1 Steam Cars : Phorum
General Steam Car topics
Skinner Engine Link
Posted by: Peter Brow (IP Logged)
Date: December 09, 2002 05:46AM
<HTML>[www.carferries.com]
Everything you ever wanted to know about Skinner engines, their valves, valve gears, etc.. Really nice engine design. Reproduction of a fully illustrated 1953 Skinner brochure.
Wonder how much of this (if any) can be applied to steam cars? The compound feature is probably out for cars; indicator card shows very little work in the LP stage even at full load. Maybe two of those nice valves at each end of each double-acting cylinder, for counterflow inlet and exhaust?
Peter</HTML>
Everything you ever wanted to know about Skinner engines, their valves, valve gears, etc.. Really nice engine design. Reproduction of a fully illustrated 1953 Skinner brochure.
Wonder how much of this (if any) can be applied to steam cars? The compound feature is probably out for cars; indicator card shows very little work in the LP stage even at full load. Maybe two of those nice valves at each end of each double-acting cylinder, for counterflow inlet and exhaust?
Peter</HTML>
Re: Skinner Engine Link
Posted by: Jim Crank (IP Logged)
Date: December 09, 2002 03:00PM
<HTML>Peter,
Of course the Skinner features can be used.
One balanced inlet valve and one common poppet exhaust in the head and unaflow for the main exhaust. Their two cam valve gear is superb and it can certainly be adapted to a car engine.
The Bugatti balanced valve also works and is a lot simpler than the Skinner.
Compounding can work; but I think only if the cutoff for the HP and LP are separate and individually adjustable. Of course one can use a radial inflow turbine for the second stage and save TONS of weight, size and balance problems.
Jim</HTML>
Of course the Skinner features can be used.
One balanced inlet valve and one common poppet exhaust in the head and unaflow for the main exhaust. Their two cam valve gear is superb and it can certainly be adapted to a car engine.
The Bugatti balanced valve also works and is a lot simpler than the Skinner.
Compounding can work; but I think only if the cutoff for the HP and LP are separate and individually adjustable. Of course one can use a radial inflow turbine for the second stage and save TONS of weight, size and balance problems.
Jim</HTML>
Re: Skinner Engine Link
Posted by: George Nutz (IP Logged)
Date: December 09, 2002 04:35PM
<HTML>Peter,
Was told by the last Skinner steam engineer that the "compound unaflow" was not any better than the straight unaflow engine in practice. There were two Skinner compound engine designs by the way. What the compound offers is much longer admission per cylinder for the same expansion ratio and much easier on the valve gear than a straight short cutoff simple. I don't know if the heavy Skinner valve gear would work well with a high speed short cutoff simple unaflow. The basic simplicity and great engine efficiency of a simple unaflow engine can be hard to beat, again I refer to the Williams engine and its dyno water rate of around 6.4#/HP-HR, easy to beat in theory but not in reality.
George</HTML>
Was told by the last Skinner steam engineer that the "compound unaflow" was not any better than the straight unaflow engine in practice. There were two Skinner compound engine designs by the way. What the compound offers is much longer admission per cylinder for the same expansion ratio and much easier on the valve gear than a straight short cutoff simple. I don't know if the heavy Skinner valve gear would work well with a high speed short cutoff simple unaflow. The basic simplicity and great engine efficiency of a simple unaflow engine can be hard to beat, again I refer to the Williams engine and its dyno water rate of around 6.4#/HP-HR, easy to beat in theory but not in reality.
George</HTML>
Re: Skinner Engine Link
Posted by: Peter Brow (IP Logged)
Date: December 10, 2002 09:39AM
<HTML>Hi Jim & George,
The Skinner data got me sketching on a "Skinnerized Stanley" counterflow engine concept. Bugatti valves could be used instead of Skinner type, or plain poppets if desired. With 4 camshafts between the cylinders, Skinner gear can be fitted. Then I simplified it to 2 camshafts with sliding cams -- up to 4 cutoff/compression timings fit in okay, with stepped cams & enough line contact on cams for durability. This took up a lot of space for a car, so to lower its profile I added 8 little bell-crank rocker/roller arms and squinched the camshafts closer together. 3 gears at first to time the camshafts together, then I figured that outboard/heat isolated EZ-change timing belts would be cheaper/easier/lighter though less durable.
But any way I slice it, seems to come up with a lot more moving parts. More compact is often more complex, one of my personal "Laws Of Mechanical Design" (along with "simpler isn't always cheaper"). A uniflow wouldn't simplify things much -- I figure a uniflow for a car should have auxiliary exhaust valves (or other mechanism) for good compression control anyway, so I usually cut to the chase, eliminate the ports, and use straight counterflow exhaust valves.
Nice thing about cam gear is that I can time the valves any which way. I even considered timing a 4th position on the inlet & exhaust cams to a "counterflow Williams cycle" mode for (diesel-beating MPG?) highway cruise, with inlet valves slightly unbalanced to lift on overcompression. Other 3 modes (reverse, long, & short cutoff) would be close to Stanley timing for performance & smoothness. A Williams cycle engine might need more cylinders to avoid running like a jackhammer. Then again, Williams used 4 SA cylinders & claimed smooth running; this = 2 DA, hmm. If I couldn't profile the Williams cams right (Murphy's Law), I could just run in the other 3 modes.
The whole thing is appealing in some ways, but has an awful lot of extra parts to design/build, and I still worry about extra friction (have dumped desmo poppets -- what a nightmare). Also, haven't gotten this concept to the graphpaper yet; problems often pop up at that stage. Does look doable though. Will probably leave this stuff to others and use the desmodromic (Stephenson) piston valves for KISS purposes.
Peter</HTML>
The Skinner data got me sketching on a "Skinnerized Stanley" counterflow engine concept. Bugatti valves could be used instead of Skinner type, or plain poppets if desired. With 4 camshafts between the cylinders, Skinner gear can be fitted. Then I simplified it to 2 camshafts with sliding cams -- up to 4 cutoff/compression timings fit in okay, with stepped cams & enough line contact on cams for durability. This took up a lot of space for a car, so to lower its profile I added 8 little bell-crank rocker/roller arms and squinched the camshafts closer together. 3 gears at first to time the camshafts together, then I figured that outboard/heat isolated EZ-change timing belts would be cheaper/easier/lighter though less durable.
But any way I slice it, seems to come up with a lot more moving parts. More compact is often more complex, one of my personal "Laws Of Mechanical Design" (along with "simpler isn't always cheaper"). A uniflow wouldn't simplify things much -- I figure a uniflow for a car should have auxiliary exhaust valves (or other mechanism) for good compression control anyway, so I usually cut to the chase, eliminate the ports, and use straight counterflow exhaust valves.
Nice thing about cam gear is that I can time the valves any which way. I even considered timing a 4th position on the inlet & exhaust cams to a "counterflow Williams cycle" mode for (diesel-beating MPG?) highway cruise, with inlet valves slightly unbalanced to lift on overcompression. Other 3 modes (reverse, long, & short cutoff) would be close to Stanley timing for performance & smoothness. A Williams cycle engine might need more cylinders to avoid running like a jackhammer. Then again, Williams used 4 SA cylinders & claimed smooth running; this = 2 DA, hmm. If I couldn't profile the Williams cams right (Murphy's Law), I could just run in the other 3 modes.
The whole thing is appealing in some ways, but has an awful lot of extra parts to design/build, and I still worry about extra friction (have dumped desmo poppets -- what a nightmare). Also, haven't gotten this concept to the graphpaper yet; problems often pop up at that stage. Does look doable though. Will probably leave this stuff to others and use the desmodromic (Stephenson) piston valves for KISS purposes.
Peter</HTML>
Re: Skinner Engine Link
Posted by: Rolly Evans (IP Logged)
Date: December 10, 2002 11:42AM
<HTML>I think a piston valve driven by a variable controlled eccentric with hydraulics would do very nicely. Oil pressure could be fed in the rotating shaft to a small cylinder built into the eccentric.
Rolly</HTML>
Rolly</HTML>
Re: Skinner Engine Link
Posted by: Wiliam L. Petitjean, P.E. (IP Logged)
Date: December 14, 2002 03:44PM
<HTML>Hi George:
I presume you are talking about your old friend, Hal Fuller as the last steam engineer at Skinner. I would like to call him, but have lost his contact information. Can you email me his phone number at my email address above. He wanted me to call him when I got my cylinder oil going.
Concerning the compound unaflows. I think Hal is essentially correct. A simple unaflow running at 5% or 10% cutoff will get just about the same water rate as the compound with a lot less complication. I think the main rationale for the compounds was less wiredrawing at the admission valves because the valves remained open at a high lift for substantially more degrees of crank angle than on a simple unaflow. Also the exhaust port area in a 54" diameter low pressure cylinder is huge compared to the exhaust port area in, say a 26" diameter simple cylinder. This means less pressure drop on admission and more effective vacuum in the cylinder where the indicator is taking its readings.
After the war G.E. was making a concerted effort to convert Great Lakes Shipping to gear reduction drive turbines running at 440 psi, 740 deg. F. inlet and about 29" vacuum exhaust. Skinner became alarmed by the inroads in their back yard and they let Herman Mueller (the old Skinner Chief Engineer who had been let go by J. LeGrand Skinner earlier) talk them into the Woolf Steeple Compound as a way to beat G.E. at their own game.
Mueller had built two similar compounds for somebody when he was working at Ajax Engine down in Corry during the war. He came back to Skinner as a consultant, adopted Skinner's valve gear and designed the same engines for the C&O ferries. The C&O already had simple Skinners in the City of Midland, so they were good customers and had faith in Skinner's ability to pull it off.
One anecdote that sticks with me is the fight Mueller and Skinner Chief Engineer George Lindsey had over crank angles and balancing. Lindsey was an excellent engineer and performed a complex study of the reciprocating weights, inertia and the cranks angles necessary to achieve an optimum balancing on an inherently unbalanced four crank engine. I can't remember Lindsey's crank angles, but they were not intuitive at all and sounded weird when Dick Whiting told me what they were. Mueller was somewhat crusty and had no patience for all Lindsey's chatter. He recommended a simple 90 degree offset on all the cranks and said it would be smooth enough. Lindsey won the battle, but lost the war because the ships heaved like a pregnant whale. They had to do a lot of work on the engines and changed props, etc. to take some of it out. But, some thirty years later when I rode the Badger I could feel a little bit of the old heave on the main deck every time the engines turned over. We will never know if Mueller's simple solution would have been better, but Lindsey would have had a better chance if the engines had been five or six crank machines.
The most charitable assessment of the engines is that they preserved Skinner's legendary maneuverability in ship engines and the present day engineer, Chuck Cart told me the Badger is the fastest reversing plant on the Lakes. They can go from half ahead to half astern in 40 seconds flat. This is important because they are coming into their tight landings all the time. This means they are stopping and restarting 47 tons of rotating iron in less than a minute!
Thermodynamically, I don't think they justified the extra complication and cost. I remember talking to some of the old timers about trying to sell some big compounds for ocean going service. They blanched at the thought and all the old nightmares of the C&O engines reappeared before their eyes. I think the compound engines nearly finished the small Skinner organization off. They really were no match for the big boys like G.E.
If anyone has a chance to ride this boat I suggest you do so. The terrorist thing has clamped down on engine room visits, but it is an anachronism and probably won't last forever.
Bill Petitjean</HTML>
I presume you are talking about your old friend, Hal Fuller as the last steam engineer at Skinner. I would like to call him, but have lost his contact information. Can you email me his phone number at my email address above. He wanted me to call him when I got my cylinder oil going.
Concerning the compound unaflows. I think Hal is essentially correct. A simple unaflow running at 5% or 10% cutoff will get just about the same water rate as the compound with a lot less complication. I think the main rationale for the compounds was less wiredrawing at the admission valves because the valves remained open at a high lift for substantially more degrees of crank angle than on a simple unaflow. Also the exhaust port area in a 54" diameter low pressure cylinder is huge compared to the exhaust port area in, say a 26" diameter simple cylinder. This means less pressure drop on admission and more effective vacuum in the cylinder where the indicator is taking its readings.
After the war G.E. was making a concerted effort to convert Great Lakes Shipping to gear reduction drive turbines running at 440 psi, 740 deg. F. inlet and about 29" vacuum exhaust. Skinner became alarmed by the inroads in their back yard and they let Herman Mueller (the old Skinner Chief Engineer who had been let go by J. LeGrand Skinner earlier) talk them into the Woolf Steeple Compound as a way to beat G.E. at their own game.
Mueller had built two similar compounds for somebody when he was working at Ajax Engine down in Corry during the war. He came back to Skinner as a consultant, adopted Skinner's valve gear and designed the same engines for the C&O ferries. The C&O already had simple Skinners in the City of Midland, so they were good customers and had faith in Skinner's ability to pull it off.
One anecdote that sticks with me is the fight Mueller and Skinner Chief Engineer George Lindsey had over crank angles and balancing. Lindsey was an excellent engineer and performed a complex study of the reciprocating weights, inertia and the cranks angles necessary to achieve an optimum balancing on an inherently unbalanced four crank engine. I can't remember Lindsey's crank angles, but they were not intuitive at all and sounded weird when Dick Whiting told me what they were. Mueller was somewhat crusty and had no patience for all Lindsey's chatter. He recommended a simple 90 degree offset on all the cranks and said it would be smooth enough. Lindsey won the battle, but lost the war because the ships heaved like a pregnant whale. They had to do a lot of work on the engines and changed props, etc. to take some of it out. But, some thirty years later when I rode the Badger I could feel a little bit of the old heave on the main deck every time the engines turned over. We will never know if Mueller's simple solution would have been better, but Lindsey would have had a better chance if the engines had been five or six crank machines.
The most charitable assessment of the engines is that they preserved Skinner's legendary maneuverability in ship engines and the present day engineer, Chuck Cart told me the Badger is the fastest reversing plant on the Lakes. They can go from half ahead to half astern in 40 seconds flat. This is important because they are coming into their tight landings all the time. This means they are stopping and restarting 47 tons of rotating iron in less than a minute!
Thermodynamically, I don't think they justified the extra complication and cost. I remember talking to some of the old timers about trying to sell some big compounds for ocean going service. They blanched at the thought and all the old nightmares of the C&O engines reappeared before their eyes. I think the compound engines nearly finished the small Skinner organization off. They really were no match for the big boys like G.E.
If anyone has a chance to ride this boat I suggest you do so. The terrorist thing has clamped down on engine room visits, but it is an anachronism and probably won't last forever.
Bill Petitjean</HTML>
Re: Skinner Engine Link
Posted by: john ruppert (IP Logged)
Date: June 20, 2004 01:25AM
<HTML>hello, my name is john ruppert and I just happened along this link because I was curious about skinner engines after having read an article about the C&O ferries in trains magazine - I am actually a train buff - but steam is steam! This yarn seems to be a little old, but for what its worth I will add two cents because I do have something to say.
Acording to the article in trains magazine, the skinner engine - the simple engine- was originally desinged to work with saturated steam or lower pressure boilers. With the increasing use of turbine engines, boilers were being built with higher pressures and superheating that was incompatible with the simple's valves.</HTML>
Acording to the article in trains magazine, the skinner engine - the simple engine- was originally desinged to work with saturated steam or lower pressure boilers. With the increasing use of turbine engines, boilers were being built with higher pressures and superheating that was incompatible with the simple's valves.</HTML>
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