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| madjackghengis:
Well Nick, that's what you get for posting a u-tube of tiny stirlings on your thread :poke: I spent almost an hour yesterday just looking at all the different tiny engines and wondering why I am planning on getting rid of any scrap at all. With all your cylinders showing no compression you either have a problem with the gauge and or its connection with the cylinders, which should be audible when cranking over, or you probably have a blown head gasket, which, with all cylinders affected, should also be audible when cranking. Unless you've got a very new vehicle which has valve controls I've never seen, even a timing belt or chain would leave at least one cylinder with the valves closed, and thus get compression. Kind of wish you were in my neighborhood, at least I could confirm your diagnosis. Hope things work out better for you, and know the level of inspiration you have raised with that tiny stirling, and the not quite as tiny flame sucker, which is absolutely stupendous. I'm also very taken with the tiny stirling set on the oak thumbnail, which runs so well and looks so perfect in all its glory, even when not running. :bugeye: :jaw: It might be time to work on a stirling powered vehicle, for reliability. :lol: mad jack |
| NickG:
Madjack, you make a good point there about scrap! Until I made my flame gulper, I'd only ever used scrap bits of metal to make my engines. For the flame gulper though I was fed up of hunting around for bits and I knew I didn't have any cast iron so just took the opportunity to buy all the bits I needed whilst there. It was a bit of a revelation for me as I found rather than struggling on, all the material I bought machined beautifully! So horses for courses I guess. For the tiny stirling I will be using scrap again! The engine on the Renault Clio is the 2.0 16v 172bhp - it has variable valve timing which I'm not that familiar with, apparently it could be something to do with that vvt pulley. I'm going to borrow another compression tester but I fear the worst, I put my hand over one of the spark plug holes and cranked - there was nothing! I'm at a loss trying to explain what's happened at the moment. I don't think it's head gasket as there is literally no compression and there is no oil in the water or vice versa. As you say, it should be audible when cranking but again, nothing! I'm with you on the cam belt - at least one of the cylinders would have both valves closed at some point and hence get compression. The only explanation I can come up with is that the at least 1 valve on each cylinder has stuck open - possibly being bent but then you would have thought I'd hear something metallic. I won't be able to confirm this until I get at least the rocker cover off though. Will see what the proper compression tester reveals and go from there! :lol: I actually hate cars at the moment! Nick |
| picclock:
Hi in your first post you stated : 'I did calculations to ensure the ratio of swept volumes between displacer piston and power piston are almost the same - this is quite important as it largely governs the temperature difference the engine can run on, of course there are a lot of other factors but I think this engine should work' If my understanding is right, this will result in a non running engine (its quite possible that I am incorrect as I have only recently started researching these). So please don't take offence. These engines work on the expansion of air caused by increase of temperature. If the volume is fixed that's about 1 psi for every 5C. To return to normal atmospheric pressure the air will expand 1 / 273rd of its volume, so for 5C that would be around 2%. For a coffee cup or LTD a reasonable differential would be 30C, with an expansion of 11% to normal atmospheric pressure. This would mean that the displacer volume / power piston ratio should be 89 - 11 or around 8 to 1. If the displacer volume is larger, heat will be lost without doing work (no big deal), however if the ratio is the smaller then the energy produced will be lost as the piston works against the atmospheric pressure, overexpanding the gas. As I said earlier, I am still coming to an understanding of these engines so feel free to tell me where I am wrong, I certainly will not be offended. Best Regards picclock |
| BillTodd:
--- Quote ---These engines work on the expansion of air caused by increase of temperature. If the volume is fixed that's about 1 psi for every 5C. To return to normal atmospheric pressure the air will expand 1 / 273rd of its volume, so for 5C that would be around 2%. For a coffee cup or LTD a reasonable differential would be 30C, with an expansion of 11% to normal atmospheric pressure. This would mean that the displacer volume / power piston ratio should be 89 - 11 or around 8 to 1. --- End quote --- Interesting stuff :D Anyone know if using a scotch yoke on the displacer would help? My thinking here is that the yoke could provide additional dwell at the top/bottom centre of the displacer movement. Bill |
| picclock:
Hi Bill Thats what my post in the design section, vertical shaft LTD was about. Its not as elegent as a scotch yoke, but would have lower friction and less load. Regards picclock |
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