Carb Heat on NX41CC

Created May 13, 2007

This is the modified carb heat muff on 41CC. It started out as a standard Aeronca heat muff but the incoming air would pretty much tend to shoot straight through to the scat hose rather than working its way around the exhaust stacks, so we welded a clip onto the front stack and bolted on a steel plate (metal locknuts on the hardware). Plenty of space was left all around the plate but as you can see, now the air has to flow around two stacks and a hot plate before it can get to the scat hose leading to the carb air box. The stacks and plate were left unpainted to maximize heat transfer to the air. Prior to this modification, there was little to no RPM drop upon application of carb heat. With this plate in place, I get a good, noticeable drop... 100 to 150 RPM on runup. It works well, as proven several times when I have experienced carb ice for certain.

Here's the outside half of the muff clamshell. The stock configuration has just a short spigot for the air to come in, and in a moment of whimsy I cut down a section of a sink P-trap (chromed brass) and secured it to the short spigot to act as a small scoop to force air into the heat muff. The inside of the scoop is painted red to make the engine look like a big radial like Beavers and Stearmans have ;o)