Mail comments or questions to: Bob Adkins - Eunice, LA, USA
How to Make a Mousse Can Muffler
This article explains how to fabricate a muffler out of a mousse can or similar small aluminum container. This muffler is inexpensive, light weight and improves the performance of t he engine to which it is attached. There are no baffles in this muffler because these have been found to be counter to the purpose of this muffler; power and simplicity. Because of the increase in RPM's available by use of this pipe, the prop makes more noise however this pipe is actually quieter than most factory mufflers.
The tools that are required to build the mousse can muffler are common tools that are found in most modelers' shops.
Macs headers are a wonder of precision, functionality, and beauty. At less than $20 they are a tremendous bargain. They will survive all but the most destructive crashes. The regular offset version is used for models with slim cowls and the long offset versions are for models with wider cowls. The headers are available from several hobby sources including Great Lakes Hobbies and Tower Hobbies.
Macs supplies a soft silicone coupler with each header. To the inexperienced modeler, this coupler is a disgusting piece of work. It's has a texture like a worm. It slips off its mounting and is easily cut. To the experienced modeler, it is a treasure. The mousse can muffler would not be possible to produce without it. The soft coupler is necessay because it "shock mounts" or isolates the JB joints from the vibration engine. A thicker, harder compound such as Blue Line tubing will cause the joint to fail. If the coupler gets cut or nicked, it will eventually fail at the damaged area. For this reason, the header pipe must be carefully de-burred and washed with alcohol before the coupler is installed. If it has installed properly, it will last indefinitely.
There are numerous products on the market which are distributed in seamless aluminum containers. The mousse can was chosen for this application because it just happens to be about the right size. The small diameter can which is about 1" in diameter and about 5" long, should be used for engine in the .15 to .28 size range. For larger engines, the larger can which is about 1 3/4" in diameter and about 6" long should be used. The cans are extremely light weight and this makes their use as a muffler possible. If the can were heavy, the joint made with the JB Weld would break loose.
The aluminum tubing from K&S is the best all around for making the "stinger". The 1/4" OD tubing works for engines up to .40 size and the 5/16" is better for larger engines. This is a low temper tubing and is not very strong but it is easy to bend. One way of making a stinger to deflect the exhaust away from the model is to close one end with a ball of well packed fiber glass cloth and pour the tube full of molten lead. The tubing is then bent around a 1/4" diameter rod to make a elbow without kinking. The stinger is then heated with a propane torch until the lead pours out.
The JB Weld adhesive if great stuff if used for the proper application. The best attributes of JB Weld are its great adhesion, compressive strength, stiffness, and heat resistance. Its weaknesses are brittleness and poor shock resistance. JB Weld will not withstand direct contact with a model engine. It will soon break from vibration. This is the reason for having the soft coupler. JB Weld degrades if exposed to temperatures over 120 degrees F. It should be allowed to cure over night at room temperature. Heating with a heat gun will weaken it and the cure time is not much improved.
Before starting construction of the mousse can muffler, ensure that all of the product is released from the can. Even a small amount of pressure can cause the thin walled container to explode when it is pierced.
Safety glasses should be worn while any work is being done on the muffler.
The stock length of the pipes is acceptable for small, high revving engines but may be too small for .36 size engines and larger. If aluminum pipe can be found which matches the diameter of the header, this can be used for the inlet of the muffler and the header will not need to be cut. This combination is better tuned for larger engines and props. The outlet pipe may seem small for this application but this helps in tuning.
Use the method described here or a similar method to mount the muffler on the plane. The mousse can muffler must be mounted freely but this can be done easily.
Use a large cable tie and wrap loosely around stinger. Cut cable tie to the proper length for use as a hanger. Drill a 1/8" hole in the free end of cable tie and attach the end to the plane with a small screw. The cable tie should be about 1" from the can. The cable tie must not exert force on stinger and there should be no strain on coupler. This is referred to as "free floating".
A much stronger, better running engine and a beautifully functioning and long lasting mini pipe can be expected. An 800 RPM increase is normal while a 2200 RPM increase is not unheard of. The engine idle will be better and throttle response will be smoother. These pipes usually work best with engine/prop combinations that run in the 13500 to 16000 RPM range. A typical power gain for a Thunder Tiger GP25 or GP40 is about 40%. An engine should sound better and will most likely be quieter than if a stock muffler were used. All this comes from an assembly that weighs only 2 ounces.