They's a hole in the piston, dear Liza, dear Liza

LAST EDITED ON Mar-12-04 AT 11:09 PM (CDT)
 
With all the fiddlin I was doing to the Cox engines last week, I put one of my FF Helicopter engines in and ran it for a bit. All seemed to be working well, for several flights anyways. But then they went South Tuesday night before the club meeting. Barely getting enough power out of the motor to fly the Viper in dead calm. Today, I swapped the motor back to the original that I had reseated the ball on and done all the other mods too. At least it's flying. But while I was doing all this, I built one of the all Coro Manwing trainers and put my Norvel .061 AME on the nose of it. Running it up to make sure everything was alright I was a little startled when the prop came up to 24.5! All this fiddlin with the Coxes and I was only getting 15.5 max and here all I did was bolt on the Norvel. I swapped back to a Big Mig when I found out that just about any manuever made me go lean and flying inverted was dead rich.

Anyways, I just tore down the Helo engine and guess what I found? A big ole hole on the top of the Ball socket. Guess I didn't get this one reset in time. Or maybe I did and about a half dozen good runs later it was time to tear down and do again?

I find a way to graft this BigMIg in and these Cxes can join the Fox hurl! Can't get a picture on this small an object without sunlight. First time I've seen the hole though.

LAST EDITED ON Mar-13-04 AT 00:35 AM (CDT)
 
I've had the piston skirt come loose from the middle part of the piston crown on Tee Dees before, though... I didn't think it was possible to run a reed valve engine hard enough to do this to it.

I've never run one hard enough to worry about it, including TeeDees. Then again I've never run TeeDees on a Bladder so I've never been up to the RPM's you Combat guys use.

Too much load on the prop, a bad crimp in the seat from the beginning or just a bad piston from the get go. I was wondering why the exhaust was all black and the power was terrible.

I put together about 5 engines out of the parts box last night, I'll be flying the product engine on it now till that gives way then I'll put one on that has a TeeDee .051 assembly on it. The plane flies pretty good, but could use a couple thousand more RPM.

I too have blown a hole in the top of the piston of a (weak) Cox. Performance or RPM's have nothing to do with it. Apparently this is what happens when the rod gets loose enough, hence the need for the "resetting" tool, which by the way I don't have and could use if any of you have a spare (whew, what a sentence).
--Ray

Go to RCUniverse.com and get into the 1/2A forum. There's a guy there that makes them for .010's to the .15's Just go there and ask to buy one.

Thanks.

LAST EDITED ON Mar-13-04 AT 07:31 PM (CDT)
 
The gentleman's name is Andrew Coholic. He was selling them for $15. Try this email address - "[email protected]".

One of the Tee Dees of mine that this happened to wasn't run at high RPM. I did use a bladder, but with the standard venturi. What I did do was use it on the nose of a 2 meter RC glider, and ran it for 15 minutes at a time (big bladder tank in the fuselage bay under the wing).

Wow, it is a good thing his name isn't Alan or Albert!