need help finding coupling
 

Hi all,

I'm converting a Ryobi 25cc engine. The crankshaft has a metric 8m x 1.00 pitch thread. I would like to use a rod coupling with that thread size, but I can't find one anywhere.

There are plenty of 8m x 1.25 pitch, but that won't work. Am I going to have to have a custom one made?

Thanks
Tom

The 1.0 pitch is a bit of an oddball. Much more common is the 1.25. 8mm is within thousandths of an inch of being 5/16". Could you buy a 1/4" coupler and drill it out to 8mm and then tap to 1.0 thread?

AV8TOR

AV8TOR, Thanks for the reply. I was beginning to think no one knew what I was talking about!

I may have to....

1. Buy a 8mm x 1.00 pitch tap and try to tap out a 1/4" coupler, but the 1/4" couplers are very small.

2. Or just use the coupler that came on the shaft. The problem with the original coupler (which is actually a coupler with a 8mm x 1.25 pitch stud on one end) is that it is just long enough to get a prop on, but with only enough thread to get on one nut in front of the prop. I have actually run it this way on a test stand but I'm a little leary about the safety of the one nut.

I find it strange that I can find many 8mm x 1.00 hex bolts but can't find a coupling anywhere. Unfortunatly I don't have a metal lathe that I could just make what want.

Thanks

Tom

You mean a washer and one nut? Or just a nut? If you can get a fender washer on there along with a nut with full thread engagement on the nut, you're "golden". I don't even run double nuts on my giant engines....

AV8TOR

Yes, I can get a fender and a nut on. I usually add a jam nut or spinner nut after that. I was thinking of putting this engine on the front of a stick.

It's a 25.4 cc. What size stick would it work on? I'm thinking it would be to big for a 60 size and. Maybe a 90 size?

It depends on the brand of Stik. Great Planes Stiks have a generous wing area, and I have put 20 to 25cc engines on the .60 size numerous times with very good results. You may have to move the servos to the tail if your engine is heavy and/or it has a magneto.

I generally figure about a 1000 square inch wing to be about the minimum (plus or minus a bit) for gas engines.

AV8TOR