Fixing Air Horn Diaphragms

I was restoring a set of air horns for a Ferrari and I found a bad diaphragm.

Air horns work by passing air across the thin piece of brass while allowing the trumpet to slightly touch the membrane. The moving air allows the brass to vibrate agains the trumpet giving that familiar Ferrari horn blast. Normally, the membrane gets cut by the end of the horn, but this one had a slight crack on the edge of the membrane where it attached to the body of the horn.

I bought a roll of brass shim stock that is the same thickness as the original membrane and cut a new piece to replace the leaky one.

I cut a piece and trimmed it so it just fit inside the body of the horn.

I used the body of the horn to form the shape of the membrane by screwing it together without the gasket.

Once the brass sheet was formed, I reinstalled the gasket and reassembled the horn assembly. I tested the horn with a light blast of compressed air and it worked great. Getting the horn balanced will have to wait after painting the horn body in hammertone grey and the trumpets in a candy red.

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