Stirlingengineforum.com

Anyone seen a boxer style design with the outer ends cool? I want to build a boat engine with the cold ends outside the hull and a fireplace in the center.

/Stina

skvamme wrote:Anyone seen a boxer style design with the outer ends cool? I want to build a boat engine with the cold ends outside the hull and a fireplace in the center.

/Stina

Instead of outside the hull why not use ducted channels that force water flow over the cold ends themselves. One could control the intake and lower drag on the hull. This would also serve to protect the cold ends from bouncing off the bottom and stuff.

The center hot box might transfer a lot of heat to the crank. I can't see your concept, so...

Can you draw up a simple sketch and post it here?

Are you thinking of a shuttle type power piston producing with each direction change?

A fireplace is not the word I'd use in connection with a boat.

R

Well, I can see the cold ends are in a little bit of danger outside the hull, but I thought if they are out in the cold the engine should be easier to start and run at standstill and simpler too.

I have read up on stirling engine design, Stirling EngineDesign Manual by William R. Martini, but couldn't find any similar construction to the one I am looking for.

I am thinking of a one piece cylinder with two sections, with two displacer pistons and one tandem cylinder with a power piston. But I was hoping for a "standard" design for this purpose. I'll see if I can draw some sketches.

hihi, a fireplace is nice.

/S

skvamme, from my interpretation of your information, your boat is going to be very wide. I imagine that you know the propportions required for a displacer, and its cylinder, ie., that the displacer should be three times longer that its diameter, therefore the cylinder shall be that length, plus the stroke, plus the end clearance, and to make your engine, it will need to be twice as long. As well as that, the rod on the displacer should exit the cylinder at the cold end, and by some means be connected to the crankshaft. I suppose that it could be made as part of the beam joining the hulls of a trimeran(3 hulls). Ian S C

I think if this were my project I'd keep the hull intact, and build an inline engine with the hot end down, just like the hosts walking beam, only a direct drive to the crank for both con rods instead of the beam. That's an extra crank throw, but less connections. I might make this a 6 cylinder with each cylinder able to be added or subtracted from the engine quickly. I'd pull water into a jacket surrounding the cold ends using a little engine power, and squirt it over the side after absorbing heat.. A variable speed drive/intake would be nice for that, so that any speed you get out of the boat would assist coolant flow. I think, with proper gearing, one might to be able to approach the power of a DC trolling motor. Then one needs to think about the use of the boat. Haul a load of folks or stuff, or scoot around by yourself? Fuel and fire assurance. Prop drive, water jet, stern wheeler or side wheeler?

Water can't ever put your hot box out of commission!

Good luck.
R

theropod2, I tend to agree with you. I have a tin boat about 2ft long with a GAMA motor in it. There is a similar looking motor in a site by Koichi Hirata in Japan, you can google Let's build a model stirling engine boat, his motor is an ALPHA. http://www.nmri.go.jp/eng/khirata/stirl ... dex_e.html

Thank you guys for your replies! I feel quite confident now that I will not invent the wheel again with my odd design ;)

I'll keep you posted on how things work (or don't)

/S

Here's a first drawing
http://www.kvamme.se/static/boxer_stirling.pdf

/stina

I agree that displacer travel should be a bit longer. It is now about 20 mm. The problem is that it was quite hard to find a suitable displacer and now that i have found it i cant make it shorter. Also it is quite hard to make cylinder longer which would be the other way to enable longer travel. But if this is the main reason for not running then i'll figure out some way to fix the problem. Another side to this coin is that the engine runs better with shorter strokes. I mean that with shorter strokes it rotates more easily.

stina, I,v had an idea(that's bad),how about two Ringbom motors with the displacers back to back, the power cylinders can be virtually anywhere as there is no crankshaft connection between the two parts, and with care it may be possible to make it self starting, just a thought that might be worth researching.
Ian S C