Maybe make diaphragm of multiple thin sheets of silicone to reduce fatigue as one does with copper cables with thin strands making them flexible and not as subject to fatigue. You could extend the piston ‘rod’ beyond the link as a round rod and support it in a tube to stop the flexing / twisting.
Sometimes in engine fuel pumps, they use multiple thinner diaphragms stacked together. Perhaps this might help? Ideally some fabric/fibres in the material would also provide some strength, but it might be hard to find?
I don't think you are going to find a polymer solution to your design and concentric corrugated metal diaphragms are unlikely to give the travel - I wonder if introducing a water vapor mist into the air might cap the temperature while increasing the expansion ratio? I was thinking of perhaps one of them little high-frequency mist probes placed in a small cavity in the cold end where condensate would pool - the high latent heat value where water turns to steam would cap the working water vapor to a little over 100c yet the expansion ratio would increase considerably.
That is an interesting idea, kind of like a Stirling / steam hybrid. I was thinking it could inject a mist at the correct timing to be heated and then the condensate could be drained off the cold side.
@@ShanePomeroy You could try introducing some water vapor via the sniffer valve with a little household spray to try it out however for continual running you need something automated - of course, you could use something with a lower boiling point than water and stop corrosion too !
@@ShanePomeroy Shane water vapor would be far more conducive too - a little sonic probe placed in a little condensate well at the cold end would allow you to control the moisture in the cycle- Indeed you could even control it with a min /max temperature sensor at the hot end that came on at say 102C and off at 98C to keep your cycle tuned to the furnace heat output - You will need to "Spin" some thin aluminum covers for your stuffing rings you can't have bits of rock flying back and forth
Just cut 1 cm off of the linkage to clear the contact point. You can try to make two kinds of composite materials: A fiberglass fabric, maybe 3 layers, with high temperature silicone as resin for the diapragm. For the lining inside the chamber, you can use the same filler, but mix a lot of fiberglass wool to avoid embrittlement... You're doing a great job with this engine. Looking forward for the power test. Thank you.
Great work! If you made the vertical linkages' bolt holes into slots you could adjust the height of the piston's center point to align it. Probably just coz it's off a little bit that it's nipping
I am so impressed with this design. There are other designs on UT and one in particular uses a large diameter piston with diaphragm and very slow rpm with high torque. Yours is so compact and neat. I must go back and follow the Mk4 to see how it has been developed. The guy mentioning parallelogram motion might help against fatigue damage. Take a look at steam train engines. They have linear motion conrods. So do ship steam engines like the Wavely. Hope this helps.
What about wood powered turbojet (turbo barrel)? I guess it should be more efficient and easier way to extract energy out from wood. Ur Stirling engine in itself is amazing, no doubt but there're many limitations which hinder its practicality.
Hi Shane, i'm going to throw my 2 cents in again! How about a chainsaw vibration isolater between the piston and bellcrank. You know the rubber mount with two studs sticking out each end . Welding blanket of the type using a core of woven glass with orange silicone bonded to each side might be worth looking into for your diaphragm problem. Also concrete is hygroscopic and can be expected to fracture when heated to much.
How about.. a piston instead. Piston has it's own troubles I know. The stresses on the high power diapragm are killing it, can the stress be reduced? How about extending the plate connected to the center of the moving plate, extending it to a guide that then keeps the plate straight?
Maybe a rolling rubber diaphragm like the ones used in air suspension systems is an idea to increase durability. It would add dead volume, but with the rubber less stressed, it probably takes the heat better and lasts longer. Also these things have a lot more travel / swept volume.
Seems like a larger diameter for the gasket would spread the flex over a larger area and reduce the amount of fatigue on any one spot. Also either the parallel linkage or if that's to hard, just move the mount point on the piston slightly down so it's just off center, it will distribute the force more evenly as on center seems to be top biased a tad. Keep going love the videos!
I agree with Paul's comments. I also have a couple suggestions. 1) Increase the outside dimension of the seal 50 to 75mm. It appears that there is a lot of seal stretching when the piston is at its extended out position. You should be able to add a larger diameter flange so you wont have to modify your original design. 2) Make a new steel piston with the distance between the bearing and seal face 6mm??? shorter. This will minimize the seal flex/stress when the piston is at its furthest "In" position. You can add more vermiculite as needed to maintain the correct piston volume. 3) Notch the connecting arm where the back of the piston was hitting. this appears to be a problem spot that maybe a small light spring could be attached to that would keep things stable. But not add much weight. I am excited to see the gain in experience and knowledge as you continue with your Stirling hobby. Hats off to you!!! Ed
1. Create slightly BIGGER GAP between two moving faces of Piston and Sleeve. 2. Use NEOPRENE instead of Silicone I don't know weather a Aluminium HEAT SHIELD on inside of Piston will make the neccessary difference but it might just help in absorbing heat slightly.
On the piston arrangement misalignment, what if you change that attachment point to allow connection to provide multiple holes...move the pin lower to apply more pressure lower to better equal the flex.
This is a great series !!! Yes make the piston end longer and make a second arm to stabilize the piston. Could the surfaces touching the diaphragms be curved not flat.
i'm glad i found this channel. i want to make a rocket mass heater, and your temperature reading gave me a great idea as to where to situate a heat exchanger for a stirling engine.
It's possible to also get heat resistant silicone. It's not very hard to make the membrane either. Just sandwich it between two glass or baking paper with suitable spacers. They are usually mainly used for sealing.
Do you think this would make a good membrane. I remember Jürgen Kleinwächter mentioning firemens suits as the material of choice for their membrane. " CARBO-FLEX® (AFLPN) Cloth AMI’s heat resistant textile-CARBO-FLEX® (ALFPN)-is a composite of a woven fabric, a non woven material and a layer of aluminized polyester film for reflectivity. It provides continuous protection up to 600°F (320°C)."
Try TPU very strong and flexable or a surface tension diffuser for silicon this will make the silicone slippery lowering friction and adding a skin to the surface. look for smooth-on SLIDE you will have to make mould this is easy with a 3d printer. If you need any help let me know.
I think you're on the right track using silicone rubber for the diaphragms. However, I do wonder if there are fillers in that particular grade of silicone sheet that somehow reduced its tear strength. Natural silicone has very high resistance to tearing, so I was surprised to see that your engine's diaphragms developed tears so quickly. (And maybe it's irrelevant, but I've never seen white silicone sheet. The stuff that I can readily source in the US is always red-orange.) I'm wondering if your silicone sheet is impregnated with titanium dioxide. If so, that particular filler would definitely reduce its tear strength. Even given the possibility that irregularities or sloughing in your concrete diaphragm landing may have contributed to the tears, I think it's unlikely that this is the root cause. Hope that you switch to a different type of silicone rubber before abandoning silicone as a preferred material for your diaphragms. Edit: high-strength silicone is tear-resistant. Regular silicone is not tear resistant.
Is a polyurethane diaphragm out of the question? A serious drawback would be the poisonous emissions if it catch fire. MPC makes thermoset polyurethane, which is more heat resistant.
1:26 Can you build a parallel articulation for the diaphragm so it keeps the piston straight in the bore? Or maybe a sliding rod like a steam engine? Would it even make any difference in this case? With all the diaphragm issues, would a traditional piston/cylinder work better?
I’ve been watching a handful of your videos. I really dig this machine. Great work. I’m not sure if you have tried but they make fiber reinforced silicone baking mats that is designed to be put in the oven. That might be a reasonable option for you
Those initial failures were right on the edge of the nylon ring, I suspect shear was the culprit tho any purely flexible membrane will ultimately balloon which will lead to trapping and uneven stresses. Hot side pistons have always been the achillese heel of heat engines, I wonder if moving the diaphragm further away from the heat source might help, the piston/diaphragm could be somewhat remote from the heat source as long as the working volume is maintained, perhaps a tube within a tube with the working part some distance from the firebox? Recon I would have guessed at lower diaphragm temps and gone cloth and rubber diaphragm material, most likely with equally disastrous results? Might be worth finding some silcon/cotton reinforced specs, see how they stack up
Pretty sure even once you align the piston with the parallel linkage will increase your durability, but still, any material is going to fail undergoing such repeat reverse stresses. I believe the flexible bellows as part of the design is a lost cause. Useful as a proof of concept for output on this size of unit definitely … and one really has to applaud your efforts.
Hvala tebi za pravi iskreni video na tu temu 🗣️☑️👏👏👏👏👏💖🕛i vrijeme curi, trebamo dokazati i pokazati kako dobiti jače, Strong Power Horses........(!)(?)🇭🇷🙏
Just double check that the IR temp gun is giving you an accurate reading, sometimes reflective and/or white surfaces (like with the silicone) can give low readings. I think matt black is the best surface. Maybe do a test with various materials/colours in the oven?
Random thought: In most diaphragm pumps, compressors etc the 'piston' is rigidly attached to the connecting rod and therefore rocks but in a controlled manner. The driving levers on your engine are quite long and the stroke short, so the change of angularity is small - what would be the effect of locking up the articulated joint between lever and piston? Easy to try if nothing else! Oh, and as suggested by others, making the diaphragms out of several layers of thinner material seems like a good idea.
I think your quite right. If/when I build another I would probably have a locked link with longer pivet arm. We will now start trialling multilayer thin diaphragms, many thanks
You don't know what you're talking about. If the machine output a third of kW, how will it power a 10 kW generator my friend?! And the function of this machine is to produce mechanical work from wood. If you're going to use electrical power in a induction coil, just get a normal eletric motor in the first place.
Hola Shane, perdona que te moleste, el volante de inercia es de un motor de tractor tipo Lamborghini, same,bueno ya me dirás, sigo con el proyecto haciendo acopio de material, bueno gracias, Champion.
As always: Amazing! On my qest ti be 100% off grid stupidity i need to know if the exhaust a 10 Kw Ice generator, run at wood gas will be able to replase your rocket stove? It will fore shure maethe "aftercooler" my freind insisted on?
Hi Shane. Commiserations on your attempts to get some power readings on this engine. Sorry, not offering any suggestions how to improve it. Hope you keep at it, until you find a suitable material or design. The best I can offer you is lots of encouragement. All the best. Looking forward to seeing some numbers.
@@ShanePomeroy Why not just use a true piston and piston rings ? That would solve three issues 1) Seal breaking 2) Rotation issue 3) And I think you might be losing 11:37 power due to volume change because of the flexing seal.
I am very interested in knowing if a metal seal would work like in a chainsaw carburetor. With roll forming you can creat a pattern on thin metal that will allow it to act as a diaphragm and it will withstand heat and chemicals
@@ShanePomeroy I think it would be a first of its kind metal diaphragm engine. Probably worth the views as if you get it seen it will bring a lot of us that enjoy engineering creativity. It's always worth seeing the what ifs using new tech. Try and work with a company doing the roll forming to build to your specs or make an inexpensive pinch roller and try it yourself on a budget
What about a parallelogram linkage to keep the pistons aligned.
Or balance the piston out over the pivot point, but will have double the weight.
This is the solution I would use
How about a shaft and linear bearing?
Yep extend the piston arm and add a slave link
@@hackofalltrades5256 but connect the pistons to each other so they operate on the same plane.
I could listen to that all day.nice machine. Phil.
Maybe make diaphragm of multiple thin sheets of silicone to reduce fatigue as one does with copper cables with thin strands making them flexible and not as subject to fatigue. You could extend the piston ‘rod’ beyond the link as a round rod and support it in a tube to stop the flexing / twisting.
silicone impregnated kevlar or fiberglass laminated with silicone?
Sometimes in engine fuel pumps, they use multiple thinner diaphragms stacked together. Perhaps this might help? Ideally some fabric/fibres in the material would also provide some strength, but it might be hard to find?
Yes. Laminated.
well, metal diaphragms are the best, however they have to be laser welded otherwise it will be hard to keep the sealing between diaphragm segments
Love your work! How about a mix of piston on the hot side and diaphragm on the cold side? Or the "rolling" seal mentioned elsewhere.
I don't think you are going to find a polymer solution to your design and concentric corrugated metal diaphragms are unlikely to give the travel - I wonder if introducing a water vapor mist into the air might cap the temperature while increasing the expansion ratio? I was thinking of perhaps one of them little high-frequency mist probes placed in a small cavity in the cold end where condensate would pool - the high latent heat value where water turns to steam would cap the working water vapor to a little over 100c yet the expansion ratio would increase considerably.
That is a very interesting idea. Is there a regenerator in this engine? It would be interesting to see how that worked with vapor.
That is an interesting idea, kind of like a Stirling / steam hybrid. I was thinking it could inject a mist at the correct timing to be heated and then the condensate could be drained off the cold side.
I will seriously think about this. The problem is my projects are simply following what happened 100 years ago!
@@ShanePomeroy You could try introducing some water vapor via the sniffer valve with a little household spray to try it out however for continual running you need something automated - of course, you could use something with a lower boiling point than water and stop corrosion too !
@@ShanePomeroy Shane water vapor would be far more conducive too - a little sonic probe placed in a little condensate well at the cold end would allow you to control the moisture in the cycle- Indeed you could even control it with a min /max temperature sensor at the hot end that came on at say 102C and off at 98C to keep your cycle tuned to the furnace heat output - You will need to "Spin" some thin aluminum covers for your stuffing rings you can't have bits of rock flying back and forth
Just cut 1 cm off of the linkage to clear the contact point.
You can try to make two kinds of composite materials: A fiberglass fabric, maybe 3 layers, with high temperature silicone as resin for the diapragm.
For the lining inside the chamber, you can use the same filler, but mix a lot of fiberglass wool to avoid embrittlement...
You're doing a great job with this engine. Looking forward for the power test. Thank you.
Hi Shane just had an idea !
What if on the hot side the silicone is two layers and water is pushed between the layers to keep it cool.
Maybe a sidewall of a tire is to stiff? But it stands a lot of motion/wear. if you can clamp it so it seals in any way.
Great work! If you made the vertical linkages' bolt holes into slots you could adjust the height of the piston's center point to align it. Probably just coz it's off a little bit that it's nipping
I am so impressed with this design. There are other designs on UT and one in particular uses a large diameter piston with diaphragm and very slow rpm with high torque. Yours is so compact and neat. I must go back and follow the Mk4 to see how it has been developed. The guy mentioning parallelogram motion might help against fatigue damage. Take a look at steam train engines. They have linear motion conrods. So do ship steam engines like the Wavely. Hope this helps.
What about wood powered turbojet (turbo barrel)? I guess it should be more efficient and easier way to extract energy out from wood. Ur Stirling engine in itself is amazing, no doubt but there're many limitations which hinder its practicality.
Hi Shane, i'm going to throw my 2 cents in again!
How about a chainsaw vibration isolater between the piston and bellcrank. You know the rubber mount with two studs
sticking out each end .
Welding blanket of the type using a core of woven glass with orange silicone bonded to each side might be worth looking into
for your diaphragm problem.
Also concrete is hygroscopic and can be expected to fracture when heated to much.
Instead of a fan/wafter which robs energy from the engine, why not create a chimney above and make use of natural convection?
very nice ! ... you can use acetic silicone to repair the punched silicone membrane.
How about.. a piston instead. Piston has it's own troubles I know. The stresses on the high power diapragm are killing it, can the stress be reduced? How about extending the plate connected to the center of the moving plate, extending it to a guide that then keeps the plate straight?
Maybe a rolling rubber diaphragm like the ones used in air suspension systems is an idea to increase durability. It would add dead volume, but with the rubber less stressed, it probably takes the heat better and lasts longer. Also these things have a lot more travel / swept volume.
Well done Jason Statham !! Nice Stirling engine build !!
Seems like a larger diameter for the gasket would spread the flex over a larger area and reduce the amount of fatigue on any one spot. Also either the parallel linkage or if that's to hard, just move the mount point on the piston slightly down so it's just off center, it will distribute the force more evenly as on center seems to be top biased a tad. Keep going love the videos!
I agree with Paul's comments. I also have a couple suggestions.
1) Increase the outside dimension of the seal 50 to 75mm. It appears that there is a lot of seal stretching when the piston is at its extended out position. You should be able to add a larger diameter flange so you wont have to modify your original design.
2) Make a new steel piston with the distance between the bearing and seal face 6mm??? shorter. This will minimize the seal flex/stress when the piston is at its furthest "In" position. You can add more vermiculite as needed to maintain the correct piston volume.
3) Notch the connecting arm where the back of the piston was hitting. this appears to be a problem spot that maybe a small light spring could be attached to that would keep things stable. But not add much weight.
I am excited to see the gain in experience and knowledge as you continue with your Stirling hobby.
Hats off to you!!!
Ed
1. Create slightly BIGGER GAP between two moving faces of Piston and Sleeve.
2. Use NEOPRENE instead of Silicone
I don't know weather a Aluminium HEAT SHIELD on inside of Piston will make the neccessary difference but it might just help in absorbing heat slightly.
Fantastic evolution of your design. It looks like you are making real power.
On the piston arrangement misalignment, what if you change that attachment point to allow connection to provide multiple holes...move the pin lower to apply more pressure lower to better equal the flex.
I shall look into that, many thanks
Maybe shafts and slide bearings guiding the pistons would keep the diaphragm from being pinched unevenly.
This is a great series !!!
Yes make the piston end longer and make a second arm to stabilize the piston. Could the surfaces touching the diaphragms be curved not flat.
i'm glad i found this channel. i want to make a rocket mass heater, and your temperature reading gave me a great idea as to where to situate a heat exchanger for a stirling engine.
I have similar conclusions about the silicone membrane. This is the material of a short life
It's possible to also get heat resistant silicone. It's not very hard to make the membrane either. Just sandwich it between two glass or baking paper with suitable spacers. They are usually mainly used for sealing.
Bit of a pain, but could you use a heatproof fabric (maybe glass fibre?) and impregnate it with silicone? I second the parallelogram linkage idea.
Dobro si njemu sugerirao,☑️ a što kažeš za membranu od na primjer tzv. presoflex gume , ..... Koja je čvrsta i fleksibilna 🙏🇭🇷🕛💖🗣️?????
Presoflex RUBER membrane.......☑️🗣️🕛🇭🇷🗣️🙏👏👏👏👏👏💖
Do you think this would make a good membrane. I remember Jürgen Kleinwächter mentioning firemens suits as the material of choice for their membrane. " CARBO-FLEX® (AFLPN) Cloth
AMI’s heat resistant textile-CARBO-FLEX® (ALFPN)-is a composite of a woven fabric, a non woven material and a layer of aluminized polyester film for reflectivity. It provides continuous protection up to 600°F (320°C)."
Try TPU very strong and flexable or a surface tension diffuser for silicon this will make the silicone slippery lowering friction and adding a skin to the surface. look for smooth-on SLIDE you will have to make mould this is easy with a 3d printer. If you need any help let me know.
I think you're on the right track using silicone rubber for the diaphragms. However, I do wonder if there are fillers in that particular grade of silicone sheet that somehow reduced its tear strength.
Natural silicone has very high resistance to tearing, so I was surprised to see that your engine's diaphragms developed tears so quickly. (And maybe it's irrelevant, but I've never seen white silicone sheet. The stuff that I can readily source in the US is always red-orange.) I'm wondering if your silicone sheet is impregnated with titanium dioxide. If so, that particular filler would definitely reduce its tear strength.
Even given the possibility that irregularities or sloughing in your concrete diaphragm landing may have contributed to the tears, I think it's unlikely that this is the root cause.
Hope that you switch to a different type of silicone rubber before abandoning silicone as a preferred material for your diaphragms.
Edit: high-strength silicone is tear-resistant. Regular silicone is not tear resistant.
very cool! I've been involved with a similar problem. Solved it by going to thinner material. Thanks and good job!!
Is a polyurethane diaphragm out of the question? A serious drawback would be the poisonous emissions if it catch fire. MPC makes thermoset polyurethane, which is more heat resistant.
1:26 Can you build a parallel articulation for the diaphragm so it keeps the piston straight in the bore? Or maybe a sliding rod like a steam engine? Would it even make any difference in this case? With all the diaphragm issues, would a traditional piston/cylinder work better?
I’ve been watching a handful of your videos. I really dig this machine. Great work. I’m not sure if you have tried but they make fiber reinforced silicone baking mats that is designed to be put in the oven. That might be a reasonable option for you
Those initial failures were right on the edge of the nylon ring, I suspect shear was the culprit tho any purely flexible membrane will ultimately balloon which will lead to trapping and uneven stresses. Hot side pistons have always been the achillese heel of heat engines, I wonder if moving the diaphragm further away from the heat source might help, the piston/diaphragm could be somewhat remote from the heat source as long as the working volume is maintained, perhaps a tube within a tube with the working part some distance from the firebox? Recon I would have guessed at lower diaphragm temps and gone cloth and rubber diaphragm material, most likely with equally disastrous results? Might be worth finding some silcon/cotton reinforced specs, see how they stack up
Pretty sure even once you align the piston with the parallel linkage will increase your durability, but still, any material is going to fail undergoing such repeat reverse stresses. I believe the flexible bellows as part of the design is a lost cause. Useful as a proof of concept for output on this size of unit definitely … and one really has to applaud your efforts.
I think you're looking for a "4 bar linkage' to keep the pressure plate perpendicular to the cylinder
Yep. This was a big problem in the 1800s engines as well. always on the hot side.
How about leather seal? And maybe add a spring at the bottom of linkage to stop it from slapping
Any chance you would make your CAD files available for open source Co-op?
Hvala tebi za pravi iskreni video na tu temu 🗣️☑️👏👏👏👏👏💖🕛i vrijeme curi, trebamo dokazati i pokazati kako dobiti jače, Strong Power Horses........(!)(?)🇭🇷🙏
you should tru a flexible chimney pipe instead of this, because its metal
subbed! I cross fingers for your experiments! ;-) Great job so far!
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What about tight weave carbon fibre cloth coated with high temp silicon
Why not use real pistons, it will also solve the alignment problem.
Hola shane prueba con goma de neumático blando aguantara creo yo más el calor, bueno cuidaros, un saludo.
Cool idea, you can charge your e-bike with wood now xD
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Sounds like a drum machine 🥁🎸
Thank you for the video!
She's a right ol' slapper she is!
Just double check that the IR temp gun is giving you an accurate reading, sometimes reflective and/or white surfaces (like with the silicone) can give low readings. I think matt black is the best surface. Maybe do a test with various materials/colours in the oven?
Thanks for the heads up : ). I've never really believed these things! I wanted a contact thermometer but it was a bit expensive, cheers
Random thought: In most diaphragm pumps, compressors etc the 'piston' is rigidly attached to the connecting rod and therefore rocks but in a controlled manner.
The driving levers on your engine are quite long and the stroke short, so the change of angularity is small - what would be the effect of locking up the articulated joint between lever and piston?
Easy to try if nothing else!
Oh, and as suggested by others, making the diaphragms out of several layers of thinner material seems like a good idea.
I think your quite right. If/when I build another I would probably have a locked link with longer pivet arm. We will now start trialling multilayer thin diaphragms, many thanks
Couldn't you just hear a giant one of these... like 50 km away?
Unless I can make it quieter......urrrrr, yes
What about an induction coil instead of wood and a 10kw axil flux alternator as the flywheel.
You don't know what you're talking about. If the machine output a third of kW, how will it power a 10 kW generator my friend?!
And the function of this machine is to produce mechanical work from wood. If you're going to use electrical power in a induction coil, just get a normal eletric motor in the first place.
Hola Shane, perdona que te moleste, el volante de inercia es de un motor de tractor tipo Lamborghini, same,bueno ya me dirás, sigo con el proyecto haciendo acopio de material, bueno gracias, Champion.
That's interesting, I wonder what it's history is? It was fitted to a boat when I got it : ) Cheers
As always: Amazing!
On my qest ti be 100% off grid stupidity i need to know if the exhaust a 10 Kw Ice generator, run at wood gas will be able to replase your rocket stove?
It will fore shure maethe "aftercooler" my freind insisted on?
Hi Shane. Commiserations on your attempts to get some power readings on this engine. Sorry, not offering any suggestions how to improve it. Hope you keep at it, until you find a suitable material or design. The best I can offer you is lots of encouragement. All the best. Looking forward to seeing some numbers.
Excellent, as always. Maybe carbon fiber? Cheers.
I didn't think of carbon fiber, I'll take a look
@@ShanePomeroy
Why not just use a true piston and piston rings ?
That would solve three issues
1) Seal breaking
2) Rotation issue
3) And I think you might be losing 11:37 power due to volume change because of the flexing seal.
I am very interested in knowing if a metal seal would work like in a chainsaw carburetor.
With roll forming you can creat a pattern on thin metal that will allow it to act as a diaphragm and it will withstand heat and chemicals
My main concern with metal is decreased movement and heavier loading on linkages. I might need to go down that route...... Cheers
@@ShanePomeroy I think it would be a first of its kind metal diaphragm engine. Probably worth the views as if you get it seen it will bring a lot of us that enjoy engineering creativity. It's always worth seeing the what ifs using new tech. Try and work with a company doing the roll forming to build to your specs or make an inexpensive pinch roller and try it yourself on a budget
What a fantastic project
good luck