Flywheel design

[rustybarrel]

Hello everyone,

I am new to this forum. I was searching internet for Stirling Engine information and stumbled upon your site. Its a good site. Keep it up guys.
I have made a stirling engine. Confrigation is as follows: Gamma engine. Power piston bore 50 mm x stroke 50mm. Displacer 70 mm x stroke 50 mm. When i first tried to start the engine it would not run. After much trial and error I added some external weight to flywheel and it started to run at about 200 rpm.
I have a question to ask. What should be the size and weight of a flywheel? How do you design a flywheel. I tried to find this on internet but the equation I found wants power and rpm of engine. How can I know them beforehand?
Sorry for spelling mistakes and bad english.
Thanks in advance.

[Ian S C]

Flywheels are a bit of guess work: If you look on my photo gallery, there are three relevent motors, first, the one called my second motor, it has a 6" dia, 2lb flywheel, this motor has a 1 3/4" bore and 3/4" stroke, the next one is the Ross Yoke motor, this has a 6" dia, 3lb flywheel, this motor has 35 mm bore X 20 mm stroke in both cylinders, ie its an ALPHA motor, and the last one has two fws 6" dia, 4lb each, this motor has a 2 1/4" bore and a 1 1/4" stroke, The motor runs OK with one flywheel. The first and last of the motors a BETA type. The first one will actually run (if you can get it to turn over), without a flywheel, although it has very little torque, and will only run at very high speed.
The best of flywheels have a reasonably large diameter, with the weight on the rim, the larger the diameter,the lighter it can be made (well sort of), You will notice that my metal supply gives me 6", and I woul suggest that 6" and 5lb would be a minimum that I would use on your motor, and the same weight but 8" would be better, and you would not be too heavy with two of those if the lay out of your motor allows them. I don't imagine that you are expecting much more than 500/600rpm with the long stroke that you have, but it shoul have quite a bit of power.
If you look closely at the flywheel on the Ross Yoke motor with the hacksaw, you will see how it is constructed, it started with three discs about 6 1/4" dia of 8 mm hot rolled (black) steel plate, its all held together with six 10-32 cap head screws, the center plate has the spokes hacked out, and the hub is held in with loctite retaining compound. Ian S C

[rustybarrel]

Thanks for the info. My current flywheel is 6 inch and about 2 pounds. I think it is unable to compress the gas and push the power piston foward after power stroke. I purposely designed a high compression engine to get power. Also I used steel wool for displacer piston. It just swells inside dispalcer cylinder and there is lot of friction. I am thinking of replacing it. Now I would have to just source a bigger flywheel from somewhere. I normally use pulleys for flywheel. Or I will have to use some cold metal repair kit like Devcon or Weldcon to increase the weight of flywheel. Anyways its again back to the workbench again.

[Ian S C]

Rustybarrel, you could try winding some light weight wire around the steel wool to compress it a bit, so that it does not rub on the cylinder, friction is one of the greatest enemies of stirling engines. Ian S C