1 Steam Cars : Phorum
General Steam Car topics
Lamont Pump Ideas
Posted by: Peter Brow (IP Logged)
Date: March 19, 2002 08:52AM
<HTML>Hi George,
Keep hammering, Lamont facts will get thru our thick skulls eventually and we probably need it. LOL. Many irons in fire, but still working on circulator pump ideas myself. Gotta get it cheap, simple & crudproof and want to make it non-electric if possible. If I have to, I'll eat the old fedora and put in a consarned electric motor. Sigh.
One idea I had -- I doubt it is original -- is putting a seal at each end of pump shaft, & shaft in one side & out the other of pump housing, to eliminate thrust load. With mil-spec graphite yarn/ribbon/yarn packing & maybe a chromed (not stainless) shaft, this can be tight & low-friction. Reportedly this packing lasts darn near forever on high-speed, high-pressure rotoshaft stuffing boxes.
Notebook: put spray disk on shaft between seal and electric motor, in case of leaks. At 500+ psi, some leaks don't just dribble, and water can ruin your motor's day.
Found out that the Tesla pump factory Jim mentioned is 15 min drive from my house. Maybe I should drop in and see what I can learn?
For reference purposes, what is the ID and length of your & Rod's Lamont coil? If this is proprietary info, I understand. Am considering bathtub pump tests with cheap plastic tubing of the same length & ID as the tube stack I am considering, to see if I can pump the required volume thru it. Actual flow resistance will (?) be different due to different density, viscosity, & steam generation in the real thing -- higher or lower?
A small drum (~3" ID) can fit in the center of the tube stack I am considering. Most compact tube stacks have drum-suitable empty cores due to minimum radius bend requirements. Did Lamont have any rules of thumb on relative internal volume of tube & drum, at say 500 psi?
Peter</HTML>
Keep hammering, Lamont facts will get thru our thick skulls eventually and we probably need it. LOL. Many irons in fire, but still working on circulator pump ideas myself. Gotta get it cheap, simple & crudproof and want to make it non-electric if possible. If I have to, I'll eat the old fedora and put in a consarned electric motor. Sigh.
One idea I had -- I doubt it is original -- is putting a seal at each end of pump shaft, & shaft in one side & out the other of pump housing, to eliminate thrust load. With mil-spec graphite yarn/ribbon/yarn packing & maybe a chromed (not stainless) shaft, this can be tight & low-friction. Reportedly this packing lasts darn near forever on high-speed, high-pressure rotoshaft stuffing boxes.
Notebook: put spray disk on shaft between seal and electric motor, in case of leaks. At 500+ psi, some leaks don't just dribble, and water can ruin your motor's day.
Found out that the Tesla pump factory Jim mentioned is 15 min drive from my house. Maybe I should drop in and see what I can learn?
For reference purposes, what is the ID and length of your & Rod's Lamont coil? If this is proprietary info, I understand. Am considering bathtub pump tests with cheap plastic tubing of the same length & ID as the tube stack I am considering, to see if I can pump the required volume thru it. Actual flow resistance will (?) be different due to different density, viscosity, & steam generation in the real thing -- higher or lower?
A small drum (~3" ID) can fit in the center of the tube stack I am considering. Most compact tube stacks have drum-suitable empty cores due to minimum radius bend requirements. Did Lamont have any rules of thumb on relative internal volume of tube & drum, at say 500 psi?
Peter</HTML>
Re: Lamont Pump Ideas
Posted by: George K. Nutz (IP Logged)
Date: March 19, 2002 11:31AM
<HTML>Peter,
I have given up on a ideal so-seal solution to the pump question after calling 15 boiler circulating pump companies and dealing with their engineers. The temperatures and pressures of an internal motor are on the ragged edge for them andone manufacturer of pumps required a separate circulating water cooling system to keep the motor temperature down---all of their feedback lead to large and very heavy pumps.
As far as shaft seals the very small ones we are using take very little drag horsepower;in old fashioned stuffing box shaft seals the seal horsepower could be 2/3rds of the entire power requirement--no thanks. we have an outboard thrust bearing that only has 30 pounds thrust load on it , very little frictional loss with it.
Rod and I are thinking about making up patterns for a bronze casting for the pump body and make sume pumps, far easier than his hogging out the spiral and cavity out of a chunk of stainless. The pump output could be changed by changing the DC motor rpm. Ihad told Jim about Discflo a year or two ago(the Tesla pumps), they had nothing available in our size and casing pressure requirements. As a matter of fact Rod made a tesla disc pump impeller to my design and I just ran tests on it last week in my bathtub, batteries/chargers/clip leads/ammeter/voltmeter/pressure gage etc, I had better move them out as its getting stinky around here. I can only say that after one spacing modification it worked very well indeed but not better than the specially designed back curved impeller on the boiler. The first pump design we developed was an Archemedis screw where the screw thrust would be equal and opposite to the shaft area thrust---it worked quite well but sooo veery hard to make.
As far as the coil diameters and lengths I will not disclose that , there are so many variables in chosing size and length for an ideal solution---one needs to know what pressure and steam output is desired before such an analysis can be done. Remember, along every foot of Lamont coil heat is being added and the viscosity, specific volume, velocity are constantly changing---each foot needs to be analyzed for its individual average parameters to get a delta P for that foot and then move on to the next foot. Add them all up and include entrance and exhaust shock losses as well to determine working pressure differential. You and Peter Heid are going the right way, we originally ran house water thru the completed coil with a pressure gauge on the inlet and that gauge would give us the pressure differential for whatever amount of water that passed thru it---it is a very good indication and starting point as to a base value to start from---in Peters case of 250psi the pressure required under fire with 20%SBW output would require six times the cold water pressure, this will change to the better dramatically as boiler pressure increases and viscosity and steam specific volume both change for the better. That is why the Lamont in much better for higher pressures.
I do not have Lamont's rule of thumb on drum volume compared to Lamont coil volume but Benson's earlier work had some very strong recommendations on this.
With out giving the whole farm away give consideration to the internal volume of the Lamont coil, filled with water when cold, then adding all of that to your drum water level and consider how much steam space you want left for non-priming. Thats about all I am going to give away right now as Rod will get mad at me!! My engineering rates are very low and could always do an analysis ;>) .
Best, George</HTML>
I have given up on a ideal so-seal solution to the pump question after calling 15 boiler circulating pump companies and dealing with their engineers. The temperatures and pressures of an internal motor are on the ragged edge for them andone manufacturer of pumps required a separate circulating water cooling system to keep the motor temperature down---all of their feedback lead to large and very heavy pumps.
As far as shaft seals the very small ones we are using take very little drag horsepower;in old fashioned stuffing box shaft seals the seal horsepower could be 2/3rds of the entire power requirement--no thanks. we have an outboard thrust bearing that only has 30 pounds thrust load on it , very little frictional loss with it.
Rod and I are thinking about making up patterns for a bronze casting for the pump body and make sume pumps, far easier than his hogging out the spiral and cavity out of a chunk of stainless. The pump output could be changed by changing the DC motor rpm. Ihad told Jim about Discflo a year or two ago(the Tesla pumps), they had nothing available in our size and casing pressure requirements. As a matter of fact Rod made a tesla disc pump impeller to my design and I just ran tests on it last week in my bathtub, batteries/chargers/clip leads/ammeter/voltmeter/pressure gage etc, I had better move them out as its getting stinky around here. I can only say that after one spacing modification it worked very well indeed but not better than the specially designed back curved impeller on the boiler. The first pump design we developed was an Archemedis screw where the screw thrust would be equal and opposite to the shaft area thrust---it worked quite well but sooo veery hard to make.
As far as the coil diameters and lengths I will not disclose that , there are so many variables in chosing size and length for an ideal solution---one needs to know what pressure and steam output is desired before such an analysis can be done. Remember, along every foot of Lamont coil heat is being added and the viscosity, specific volume, velocity are constantly changing---each foot needs to be analyzed for its individual average parameters to get a delta P for that foot and then move on to the next foot. Add them all up and include entrance and exhaust shock losses as well to determine working pressure differential. You and Peter Heid are going the right way, we originally ran house water thru the completed coil with a pressure gauge on the inlet and that gauge would give us the pressure differential for whatever amount of water that passed thru it---it is a very good indication and starting point as to a base value to start from---in Peters case of 250psi the pressure required under fire with 20%SBW output would require six times the cold water pressure, this will change to the better dramatically as boiler pressure increases and viscosity and steam specific volume both change for the better. That is why the Lamont in much better for higher pressures.
I do not have Lamont's rule of thumb on drum volume compared to Lamont coil volume but Benson's earlier work had some very strong recommendations on this.
With out giving the whole farm away give consideration to the internal volume of the Lamont coil, filled with water when cold, then adding all of that to your drum water level and consider how much steam space you want left for non-priming. Thats about all I am going to give away right now as Rod will get mad at me!! My engineering rates are very low and could always do an analysis ;>) .
Best, George</HTML>
Re: Lamont Pump Ideas
Posted by: Peter Brow (IP Logged)
Date: March 21, 2002 04:46AM
<HTML>Hi George,
Don't know much about canned motors, so can't really comment except that I wouldn't know where to begin designing one. Electrical engineering is one of my weak points -- designing impeller curves and other hydrodynamic components another, hence the appeal of a Tesla pump. Your seal & thrust bearing setup sounds almost ideal. The highest pressure shaft seals I have been able to find, though, are 250 psi, and I am aiming for 500 psi. Makes sense that a stuffing box would have more friction than a thrust bearing.
I currently plan to make everything from billet & off the shelf bits, but one of these days should set up my small Pyramid propane furnace & do some home foundry work. It has been in storage since I moved, hope I still have all the equipment. Crucible is like 4" ID x a foot tall, too tired now to calculate the pour weight. I think it will also run on natural gas, so maybe I should go hog wild and run a gas line to a sand pit in the corner of my garage. Though I might keel over at the sight of the gas bill. Even a small furnace poses a lot of problems for a safety nut (dry sand floor, venting, radiant heat, fireproofing, gas, etc) -- probably one of the most dangerous operations you can get into in a home shop. Then again, making your own castings, cool! Taking patterns to a commercial foundry is the safe way, but an artist friend told me what local foundries charge for small castings, phew!
May take you up on an engineering analysis. I'd have to draw up some halfway decent pix of the bizarre coil stack, words won't do and the current idiosyncratic shop drawings would be incomprehensible to anyone but me. It was originally designed for once-thru operation, & flow resistance may be too high for practical "Lamontizing". Sit down before you open the envelope. :)
One of these days, I am going to dive into my Scrooge McDuck vault and buy a certain heat exchanger engineering book at a certain local used book place. A vast, costly, ponderous tome. Then maybe I can train myself to do the analysis on these things.
Thanks for the tips; fascinating stuff, these Lamont boilers.
Peter</HTML>
Don't know much about canned motors, so can't really comment except that I wouldn't know where to begin designing one. Electrical engineering is one of my weak points -- designing impeller curves and other hydrodynamic components another, hence the appeal of a Tesla pump. Your seal & thrust bearing setup sounds almost ideal. The highest pressure shaft seals I have been able to find, though, are 250 psi, and I am aiming for 500 psi. Makes sense that a stuffing box would have more friction than a thrust bearing.
I currently plan to make everything from billet & off the shelf bits, but one of these days should set up my small Pyramid propane furnace & do some home foundry work. It has been in storage since I moved, hope I still have all the equipment. Crucible is like 4" ID x a foot tall, too tired now to calculate the pour weight. I think it will also run on natural gas, so maybe I should go hog wild and run a gas line to a sand pit in the corner of my garage. Though I might keel over at the sight of the gas bill. Even a small furnace poses a lot of problems for a safety nut (dry sand floor, venting, radiant heat, fireproofing, gas, etc) -- probably one of the most dangerous operations you can get into in a home shop. Then again, making your own castings, cool! Taking patterns to a commercial foundry is the safe way, but an artist friend told me what local foundries charge for small castings, phew!
May take you up on an engineering analysis. I'd have to draw up some halfway decent pix of the bizarre coil stack, words won't do and the current idiosyncratic shop drawings would be incomprehensible to anyone but me. It was originally designed for once-thru operation, & flow resistance may be too high for practical "Lamontizing". Sit down before you open the envelope. :)
One of these days, I am going to dive into my Scrooge McDuck vault and buy a certain heat exchanger engineering book at a certain local used book place. A vast, costly, ponderous tome. Then maybe I can train myself to do the analysis on these things.
Thanks for the tips; fascinating stuff, these Lamont boilers.
Peter</HTML>
Re: Lamont Pump Ideas
Posted by: John Winter (IP Logged)
Date: March 21, 2002 05:41AM
<HTML>I do not know how much pressure is required to circulate the water but would a cast iron auto water pump work. Some have a very nice ceramic water seal and two ball berrings lubed for life. A stronger seal spring would be required for the greater pressure. The pump assy could bolt to a matching plate on the out side of the boiler.
Just an idea that came to mind. John</HTML>
Just an idea that came to mind. John</HTML>
Re: Lamont Pump Ideas
Posted by: Francis Church 111 (IP Logged)
Date: March 21, 2002 07:08AM
<HTML>If you are worried about seal leaking @500psi and who wouldn't what about a magnetic pump, the're Ac, Dc, solar and some stuff inbetween. Just a thought, have a nice day and a wonderful tomarrow. No sales pitch here! Oh peruse Google for Magnetic Pumps there's a million or more</HTML>
Re: Lamont Pump Ideas
Posted by: Peter Brow (IP Logged)
Date: March 21, 2002 07:28AM
<HTML>Hi John,
I'm not sure about the pressure IC coolant pumps run at, but it is well below 500 psi. 10-15 psi max, I think. Perhaps one of these pumps could be used if the stock housing were enclosed in a pressure vessel, and new seals installed. Or the rotor could be removed from the stock housing and re-installed in a high-pressure housing with proper seals. I have a coolant pump from an '80s Chevy, and it seems to be stainless steel, though far from hydrodynamically efficient from the looks of it. The next question would be how much water will it pump, at what rpm, etc..
Peter</HTML>
I'm not sure about the pressure IC coolant pumps run at, but it is well below 500 psi. 10-15 psi max, I think. Perhaps one of these pumps could be used if the stock housing were enclosed in a pressure vessel, and new seals installed. Or the rotor could be removed from the stock housing and re-installed in a high-pressure housing with proper seals. I have a coolant pump from an '80s Chevy, and it seems to be stainless steel, though far from hydrodynamically efficient from the looks of it. The next question would be how much water will it pump, at what rpm, etc..
Peter</HTML>
Re: Lamont Pump Ideas
Posted by: Peter Brow (IP Logged)
Date: March 21, 2002 07:47AM
<HTML>Hi Francis,
Thanks for the tip; I'll check it out. Are these internal motors or a sealed magnetic drive coupling between an external motor and the pump rotor shaft? If a magnetic coupling could be isolated from the heat, and could be home-built to handle 500 psi, then that might be the way to go. No seals, no thrust loads, no heat problems, no advanced electrical engineering. Spinning permanent magnet on one side, spinning iron bar on the other side. Heat migration might be a problem though, especially on standby.
Old Stanley "kidney bottle" boiler water gauges have a float-operated magnetic coupling of this type, though this only moves a tiny indicator needle, and only slightly, not spinning. Still, they take the heat & pressure without demagnetizing anything. Wonder how much heat goes out that finned tube?
Peter</HTML>
Thanks for the tip; I'll check it out. Are these internal motors or a sealed magnetic drive coupling between an external motor and the pump rotor shaft? If a magnetic coupling could be isolated from the heat, and could be home-built to handle 500 psi, then that might be the way to go. No seals, no thrust loads, no heat problems, no advanced electrical engineering. Spinning permanent magnet on one side, spinning iron bar on the other side. Heat migration might be a problem though, especially on standby.
Old Stanley "kidney bottle" boiler water gauges have a float-operated magnetic coupling of this type, though this only moves a tiny indicator needle, and only slightly, not spinning. Still, they take the heat & pressure without demagnetizing anything. Wonder how much heat goes out that finned tube?
Peter</HTML>
Re: Lamont Pump Ideas -- Magnetic Coupling?
Posted by: Peter Brow (IP Logged)
Date: March 21, 2002 08:04AM
<HTML>Francis, you're a genius. Look what I found at Allegheny Pump:
====================
(snip)
Containment Shells
Molded for strength and tested for safety
Containment and movement of hazardous media in CPI applications is of paramount importance
to the safety of people and the environment. Sealless magnetic pumps are designed to transport hazardous liquids while minimizing the risk of catastrophic leakage. Part of the success of this design is to eliminate the use of all dynamic seals where the risk of potential leakage paths is highest. But how are the rotating interfaces sealed? One of the keys to the success of this design is to impart rotational movement to the pump by way of electromagnetism through a statically sealed containment shell. However, to make the design work effectively, the Shell has critical requirements that have to be overcome. The Shell must be transparent to electromagnetic waves, strong enough to withstand internal pressures of up to 500psi, and chemically resistant enough to withstand a broad range of aggressive chemical media conventionally contained using exotic metallic alloys such as HastelloyÒ . The material of choice…..VictrexÒ PEEK (polyaryletherketone, polyetheretherketone).
Allegheny's expertise in molding VictrexÒ PEEK is unparalleled in the industry. Previous molders had supplied the Shells but were unable to provide parts that could withstand even the lower pressure requirement of 300psi. Allegheny designed and built a tool ensuring that the material properties would be optimized for maximum strength and eliminate the risk of any weld lines. Mold heating was carefully configured to ensure maximum "as molded" crystallinity of the material and thus optimal strength and chemical resistance.
Allegheny now supplies a range of Shells, all of which are 100% pressure tested to 500psi.
A part from each lot is burst test and regularly exceeds 750psi.
(snip)
===============================
Thanks Francis! These shells are right off the shelf!
PEEK, interesting material -- also good for up to 500°F, btw. I've been keeping an eye on this stuff for quite some time, and had a feeling I might end up with some in my steam car.
Peter</HTML>
====================
(snip)
Containment Shells
Molded for strength and tested for safety
Containment and movement of hazardous media in CPI applications is of paramount importance
to the safety of people and the environment. Sealless magnetic pumps are designed to transport hazardous liquids while minimizing the risk of catastrophic leakage. Part of the success of this design is to eliminate the use of all dynamic seals where the risk of potential leakage paths is highest. But how are the rotating interfaces sealed? One of the keys to the success of this design is to impart rotational movement to the pump by way of electromagnetism through a statically sealed containment shell. However, to make the design work effectively, the Shell has critical requirements that have to be overcome. The Shell must be transparent to electromagnetic waves, strong enough to withstand internal pressures of up to 500psi, and chemically resistant enough to withstand a broad range of aggressive chemical media conventionally contained using exotic metallic alloys such as HastelloyÒ . The material of choice…..VictrexÒ PEEK (polyaryletherketone, polyetheretherketone).
Allegheny's expertise in molding VictrexÒ PEEK is unparalleled in the industry. Previous molders had supplied the Shells but were unable to provide parts that could withstand even the lower pressure requirement of 300psi. Allegheny designed and built a tool ensuring that the material properties would be optimized for maximum strength and eliminate the risk of any weld lines. Mold heating was carefully configured to ensure maximum "as molded" crystallinity of the material and thus optimal strength and chemical resistance.
Allegheny now supplies a range of Shells, all of which are 100% pressure tested to 500psi.
A part from each lot is burst test and regularly exceeds 750psi.
(snip)
===============================
Thanks Francis! These shells are right off the shelf!
PEEK, interesting material -- also good for up to 500°F, btw. I've been keeping an eye on this stuff for quite some time, and had a feeling I might end up with some in my steam car.
Peter</HTML>
Re: Lamont Pump Ideas
Posted by: George K. Nutz (IP Logged)
Date: March 21, 2002 01:50PM
<HTML>John and et al,
An automotive pump is not built to withstand any form of high pressure plus the ceramic seal, under 500-1000psi would create a lot of drag loss and blow the housing to bits plus the shaft is way to big in diameter and creates very high thrust loads,
but remember I have been wrong many times.
Francis, great idea to search under magnetic pumps on Google, I had searched under boiler circulating pumps in the Thomas register only. I don't think that miracle material would be good enough for high pressure applications Call them up and talk to an engineering rep: ask them if they have a pump that will handle 1000psi case pressure with a factor of safety of 4(burst pressure of 4,000psi) and handle 550 degreeF water, pump a maximum of 10,000#/hr with a 10 psi pressure differential. I know Jim Crank wants at least 1200psi or more, please let us know of their response. Remember the number you gaave was a case burst pressure of 750psi?? And i do know of a case where the magnets in a Stanley water level gauge lost their flux density and had to be remagnetized, its failure led to the boiler crown sheet failure due to low water.
I really hope your combined energies will come up with a commercially available product, pump design is not my forte either!!
George</HTML>
An automotive pump is not built to withstand any form of high pressure plus the ceramic seal, under 500-1000psi would create a lot of drag loss and blow the housing to bits plus the shaft is way to big in diameter and creates very high thrust loads,
but remember I have been wrong many times.
Francis, great idea to search under magnetic pumps on Google, I had searched under boiler circulating pumps in the Thomas register only. I don't think that miracle material would be good enough for high pressure applications Call them up and talk to an engineering rep: ask them if they have a pump that will handle 1000psi case pressure with a factor of safety of 4(burst pressure of 4,000psi) and handle 550 degreeF water, pump a maximum of 10,000#/hr with a 10 psi pressure differential. I know Jim Crank wants at least 1200psi or more, please let us know of their response. Remember the number you gaave was a case burst pressure of 750psi?? And i do know of a case where the magnets in a Stanley water level gauge lost their flux density and had to be remagnetized, its failure led to the boiler crown sheet failure due to low water.
I really hope your combined energies will come up with a commercially available product, pump design is not my forte either!!
George</HTML>
Re: Lamont Pump Ideas
Posted by: Peter Heid (IP Logged)
Date: March 21, 2002 05:28PM
<HTML>I ran across a pump forum that some might find interesting at [www.pump-zone.com]. I am just reading some stuff now so I can't tell you what it is like. I think it is open to anyone.
Peter Heid</HTML>
Peter Heid</HTML>
Re: Lamont Pump Ideas
Posted by: Jeff Theobald (IP Logged)
Date: March 21, 2002 09:00PM
<HTML>Hi All,
I read with interest, all the ideas on the Lamont boiler pump, as the main problem seems to be a way of getting a perfect seal, why not have an arrangment that allows a certain amount of leakage, with two pumps on the same shaft, i.e. your normal internal boiler circulating pump with packing glands which are allowed to leak to a degree, then a second sealed compartment with small pump picking up the leakage with return to feed water tank, or have I got hold of the wrong end of the stick, regards Jeff.</HTML>
I read with interest, all the ideas on the Lamont boiler pump, as the main problem seems to be a way of getting a perfect seal, why not have an arrangment that allows a certain amount of leakage, with two pumps on the same shaft, i.e. your normal internal boiler circulating pump with packing glands which are allowed to leak to a degree, then a second sealed compartment with small pump picking up the leakage with return to feed water tank, or have I got hold of the wrong end of the stick, regards Jeff.</HTML>
Re: Lamont Pump Ideas
Posted by: Peter Brow (IP Logged)
Date: March 22, 2002 07:35AM
<HTML>Hi George,
If they had anything suitable for 1000+ psi, I'm sure they'd be bragging about it on their website. Obviously these are no good for anything which has to survive a pressure test over 750 psi. Safe but not code, I think, for a 500 psi boiler (with an accurate & reliable popoff valve set well below 750). If the popoff sticks, the small magnet vessel would act as a sort of fusible plug or rupture disk!
However, PEEK is available in all sorts of sizes, shapes, and styles, including tube & fiberglass-reinforced tube. A little searching and testing might turn up a small-dia PEEK tube which would handle higher pressures without excessively blocking the effects of a drive magnet. Then figure out how to cap the tube and build a rotating magnetic yoke around it.
In any of these things, I'd isolate the magnetic element itself from boiler heat, similar to (but better than) the "kidney bottle" Stanley gauge shafts. The magnet would be outside the pressure zone, for easy replacement and air cooling. The motor can have a small fan on shaft to pull cooling air thru an insulated duct, then thru insulated case surrounding motor. This cools both motor and magnetic coupling, allowing use of stock 12vdc PM motor & no inverter. Have cooling air inlet below front bumper and air outlet vent in low pressure area of hood, for some natural thermosiphon aircooling while standing & ram air effect while running.
Just a few ideas. Maybe good, maybe dud.
Peter</HTML>
If they had anything suitable for 1000+ psi, I'm sure they'd be bragging about it on their website. Obviously these are no good for anything which has to survive a pressure test over 750 psi. Safe but not code, I think, for a 500 psi boiler (with an accurate & reliable popoff valve set well below 750). If the popoff sticks, the small magnet vessel would act as a sort of fusible plug or rupture disk!
However, PEEK is available in all sorts of sizes, shapes, and styles, including tube & fiberglass-reinforced tube. A little searching and testing might turn up a small-dia PEEK tube which would handle higher pressures without excessively blocking the effects of a drive magnet. Then figure out how to cap the tube and build a rotating magnetic yoke around it.
In any of these things, I'd isolate the magnetic element itself from boiler heat, similar to (but better than) the "kidney bottle" Stanley gauge shafts. The magnet would be outside the pressure zone, for easy replacement and air cooling. The motor can have a small fan on shaft to pull cooling air thru an insulated duct, then thru insulated case surrounding motor. This cools both motor and magnetic coupling, allowing use of stock 12vdc PM motor & no inverter. Have cooling air inlet below front bumper and air outlet vent in low pressure area of hood, for some natural thermosiphon aircooling while standing & ram air effect while running.
Just a few ideas. Maybe good, maybe dud.
Peter</HTML>
Sorry, only registered users may post in this forum.