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.

• Tubing cutter
• Fine file
• Flat (spade) wood bit (Same diameter as header)
• Variable speed drill
• Needle nose pliers
• Screw tap to match pressure fitting thread
• Ice pick
• Safety glasses

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.

1. Punch the center of the bottom of the can and drill a small pilot hole
2. Drill the header hole with wood bit using a very low speed
3. Remove plastic valve and stem. Using needle the nose pliers, peel open valve Being careful not to break off any metal. Force the pliers under thin steel and peel upward. Form the metal gently with pliers to make a round but ragged hole.
4. Locate a point about 1" from the bottom of the can for the pressure nipple. Punch a hole with the ice pick. This will leave a flared hole. Tap the hole with the appropriate tap to match the pressure fitting, and test the fit of the pressure nipple. Sand off the paint around pressure hole with rough paper.
5. Roughen the bottom surface around the hole to about 1/4" from the hole. Thoroughly wash the can with alcohol and lay it aside.
6. Cut 1 3/4" off the end of header. Thoroughly deburr the cut end of the header and both ends of the section that was just cut off to remove all sharp edges. Lay the header aside.
7. Test fit the 1 3/4" stub into the hole in the can. It should be a snug fit.
8. Cut the aluminum stinger pipe to length and deburr. If an angled pipe is desired, bend the elbow in the tube as described above. Test fit the pipe into the valve hole of the can. Bend the metal edges inward until a snug fit is achieved. Roughen the end of the pipe.
9. Temporarily assemble the header stub and stinger to the can. If an angled stinger pipe is being used, rotate the pipe so that it is in the correct orientation in relation to the pressure nipple. Use small wooden blocks of the proper thickness to hold the stinger and stub to the proper height to be straight. Clean all parts and wipe hands with alcohol.
10. Mix a ball of JB Weld the approximately size of a Hershey's Kiss. Using a popsicle stick or similar, spread the JB Weld generously over all mating parts including pressure nipple threads and the inside edges of large drilled hole.
11. Insert the stub and the stinger into their respective holes about 1/4" inside the can and form a small fillet of JB Weld around them. Screw in the pressure nipple. Place the assembly on the blocks to hold everything straight while the JB Weld cures overnight.
12. Check to ensure that no JB Weld was forced inside the pipes nor the pressure fitting. If any is found, it must be cleaned out.
13. Clean the header, inlet pipe, and coupler with alcohol and slip coupler onto the header and inlet pipe while wet. Rotate the muffler for proper orientation of the pressure nipple. Leave a 1/4" gap between end of the header and the end of the inlet pipe. Wrap cable ties over the coupler joints and pull tight avoiding pinching the coupler. Allow to the coupler to seat for 30 minutes before installing the assembly on the engine.

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.