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OS 46AX Muffler

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OS 46AX Muffler

Old 02-23-2010, 12:19 PM
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Default OS 46AX Muffler

The OS46 AX mufflers seem prone to falling apart in the air and are EXPENSIVE!!! I know the Tower muffler will fit, and give extra power, but for the racing our club does, you need to stay with the original OS Muffler. I'm looking for a "belt and suspenders" approach that does not rely completely on the through bolt to keep the muffler parts together. I've considered epoxying the parts together but suspect that, since the muffler has been used, the epoxy will not stick well enough. I tried a 6-32 threaded rod but it did not last much longer than the original one.

Racing starts in 3 weeks so I need to get this fixed pronto! TIA

Old 02-23-2010, 12:30 PM
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Jetdesign
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Default RE: OS 46AX Muffler

I've never had this problem, but if I did, I might try JB Weld. Handles heat and metal very well. Very important to properly clean the mating surfaces.

Another idea is a longer screw/rod - drill a hole through it and use a cotter pin, or maybe try a C-clip.
Old 02-23-2010, 12:39 PM
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ChuckW
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Default RE: OS 46AX Muffler

Never had one come apart but I do know it is more common in applications like racing. A lot of people are welding the two halves together. I'm not sure how that would go with a used muffler after the oil has soaked into the porous aluminum though.
Old 02-23-2010, 12:52 PM
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RCKen
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Default RE: OS 46AX Muffler

Yes, there is a problem with OSmufflers coming apart. It seems hit or miss though. Some people will never have problems while others will. I've had to purchase 2 new OSmufflers because of losing the back half of it. Get yourself some steel floral (craft) wire and wire it so that the back half of the muffler won't fall to the ground if the bolt breaks. See the picture below. Don't worry about the metal to metal contact creating RFinterference. The mufflers are made of aluminum and won't cause that problem. The RFinterference only happens from metal to metal contact of ferrous metals.

Once that bolt breaks I will simply replace the bolt with a piece of all-thread with nuts on either end of the muffler. You can skip the retaining wire if you want to just use the all-thread solution.

Ken
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Old 02-23-2010, 01:17 PM
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macdona
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Default RE: OS 46AX Muffler

I put three little screws where the muffler joins together. Haven't lost one in ages.
Old 02-23-2010, 02:00 PM
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Default RE: OS 46AX Muffler

Thanks all for your suggestions. I had 4-40 screws through the joint but they fretted through when the assembly bolt broke. I'm washing the parts in boiling water and dishwasher detergent now to try to get most of the oil out. I think I will JB Weld the two halves together after drilling some holes in the joint line to let the JB Weld form "rivets", install the 6-32 through bolt and wire the two halves together. I used to have a problem with the attachment bolts breaking but the Tower ones seem stronger than the OS. However, I will still wire that on as well.

I just got another engine for a spare plane. T-34 racing is hard on planes and engines!! I think I will epoxy that one together from the start.
Old 02-23-2010, 06:16 PM
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RVman
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Default RE: OS 46AX Muffler

Don't tighten the through bolt so much. The aluminum muffler expands more and can break the steel screw if its too tight.
Old 02-23-2010, 06:56 PM
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dbacque
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Default RE: OS 46AX Muffler

I've lost the back half of a couple of OS mufflers. Now I Locktite the bolt to the muffler back half and replace the nut with a lock nut with nylon insert.

I've never had one loosen when assembled this way and you can still loosen it to adjust the exhaust position.

Dave
Old 02-25-2010, 11:19 PM
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Default RE: OS 46AX Muffler


ORIGINAL: dbacque

I've lost the back half of a couple of OS mufflers. Now I Locktite the bolt to the muffler back half and replace the nut with a lock nut with nylon insert.

I've never had one loosen when assembled this way and you can still loosen it to adjust the exhaust position.

Dave
Well, I used a Nylock nut on the back in addition to what I described above. After one flight, the Nylock nut backed off and the JB Weld holding the two halves together cracked. Fortunately, the safety wire held the pieces together so I did not lose anything. Next try is to Loctite the through bolt to the rear of the muffler as above and use jam nuts with split washers. The engine is turning over 14.5k with a 10x6 APC. The prop is well balanced but I guess the vibration is too much. We use a 9.5x6 APC for racing and the engine turns close to 16k. It's hard on everything. I've had 3 of the stock needle valve brackets break and finally made one of thicker aluminum with more meat around the holes.


Old 02-26-2010, 11:13 AM
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Default RE: OS 46AX Muffler

Just "brad" the end of the long bolt so that the nut can not come off. True once you have bradded the end of the bolt, you can not get the nut off since bradding mushes the end of the bolt (to big for the nut to pass over and messes up the end so bad there is usually no thread to carry the nut off). Just turn the muffler up on end on a anvil or similar hard surface and hit it three or four times with a hammer. That's called bradding. Of course, once done do not think about taking it apart ever again or you will have to replace the long bolt and its nut.

Also balance your prop. That will reduce parasitic vibration that causes the nuts to come loose. The vibration along with temperature expansion is what is doing you in. You can not get rid of the temperature but you can ease the vibration a little bit by proper balancing the prop.

God luck,

Chip
Old 02-26-2010, 11:45 AM
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timcat26
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Default RE: OS 46AX Muffler

Once the muffler is tightened properly, I put JBWeld on the nut/part of the boltto make sure it stays. Never had a problem with them after doing this.
Old 03-02-2010, 08:47 PM
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Default RE: OS 46AX Muffler

Chip,

I always balance the props but there is still some vibration, especially when racing. It seems I've worn out the engine which may explain why there was more vibration recently. Bearings look to be shot. I've installed a new 46AX and noticed that the assembly bolt is heavier than on the first muffler I had.
Old 03-02-2010, 10:20 PM
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Default RE: OS 46AX Muffler

Haven't run into it with the AX but I did a few times with the FX. One new all thread rod, tighten and double nut it. Not the nylock type, the heat tends to melt or loosen the nuts nylon. I used to always drill a hole in the mufflers outlet and add a safety wire just in case. I fly off of a dry lake bed now days so loosing a muffler or parts is no big thing, it's so flat you can't miss finding your parts again!!!
Old 03-02-2010, 10:30 PM
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Default RE: OS 46AX Muffler

I did the all-thread rod when i fixed the muffler, then discovered the engine was shot. I do agree with the problem with the Nylok melting as that did happen the time before. Safety wires are necessary as the mufflers are ridiculously expensive and we have plenty of vegetation around the field.
Old 03-03-2010, 03:55 PM
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Default RE: OS 46AX Muffler

After losing my 2nd muffler "back half" I replaced the entire muffler with a one piece Macs Muffler (not the tuned variety). Price is similar (maybe a couple of bucks more) to the OEM stuff 'cause you can't just buy the rear half.

Safety wiring (like RCKen suggested) will keep that parts - you'll still end up with a dead stick landing. Keep an eye on the wire unless it's stainless steel (I've been safety wiring motorcycle components with SS wire for years).
Old 03-03-2010, 04:20 PM
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Default RE: OS 46AX Muffler

Given the option, I'd use a Tower muffler as they are cheaper and, from my experience, give more power. I've never had one fall apart either. However, the racing rules require a stock OS 46AX muffler.

Hmmm. i should check the local cycle shops for the SS wire as I've used up my stock from the days when I owned a home-built sailplane.


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