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| Another version of how not to build a model engine |
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| NickG:
I think you need to find where the blowback is coming from and get to the route cause - there must be something leaking on the compression stroke for that to happen. I would try submerging the engine in water, turning it over past the compression cycle and look for the bubbles. Nick |
| sorveltaja:
Nick, most probable source of leak is the inlet valve, but as the engine has tight springy compression, leak must be quite minimal. But even that is enough to cause flowback. I guess that the air in the fuel hose "lives" between intake strokes. Don't know how to explain it, must be one of those hunch things :smart:. In the meantime, I have made primitive vapor carb: Upper brassy thing is simple air/fuel mix adjustment, and it is to be modified, as it's bit too touchy to adjust. The inlet tube goes below the fuel level, causing bubbles, as Jan Ridder's carb does. Then there is the spring loaded valve combo, that was mentioned earlier. With it, flowbacks are gone :ddb:. Even the short running tests have proved, that it works very well. Therefore, I strongly encourage to test that, if flowbacks occur. |
| NickG:
S, On Jans later version he stopped the inlet tube short of the petrol. Can't remember why :doh: but he said it improved matters! Good work, it only needs to be primitive to test the concept out. Does it solve your over rich mixture and sooting up problems? |
| sorveltaja:
Nick, the spark plug stays dry, and that hopefully makes it last longer, and keep the engine cleaner, than with recent carbs. I could even pass that ceramic rings -session ::). |
| sorveltaja:
I attached that spring loaded valve thing straight to engines inlet. But the engine ran poorly after that. So I went back to setup, that is shown in the previous picture. There is about 5cm(~2") hose between the valve and engine. Strange, but with that the engine runs much better :scratch:. But for example, on backpressure valves, that are used on gas welding equipment, the valves aren't attached to handle, are they? There is most certainly a piece of hose between handle and backpressure valves. Conclusion is, that backpressure valves require some matter, be it oxygen, acetylene or air, between them and the source to work. |
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