No, I installed a 2.17 RD-1B in Dec. 2004. Now it's a 62" prop/6400 engine rpm, used to be 38" fan/5400 RPM.

 

I presume a Buttercup is a tractor design? I can't see direct-drive working in a rotary except in a ducted fan, because the engine just doesn't develop enough power at 3000 RPM. Maybe with PPorts and supercharger, and aluminum side housings to reduce weight?

 

>Perry are you still using direct drive? What max RPM are you or >were you using, what prop, etc. A friend who is building a >Buttercup (Steve Whitman design) that only needs 100/125 hp. 13B >with redrive is too heavy but without a drive it is a >possibility. Jerry