Two questions; Cox .049/051 con rod & Fox .35 stuffer backplates.

[Phil Hawkins]

Have any of you's guys replaced the connecting rod on a Cox 049/051 piston? Of course I imagine some of you are asking "Why???" Well only because I snapped the rod on an .051 piston and have a few extra .049's laying around. So basically Ihave nothing to lose. Any help or ideas would be great! I am thinking glowing red heat, a firm yank and have the replacement rod ready to pop back in. The question is how to not completely distort the piston. 
Second: is there any source available for Fox .35 stuffer plates? I have probably 6 engines that would benefit from it.

[Dan McEntee]

Have any of you's guys replaced the connecting rod on a Cox 049/051 piston? Of course I imagine some of you are asking "Why???" Well only because I snapped the rod on an .051 piston and have a few extra .049's laying around. So basically Ihave nothing to lose. Any help or ideas would be great! I am thinking glowing red heat, a firm yank and have the replacement rod ready to pop back in. The question is how to not completely distort the piston. 
Second: is there any source available for Fox .35 stuffer plates? I have probably 6 engines that would benefit from it.

   I would have my doubts about replacing the rod in a Cox .049/.051. Anything is worth a try to see if it can be done. I think you are on the right track with distorting the piston. I would take a piece of 1/4" plywood and dill a hole big enough for the rod end to pass through, and the piston skirt will sit nice and flat against the other side. Heat the piston as slow as you can and when ready, put the rod through the hole, grab what you can and give it a yank. You are exploring uncharted territory here, so keep us posted on results. I think Cox piston/liner fits were down in the 4 o r 5 decimal places for clearances?  That is what you are facing.
   I don't know of anyone making the Fox stuffer back plates. using a business card as a gasket will get a stock one in closer. try and measure the clearance from the rod pin to the back plate and see if you can get some Teflon sheet that is a fuzz thinner, and attach it with a rivet right in the middle so the crank pin rotates around it. Seal the rivet on the outside with some JB-Weld. That will get you the same effect with not too much work. If you know anyone that does ceramic coating, it may be possible to coat the surface with enough material to get the gap minimal and still be slick enough for the rod/crank p in  to run against it occasionally.
    Just my 2-cents,
    Dan McEntee

[Motorman]

I've never heard of anyone that replaced the rod on a Cox. Those pistons are tempered, I wouldn't use heat on them. You would need a special size tubing to go up in the piston to put support closest to the ball joint or I believe you'd collapse the top of the piston. The pulling force needed would be in the slap hammer realm.

Also, getting a good rod out of a piston would be a trick. The crank end is very prone to splitting if you pull on it. If you use enough heat to make the pull easy, you'll take the temper out of the piston sides and probably the top of the rod too. Maybe you could cut the piston in half with a cut off wheel if you're careful.

Seems an impossible task.

Motorman

[Larry Wong]

Cox rod can be changed with a special rod set tool ...

[Dave Hull]

Care to share your experience on successfully removing a rod from a piston, Larry?

I have never tried this before, and don't see a sure-fire way to do it off the top of my head. The .049 parts are easy to find. I don't have any .051's, but those parts may be (much?) harder to come by....

Dave

[kenneth cook]

             I would contact Matt from EX Model Engines. I believe he has a tool that can do what your asking. I think it is the tool that Cox used. He may even have rods that were not assembled. He responds quickly to e-mail.

[Larry Renger]

I never heard of a rod removal tool. 10 years at Cox.

However the rod socket is not hardened.  The copper plate keeps the Nitride process at bay. I If I were to try this, I would machine a close fitting Aluminum collar to act as a shape holder and heat sink for the piston wall. Thenq direct a pencil flame onto the rod socket to soften it, then do the pull.

Simpler to find a new piston on e-bay or just use an 049 setup as there is no power difference. That groove in the 051 piston bleeds enough mix to make the sizes match in power. This was on purpose so free-flight models could be flown in 1/2/A or A class with no trim change.

[Phil Hawkins]

Thank you gentlemen!
I have pretty much decided to abandon the idea and chalking it up to a lesson learned (remove piston before attempting to replace the prop drive) and will eventually pick up a replacement piston assembly.  I have more than enough unfinished airplanes to occupy my time and will focus my efforts there! It would be worth an email to EX so eventually I will, I will let everyone know what I find out.
Thanks again! Tight lines!

[Phil Hawkins]

Larry Renger:
I just recently read that truth about the .051. I guess the only advantage for me would be that I feel pretty confident that I will be getting the tapered cylinder. Thank you for your insights!

[Motorman]

Phil, I have a box of Cox pistons. If you want to send me the sleeve I could see if I have a fit.

[Phil Hawkins]

Phil, I have a box of Cox pistons. If you want to send me the sleeve I could see if I have a fit.

That would would be great! I have a few things I need to ship out this week, so if I actually get to it, I will send the piston and sleeve. Thank you!