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| Another version of how not to build a model engine |
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| Darren:
Forget the radius, far too fine a pitch to manage that I would have thought. In essence you don't need to worry about exact angles and stuff because you will make both the male and female parts from the same cutting tool :thumbup: |
| sorveltaja:
Another thing popped to my mind. There is noticeable difference between the glow engine needle system, and the one I made. The former doesn't have its needle going across the carb throat. Thus allowing smaller throat size. When using the latter with same throat size, needle itself restricts the air flow. So I drilled the throat to 1.9 mm size, and the engine starts easier with that. Engine flooding is also reduced greatly. |
| NickG:
Was just thinking, have you considered making it glow ignition? It might be easier to trouble shoot carb problems if you have reliable ignition initially? Just a thought. Nick |
| sorveltaja:
The ignition seems to work, as the engine did just run at a horribly fast speed. I thought it was going to explode :borg:. To tame it, I'll add an air shutter to the throat. Glow ignition would be simpler, but it wouldn't allow low rpm. |
| sorveltaja:
--- Quote from: NickG on November 07, 2009, 05:38:49 AM ---Is a compression ratio of 3:1 high enough? Nick --- End quote --- The approximation, that I presented about the compression ratio, is based to my own calculations, and has proven to be somewhat misleading. The math really isn't my strongest virtue :smart:. The engine behaves like it had something like 8:1-10:1 comp ratio on it, regarding the speed it has run. Next time I'm going to warm up the tachometer to get some readings. |
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