ORIGINAL: rmh
I hope the OS works better than the other gassers we tried .
The basic problem in single cyl engines is an unbalance which is typically stuck at somewhere around 3000rpm
The ignition curve can be tailered to lessen this thump
We tried various motormounts which can help but it all adds up in more weight
If you want to use lighweight Carbon fiber fuselages - the problem can get worse as the lighter the fuselage the more resonance you encounter .
Wood done right soaks up various resonant stuf much better but you also have to fiddle with locations of formers and such to cancel low rpm nodes.
Hope you get a good workable combo- I used Ed Skorepa pipe and we finally threw in the towel as the electric could be built much lighter and power was more constant.
Actually the OS33GT works fine in 11 pound pattern planes. OS has done alot to get us torque where we need it. I do not lead the throttle at all with this engine as compared, say, to the SAP180. The SAP180 was not really close to the YS170..the OS is at least on par with it, now, after about 6 gallons
I saw a considerable "thump" at around 3K with the SAP180. I don't see that with the OS...much smoother output throughout the curve. And the rubber isolation mount works well on glass and carbon fuses. No need for heavy wood reinforcements/absorbers. One of these days I should take a movie so you guys can see what I see and hear. Also figured out how to build a nose ring around the hall sensor that works well. The soft mount and nose ring added around 5 ounces to the airframe....