walking beam improvement ?

rammstein · Post by **rammstein** » Sun Oct 26, 2008 3:08 pm

My second stirling engine is working

The first was the famous cokecan engine,but after 3 turns the membrane tore apart. I decided to make a walking beam instead.
It is a basic "boyd" engine,but with a larger displacer from balsa wood.
The displacer is 2/3 of the cilinder with 3mm between displacer and wall on each side. The power piston is made off epoxy resin with a coin in front to keep the leak low as the power cilinder heats up (aka coins expands to)
power piston is 20mm,displacer 54, displacer cilinder 60 mm, 180mm long
(paint spraycan). the crank offset on the flywheel is 25 mm for the both pistons at the same point.
The engine has run for 2 hours on 2 candles (small theelights) till I stopped it. Rpm was 60 -100. even with a rubber band attached to the displacer side of the beam and the centre pole to act a a load the rpm was the same. only the noise of sloppy rods went down.
As the subject stated how can I improve the walking beam engine??
or asked different> what is the power maker? double the bore or the stroke of the displacer or power piston? regeneration is for later if (if you help me)I find the best combination for torque.
It turns out to be a lot of reading,sorry
Greeds from the netherlands
8-)

rammstein · Post by **rammstein** » Sat Nov 01, 2008 4:13 pm

I cut the displacer in half and added 3 layers of "scotch brite" in the middle to act as a regenerator. The displacer piston is smaller close to the regenerator to lower the flow resistance and I hear a low brushing noise when I spin it by hand, so the air has to go throu the scotch brite.
I`m surprised what it did to the engine. The rpm is higher and it seems to be limited to the play in the system. When the engine is starting up, the rpm goes up till the whole system starts to vibrate, then revs down and up again, after 9 seconds it finds it balance and stays there. My rpm sensor has very low battery so no rpm indication today. Also a counter weight on the walking beam side flywheel WITH a rubber band on the displacer walking beam side streched all the way to the walking beam base helps. without the rubber band and WITH the counter weight rpm is dropping. It might be the resistance if the regenerator....
More to come

Robinson · Post by **Robinson** » Mon Nov 03, 2008 3:04 pm

rammstein wrote:More to come

Looking forward to it!

rammstein · Post by **rammstein** » Tue Nov 11, 2008 2:22 pm

I`ve rebuild the walking beam with very light material and shaped it as a crane structure and used parts of an old vcr for bearings and flywheel.
The whole system is now play free and cheerfully turns almost silent @ 170 rpm till the water heats up. I played with the offset/arm on the flywheel en 28 mm seems to be the right spot on my engine.
I put a rubber hose on the power cilinder without the piston and checked for leaks @ the displacer seal by blowing on it and hold the pressure while I filled the cooling can with water above the displacer seal and rotated the flywheel. there were very small bubbles, so I think the seal is ok.
When I disconnect the power piston linkage and turn the flywheel with the heater on, the piston shoots out of the cilinder.
The engine will not go above 170 rpm so I think something (dimentions) is not right.
OR is it common for a walking beam?
Any ideas to improve my engine ?

Robinson · Post by **Robinson** » Tue Nov 11, 2008 2:55 pm

AFAIK these engines are generally supposed to turn at a slow RPM but I've not made either the coke can or walking beam versions so I can't say for certain if yours can be 'improved'.

Any chance of some pictures or video?