My Stalker 51 uses two "O" rings to couple the muffler to the engine.  They last about 3 flights, then get loose and hard.  I've tried O rings from the hardware, but they are the same.

So, since I know almost nothing about O rings, what material should I look for?  What O-ring application is intended for high temps?

Floyd

The source of All Things Machining (and expensive):
http://www.mcmaster.com/#o-rings/=fs0l5d

They have a pretty good discussion of each material's properties.  Unfortunately I don't know how hot a nitro-burning engine exhaust gets, other than it'll make a shiny spot when it burns you -- that's in excess of 100C, but I don't know by how much.

or you could just buy Viton, Hi Temp O-Rings ,and use them , That is the same type that I have supplied with my RE mufflers for many years now.
The ones I use are black and harder than the typical O-Rings, the orange-red  silicone O-Rings also have worked pretty well in many engines and take heat pretty well.

Remember nothing is going to last forever, and the closer to the engine, the shorter their lifespan will be

Randy

 Hi.

 I just found very good Viton O-rings for Retro Discovery engines from:

 www.smallparts.com

 I think they are better than the originals. They have several sizes available, my guess is that for Stalker you'd better look for the metric sizes.
 Also, the O-rings seem to last a little longer if you wrap 2-3 layers of plumbers teflon tape (the very thin one) over the header before slipping it in place. Good teflon grease does no harm too.

 Lauri

Hi ,

I work as a hydraulic tech , for a living and I use a lot of different o ring products .

The Markez Z1213  has an operating temperature , up to 320 degrees C , or about 610 dgrees F.

Hope this might help ?

Rob K.

Are the Markez O-rings better than the Viton?

     Question  for stalker/Eastern European rear-exhaust engine experts, slightly off-topic - what is positively retaining the muffler on these "slip-on" rear exhaust mufflers. The only thing that appeared to work consistently is something built into the airplane to keep of from being pushed off the back. I and others have had the same issue with even the Rustler/Merco engines with screw-on mufflers - they shake loose and tend to damage/destroy the threads on the header, and there's no too way to really crank down on the jam nut in some cases.

Without seeing the engine in question, it might work to modify the muffler with some pegs or hooks, and wrap a honkin' strong spring around the cylinder to hold the muffler on.  To be positive it'd almost have to be strong enough to suck the muffler in when it's misplaced (otherwise it will find a way to walk out).

I dunno if it'd work with these particular engines, how hard the "pegs or hooks" would be to add on (or clamp on, or whatever), or if it'd be any better than nailing the muffler or pipe to the airframe -- a picture just popped into my head, I thought I should share.

Most of the Stalker mufflers that are plug in type have a round hollow tube cast onto the back of the muffler. The idea is to have a dowel mounted in the rear part of the engine/tank compartment that the tube slips over to retain it in position.  Of course this does not keep the muffler from rotating.  I cut the round stud along it horizontal axis and then drill a hole vertically throught the remaining flat bottomed stud.  This then rests on a plywood plate between the fuse sides with a blind nut on the bottom to secure the muffler. This way the muffer is secured from fore and aft movement and from rotation.  O-rings last a lot longer this way.  I use Vitron rings I got from McMaster-Carr.  The #014 is the proper size.  100 will cost about $8.50.

SUNDAY,1/15  I ordered the recommended O-rings from McMaster-Carr.

What am I going to do with 100 of them?

Thanks to all for the great advice.

Floyd