Hello,

I'm flying a GP Eagle II powered by a Zenoah G45 and a Bison Muffler. It run's great but after three flights the muffler keeps getting loose. It doesn't matter how tight I screw the two screws.
Is there any body who's having a fix for this problem?

Greetz

Thierry Brandjes

Great looking plane! I have one still in the box sitting in the spare bedroom.

Is your engine soft mounted or on some standoffs. I have seen a gasser that would shake its muffler right off because its mount allowed it to shake too much.
You could also try sealing the bolt threads w/hi-temp silicone. Clean the muffler bolts and exh port threads good first.
If that don't work, red lock-tite may. The red will release at a temp. of 500F according to the inst. on the package I have here.

Just drill through the bolt heads from the side ( assuming you have allen bolts) and thread some safety wire bhetween them.

Once you have done all the above,
The make a bracket for the muffleer and attach it the motor mount of the engine,
These mufflers can not be left unsupported, period.

Put in some extra long screws and put a steel tube between the head and muffler, that way you extend the screw when you tighten it and it would sit there better when it's hot because of the expansion.

Thanx for all the quick responses out there.

First of all, most of the suggestions will not apply, because simply the construction will not allow it.
I've attached a few pictures so you'll see. I will try the loc-tite stuff and wait for better weather to give it a try.
Strange that I didn't overcome this problem with my other muffler, only that one was made from Stainless Steel.
Maybe it has something to do with material and expansion with it.
By the way how hot will the muffler be at a regular aerobatic flight? And does it matter if I inject smoke, because I inject diesel.

Greetz

Thierry

A sharp engine guy I know suggested torquing the bolts down on a hot engine. That would enable the bolts to bite in further than if you torque them on a cold engine. To increase that effect, put a couple of spare bolts in your cooler, in a plastic bag but in contact with ice. Have a little teflon pipe joint compound wiped onto the threads, to make the last quarter turn a bit deeper. Run the engine up to heat (without muffler if possible), shut it down, quickly remove the muffler if necessary, re-mount using the chilled tefloned screws, torque them as tight as you can by hand with an ell wrench, and I'll bet you'll have no more problem.

I used high temp red loctite (272 I believe) on my Brison 2.4 with BCM wraparound muffler. Had about two hours of run time when a dorked landing spread the gear and cracked the pipes. Upon trying to remove the muffler, I had to use a heat gun and a micro butane torch to get the muffler bolts out. The regular red loctite(262) is good only to 300 degrees. The 272 is good to 450 degrees.

Marty

OK
1) since the bolts are steel there is a different affect of expansion rate between the aluminum and the bolts.
2) since the muffler has already come loose that indicates the threads in the head have been worn.
3) try the red stuff, but you have to tie the muffler down.
4) Use GREEN locktite
last resort heli arc the holes closed, redrill and tap.
Good luck

I'll reiterate. You simply need to drill a hole in the head of the bolt and safety wire it.

Most everyone I know does this.

Here's a link to a thread that discusses the way to do this...... There's really no other way to reliably keep those bolts tight!


http://www.rcuniverse.com/forum/m_27...tm.htm#2743372

Branded,
The bolt heads on that muffler are recessed about an inch into the muffler. How would you safety wire them together? I suppose you could use a longer bolt and large washers to keep the head outside of the recess but now you have a lot of the bolt sitting in free space which may cause more problems. I had these same problems until I used the high temp red loctite. The regular red would loosen up after the first engine run. Safety wiring the bolts will save you from losing your bolts and muffler but the bolts will be able to loosen a small amount sometimes even with the wire.

There's no room in the cavity for wire?

No