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After a reasonably-thorough review of our options, Alex decided he’d try to make new air horns with a little more bend to them. Taking two of the stock rubber air horns, he poured plaster molds that he then sanded, and filed, and puttied, and sanded some more until they were a more appropriate shape.
Next, Alex slathered the plugs in mold release wax, slid a carbon fiber sock over it, slathered it in resin, and used a roll of that fancy plastic shipping stetch wrap stuff to hold it tight while it cured. Afterward, the plaster had to be chipped out.
Not half bad for a first try.
The long horn sits nearly an inch lower than the original, without a significant change in length.
The outer horns now have enough of a bend to pull them away from the roof of the plenum that was shrouding them in our first prototype.
With the basic shape approved, the next step was to make a tool so we could make a few more of them. Making each plaster plug ruins one factory rubber horn, and each plaster plug can only be used once. The first step toward mass production was to ruin one of my funnels. After bending the funnel with a heat gun, it could serve as a solid plug in the middle of what would eventually be a silicone mold.
Sealing the carbon horn with tape, a cupfull of liquidy silicone goo makes up the gap between funnel and trumpet.
The new silicone mold can be removed from the cured horn by first slipping out the funnel, then squishing out the silicone, which instantly springs back into shape.
Now, about that stretch wrap stuff Alex used on the first horns… Though it did a good job of holding the carbon tight against the plaster plug while the resin cured, the wrap is wrinkly, which leaves wrinkles in the surface of the horn. Not cool. We needed something cylindrical and stretchy that could hold the carbon tight against the silicone plug without unsightly wrinkles. Alex had an idea…
