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Trouble keeping pitts stile muffler tight

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Trouble keeping pitts stile muffler tight

Old 09-27-2014, 03:02 PM
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rzingsheim
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Default Trouble keeping pitts stile muffler tight

I'm having trouble keeping my J-Tec Pitts stile muffler tight on my DLE55. I purchased the motor and muffler assembled with a gasket but it had not been run. After the first flight it was loose. I replaced the gasket with another gasket because the area where the bolts goes through the muffler were slightly depressed (probably because of the gasket) and it would rock a little against the motor with out it. I used blue lock-tite on the bolts and wire tied the muffler bolts. Flew it again and it was loose again. Is seems a gasket is a bad idea. Another member suggested I file or sand flat the part of the muffler that mates to the motor so it sits flat and use a hi-temp silicone instead of a gasket. He also recommended using red lock-tite on the bolts and wire tying. What do you guys think of this solution? What type of hi-temp silicone? I'm a little nervous about the red lock-tite on the bolts.
Thanks,
Roy
Old 09-27-2014, 03:41 PM
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CK1
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It sounds like you have already been given very good advise. Ditch the gasket . Reface the mating surfaces . Use Red loctite and high temp silicon gasket maker/sealant.
Iwould also add a support strap from the muffler body to the engine to relieve some of the strain of the muffler weight on the bolts.
Old 09-27-2014, 03:45 PM
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All Day Dan
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If those screws have come loose more than once, it is possible that the tapped holes in the engine have been ruined. The bolts are steel and the cylinder is soft cast aluminum a formula for failure. Make sure you a using metric threaded screws. It’s a sure bet that threads in the cylinder are metric. If the screws still come loose, you can use Helicoils to save the cylinder. They are a little hazardous to use but they do the job. Lock washers usually do the trick to keep the screws from coming loose. Use Permatex Ultra Copper Gasket Maker. It’s a high temperature silicone RTV that is made just for this situation. Never use a gasket. Dan.
Old 09-27-2014, 04:18 PM
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ahicks
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Using the red (or any) Loctite on the muffler bolts isn't a real good plan in my experience. To get red to release, generally you would warm it. Running it on any type of exhaust application will warm it the same way - and generally it will get plenty hot enough to release. Instead, consider cleaning up the threads the same way you would if using Loctite, but use a little of the same silicone you're using between the exhaust port and muffler on the bolt threads. Doesn't take a lot. If everything else is right, that generally works pretty good.

Flat mating surfaces is absolutely critical - both sides. If that muffler had a couple of tanks of gas run through it while loose, I can almost guarantee BOTH sides will need dressing.....
Old 09-27-2014, 05:06 PM
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speedracerntrixie
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Great advise so far. Personally I use red loctite after cleaning the screws and holes with acetone. My experience is that most of the time when a muffler comes loose it's because the engine is being run too hot.
Old 09-27-2014, 05:17 PM
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tande
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Good advice so/far.......also a lot of us who fly giant/scale, use this on all muffler retaining bolts.......FWIW
Old 09-27-2014, 06:30 PM
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speedracerntrixie
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It's funny, I have been to well over 150 IMAC contests and have built some giant scale airplanes for some well known pilots and have never seen one of those washers in person. Not saying that they don't work just never seen any. I have no doubt that if the issue is that the screw is backing out that they would solve the issue. If the issue is excessive heat I don't see them as a viable solution. All the parts associated have different heat expansion rates, the hotter they get the more differential. The key is to minimize the heat expansion by not running the engine too hot.
Old 09-27-2014, 06:45 PM
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tande
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Well, we use them with great success.......what can I say......they were not invented just for us RC folks......they are an industry standard in a lot of high/vibration applications......
Old 09-27-2014, 08:36 PM
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speedracerntrixie
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Originally Posted by tande View Post
Well, we use them with great success.......what can I say......they were not invented just for us RC folks......they are an industry standard in a lot of high/vibration applications......
Well as long as they work for you. I build aircraft antennas for a living, haven't seen them there either. I guess I look at things a bit different. If I had an issue with things coming loose I would fix the source of vibration or in the case of a muffler make sure the engine wasn't running too hot and then look to other fixes. One of the things I picked up in the manufacturing of aircraft components is root cause analysis. The theory is to look beyond the symptom and find/fix the actual cause. IMO adding special washers to keep things from coming loose rather then fixing the cause of the vibration is just a band aid. I do agree that sometimes the root fix is not possible and you have to go with the band aid.
Old 09-27-2014, 09:18 PM
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Spridal
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+1 for the Nord-Lock washers. I've owned several engines that were not set lean nor run hot and the muffler bolts still would not stay put, even with white, red or blue locktite.
Old 09-28-2014, 03:25 AM
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Granpooba
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Originally Posted by Spridal View Post
+1 for the Nord-Lock washers. I've owned several engines that were not set lean nor run hot and the muffler bolts still would not stay put, even with white, red or blue locktite.
+2
Old 09-28-2014, 05:37 AM
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I take a little different approach. I use the gasket with Permatex Ultra Copper Gasket Maker on both sides. If the muffler bolt heads are not recessed, I drill holes in the bolt heads perpendicular to the bolt shafts. I run piano wire threw the holes. I bend the ends of the piano together and solder them together. I have done this on all my gas engines, Q35,DLE 20,30,35,55, G23,26,62. After hundreds of flights, I have yet to have a loose muffler.
Old 09-28-2014, 07:32 AM
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Originally Posted by Spridal View Post
+1 for the Nord-Lock washers. I've owned several engines that were not set lean nor run hot and the muffler bolts still would not stay put, even with white, red or blue locktite.
Im not trying to be argumentative here but I have been told by numerous guys that their engine is not running hot. When asked how they are gauging the temps I was told it was because the engine did not sag at full throttle. From my perspective if the mixture is set correctly, fuel is the correct ratio and there is ducting/baffling that directs the airflow through the cylinder fins with enough exit area then I would say the engine is not running too hot. Anything less then this and your engine is indeed running hotter then it could be with some additional effort. Here is a picture of the simple baffle that is in my 40% Extra. It devides the cowl onto upper and lower chambers. Air is drawn through the cylinder fins and exits out the bottom of the cowl while some air passes around the dual canister exhaust system and out the fuse bottom just behind the canisters.
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Old 09-28-2014, 09:01 AM
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Originally Posted by speedracerntrixie View Post
It's funny, I have been to well over 150 IMAC contests and have built some giant scale airplanes for some well known pilots and have never seen one of those washers in person. Not saying that they don't work just never seen any. I have no doubt that if the issue is that the screw is backing out that they would solve the issue. If the issue is excessive heat I don't see them as a viable solution. All the parts associated have different heat expansion rates, the hotter they get the more differential. The key is to minimize the heat expansion by not running the engine too hot.
speedracer, I'm in your camp on the engines running too hot. Keep the temperatures to a reasonable level and the mufflers will stay in place if they are installed per some of the suggestions above. I never use a gasket and have not required the NordLock washers to keep my mufflers in place (except on the one Syssa engine I owned)! Very few people use adequate engine baffling but still feel their engines are well cooled. I'm not sure that passes my reasonableness test.
Old 09-28-2014, 12:32 PM
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Had a friend that had the same problem with a 3W. After trying EVERYTHING he found there was a lot of crud in the bottom of the hole and the bolts were bottoming out before getting tight. Wasn't much, just enough to keep it from being tight enough to hold.
Old 09-28-2014, 02:21 PM
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Well I will have to add my 2 pennies worth, Speedracer is right about baffling it is a must, and so are some of the other suggestions permatex copper is great, when I was having some trouble with a muffler on an old G-38 a frind of mine who works every day with HI Temp joints had me try a loctite product #515 joint sealer made for aluminum material, but it also critical to have both surfaces FLAT, I also use the Nord-washers just to be safe, but some times the OD of the washer has to be ground down to fit the ID of the muffler tube.

Now I will go back to my dish and lay down

cheers Bob t
Old 09-28-2014, 03:44 PM
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Smoking Loon
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After 9 years of rebuilding Jet Engines, you are spot on. We also use Anti-Seize on all bolts. You may want to remove them in the future.
Old 09-28-2014, 03:46 PM
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ahicks
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Wow, this conversation sucked in a lurcker!

Welcome Smoking Loon!
Old 09-29-2014, 01:48 AM
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I had the same problem on my DLE 55, it got to the point that on the wrap around pitts muffler I pinned it with wire and it held. UNTIL!! the vibration emulating from the engine is a differant frequency than that of the muffler and not having the muffler braced caused the threaded holes in the crankcase to wear out!! So, even with pinned muffler bolts your muffler can come loose by vibration. My fix was to Drill out the crankcase holes and fit them with 10/32 Helicoils. I used two new 10/32 bolts and A MUFFLER BRACKET FOR SUPPORT ATTACHED TO THE MUFFLER AND THE BACK OF ONE OF THE STANDOFFS!! Ultra Copper Silicone for the gasket. Apply it finger tight and let it dry for an hour or two. now take out your bolts and apply your red heatproof loctight,crank down your bolts and let it dry overnight.
Old 09-29-2014, 10:48 AM
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I agree the wrap around Pitts mufflers should have a strap on them from the can to somewhere on the engine case. Some are built this way but most are not. It would be good if the muffler companies would just weld a nut on the can that a support strap could be bolted to for support. Unsupported weight is never good where vibration is concerned.
Old 09-29-2014, 11:08 AM
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speedracerntrixie
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So true. I think exhaust systems is one of the areas we are lacking in. I agree that any gasket seal or loc-tite has to be given enough time to fully dry. I go one step farther and use primer for both loc-tite and RTV. But if I get an engine too hot that is muffler equipped the muffler can still come loose. My last 2 gassers have had canister systems which I think is more reliable but has it's quirks too.
Old 09-29-2014, 04:23 PM
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ahicks
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I spoke with Al at Jtec about adding a strap or support of some sort to one of his wrap arounds. He absolutely forbade it. Said he would void any warranty claims on mufflers where there was evidence that had been done. For those of you that don't know Al, I'll just leave it at he doesn't care for the idea. You can discuss the details with him....
Old 09-29-2014, 04:59 PM
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Al, I get a chuckle out of that. I once was running a set of Jtec mufflers on a 3W 170. About 8 weeks of use one broke at the mounting flange. I called Jtec 3 times and never did get a return call. Payed a local guy 20.00 to weld it back together. Never considerd buying anything else from them.
Old 09-29-2014, 05:41 PM
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In all fairness, he's always done me right, though sometimes begrudgingly. Typical of guys that can get away with being that way because they're just that good at what they do. -Al
Old 09-29-2014, 06:54 PM
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I think you and I go back far enough to remember what the business end of our hobby used to be. While this is certainly off topic here we used to have many more vendors and much better quality items. Look at what happened to Monokote. Have you bent up some music wire for landing gear lately? The stuff bends so easily. I have to straighten the gear legs on my pylon airplane after almost every landing. I would think that the U.S. based vendors would be providing much better customer service to keep the customers they have coming back. I've been in the retail side of the business, I know how difficult it is to survive in this hobby and take this into consideration when dealing with vendors. Yet there are at least 5 big name vendors that I will never buy from nor will I suggest.

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