ORIGINAL: Micropuller
Hello Pe,
I must say that the 116 is very tempting. The power is good, the looks are good (I like the carburettor on the back of the engine, instead of it towering above the crankase), if what you say about the plug caps can be done, the dimensions are also OK. It's just the weight that I'm worried about. Do you think it would be possible to put the engine on a bit of a diet, without damaging it's structural integrity?
For your application, the engine diet could mean removing most of the cooling fins, and other metal stuff that is not needed for the very short power burst that is asked for (form follows function) . A weight loss of 20%, if cleverly approached maybe? The approach is much like drag racing. Get the engine up to temperature, ask for a power burst, and before the engine gets into the distress zone, shut it down. The total engine mass that can absorb and conduct heat is of very little importance here. Even if cylinder temperatures reach 200C at the end of a run, the oil inside still needs time to evaporate, which time is not available, so your engine will not be subjected to marginal lubrication. The crankcase will stay quite cool because time to conduct cylinder heat also is not available, so the main bearings will need little lubrication. The reed induction will help tractability quite a lot.
The spark plug caps, if removed may provide extra radio interference, but since you never are far away with your transmitter that wil hopefully not play a large role in RC control over your puller.