The RCGF 26cc engine on the Pulse XT60 is of course a bit loud (less loud now that I put the muffler back on... it was falling off and lost a screw, so I think that is one reason it was so loud at RC Aces last week). I decided to buy a pair of silencers from MHRC, having one on the MX-Bach's 36cc RCGF engine with its one big pipe. It took out the high pitched pops and gave the engine nice tuned sound. The larger silencer fits it perfectly. I know the smaller ones are just a touch big for these pipes at 14.4mm (they fit a pipe with a 14.4mm ID), as the OD is 14.4 on these pipes. But I had an idea, and this seems to work. We'll know when I can fire up the engine. I know the tip will fit inside the pipe, and that the outer edge will be flush with the pipes outer edge. it won't go in. I suspected that the silicone attaching tube would fit just right on the pipe, and that the silencer doesn't care if its in the pipe or the silicone. I also needed some guarantee that the silicone tube would not get blown off. This is what I came up with.
A piece of painter's tape to help keep the drill bit from wandering too much.
Drilled an approx 1 mm hole.
Put a M2 short hex screw...
In the hole. Snug, not gorilla-tight. Repeated on the other pipe.
Pushed the silicone tubes onto the pipes, having already used hot water to press the silencers into the silicone tubing and set an electrical tie around them. I then used the supplied ties to put one above and one under the protuberance created by the screw. Snug, doubt they will blow off. Now this will increase the exhaust manifold pressure a little, so I will lose a few RPMs, but this plane is over powered and will tolerate that fine. I won't be surprised if I have to make a few adjustments to the needles or idle end point settings.
UPDATE: They actually do make a noise difference, with no noticeable performance loss!
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