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| Jan Ridders' Simple LTD Stirling Engine - craynerd build log |
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| NickG:
Chris, This nearly always happens with Stirling engines and I've heard LTD are notoriously difficult to get to run. If you're confident of the seal between top and bottom plates I would start by taking the flywheel / frame assembly off, leave the the displacer piston rod in, submerge the displacement cylinder in water and blow into the power cylinder to see if any bubbles come from around the displacer piston rod. If it's a good seal there shouldn't be any, or very little. It sounded like the power piston was a good fit in its cylinder, does it move very very freely because it needs to. The displacer rod also needs to run very very freely in its guide. What is the clearance between the displacer piston and cylinder wall? You don't want any unnecessary drag caused by friction or too small a clearance. Finally, the crankshaft needs to be extremely free running. if you spin it over with nothing connected it should keep spinning for about 20 seconds. Hope this helps, I know how difficult it was trouble shooting my stirling and flame gulper but if you take a systematic approach you'll get there. Cheers Nick |
| raynerd:
Removed the bottom cover and re-balanced the system. I think I did this correctly yesterday dispite my concerns and so things haven`t changed at all. Now, call it impatience, I call it experimenting but I sealed the bottom plate on again and with the sealant still tacky, I put it on a hot plate. The sealant started to buldge out as the gas expanded inside the engine....does this tell me that the system is well sealed and also, more importantly that I have a good seal on the power piston and displacer bushing?!? What could be wrong ... :smart: |
| raynerd:
--- Quote from: NickG on August 11, 2010, 07:23:19 AM ---Chris, This nearly always happens with Stirling engines and I've heard LTD are notoriously difficult to get to run. If you're confident of the seal between top and bottom plates I would start by taking the flywheel / frame assembly off, leave the the displacer piston rod in, submerge the displacement cylinder in water and blow into the power cylinder to see if any bubbles come from around the displacer piston rod. If it's a good seal there shouldn't be any, or very little. It sounded like the power piston was a good fit in its cylinder, does it move very very freely because it needs to. The displacer rod also needs to run very very freely in its guide. What is the clearance between the displacer piston and cylinder wall? You don't want any unnecessary drag caused by friction or too small a clearance. Finally, the crankshaft needs to be extremely free running. if you spin it over with nothing connected it should keep spinning for about 20 seconds. Hope this helps, I know how difficult it was trouble shooting my stirling and flame gulper but if you take a systematic approach you'll get there. Cheers Nick --- End quote --- Hi Nick Thanks for the reply, we were typing at the same time! But if you look at my last response you`ll see I`ve ensured the system is balanced and I think you`ll see from the video that the crank seems to be freely moving. I`m happy with everything... I`ll have a bit more of a play once the sealant has gone off again. My main concern, and perhaps I should have changed it just now when I had the bottom plate off, but the displacer piston has a gap of about 1mm - 1.5mm. I know this is uneven but it is due to the foam board not cutting quite as clean as hoped in the end. Perhaps the 1.5mm gap is too large. The plans do state balsa wood but I know foam board is used. The plans also call for only 5mm thick balsa and this is quite thin, I know most stirlings take up a lot more of the displacer cylinders volume up with the piston itself!! Perhaps if after a little more fiddling I can`t get this to run, I`ll turn to the displacer cylinder and change that. Thanks for the support and advice..I appreciate it! |
| Brass_Machine:
Chris I have no advice as I haven't built a LTD Sterling (yet!). Keep plugging at it though... you are bound to get it. Eric |
| Dean W:
Chris, here's my take on your first video; I think it's making a little power. When you rotate it CCW, it seems to try to make a little go of it. When you rotate it CW, it appears that the engine doesn't want to go that way, and just from looking at it, seems to be making power enough to try to "push back" when turned the wrong direction. When the glue dries, try it again. Use a little more heat to see if it will make even a bit of a show at working. If it does, you probably just have some tuning work to do in the area of the crank bearings and alignment of the crank journals, and in tracking down friction in the power piston and the displacer bushing. It may have been my imagination, but I think I heard a squeak a couple of time when you were spinning it. Squeaks are a pretty sure sign of friction on some point. Sometimes it just takes a while to sort these out. The first one I made took me many hours to get running, mainly because I didn't know "how much is too much" when it came to friction. The last one I built started on the first flip. You'll figure it out! Keep at it. (BTW, the balance looks quite good.) Dean |
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