Building Mufflers Made Easy
By Martin Dietrich
Here's a muffler that will give you 90 dB at 9 feet with your .40/.46 running full bore over a concrete slab. What's more, it's quick and easy to build.
Overview
This is a novel muffler that scale builders may find interesting. It is made of thin-walled stainless steel tubing and was installed on an O.S. .46 in an EZ ARF Focke-Wulf FW-190.
Materials and tools mentioned
- Thin-walled stainless steel tubing (flex tube)
- 1/16" sheet stainless steel (for the exhaust flange)
- Thin brass sheet (to close the opposite end)
- Silver-brazing materials (to join tubing to flange)
- 450°F soft solder (to attach the brass end)
- Coping saw (expect to break a few blades)
Construction
- Cut the exhaust flange from 1/16" sheet stainless steel using a coping saw. (Expect to break at least four saw blades.)
- Bend the flex tubing by hand to the desired shape.
- Silver-braze the flex tubing to the exhaust flange.
- Close the opposite end of the flex tube with a thin brass sheet and soft-solder it using 450°F solder. The large cooling surface keeps temperatures low, so the solder’s temperature is not a problem.
- Install two internal tubes: a large exhaust tube that reaches to the upper wall inside the flex tube (to help reduce noise), and a smaller tube that does not reach far and is used as a drain for exhaust oil.
Performance and comparison
- Running full bore with a 12 x 6 prop, the O.S. .46 produced 90 decibels measured at 9 feet while the model sat on a concrete slab.
- Factory muffler: weighs 3.3 oz and holds 2.5 oz of water.
- Homemade flex tube (one foot of 1-1/4" O.D. flex tube): weighs 4.2 oz and holds 7 oz of water.
Transcribed from original scans by AI. Minor OCR errors may remain.
