conversion kit idea. A beautiful Chevy Corvair convertible. Still a nice car and certainly available and for sure there is room for a well done steam plant in it. Boiler in front and engine in the back. Condensers on the front, under the front hood and in the back. Ought to work well.
Jim</HTML>
Re: Valve port limits as a Wankel Hmmm??
Posted by: Garry Hunsaker (IP Logged)
Date: March 22, 2002 05:00PM
<HTML>I believe it was about 1980 I was up at Oshkosh for the fly in. At the time every one was hopped up on the idea of trying to fly one of the Mazda engines. Now admittedly, what it takes to drive a car down the road, and keep an airplane in the air, are miles apart as far as horse power requirements are concerned. However, everyone that worked on this idea as an aircraft engine had major problems.
It seems at continuous high out put, the Wankel had a nasty habit of distorting its rotor housings and even the side plates. If I remember correctly, Boeing spent several millions of dollars trying to create a reliable Wankel aircraft engine. When they finally gave up, they sold the project to John Dear, who then spent a few more million on it trying to create a tractor engine.
I will never forget setting in on a seminar held by some of the NASA propulsion group folks, where the discussion of the Wankel was raised by an engineer, who turned out to be from John Dear. ‘Apparently NASA had been doing some work on this engine for the military’. The engineer was looking for high efficiency and high output out of the Wankel and wanted to know what could be done to cure its problems. Basically the NASA answer was to repeat who had spent way much-oh money on this problem, what those problems were, and that the problems appeared unsolvable to NASA. The NASA rep further told us that we should look at the two cycle piston engine. According to him, the most efficient industrial internal combustion engines in the world are all two cycles. Hmmm... Maybe Williams wasn’t that far off the mark.
Jim, I am not saying the Wankel wont work in a steamer, but if you are looking at the steam car land speed record again, I would do a whole lot of bench testing on any Wankel based steam design you come up with. Steam is a whole different ball game though, as it is far removed from the peak pressure loads and temps of an IC engine. In other words, the danged thing just might work as a high output steamer...
Garry</HTML>
It seems at continuous high out put, the Wankel had a nasty habit of distorting its rotor housings and even the side plates. If I remember correctly, Boeing spent several millions of dollars trying to create a reliable Wankel aircraft engine. When they finally gave up, they sold the project to John Dear, who then spent a few more million on it trying to create a tractor engine.
I will never forget setting in on a seminar held by some of the NASA propulsion group folks, where the discussion of the Wankel was raised by an engineer, who turned out to be from John Dear. ‘Apparently NASA had been doing some work on this engine for the military’. The engineer was looking for high efficiency and high output out of the Wankel and wanted to know what could be done to cure its problems. Basically the NASA answer was to repeat who had spent way much-oh money on this problem, what those problems were, and that the problems appeared unsolvable to NASA. The NASA rep further told us that we should look at the two cycle piston engine. According to him, the most efficient industrial internal combustion engines in the world are all two cycles. Hmmm... Maybe Williams wasn’t that far off the mark.
Jim, I am not saying the Wankel wont work in a steamer, but if you are looking at the steam car land speed record again, I would do a whole lot of bench testing on any Wankel based steam design you come up with. Steam is a whole different ball game though, as it is far removed from the peak pressure loads and temps of an IC engine. In other words, the danged thing just might work as a high output steamer...
Garry</HTML>
Re: Valve ports, engine rpm & Coates valvetheir effective limits?
Posted by: Peter Heid (IP Logged)
Date: March 22, 2002 05:01PM
<HTML>Jim,
I have most every popular mechanics from 1939 on and I have seen ads for the wankel outboard. I have never seen a wankel outboard though. I don't know if it was ever actually produced and by whom. I could skim through the PMs and let you know more about the ads if you wish. Maybe it is like the Ford advertisments for the gas turbine tractor trailer rigs with a fridge, AC, sleeper capacity and all the comforts of home. Nothing but vaporware.
For those of you wondering, I have not run across any ads for converting IC cars to steam, though there are a few article on steam autos. There may be ads and I may have missed them but I go thru the issues one page at a time and catalog the articles.
Peter Heid</HTML>
I have most every popular mechanics from 1939 on and I have seen ads for the wankel outboard. I have never seen a wankel outboard though. I don't know if it was ever actually produced and by whom. I could skim through the PMs and let you know more about the ads if you wish. Maybe it is like the Ford advertisments for the gas turbine tractor trailer rigs with a fridge, AC, sleeper capacity and all the comforts of home. Nothing but vaporware.
For those of you wondering, I have not run across any ads for converting IC cars to steam, though there are a few article on steam autos. There may be ads and I may have missed them but I go thru the issues one page at a time and catalog the articles.
Peter Heid</HTML>
Re: Valve port limits as a Wankel Hmmm??
Posted by: Jim Crank (IP Logged)
Date: March 23, 2002 03:11AM
<HTML>Garry,
Yes, the IC Wankel if overheated can sure fail. They solved this in 1989-91. The water passages were totally redone and the flow changed drastically. It was a problem earlier.
As an IC, the housings can certainly overheat to the point where they warp and the rubber seals fail. As a steam engine, the overall temperature is much less by a large magnitude than as an IC engine. Re-plotting the clearances for the mean operting temperature, which is not going above 750° F and really not anywhere that high in practice, insulate the thing and I don't see any problem.
On steam the highest temperature is low compared to what happens in a highly turbocharged IC Wankel.
The speed record idea has departed, since the British "challanger" has done the same. As predicted.
Jim</HTML>
Yes, the IC Wankel if overheated can sure fail. They solved this in 1989-91. The water passages were totally redone and the flow changed drastically. It was a problem earlier.
As an IC, the housings can certainly overheat to the point where they warp and the rubber seals fail. As a steam engine, the overall temperature is much less by a large magnitude than as an IC engine. Re-plotting the clearances for the mean operting temperature, which is not going above 750° F and really not anywhere that high in practice, insulate the thing and I don't see any problem.
On steam the highest temperature is low compared to what happens in a highly turbocharged IC Wankel.
The speed record idea has departed, since the British "challanger" has done the same. As predicted.
Jim</HTML>
Re: Valve ports, engine rpm, tandem poppets & hydraulic valves
Posted by: Peter Brow (IP Logged)
Date: March 23, 2002 10:45AM
<HTML>Hi George,
Kent probably was talking about slide valves.
The poppet-balancing effect of "complete" exhaust compression is one of the advantages of Williams and similar steam engines. Of course when the rpms get up there, the kinetic loads are much higher than the pressure loads, even w/unbalanced valves.
Hydraulic valve systems are really fascinating stuff. At the San Diego Auto Museum, there is a large display case (near the uncased Stanley engine on the floor in the engine room) containing a Preston Tucker experimental hydraulic-actuated valve system -- a failed experiment when Tucker's guys were working to adapt the Franklin aircraft engine to automotive use. Pearson (The Indomitable Tin Goose) quotes a Tucker engineer saying that air kept getting in the system and the valves went haywire, so they finally round-filed it. Museum display sez something about cavitation and inferior 1940s hydro fluid.
Anyway, the museum display inspired me to sketch up a bunch of possible hydraulic valve systems. I kept running into problems, and dropped the idea. A couple of hydraulic engineers warned me to look out for air ingress, fluid expansion with heat, recip fluid masses, fluid friction, and inevitable seal leaks (all solveable). However, continuously variable valve actuation is certainly achievable with a hydraulic system, with relatively simple equipment. Glad to hear that somebody has got this running well.
Those SES veterans keep popping up. Andy corresponded with one of the SES guys for a while, even forwarded some of his comments to the discussion list we were on. All kinds of advanced concepts in that powerplant. All leading to the same efficiency that Rollin White got 50 years earlier with much simpler equipment. Interesting stuff, though. Who knows, control the heat & friction losses, size it better for actual road use, and a few other tweaks, and some of these ideas might still go places.
Personally, if I were going with poppet valves and short cutoff, I'd use tandem poppets. Simple, continuously variable cutoff/compression control, and reasonable valve speeds, the last one very important in steam engines with supershort cutoff unless you dig busting things as a learning process. The tradeoff is twice as many valves, but many gas engines today have 4 valves (even 5) per cylinder, and a good steamer can (& IMHO should) have fewer cylinders.
The phase change on one of a pair of tandem poppet valves, btw (you know this George, this is in case anyone is wondering) is by sliding a fast screw sleeve along a toothed sleeve attached to one of the cams. The screw cannot rotate relative to camshaft, so its helical groove pivots the teeth/sleeve/cam inside it to a new phase on camshaft. One valve (usually upline in steam inlet) has a set timing, and always opens at ~TDC; the variable-phase valve opens before it, and can be profiled/adjusted to close at any point in the stroke.
This way, both valves can open & close nice and easy, but the cutoff can be shortened tremendously. Combine that with exhaust compression balance and reasonable rpms, and you've got a smooth million-mile valvetrain, about as sweet-running as poppets can get.
Oh, don't forget the old Mercedes trick of rotating the poppet valves a smidge each cycle -- valves and seats stay tight darn near forever. Or the Scott-Newcomb engine, poppet side valves with a double-acting Stanley/Doble layout & camshafts along middle of block (outboard toothed belt drive in modern version?). Try squeezing all that junk together in the space available -- I tried on paper, whew.
Then you figure out overlapping cutoff for self-start & smooth lo-rpm, number of cylinders, friction losses, heat losses related to surface/volume ratios, size it right to load range, and on and on. Every design decision has tradeoffs and gets you erasing/redrawing previous features. You can have years of fun in the concept stage alone. :)
Peter</HTML>
Kent probably was talking about slide valves.
The poppet-balancing effect of "complete" exhaust compression is one of the advantages of Williams and similar steam engines. Of course when the rpms get up there, the kinetic loads are much higher than the pressure loads, even w/unbalanced valves.
Hydraulic valve systems are really fascinating stuff. At the San Diego Auto Museum, there is a large display case (near the uncased Stanley engine on the floor in the engine room) containing a Preston Tucker experimental hydraulic-actuated valve system -- a failed experiment when Tucker's guys were working to adapt the Franklin aircraft engine to automotive use. Pearson (The Indomitable Tin Goose) quotes a Tucker engineer saying that air kept getting in the system and the valves went haywire, so they finally round-filed it. Museum display sez something about cavitation and inferior 1940s hydro fluid.
Anyway, the museum display inspired me to sketch up a bunch of possible hydraulic valve systems. I kept running into problems, and dropped the idea. A couple of hydraulic engineers warned me to look out for air ingress, fluid expansion with heat, recip fluid masses, fluid friction, and inevitable seal leaks (all solveable). However, continuously variable valve actuation is certainly achievable with a hydraulic system, with relatively simple equipment. Glad to hear that somebody has got this running well.
Those SES veterans keep popping up. Andy corresponded with one of the SES guys for a while, even forwarded some of his comments to the discussion list we were on. All kinds of advanced concepts in that powerplant. All leading to the same efficiency that Rollin White got 50 years earlier with much simpler equipment. Interesting stuff, though. Who knows, control the heat & friction losses, size it better for actual road use, and a few other tweaks, and some of these ideas might still go places.
Personally, if I were going with poppet valves and short cutoff, I'd use tandem poppets. Simple, continuously variable cutoff/compression control, and reasonable valve speeds, the last one very important in steam engines with supershort cutoff unless you dig busting things as a learning process. The tradeoff is twice as many valves, but many gas engines today have 4 valves (even 5) per cylinder, and a good steamer can (& IMHO should) have fewer cylinders.
The phase change on one of a pair of tandem poppet valves, btw (you know this George, this is in case anyone is wondering) is by sliding a fast screw sleeve along a toothed sleeve attached to one of the cams. The screw cannot rotate relative to camshaft, so its helical groove pivots the teeth/sleeve/cam inside it to a new phase on camshaft. One valve (usually upline in steam inlet) has a set timing, and always opens at ~TDC; the variable-phase valve opens before it, and can be profiled/adjusted to close at any point in the stroke.
This way, both valves can open & close nice and easy, but the cutoff can be shortened tremendously. Combine that with exhaust compression balance and reasonable rpms, and you've got a smooth million-mile valvetrain, about as sweet-running as poppets can get.
Oh, don't forget the old Mercedes trick of rotating the poppet valves a smidge each cycle -- valves and seats stay tight darn near forever. Or the Scott-Newcomb engine, poppet side valves with a double-acting Stanley/Doble layout & camshafts along middle of block (outboard toothed belt drive in modern version?). Try squeezing all that junk together in the space available -- I tried on paper, whew.
Then you figure out overlapping cutoff for self-start & smooth lo-rpm, number of cylinders, friction losses, heat losses related to surface/volume ratios, size it right to load range, and on and on. Every design decision has tradeoffs and gets you erasing/redrawing previous features. You can have years of fun in the concept stage alone. :)
Peter</HTML>
Re: Valve ports, engine rpm & Coates valvetheir effective limits?
Posted by: Peter Brow (IP Logged)
Date: March 23, 2002 11:24AM
<HTML>Hi Jim,
I completely agree with your doubts about rotary valves. I've researched the things with a fine tooth comb, haven't found a single one that was successful with superheated steam, and have long since dropped the idea.
Barrel valves are either made loose, in which case they leak horribly while warming up, or tight, in which case they seize when hot. They can also oscillate in their bores.
Disk valves can not only warp, but expand radially/differentially with heat, and the microgrooves don't line up with the microlands, meaning high wear and leakage.
The Coates, in theory, can expand radially from the center of the sphere, maintaining a spherical shape and a contact circle on the ring. However, they'd have to be HARD and micro-polished. As I recall, Coates uses advanced ceramics.
On patent servers, I am wracking my brain and drawing a blank. I think it is the IBM Patent Server, but will check. There is one that allows all kinds of search modes, and is easy to find things with. Or at least there _was_; haven't used one in a year or two.
Peter</HTML>
I completely agree with your doubts about rotary valves. I've researched the things with a fine tooth comb, haven't found a single one that was successful with superheated steam, and have long since dropped the idea.
Barrel valves are either made loose, in which case they leak horribly while warming up, or tight, in which case they seize when hot. They can also oscillate in their bores.
Disk valves can not only warp, but expand radially/differentially with heat, and the microgrooves don't line up with the microlands, meaning high wear and leakage.
The Coates, in theory, can expand radially from the center of the sphere, maintaining a spherical shape and a contact circle on the ring. However, they'd have to be HARD and micro-polished. As I recall, Coates uses advanced ceramics.
On patent servers, I am wracking my brain and drawing a blank. I think it is the IBM Patent Server, but will check. There is one that allows all kinds of search modes, and is easy to find things with. Or at least there _was_; haven't used one in a year or two.
Peter</HTML>
Re: Valve ports, engine rpm & Coates valvetheir effective limits?
Posted by: Jim Crank (IP Logged)
Date: March 23, 2002 02:58PM
<HTML>Peter,
I see again we are in total agreement.
The Coates valve may expand equally; but now what about all the cutouts he has in his valve? Interesting for sure; but I have grave doubts about it with 750° steam.
What I am pondering now, is the fact that if the Wankel output shaft runs at say 4,000. the rotor only goes 1/3 that speed. Nice for low seal wear; but there are three firing sequences per turn of the rotor, so the valve gear has to run at shaft speed, not rotor speed. This puts loads on a single poppet valve gear that is about as fierce as a NASCAR engine, not nice at all.
Although I don't like it from a clearance standpoint, I could use three poppets per chamber, then the cam gear only runs at 1/3 the shaft speed. More acceptable.
This sure needs more work.
I am just hoping like mad that Dr. Wilson comes back and says "Yes, that turbine design you found will do the job and give good efficiency at part peak speed." Never found any turbine that is really acceptable; but this one is most unique and so easy to make.
Nothing radical, just a good combination of designs that may do the job, if Ford does come out with that high torque CVT transmission later this year for their trucks.
Good efficiency at lower speeds and NO OIL.
Oh, the fun of steam car designing.
Jim</HTML>
I see again we are in total agreement.
The Coates valve may expand equally; but now what about all the cutouts he has in his valve? Interesting for sure; but I have grave doubts about it with 750° steam.
What I am pondering now, is the fact that if the Wankel output shaft runs at say 4,000. the rotor only goes 1/3 that speed. Nice for low seal wear; but there are three firing sequences per turn of the rotor, so the valve gear has to run at shaft speed, not rotor speed. This puts loads on a single poppet valve gear that is about as fierce as a NASCAR engine, not nice at all.
Although I don't like it from a clearance standpoint, I could use three poppets per chamber, then the cam gear only runs at 1/3 the shaft speed. More acceptable.
This sure needs more work.
I am just hoping like mad that Dr. Wilson comes back and says "Yes, that turbine design you found will do the job and give good efficiency at part peak speed." Never found any turbine that is really acceptable; but this one is most unique and so easy to make.
Nothing radical, just a good combination of designs that may do the job, if Ford does come out with that high torque CVT transmission later this year for their trucks.
Good efficiency at lower speeds and NO OIL.
Oh, the fun of steam car designing.
Jim</HTML>
Re: Valve ports, engine rpm & Coates valvetheir effective limits?
Posted by: Peter Brow (IP Logged)
Date: March 24, 2002 07:12AM
<HTML>Hi Jim,
Yep, funfunfun. :) A high-pressure, high-expansion turbine could drop quite a bit in efficiency at low load, and still compete with today's gas cars, so there may be some hope there. As you say, NO OIL -- and I would add NO VALVES! The valves are the toughest part of any good steam engine, bar none.
If that dog don't hunt, I bet some kind of good valvetrain can be worked out for the steam Wankel, and the thermal/sealing situation looks positive. If nothing else, rpm can be limited to get poppet valves into a proven load/speed regime. Lower rpm can be compensated for with a higher mep via longer admission. Ultrahigh expansion may not be necessary anyway, to equal or even beat modern car engines loaded with auto trannies, smog junk, etc and usually running at 1/10 or less their optimum load on our increasingly congested city streets.
If you used ~700°F steam & Stanley cutoffs (~28-60%), internal surface temps would run about 500°F (ref Stanley notes from H.O. Baker's shop). I doubt you'd want to put in that much steam, and higher expansion would cut surface temps below that, even with slightly hotter inlet steam. So I'd expect under 500°F -- MAX -- can an iron Wankel take that? I know the oil & iron can handle it, and with seals taking lower peak pressures than in IC trim, hmmm...
Frankly, I think the Coates valve is a long shot too, just less long than the old disk & barrel valves, and "just barely" promising enough to investigate. They actually run well in real engines, even as IC exhaust valves -- and that's tough service.
Best of luck with both of your expander ideas, either one could be a real step ahead.
Peter</HTML>
Yep, funfunfun. :) A high-pressure, high-expansion turbine could drop quite a bit in efficiency at low load, and still compete with today's gas cars, so there may be some hope there. As you say, NO OIL -- and I would add NO VALVES! The valves are the toughest part of any good steam engine, bar none.
If that dog don't hunt, I bet some kind of good valvetrain can be worked out for the steam Wankel, and the thermal/sealing situation looks positive. If nothing else, rpm can be limited to get poppet valves into a proven load/speed regime. Lower rpm can be compensated for with a higher mep via longer admission. Ultrahigh expansion may not be necessary anyway, to equal or even beat modern car engines loaded with auto trannies, smog junk, etc and usually running at 1/10 or less their optimum load on our increasingly congested city streets.
If you used ~700°F steam & Stanley cutoffs (~28-60%), internal surface temps would run about 500°F (ref Stanley notes from H.O. Baker's shop). I doubt you'd want to put in that much steam, and higher expansion would cut surface temps below that, even with slightly hotter inlet steam. So I'd expect under 500°F -- MAX -- can an iron Wankel take that? I know the oil & iron can handle it, and with seals taking lower peak pressures than in IC trim, hmmm...
Frankly, I think the Coates valve is a long shot too, just less long than the old disk & barrel valves, and "just barely" promising enough to investigate. They actually run well in real engines, even as IC exhaust valves -- and that's tough service.
Best of luck with both of your expander ideas, either one could be a real step ahead.
Peter</HTML>
Re: Valve ports, engine rpm & Coates valvetheir effective limits?
Posted by: Jim Crank (IP Logged)
Date: March 24, 2002 03:03PM
<HTML>Peter,
YUP, right again on all counts.
The mean temperature in the Wankel would be around 450°-500°F. Doble E-14 used to have a thermocouple on the HP cylinder under the insulation. That temp is what we always saw with 750° on the outlet of the superheater.
All gaskets are changed to copper "O" rings, exept the ones down on the eccentric shaft for oil control. Iron housings-iron side plates will definitely take the temperature with ease, and now expanding equally, the one big problem with overheating the I.C. Wankel.
Heat barrier coatings on the rotor surfaces.
Cutoff probably 15/25% and 50%. Two speed trans makes for a good power-speed match.
OH YES, no valves and no oil with the turbine; but only if it is at least reasonable in water rate at part speed. That is what Dr. Wilson could consult on and that is what I am waiting to hear.
That Ford CVT is key to this, or maybe G.M. will have one for big trucks, have to wait on this one for a few months.
However, the 20-B Wankel is most promising and while I await Wilson's letter, I am moving on with that analysis and design work. I think you are seeing the advantages of the Wankel, as I am. Problems with a valve gear; but solvable. Three in series? Desmodromics? Electric? Interesting design problem.
Needs a really good oil separator.
While the Coates valve is sure interesting, I see some problems when used with steam.
Jim</HTML>
YUP, right again on all counts.
The mean temperature in the Wankel would be around 450°-500°F. Doble E-14 used to have a thermocouple on the HP cylinder under the insulation. That temp is what we always saw with 750° on the outlet of the superheater.
All gaskets are changed to copper "O" rings, exept the ones down on the eccentric shaft for oil control. Iron housings-iron side plates will definitely take the temperature with ease, and now expanding equally, the one big problem with overheating the I.C. Wankel.
Heat barrier coatings on the rotor surfaces.
Cutoff probably 15/25% and 50%. Two speed trans makes for a good power-speed match.
OH YES, no valves and no oil with the turbine; but only if it is at least reasonable in water rate at part speed. That is what Dr. Wilson could consult on and that is what I am waiting to hear.
That Ford CVT is key to this, or maybe G.M. will have one for big trucks, have to wait on this one for a few months.
However, the 20-B Wankel is most promising and while I await Wilson's letter, I am moving on with that analysis and design work. I think you are seeing the advantages of the Wankel, as I am. Problems with a valve gear; but solvable. Three in series? Desmodromics? Electric? Interesting design problem.
Needs a really good oil separator.
While the Coates valve is sure interesting, I see some problems when used with steam.
Jim</HTML>
Re: Valve ports, engine rpm & their effective limits?
Posted by: Arnold Walker (IP Logged)
Date: June 06, 2002 07:44PM
<HTML>I don't if it will help or not ,but ran across a live steamer fan with a valve gear simulator that he uses to lineout designs with.At www.tcsn.net/charlied.
And I too much of rookie on this to know.</HTML>
And I too much of rookie on this to know.</HTML>
Re: Valve ports, engine rpm & their effective limits?
Posted by: Carl Helsing (IP Logged)
Date: June 08, 2006 04:35AM
<HTML>I have had a few ideas and also experienced strange coincidences.Back in the 1970's I worked mounting tires at a Firestone store.An old fellow,probably in his 70's happened to walk in and I heard him mention that he had a Wiily's Knight with the sleeve valve engine.Those disappeared probably by the early 1930's.Someone who knew I did small engine repairs(lawn and garden size)had left a technical manual by a guy named Smolen,showing the complete workings of the sleeve valve system.If you're not familiar with it,the valves were simply two sleeves around the piston,attached to, their own cranks,and sliding up and down just as the piston does,opening and closing ports at the head area.The manual had a late1920's date.Anyway,I told the old fellow he could have the manual,since it was of no use to me,and he had the actual automobile.I think he gave me 5 dollars for it.I have a model steam oscillating engine from Germany,given as a gift by my brother.I played with it for a couple weeks,and the piston seized in the cylinder.They had used a short little slug of metal as the piston.There was no crosshead or guide of any type at the piston end.Instead of mounting a guide bearing,which I could have done,I instead used a brass sleeve,internal precision fit,and a longer cylinder of the same brass.The brass is model material of close increments,one tube sliding within the other,maybe a thousandth tolerance.The engine is still running after ten years of fiddling.Valve and piston ideas-(some for toys)The main thing I wanted to tell you,since yoy have some ideas,is of a concept I have had of having a "hybrid" of an internal combustion engine with a steam auxilliary utilizing all the water the internal combustion engine can boil to steam,right down to ends of the exhaust manifolds.A thermal efficiency concept.Could have been some of that type somewhere,tho they would likely be isolated so-called specialty items in possibly small industrial use,time period,20'-30's-Just ideas and stories-enjoy-(also-valve idea for all the air that can be packed into a cylinder)
<a href="mailto:ghunsaker@mexicomo.net?subject=Valve ports, engine rpm & their effective limits?">Garry Hunsaker</a> wrote:
>
>
> I am wondering if there is anything remotely like a rule of
> thumb as to how short a stroke, and therefore a limit to how
> short a duration a steam engine’s ports can remain open and
> still properly ‘charge’ the cylinder. The steam engine has
> enough problems with out adding windage restrictions. (Or is
> this what engineers refer to as ‘shock’?) What has brought me
> to this question is looking at the three cylinder engine in
> my old Subaru Justy. It’s 3.27” stroke is almost liveable.
> (To be honest, I think I need to check out the crankshaft on
> the Chevy Geo. There are a heck of a lot more of them around
> to choose from)
>
> The only thing in the way of data I have had in the past to
> work with was J. N. Walton’s book on Doble. I have been
> hunting around today for the numbers I ran several years ago,
> that Doble outlined for his triple expansion engine, but I
> still haven’t come up with the place I put them to make sure
> I didn’t lose them... (So what else is new.)
>
> Shooting from memory, I believe I was aiming at 50 to 60 hp.
> Any way, the one thing I do remember is measuring my old 1970
> VW van. The best I remember I came to the conclusion that by
> running the engine at roughly twice the speed of the
> differential gear I would have the effective torque of the
> standard VW van about half way between first and second
> gear. (The acceleration should be interesting to say the
> least)
>
> For those that might be curious, I had intended to lay the
> resulting engine on its side on the left side of engine
> compartment. By adding a splined stub shaft to the end of
> the crank, and running that into a gear box, I would have to
> create using the side plates, bearings, and third member from
> the VW, I thought I could make this work.
>
> I was still scratching my head on how, or if I needed to, set
> the gear box up for backlash adjustment on the deferential
> gears I would have to come up with. The thought did occur to
> me to create new side plates so the outer bolt circle, and
> its corresponding surface would be slightly eccentric in
> relation to the third member support bearings. I figured
> throwing the axles a few thousandths out of their original
> position wouldn’t bother those CV joints too much. Though
> making exactly matching eccentric side plates in relation to
> a set of perfectly divided and aligned bolt circles still had
> me wondering on the how the heck am I going to do that???
>
> The advantage of placing the engine to one side was it would
> leave better than three quarters of the engine compartment
> open for a steam generator. Using the info I was beginning
> to pick up from the SACA back then, I figured by using
> extended surface tubing in the pre-boil sections of a
> monotube boiler, I could keep the size down to where the
> whole package could be hung on a square tube frame and
> attached to beefed up versions of the original engine and
> transmission mounts. There should even be room for a water
> tank forward of the differential, and enough room to place
> most of the auxiliaries above the engine and out of the road
> grit and grime. The exception being the water pumps, I hoped
> to get those below the level of the bottom of the water tank.
> The only thing I didn’t envision attaching to this package
> was the condenser. That I planned placing on the left side
> of the body with lovers cut in the body to shove the heat out
> with an electric fan-s.
>
> I was still finding myself with too many questions. A few of
> which I have had answered thanks to this form and the SACA
> discussion list. Before I started hacking out metal, melting
> down old Cummins diesel pistons, making patterns, and all the
> other fun stuff that goes with experimental prototypes built
> on no budget, I thought I had better have a bit more
> understanding of what is going on, and if such a short stroke
> engine could ‘breath’ properly under steam at the RPM I
> envisioned. I believe that may have been around 800 foot per
> minute piston speed at 70 mph and 2100 rpm, which is
> considerably faster than I care to drive one of those old
> vans. Though mainly, I didn’t want to end up spending a few
> years creating such a monstrosity and discover later it would
> have a top speed of twenty two miles and hour.
>
> I have several other questions, but they can wait till
> later. And don’t get too freaked on my original tipple
> expansion thoughts. As far as piston engines go, I am now
> convinced the uniflow is the only way to go. And the use of a
> constant volume steam exaust motor to drive the water pumps
> and cylinder oil injection in relationship to engine load
> seems wise.., and will probably lead me to even more questions.
>
> So if you are still reading this...
> You must be as addicted to steam as I am..
> Garry
> PS: I envisioned this menagerie at around 800 psi and 800F of
> steam, though at the moment, I don't remember the lbs per
> hour I came up with. It does seem like I was going to end up
> with about half the surface area in tubing of the engine
> Doble had outlined in Walton's book. (This was before I had
> heard of extended surface tubing, and about that time the
> universe put my life on hold)</HTML>
<a href="mailto:ghunsaker@mexicomo.net?subject=Valve ports, engine rpm & their effective limits?">Garry Hunsaker</a> wrote:
>
>
> I am wondering if there is anything remotely like a rule of
> thumb as to how short a stroke, and therefore a limit to how
> short a duration a steam engine’s ports can remain open and
> still properly ‘charge’ the cylinder. The steam engine has
> enough problems with out adding windage restrictions. (Or is
> this what engineers refer to as ‘shock’?) What has brought me
> to this question is looking at the three cylinder engine in
> my old Subaru Justy. It’s 3.27” stroke is almost liveable.
> (To be honest, I think I need to check out the crankshaft on
> the Chevy Geo. There are a heck of a lot more of them around
> to choose from)
>
> The only thing in the way of data I have had in the past to
> work with was J. N. Walton’s book on Doble. I have been
> hunting around today for the numbers I ran several years ago,
> that Doble outlined for his triple expansion engine, but I
> still haven’t come up with the place I put them to make sure
> I didn’t lose them... (So what else is new.)
>
> Shooting from memory, I believe I was aiming at 50 to 60 hp.
> Any way, the one thing I do remember is measuring my old 1970
> VW van. The best I remember I came to the conclusion that by
> running the engine at roughly twice the speed of the
> differential gear I would have the effective torque of the
> standard VW van about half way between first and second
> gear. (The acceleration should be interesting to say the
> least)
>
> For those that might be curious, I had intended to lay the
> resulting engine on its side on the left side of engine
> compartment. By adding a splined stub shaft to the end of
> the crank, and running that into a gear box, I would have to
> create using the side plates, bearings, and third member from
> the VW, I thought I could make this work.
>
> I was still scratching my head on how, or if I needed to, set
> the gear box up for backlash adjustment on the deferential
> gears I would have to come up with. The thought did occur to
> me to create new side plates so the outer bolt circle, and
> its corresponding surface would be slightly eccentric in
> relation to the third member support bearings. I figured
> throwing the axles a few thousandths out of their original
> position wouldn’t bother those CV joints too much. Though
> making exactly matching eccentric side plates in relation to
> a set of perfectly divided and aligned bolt circles still had
> me wondering on the how the heck am I going to do that???
>
> The advantage of placing the engine to one side was it would
> leave better than three quarters of the engine compartment
> open for a steam generator. Using the info I was beginning
> to pick up from the SACA back then, I figured by using
> extended surface tubing in the pre-boil sections of a
> monotube boiler, I could keep the size down to where the
> whole package could be hung on a square tube frame and
> attached to beefed up versions of the original engine and
> transmission mounts. There should even be room for a water
> tank forward of the differential, and enough room to place
> most of the auxiliaries above the engine and out of the road
> grit and grime. The exception being the water pumps, I hoped
> to get those below the level of the bottom of the water tank.
> The only thing I didn’t envision attaching to this package
> was the condenser. That I planned placing on the left side
> of the body with lovers cut in the body to shove the heat out
> with an electric fan-s.
>
> I was still finding myself with too many questions. A few of
> which I have had answered thanks to this form and the SACA
> discussion list. Before I started hacking out metal, melting
> down old Cummins diesel pistons, making patterns, and all the
> other fun stuff that goes with experimental prototypes built
> on no budget, I thought I had better have a bit more
> understanding of what is going on, and if such a short stroke
> engine could ‘breath’ properly under steam at the RPM I
> envisioned. I believe that may have been around 800 foot per
> minute piston speed at 70 mph and 2100 rpm, which is
> considerably faster than I care to drive one of those old
> vans. Though mainly, I didn’t want to end up spending a few
> years creating such a monstrosity and discover later it would
> have a top speed of twenty two miles and hour.
>
> I have several other questions, but they can wait till
> later. And don’t get too freaked on my original tipple
> expansion thoughts. As far as piston engines go, I am now
> convinced the uniflow is the only way to go. And the use of a
> constant volume steam exaust motor to drive the water pumps
> and cylinder oil injection in relationship to engine load
> seems wise.., and will probably lead me to even more questions.
>
> So if you are still reading this...
> You must be as addicted to steam as I am..
> Garry
> PS: I envisioned this menagerie at around 800 psi and 800F of
> steam, though at the moment, I don't remember the lbs per
> hour I came up with. It does seem like I was going to end up
> with about half the surface area in tubing of the engine
> Doble had outlined in Walton's book. (This was before I had
> heard of extended surface tubing, and about that time the
> universe put my life on hold)</HTML>
Re: Valve ports, engine rpm & their effective limits?
Posted by: Carl Helsing (IP Logged)
Date: June 08, 2006 04:35AM
<HTML>I have had a few ideas and also experienced strange coincidences.Back in the 1970's I worked mounting tires at a Firestone store.An old fellow,probably in his 70's happened to walk in and I heard him mention that he had a Wiily's Knight with the sleeve valve engine.Those disappeared probably by the early 1930's.Someone who knew I did small engine repairs(lawn and garden size)had left a technical manual by a guy named Smolen,showing the complete workings of the sleeve valve system.If you're not familiar with it,the valves were simply two sleeves around the piston,attached to, their own cranks,and sliding up and down just as the piston does,opening and closing ports at the head area.The manual had a late1920's date.Anyway,I told the old fellow he could have the manual,since it was of no use to me,and he had the actual automobile.I think he gave me 5 dollars for it.I have a model steam oscillating engine from Germany,given as a gift by my brother.I played with it for a couple weeks,and the piston seized in the cylinder.They had used a short little slug of metal as the piston.There was no crosshead or guide of any type at the piston end.Instead of mounting a guide bearing,which I could have done,I instead used a brass sleeve,internal precision fit,and a longer cylinder of the same brass.The brass is model material of close increments,one tube sliding within the other,maybe a thousandth tolerance.The engine is still running after ten years of fiddling.Valve and piston ideas-(some for toys)The main thing I wanted to tell you,since yoy have some ideas,is of a concept I have had of having a "hybrid" of an internal combustion engine with a steam auxilliary utilizing all the water the internal combustion engine can boil to steam,right down to ends of the exhaust manifolds.A thermal efficiency concept.Could have been some of that type somewhere,tho they would likely be isolated so-called specialty items in possibly small industrial use,time period,20'-30's-Just ideas and stories-enjoy-(also-valve idea for all the air that can be packed into a cylinder)
<a href="mailto:ghunsaker@mexicomo.net?subject=Valve ports, engine rpm & their effective limits?">Garry Hunsaker</a> wrote:
>
>
> I am wondering if there is anything remotely like a rule of
> thumb as to how short a stroke, and therefore a limit to how
> short a duration a steam engine’s ports can remain open and
> still properly ‘charge’ the cylinder. The steam engine has
> enough problems with out adding windage restrictions. (Or is
> this what engineers refer to as ‘shock’?) What has brought me
> to this question is looking at the three cylinder engine in
> my old Subaru Justy. It’s 3.27” stroke is almost liveable.
> (To be honest, I think I need to check out the crankshaft on
> the Chevy Geo. There are a heck of a lot more of them around
> to choose from)
>
> The only thing in the way of data I have had in the past to
> work with was J. N. Walton’s book on Doble. I have been
> hunting around today for the numbers I ran several years ago,
> that Doble outlined for his triple expansion engine, but I
> still haven’t come up with the place I put them to make sure
> I didn’t lose them... (So what else is new.)
>
> Shooting from memory, I believe I was aiming at 50 to 60 hp.
> Any way, the one thing I do remember is measuring my old 1970
> VW van. The best I remember I came to the conclusion that by
> running the engine at roughly twice the speed of the
> differential gear I would have the effective torque of the
> standard VW van about half way between first and second
> gear. (The acceleration should be interesting to say the
> least)
>
> For those that might be curious, I had intended to lay the
> resulting engine on its side on the left side of engine
> compartment. By adding a splined stub shaft to the end of
> the crank, and running that into a gear box, I would have to
> create using the side plates, bearings, and third member from
> the VW, I thought I could make this work.
>
> I was still scratching my head on how, or if I needed to, set
> the gear box up for backlash adjustment on the deferential
> gears I would have to come up with. The thought did occur to
> me to create new side plates so the outer bolt circle, and
> its corresponding surface would be slightly eccentric in
> relation to the third member support bearings. I figured
> throwing the axles a few thousandths out of their original
> position wouldn’t bother those CV joints too much. Though
> making exactly matching eccentric side plates in relation to
> a set of perfectly divided and aligned bolt circles still had
> me wondering on the how the heck am I going to do that???
>
> The advantage of placing the engine to one side was it would
> leave better than three quarters of the engine compartment
> open for a steam generator. Using the info I was beginning
> to pick up from the SACA back then, I figured by using
> extended surface tubing in the pre-boil sections of a
> monotube boiler, I could keep the size down to where the
> whole package could be hung on a square tube frame and
> attached to beefed up versions of the original engine and
> transmission mounts. There should even be room for a water
> tank forward of the differential, and enough room to place
> most of the auxiliaries above the engine and out of the road
> grit and grime. The exception being the water pumps, I hoped
> to get those below the level of the bottom of the water tank.
> The only thing I didn’t envision attaching to this package
> was the condenser. That I planned placing on the left side
> of the body with lovers cut in the body to shove the heat out
> with an electric fan-s.
>
> I was still finding myself with too many questions. A few of
> which I have had answered thanks to this form and the SACA
> discussion list. Before I started hacking out metal, melting
> down old Cummins diesel pistons, making patterns, and all the
> other fun stuff that goes with experimental prototypes built
> on no budget, I thought I had better have a bit more
> understanding of what is going on, and if such a short stroke
> engine could ‘breath’ properly under steam at the RPM I
> envisioned. I believe that may have been around 800 foot per
> minute piston speed at 70 mph and 2100 rpm, which is
> considerably faster than I care to drive one of those old
> vans. Though mainly, I didn’t want to end up spending a few
> years creating such a monstrosity and discover later it would
> have a top speed of twenty two miles and hour.
>
> I have several other questions, but they can wait till
> later. And don’t get too freaked on my original tipple
> expansion thoughts. As far as piston engines go, I am now
> convinced the uniflow is the only way to go. And the use of a
> constant volume steam exaust motor to drive the water pumps
> and cylinder oil injection in relationship to engine load
> seems wise.., and will probably lead me to even more questions.
>
> So if you are still reading this...
> You must be as addicted to steam as I am..
> Garry
> PS: I envisioned this menagerie at around 800 psi and 800F of
> steam, though at the moment, I don't remember the lbs per
> hour I came up with. It does seem like I was going to end up
> with about half the surface area in tubing of the engine
> Doble had outlined in Walton's book. (This was before I had
> heard of extended surface tubing, and about that time the
> universe put my life on hold)</HTML>
<a href="mailto:ghunsaker@mexicomo.net?subject=Valve ports, engine rpm & their effective limits?">Garry Hunsaker</a> wrote:
>
>
> I am wondering if there is anything remotely like a rule of
> thumb as to how short a stroke, and therefore a limit to how
> short a duration a steam engine’s ports can remain open and
> still properly ‘charge’ the cylinder. The steam engine has
> enough problems with out adding windage restrictions. (Or is
> this what engineers refer to as ‘shock’?) What has brought me
> to this question is looking at the three cylinder engine in
> my old Subaru Justy. It’s 3.27” stroke is almost liveable.
> (To be honest, I think I need to check out the crankshaft on
> the Chevy Geo. There are a heck of a lot more of them around
> to choose from)
>
> The only thing in the way of data I have had in the past to
> work with was J. N. Walton’s book on Doble. I have been
> hunting around today for the numbers I ran several years ago,
> that Doble outlined for his triple expansion engine, but I
> still haven’t come up with the place I put them to make sure
> I didn’t lose them... (So what else is new.)
>
> Shooting from memory, I believe I was aiming at 50 to 60 hp.
> Any way, the one thing I do remember is measuring my old 1970
> VW van. The best I remember I came to the conclusion that by
> running the engine at roughly twice the speed of the
> differential gear I would have the effective torque of the
> standard VW van about half way between first and second
> gear. (The acceleration should be interesting to say the
> least)
>
> For those that might be curious, I had intended to lay the
> resulting engine on its side on the left side of engine
> compartment. By adding a splined stub shaft to the end of
> the crank, and running that into a gear box, I would have to
> create using the side plates, bearings, and third member from
> the VW, I thought I could make this work.
>
> I was still scratching my head on how, or if I needed to, set
> the gear box up for backlash adjustment on the deferential
> gears I would have to come up with. The thought did occur to
> me to create new side plates so the outer bolt circle, and
> its corresponding surface would be slightly eccentric in
> relation to the third member support bearings. I figured
> throwing the axles a few thousandths out of their original
> position wouldn’t bother those CV joints too much. Though
> making exactly matching eccentric side plates in relation to
> a set of perfectly divided and aligned bolt circles still had
> me wondering on the how the heck am I going to do that???
>
> The advantage of placing the engine to one side was it would
> leave better than three quarters of the engine compartment
> open for a steam generator. Using the info I was beginning
> to pick up from the SACA back then, I figured by using
> extended surface tubing in the pre-boil sections of a
> monotube boiler, I could keep the size down to where the
> whole package could be hung on a square tube frame and
> attached to beefed up versions of the original engine and
> transmission mounts. There should even be room for a water
> tank forward of the differential, and enough room to place
> most of the auxiliaries above the engine and out of the road
> grit and grime. The exception being the water pumps, I hoped
> to get those below the level of the bottom of the water tank.
> The only thing I didn’t envision attaching to this package
> was the condenser. That I planned placing on the left side
> of the body with lovers cut in the body to shove the heat out
> with an electric fan-s.
>
> I was still finding myself with too many questions. A few of
> which I have had answered thanks to this form and the SACA
> discussion list. Before I started hacking out metal, melting
> down old Cummins diesel pistons, making patterns, and all the
> other fun stuff that goes with experimental prototypes built
> on no budget, I thought I had better have a bit more
> understanding of what is going on, and if such a short stroke
> engine could ‘breath’ properly under steam at the RPM I
> envisioned. I believe that may have been around 800 foot per
> minute piston speed at 70 mph and 2100 rpm, which is
> considerably faster than I care to drive one of those old
> vans. Though mainly, I didn’t want to end up spending a few
> years creating such a monstrosity and discover later it would
> have a top speed of twenty two miles and hour.
>
> I have several other questions, but they can wait till
> later. And don’t get too freaked on my original tipple
> expansion thoughts. As far as piston engines go, I am now
> convinced the uniflow is the only way to go. And the use of a
> constant volume steam exaust motor to drive the water pumps
> and cylinder oil injection in relationship to engine load
> seems wise.., and will probably lead me to even more questions.
>
> So if you are still reading this...
> You must be as addicted to steam as I am..
> Garry
> PS: I envisioned this menagerie at around 800 psi and 800F of
> steam, though at the moment, I don't remember the lbs per
> hour I came up with. It does seem like I was going to end up
> with about half the surface area in tubing of the engine
> Doble had outlined in Walton's book. (This was before I had
> heard of extended surface tubing, and about that time the
> universe put my life on hold)</HTML>
Re: Valve ports, engine rpm & their effective limits?
Posted by: Carl Helsing (IP Logged)
Date: June 08, 2006 05:51AM
<HTML>As I got into stories on my previous item,I forgot to describe my valve idea for maximum volume air admission into the cylinder.Use one vertical poppet valve equalling the diameter of the cylinder minus clearance requirements.Then,a distribution chamber with two more valves,one to exhaust manifold,one to intake manifold.A somewhat large valve assembly would,of course result.Vacuum aspiration velocities would need to be figured out for carbueration.Fuel injection might be preferred for maximal results.Virtual zero restriction of air intake.Actually,the valve would need to be somewhat less in diameter than the cylinder to allow space for air movement.I was working against a hypothetical maximum,without considering practical requirements.The idea amounts to one valve of maximum possible size for both intake and exhaust,with the external valves to operate selectively for intake and exhaust.Obtaining the right proportions on the single valve could be a key number,as such.Longer strokes are preferential.For some special purpose,unkown to me,shorter than "square"strokes may have a value.My 3 valve idea,unless I heard it mentioned somewhere or I heard something else and figured this out from it-(in the 90's)</HTML>
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