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silent beauty muffler mounting bracket problems

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silent beauty muffler mounting bracket problems

Old 08-12-2009, 03:35 PM
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Cambo
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Default silent beauty muffler mounting bracket problems

so i tried to follow the instructions provided by TBM and make a bracket to help support the silent beauty pitss (50cc) muffler. Well, the bracket was easy, and bolting it to the plane was even easier. However, i have had terrible luck getting the bolt to stay in the muffler. I tried tapping the muffler. Well it started as a 2mm and eventually became a 4mm. After the 4mm stripped i tried a self tapping screw. That lasted 1 flight. I don't think there is enough material to support a srew. What is the solution here. Do i ultimately need to go get it welded?
Cameron
Old 08-12-2009, 04:00 PM
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Bob Pastorello
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Default RE: silent beauty muffler mounting bracket problems

Unfortunately, you probably DO. I have purchased, and actually had success, with a product called "alumaweld" brazing rods. Took some practice to learn how to make it truly flow and bond, but after I got it worked out, I was able to braze on an aluminum washer to the thin metal, then drill and tap that whole thing. Much better.
The other thing is to be absolutely certain that the muffler is bolted into final position on the engine, and then the bracket is mounted in such a way as there is NO torsional or tensile stresses on the bracket. THAT will solve the stressing of the attachment point. One other issue is to be sure the strap/attachment itself is of rigid enough material so that it is NOT flexing under dynamic twisting force from the engine. The idea is to make the box, strap, muffler, and engine a single "unit" of mass that moves as a "single unit". Stuff won't break when those considerations are made.

The whole strapping mufflers and headers and canisters issue is more art than science, and I think more frequently "luck" than "skill", honestly.

Don't give up on it! I'd get some of that aluminum rod stuff and learn something new!! It can be fun to learn your own fixes for stuff, if you're inclined.
Old 08-12-2009, 04:04 PM
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Default RE: silent beauty muffler mounting bracket problems

I had the same problem with the Silent muffler. I just drilled and tapped it a size bigger so I had some good threads and then used JB Weld to attach the braket to the muffler and then put some more JB on the screw. So far its holding great.
Old 08-12-2009, 04:06 PM
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Default RE: silent beauty muffler mounting bracket problems

Hmm
I don't have brazing equipment, yet. I guess i could look into getting some.

I was carefull to bolt the muffler first, then make the bracket, then bolt them together so there were no awkward stresses.
Old 08-12-2009, 04:29 PM
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Default RE: silent beauty muffler mounting bracket problems

The aluminum brazing stuff I use only requires a standard propane household torch. Nothing fancy, I'm too lazy and tight to go further. For me, it has to be cheap and easy, or I won't play. Learning to do my own thing with that rod meets both of my prime directives....

Sorry you're fighting that stuff; it sucks.
Old 08-12-2009, 07:21 PM
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Default RE: silent beauty muffler mounting bracket problems

Time for round two
I decided to do a new bracket that was about 1/2inch longer. Used a hammer and vise grip to once again get the dimensions as close as possible. Once done, i used three self tapping screws with allen heads. This allowed me to essentially drill a whole a little to small for the screw so i could get maximum thread contact. A phillips screw wouldn't even go in. Hopefully this will work. It is on there really tight.

Cameron
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Old 08-13-2009, 09:40 AM
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Default RE: silent beauty muffler mounting bracket problems

I prefer to run my bracing strap back up to one of the engine mounting 'ears', or even one of the cylinder mounting bolts, whichever is more convenient, especially when the engine is standing on long legs. There is more vibration than you think, due to using aluminum standoffs, and I feel you'd be better off having the muffler support moving right along with the engine rather than splitting the support between the engine and the frame. If you were using hardwood standoffs, with a couple sides boxed in....I wouldn't worry about your method as much.
Old 08-13-2009, 11:54 AM
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Default RE: silent beauty muffler mounting bracket problems

cambo;
What you could do, instead of brazing a washer onto the end of the muffler is this: You already have a hole drilled thru one end. Drill another on in the opposite side and get a 6-32 Althread (or also called threaded rod) and two nuts. But a big washer under the other nut opposite from the bracket and secure the muffler with this rod going thru it. Secure the nuts with red Loctite and you'r good to go.
Old 08-13-2009, 01:23 PM
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Default RE: silent beauty muffler mounting bracket problems

I made my strap and pop-riveted it to the muffler and used a 4-40 allen for the firewall. A lot less complicated than all the drilling and tapping. I tried that first and there isn't enough metal to cut threads. You could rivet it then use aluminum solder to really make it super solid.
Old 08-13-2009, 04:54 PM
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Cambo
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Default RE: silent beauty muffler mounting bracket problems

Hi all
I squeezed in 40 minutes this morning. So far it is holding. I think i will go with the threaded rod technique if this comes loose
Cameron
Old 08-13-2009, 09:52 PM
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ec121
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Default RE: silent beauty muffler mounting bracket problems

I forgot to add that I sealed the holes with that copper colored hi-temp silicone during the final assy. Should also work for the 6-32 method. Keeps things a little cleaner.
Old 08-14-2009, 01:51 PM
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Cambo
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Default RE: silent beauty muffler mounting bracket problems

ec121, i also used silicon to seal around the bracket
The new mount has about 2 hours on it so far and it is still holding. Got out to the field early and did 1.5 hours of flying.
Cameron
Old 08-15-2009, 01:37 AM
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Default RE: silent beauty muffler mounting bracket problems

cambo, aerobatx is 100% correct.you must mount the muffler strap to the engine not the firewall as seen in your photo.that will solve your problem.

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