Stirlingengineforum.com

Hi,

I'm new to engine building. I just completed building my first, a "Beamer" designed by Jerry Howell. Is anyone here familiar with that engine?

The Beamer is a small model gamma engine with a graphite piston 0.6" dia running in a brass cylinder and a hollow 1" diameter aluminum displacer in an finned aluminum cylinder with insulated stainless steel hot cap. Jerry recommended running it from a small alcohol lamp or miniature propane flame.
http://www.jerry-howell.com/Beamer.html

Here's my observations so far.

First, Jerry's plans are excellent, detailed, and accurate. My building isn't, but that's what makes life interesting. :-) I had to adjust some hole locations due to my poor drilling techniques and other things like that, but basically I followed the plans. After enough fixing and tweaking, I was able to complete the engine and have it operate smoothly.

With my fingers, it operated without binding. There was the expected compression feel at certain points in rotation, so I think that I got the piston fairly tight.

I first tested the engine with an alcohol lamp and a fairly big flame. The flame engulfed the whole 1.2" OD hot cap, so I think that the flame is larger than appropriate. With enough warm-up time, I could spin the flywheel and it would keep going. Then I put the belt (rubber band) on to drive the fan and phony governor, and it wouldn't keep going. I was able to drive the phony governor alone, so it seems that the fan plus governor load is more than this tiny engine can handle.

The phony governor is just a pair of light-weight flying balls for show. It doesn't really have any governing function. The fan is intended to blow cool air on the cool part of the cylinder. It's five blades, roughly 2" diameter, on two small ball bearings. I wouldn't expect that it would put much load on the engine.

I experimented with a common, small tip propane torch rather than the alcohol lamp, thinking that more heat would produce more power, but that wasn't more effective. Then I tried a bank of resistors (Dale aluminum cased resistors) and a power supply for controlled heat, and monitored the hot cap temperature with a thermocouple. I had to get the hot cap above 210C before the flywheel would continue on its own, without governor or fan load. That's really the upper end of the resistor temperature operating range, so I don't think that I should push it further.

I read somewhere that small engines have to "break in". Perhaps I need to just run the engine from a small electric motor for an hour to loosen everything up.

Can someone here advise me, either on list or off list, what I might do next to get this engine performing a little better? Are there tweaks or adjustments to optimize one of these engines?

Thank you.

Bob

Hi Bob, welcome, I,v built a few(14) motors, your thoughts on running the motor over for an hour or so with an electric motor is the right way to go, and a number of the published builders have this as the last stage of building a motor. After that as you run the motor it improves with age, and if you have designed it well it will go for years with very little maintainance.
My first one in 1990 was a small V type that wore out about 7/8 years ago, but 90%of it is now a small Ringbom motor, similar to the motor called Tapper, Designed and built by J.R. Senft. The second one was built in 1994, an is similar to James G. Rizzo's Dyna, it has power enough to drive a generator to run a radio, or to run a power hacksaw with a junior hacksaw blade, it will cut 1/2" steel bar in 15/20 min (to liven things up a bit you can watch the grass grow).
As long as you have minimum friction, by choosing the correct materials running against each other. Make sure there are no leaks, there will be a very minor leak at the gland where the displacer rod comes out. Keep the weight of the moving parts to a minimum. You could get an advantage by replacing the aluminium displacer with a light weight stainless, or even mild steel one. The aluminium conducts the heat to the cold end too fast, also you can safely use more heat, when the aluminium gets hot, say 400degC it looses its strenght and can collapse, I know I did in 3 displacers earlier this year before going stainless steel(if you dont bend or break some thing your not trying hard enough). Ian S C ps try a fan with fewer blades, and or a finer pitch. 3 blades should be plenty.