200HP 4 cylinder 2-stroke Martin engine - 132 lbs!

rv8ch · #1 07-31-2008, 02:02 AM

Check this out:

I think this time I'll wait until several dozen are flying before I jump in.

pierre smith · #2 07-31-2008, 05:11 AM

......as you know Mickey, 2 strokes do deliver very high horsepower per pound. A couple of caveats are :

1: The need for a PSRU....yawn...again
2: Fuel consumption is usually far worse than 4 strokes
3: Life expectancy/low hour TBO

Regards,

Ted RV8 · #3 07-31-2008, 10:34 AM

Two strokes are great and can make alot of horsepower per pound.

As Pierre mentioned there are drawbacks. The biggest one to me is what I call the stick factor.

You see a two stoke does as the name implies, it fires on every second stroke as the piston nears TDC. Great for power, bad for emissions and fuel economy unless you go direct injection. Also bad is the piston has minimal time for cool down so the tend to build alot of heat. As they build heat the piston looses it's heat treat(strength) and goes soft. Once it goes soft it can't hold dimensional stability and looses it's shape. Then as clearances diminish the stick factor come in!

Piston seizure is the most common failure in a two stroke. Not that big a deal for a motorcycle, if your quick enough to pull in the clutch. A boat you just drift to a stop. Neither are nearly as life threatening as in an airplane.

If the prop stops spinning your coming down, it's that gravity thing. If it's locked up you've got the locked prop trying to autogyro the airplane.

I've built two strokes for a long time. Know them well. That's why I would never put one on an airplane.

Ted