I got my test tubes out. They have a lip around the end that would make it impossible to insert the piston. However, I measures the inside past the lip and I think they are round enough to seal a piston:O) I had worried about that? I think I can grind the lip off with a diamond blade? I'll have to give it a try.
Hi kustomkb, congratulations, very nice job!
If you are fan of the higher speeds I would recommend you using smaller volume test tubes while keeping the same piston size. This of course is not possible with the thermo-pulse mobile of Jan, because he uses the test tube as a working cylinder. Separating the working cylinder and the test tube gives many opportunities to play with different test tube sizes, different restrictors sizes and shapes It also provides better heat insulation between the hot chamber (test tube) and the cold area (piston side). In such a construction the test tube lips might facilitate the assembly See this post: http://www.homemodelenginemachinist.com/index.php?topic=1171.0
Ive made several experiments with different test tube sizes. In an earlier version I had 155 x 14 test tube and the engine top speed was ~1000 rpm. Now I use a smaller volume one 100 x 11, which almost doubled the speed. Now Lamina reaches 1800 rpm.
In my eyes, further improvement would be using a longer and narrower tube, which would better separate the hot and cold areas. Brass pipe can be used for improved heat conduction.
Thanks guys, I had a hard time finding the specified test tubes but I was able to get 4 feet of 18mm OD glass from a local scientific glass blower. I thought I could just plug one end. Do you think that might cause any problems?
thanks for the tips, and I like your flywheel in your avatar, PalmRunner.
I teamed up with a buddy at work and we made two of these. They haven't run yet. Everything is to spec. except for the
test tube which I couldn't find. (PowderKeg, I can't see them on that site..)We cut a tube to length and plugged one end to no avail and tried bonding the hemispherical end of one tube to a tube section and that was a no go as well. Any ideas will be appreciated. We may have go to the different size cylinders as PalmRunner suggested.
Looking good. You must have read Jan's set up instructions, it just might be one of your settings in relation to his is out slightly. Just looking at this nearly finished one looks like the internal fill is not where it should be, or it just might be an optical illusion.
Great looking engine! Only one remark - this engine is a very low power device, max. 100mW. Therefore it is very important to minimize all possible frictions. I cleaned the bearings from the grease and used some light oil. Turning the flywheel by hand it takes quite a long time before it stops.
The engine runs at relatively high speeds, so small leakage is allowed, but it is worth to try this small test: disconnect the piston rod from the flywheel, pull and release the piston - if it oscillates like a spring this means that there are no significant leaks and frictions.
The test tube size influences the top speed, but should not be a reason for the engine not to run. I would put more attention on the restrictor, the design was a little tricky a think.
thanks, Ill try degreasing the bearings, the piston does bounce like a shock absorber, and the restrictor is just as
the drawing dictates. Bogstandard, by fill do you mean the steel wool? I packed it in 8 cm long and located the flame at the intersection then secured the tube and then rotated the flywheel and piston to push the restrictor into position.
Sorry I can add anything in the way of help as I have no experience in this type of engine. I looks like the flywheel is as friction free as possible and that the damper is "springy" as others have noted. Watching the video I can certainly feel and sympathize with your frustration. I appreciate your sharing the "trials" of getting it to run and will be watching the thread for the comments and suggestions of others. I am sure someone here can provide the help you need so that the next video will be of it running!! Its a very nice looking little engine so hang in there.