garywi

My Feedback: (3)

I have this muffler:

http://www2.towerhobbies.com/cgi-bin...?&I=LXVH43&P=0

It's the only one that fits the Tower .75, or I would have tossed it by now. It's a three part muffler that vibrates apart and leaks or pieces fall off the plane.

How can I stop the leaks and keep together? Should I JB Weld? High Temp Epoxy? Duct Tape??

Please share your secrets....

Thanks

AERORICH73

Ok Gary, but give me some idea of what you have tried already. No need for me to go over
what you have already tried, Ok.

Rich S.

Dr1Driver

JB Weld will work, provided the muffler is completely cleaned of oil. You can also take it to a machine shop and have them heli-arc it together.

Dr.1

garywi

My Feedback: (3)

I have tried two of these mufflers. The first I JB Weld'd, high temp version, the two seams. The vibration broke the one closest to the engine. My prop is balanced.

I ordered a new one. One seam was glued from the factory. I left this one alone. The other seam, towards the end of the muffler was not glued. I JBd this one. I put red lock-tight on both ends of the long screw. I ran the muffler, and the glued seam leaked, the bolt came loose.

Thanks

w8ye

My Feedback: (16)

I used a piece of threaded rod all the way through the muffler with double nuts front and rear

garywi

My Feedback: (3)

Threaded rod? Do you know what size? Also, how did you plug up the area where the phillips head went? Do you have leakage?

Ugo Ferrari

My Feedback: (1)

I lost this muffler due to engine vibration ! My spinner was not balanced and the vibration loosened the thru bolt nut and I lost everything not bolted to the engine... I JB'd the second muffler at the joints and it came loose, but stayed with the engine this time. I failed to remove the spinner til the second event ! Now I used a fiber lock nut on the end of the long rod and covered it and the front end Phillips head with Z-56 Canopy Cement to prevent the nut from turning. The muffler is still there after 30 or so flights. Vibration was the culprit in my case ! I still check it every time now !!
Ugo

dszabo2

My Feedback: (1)

I suggest you seal the three pieces together with Permatex ultra copper RTV. This will provide a good gasket and not corrode the aluminum. I would then replace the two nuts with nylok impregnated nuts. They will never loosen due to vibration. Locktite may work, but
could loosen due to the heat.


Dave

carrellh

Some people call it "all thread" and you can usually get it at hardware stores or specialty screw and nut stores. A 4-40 rod would probably work. Poke screws into the hole until you find one that fits. You might even need to drill the holes out slightly.



You don't plug an end. The rod runs all the way through and has nuts on both ends to hold it together. I'd use a silicone RTV sealant like Permatex on the seams and I'd use nylon insert lock nuts on the ends.

blw

My Feedback: (3)

Put some epoxy on the threads of the bolt before you tighten the halves. This also works for attaching the muffler to the engine. I haven't had any loosen after doing this, and you can always back out the nuts/bolts easily. It's fuelproof and seems to be temp proof.

rcuser004

My Feedback: (287)

I have a Tower .46 and have had the same problem. I lost the first muffler and was sent a second one under warranty. The problem is the
recessed flanges from each end are too short to support the long cylindrical muffler body, especially from the section that bolts to the engine. Because the muffler is long, the load (an up and down rocking motion) is placed entirely of the screw to hold the three pieces together. The up and down motion, combined with the stretching due to expansion and contraction, causes fatigue under the screw head. If you tighten the screw too much, it will be stretched with the muffler expansion from the heat. When it cools off, the muffler will be loose again and the screw will be re-tightened. This cycle repeats until the screw shank breaks from constant stretching and re-tightening, usually just under the screw head. In fact, if you remove the screw, you can see the fatigue marks on the shank, just under the head of the screw.

JB weld will not work to assemble the front section. The glue joint breaks NOT from vibration but from expanding and contracting when the muffler heats up and cools down. I was successful with JB Weld on the rear section, and RTV High Temp silicon on the front section and under the screw head. Tighten the screw to a snug fit only, then tighten the lock nut VERY tight on the end of the screw. If you overtighten
the screw, even with the RTV, it can still be stretched when the muffler expands from heat and will eventually break again.

Regards,

AERORICH73

Thanks for the great info. I purchase a Royal trainer which came with an Evolution Apha engine, and have the same kind of trouble with the muffler. Running the engine in on the test stand, the muffler started coming apart and I was not fast enough to shut it off before the end nut and lock washer blew away in the prop blast. Finding another nut and lock washer, I reassembled with blue locktite which kept the nut on during the next run, but everything came loose again. Your threaded rod repair sounds like a solid repair. Will have to track down some 4-40 threaded rod. Having worked on full size most of my career, did not use nylon lock nuts in high temp applications. I am surprised that they will take the muffler temp without failing. Learn something new every day.

Rich S.

65 Chevy

My Feedback: (1)

When New, I heat all three parts of the muffler with a propane torch to remove all oils from the parts. Then wipe the parts down inside and out with an Alcohol soaked paper towel as the parts cool to further insure that there is no OIL RESIDUE anywhere. Once the parts have cooled to room temp, I coat both ends is the Aluminum Cylinder with Permetex Ultra Copper which is highly recommended for Automotive Header applications. I then assemble all three parts, and wipe off any excess Sealant on the outside of the muffler. Then while the Ultra Copper is still curing, I place the muffler parts in a toaster oven on medium temp (350) for about 20 minutes. When removing the muffler (still hot), i lightly chuck the muffler in a bench vice, and tighten the nut on the back only a little more than snug and allow the whole assembly to cool. Then as a last step, I add a second nut to the end of the muffler bolt using RED locktite (High Temp). I believe the nut I used was a 2.5mm. The threads are just slightly different from the 4-40 bolt that runs through the muffler. The threads on the bolt do not deform from what I can see, but the threads on the 2.5mm nut do. This along with the red locktite keeps everything good and tite.

Be sure to have the muffler stinger in the position that you want it to stay in. It does not rotate very easily without complete disassembly. The whole thing can be disassembled if necessary after doing this, but you have to work at it. You can also reassemble the unit following this procedure even after the engine has been run a long time. The heating and alcohol cleaning procedure does a good job of removing the oil residue that is always present after running the engine.

Doing this also insures that you will have a good pressure seal to provide muffler pressure to the tank.

Allot of running problems that are sometimes associated with this engine can be attributed to poor muffler pressure to the tank.

I know that this sounds like a really involved process, but it works. I have three of these engines and since the first and second muffler had to be replaced after coming apart, A friend and I that also had the same problem came up with this and we have never had any sealing or stinger rotation since. Not to mention never had another Tower Muffler come apart again.

For what its worth

wcmorrison

My Feedback: (2)

I have used safety wire looped around both ends of the muffler to hold it together. I do get some leakage but it is of no concern. If you are not concerned about replacing parts of the muffler, you can "brad" the end of the connecting rod. Stand the fully assembled muffler up on a solid base and give it four or five solid hits, that will deform the end of the rod and the nut can not shake loose. Hav not lost any parts now for three or four years.

Cheers,

Chip

bob27s

My Feedback: (19)

Threaded 4-40 rod, locknuts both ends. If so inspired, use a 6-32 rod.

Nylon locking nuts work just fine - they do not see extraordinary heat. Been using those on the bolt-thru type mufflers since the OLD old old OS days. If still concerned, you can purchase all-metal 4-40 lock nuts, or simply use two conventional nuts at each end as a jam setup.

Of particular note to those reading this...... if you have a similar, new muffler, it is worth while replacing that through bolt right up front, or at the very least replacing the stock assembly nut with a locknut.

Once the muffler has shaken apart, the piece fit (although not great to start with) will be ruined due to the vibration and resulting surface damage/wear. Ensure the seams are sealed with hi-temp rtv when you bolt it back together.

garywi

My Feedback: (3)

Seems like a lot of fuss. Is there a tuned pipe or other muffler that can be pieced tother for this Tower .75?

G

carrellh

For a tuned pipe, possibly these guys?
http://www.justengines.unseen.org
Possibly Macs?
http://www.macspro.com/default.asp
I’m sure there are many suppliers but these are the ones I know about.
You will have to measure your port and bolt spacing, then contact the suppliers to see if they have a header that matches; or is close enough you can modify it to fit.


A length of ‘all thread’ and 2 lock nuts is not a lot of hassle compared to finding, fitting, and tuning an aftermarket exhaust system. Sealants, and all of the various cleaning methods mentioned, are not necessary. I ran a thin bead of sealant around the seam of one muffler, because oil collected in the muffler and seeped out the seam, but it made absolutely no difference in the way the engine ran.

bob27s

My Feedback: (19)

Macs pipe if you want a full-size header and pipe.

Jett has a jett-stream and a turbo-jett muffler that will fit and add performance.

Performance Specialties has a similar Ultrathrust muffer.

Several aftermarket pitts type mufflers available too.

garywi

My Feedback: (3)

Thanks Bob. What I am not clear on is, if I get a long screw with lock nuts or nylon, this will still expand when heated, loosen up, leak etc, correct?

Thanks

w8ye

My Feedback: (16)

This is what the 4-40 threaded rod looks like

http://www2.towerhobbies.com/cgi-bin...?&I=LXD872&P=7

garywi

My Feedback: (3)

yes, I know what they are, but they still expand under heat, which gives me the same problem, correct?

w8ye

My Feedback: (16)

Aluminum has 150% of the expansion rate of steel. So it gets tighter when hot.

I've done it to mine. I never had to mess with it again. No leaks or anything

rainedave

My Feedback: (1)

After reading this thread I'm starting to think I got a newer, improved muffler on my Tower .61. It came with a 4-40 bolt, a small red washer/gasket and a split lock washer under the nut. I could add a nylon lock nut on top of the stock nut, I guess, but in all the years I've been flying r/c I have never lost a muffler on any engine. I think I spend way too much time balancing props. The only time I ever lost a part was when my .91 Surpass threw a prop and I lost the prop nut in the grass. But that was my fault for leaning it out too much.

w8ye

My Feedback: (16)

For those reading this thread, the Tower and GMS mufflers have been made several different ways over the years.

There are ones with a rod threaded into the head piece with some form of Locktite on the threads. These tend to pull the guts out of the threads in the head piece.

There are also ones with the rod having a almost flat Phillips head like on a screw.

Probably other variations too?

Some styles work better than others.

Heat seems to make a big difference to how they hold up and expansion-contraction is one of the roots of evil.

Typically, if the back of your muffler falls off, the engine will keep running at low throttle but will lean out and quit at higher throttle settings. This might be a thought as to how to get the plane back to the field.

AERORICH73

Thanks for the info where to get fully threaded 4-40 rod material. Believe it is time to start
converting those mufflers that come apart.

Rich S.