Hi,

My first gas engine was completed yesterday by a friend in my club. Its a 52cc conversion engine. [link=http://duropower.com/item.asp?PID=86&FID=3&level=1]http://duropower.com/item.asp?PID=86&FID=3&level=1[/link] (they went up on their price by $40 since I bought it). What I was wondering is, how many pounds of thrust can this engine produce? When it was on the test stand it turned an old 20x10 Dynathrust prop at 9600 rpm.

I'm basicly going to desing and build a Biplane around this engine. I want it to be capable of performing basic 3D manuevers. What should target weight be? I'm thinking 72" wingspan and aiming for 20-24lbs. Will this be enough engine or should I scale down the plane?

Heres some pictures and video of the engine.

[link=http://video.google.com/videoplay?docid=7063498753981003477]Running[/link]
[link=http://video.google.com/videoplay?docid=1899399485091143431]Starting[/link]

Thanks for reading

EDIT: The muffler has been modified since the pictures...the new version is in the videos

You better aim for 12 to 15 lbs.
At 20 lbs. it'll putter the bipe around at scale speed, but if you want a two wing helicopter, you'll need closer to 80 or 100cc.

My the 20-24 lbs included the 6lbs this engine weighs. When you say 12-15 you're talking about the weight of the airframe alone or ready to fly? Sorry if I seem a bit slow.... but I've never messed with anything over a .61 glow .

That's with the engine. If you'd forget about 3D, you still should aim for 15 to 18 lbs to fly with some reserve power.

Well, heres the next question... Could I build a 68-72" wingspan profile biplane somewhere around 14lbs? Or am I dreaming?

My first weight estimate (when I first started designing) was 16lbs...That got me some doubtful looks at the field. A couple of them think it would come out around 25lbs. I think it can be done for much less, but then again thats probably inexperiance talking.

I'm thinking its not out of the realm of posibility...I'm afraid it would just wind up to fragile.

After todays game, I should have told you the 20 lb combo would hover like a hummingbird and pull vertical like a rocket.
I've had a 50cc conversion (at least 6 lbs) like your's in a 1/4 scale Extra. It flew very heavy and didn't have much vertical. Been that route. The 50cc engines with mucho grunt like the DA, 3W or ZDZ have small lite-weight crank cases and electric spark in place of the heavy magneto system.

ArmedZagi:

Just a note of caution. Better be careful with that Dynathrust prop. That's in the size range noted for throwing blades.

If I were you, I'd get another prop fast. Better to be safe than sorry.

No worries...That prop was just for testing..I have NO intentions of flying with it.