silicon for muffler?

[gcedillo]

Hi , after yesterday flight my tower hobbies .46 muffler loosened its middle section, someone recommended me to use silicon and retighten but I have my doubts since the muffler gets hot and is constantly exposed to fuel.
What should I do, just tighten or try the silicon ?

[ivanc]

A loooong bolt comes from the front of the muffler and screws in to the back piece. Then a lock nut screws into the bolt.
Take the lock nut out. Unscrew the bolt from the back piece and remove the back piece. Do not take the bolt out of the front piece and keep the middle part in place. Put 2-3 drops of threadlocker (I'm using the red one not the blue, so I can eventually disassemble it which might be hard if using the strong - blue - threadlocker). Screw the back piece in place. Adjust the exit of the back piece so it blows the exaust in the desired direction - away from the fuse and up/down (depending on the wong configuration of your plane) from the wing. Tighten the bolt. Put another 2-3 drops of the threadlocker and screw the lock nut onto the bolt. Now a third hand will be very helpful: While keeping the bolt tight to the back piece (one hand on the center part and back piece, another on the screwdriver at the bolt head) tighten the lock nut (third hand on the wrench at the lock nut) WITHOUT untightening the bolt from the back muffler piece - this is the tricky part. If not doing it right you will unscrew the bolt a little from the back piece while tightening the lock nut into it thus loosening the center part of the muffler. No silicon involved.

[Bako]

I have idea too. tighten this loong bolt. then drop CA on both sides. 1 drop is enough. I made such thing with my os40LA and it newer loosened.

[DaveSawers]

If the joint is leaking and if you never intend to take the muffler apart (Why would you?) then use high temperatue epoxy on the joint and either threadlock or epoxy the bolt in place too.

[Lorddrek]

I think whoever mentioned that trick to you was thinking of hi temp gasket making silicon for use on automotive engines so heat won't be a problem and I doubt nitro would be either.

D

[BuzzBomber]

FWIW, I used hi-temp (red) gasket silicone to seal the fuel line outlet on my engine test stand's fuel tank. After 20 minutes of runtime(2 tankfulls) I noticed the remaining fuel was redder than before(dissolved sealant) and a lot of the sealant fillet around the joint was gone :eek:. I just hope that garbage doesn't gum up my new Saito! Cure time is not at issue--it had several weeks to cure before being used. Curiously, sealant from the same tube has held up for over a year used in the carb throat and exhaust flange of another motor--perhaps it only deteriorates from exposure to raw liquid fuel? BTW, I too would suggest trying the threadlocker before anything else.

[Joe Ford]

or if you want a permanent connection, go with JB weld

[gcedillo]

Thank you guys I`ll try the threadlocker!

Happy flights. :)

[mikenlapaz]

the subject was exhaust(muffler) where the problem is mainly heat and vibration. Heat is used to remove/soften theadlockers. RTV (red) silicon is designed and used for many applications for high heat. I'd use some and a nylock nut it applicable.

[ivanc]

I've tried the nylon lock nut - it becomes a regular nut after the first flight. I have TH.40, TH.46, TH.75 and GMS.32 (same manufacturer on the last 3 ones?). The procedure described above by me worked 100% on the engines. I think that the key is the proper tightening (or to be precise being careful not to untighten it while tightening the lock nut) of the bolt and the lock nut. I put red threadlocker on every screw/bolt/nut (metal-to-metal only) just as a precaution. I started doing this after a screw on the elevator servo pushrod connector got loose on a SuperStar EP (on the ground - am I lucky or what).

[rkramer]

jbweld is sometimes pretty useless on exhausts, it will tend to let loose if you have enough heat.

instead, go get yourself a foot of threaded 6x32 rod. drill out the holes in the ends of the exhaust enough to allow this to pass through, and then just put locknuts on each end. it won't come loose again!

[LostMyPlane]

I agree with rkramer.

I had the worst time with a muffler once. tried threadlocker, ca, epoxy ect. finally took my muffler to a hardware store found some threaded rod that would fit my muffler. I then used a locknut, a nut and then a wing nut. the wing nut lets me take everything apart easy, yet tightens easy with just a pair of pliers.