[marshall]

Originally Posted by Mike Marandola

The mold was made of silicone. The process was pretty similar to what Joey said. First you have to make a master wheel. The version 1 was 3D printed which is the orange one in the photos. It turned out to be not accurate at all so I then machined one out of a block of HDPE. That turned out to be nice and true. Once you have the master I like to glue it down to a piece of acrylic then pack an oil based clay half way up the mold (the 7th photo). After a coat of mold release the silicone (pink material) is poured in and allowed to cure. The clay is then removed and everything is flipped over inside the cylinder, I used a large piece of PVC (photo 8). After another generous coat of mold release, more silicone is poured in. Once cured, the two halves can be separated, the master removed, and urethane and be poured. Another thing to note is that all of the curing is done in a pressure chamber at 60 PSI to compress the air bubbles.

This is all very simplified and I will go into much more detail of how to use the process for more than just wheels in a whitepaper later this summer. I would be more than happy to answer any questions though.

This video might give you a good idea of how it's done.

This is awesome! Thank you for sharing!