I have a Tower .46 engine and have a problem with the long muffler screw. I wanted to find out if anyone else is having the problem detailed below.

I am a fastener engineer and in my opinion, the design is faulty in that the two recessed shoulders (on the front and rear castings) the center tube fits over are too small and provide minimal support. The long screw then takes all the stress in both a stretching and rocking motion due to movement from the long muffler. The screw shank fatigues just under the head, then breaks off and the muffler is lost.

I have had my first muffler tube and rear casting lost due to the screw breaking under the head.
Tower Hobbies replaced the muffler under warranty. I used permanent thread lock on the new muffler threads, both the screw and the lock nut, and installed the new muffler. After 5 flights, the rear of the muffler was turnng, but not because the threads loosened, but because the muffler screw is stretching from fatigue. I worked very hard to remove the locknuts and rear muffler casting. The shank under the head was discolored and showed evidence of stretching: It will fail again.

My solution is to use an oversized "case hardened" screw (the stock screw does not appear to be case hardened), or hardened "All-Thread" with a locknut on each end, and JB Weld the three muffler pieces together to make the unit solid.

Is there anyone else having this problem?

Regards,