Cox .049 question

Someone told me I should check this... Anyone know how much play the Cox .049 is supose to have in the rod-piston ball joint? I have 3 piston assemblies two used and one new. They all 3 have some play and they seem pretty close to the same. My inacurate calipers shows about .03 on the new piston and this seems like alot...

Bob:

My understanding from our local "Mr. Cox" Bill Osborne is that it should have no play. I have had him tighten up a couple with his handy dandy tool and he sets them with no slop but also not tight.

Cary

That Is how I have tightened all of the ones I have done. I tap the setter untill there is almost no slop but the joint is still loose enough so there is no drag. lOOSE SLIP FIT.

I've got a piston joint resetting tool buried around here somewhere. You're welcome to try it out. I've only used it once and due to inexperince or just horribly worn parts I couldn't seem to make much improvement with it.

Thanks,

Planning on flying Wednesday evening, bring it to the field if you find it..

If you use the tool at the field be warned that the surface that the piston is placed on must be rigid and flat. If either of these are not met the piston will deform.

Naw, I was going to borrow it and take it to my shop, I would never take an engine that far apart at the field unless a trophy was on the line...

.03 sounds about right. If the thing runs backwards way tooo often, it may be too loose. I dont know why ,but that seems to be the limit. If the TDC has a clik/clik as it goes by, tighten it up a tad. Conrete floor with with a block of wood. Some BN ones come way loose, go figure. OF course a little bit of Castor goo keeps em running . 03, MM

I concur..I agree with you Steve..that is exactly how I fit the
ball socket joint..I flew a lot of 1/2a combat, and I propped
the T.D's to turn at least 24+K on the ground..this required
the ball joint be checked after each day's flying..I still broke
3 pistons(joint failure) maintaining these checks......
By the way Steve.. I regret giving up combat flying because I
really wanted to build one(or more?) of your "Sickle" designs..
Bare(Barry B.)gave me plans(the FAI Sickle)..shrunk down to
200sq".....I prefer the foam LE and built-up wing construction
for combat..It's a great weight saver...sorry about the tangital
off-topic foray Guys...Tony