Urethane is in, and I am beginning to run tires. Doing some tests to see what combination of vacuum de-airing the uncured rubber, and pressure casting gives the best results. I do need the pressure pots to fill orders, so there is a bit of a bottleneck there, but it looks like both vacuum and pressure is best. I did learn you need to let the rubber fullly cure before relieving the pressure, or you get some odd little balloons on the tire. So tires get run last thing, and sit under pressure overnight (16 hour cure time).
I thought I would lay out the steps of how the patterns and molds were made.
First step was to measure the Thunderslot wheel and tire, and then make some 3D files for printing.
[attachment file="Wireframe tire.jpg"]
This was exported as a .stl file, and set up for printing on my resin DLP printer I gave the tire a little standoff and placed it on a base, so that with any luck the back side of the tire won't be to hard to tidy up.
[attachment file="Mold Tray Render.jpg"]
Here is the printed part on the build-table
[attachment file="02-part on build table.jpg"]
Now to make a silicone mold. I drilled some vent holes in the base in hopes it will ease de-molding. Remember to tape them up, though, or the silicone will run out.
[attachment file="03-vent hole.jpg"]
ABS sheet is used for mold walls. Taped together flat like this, so the walls can be folded up and taped for a re-useable mold box.
[attachment file="04-mold box.jpg"]
Time for RTV
[attachment file="06-silicone poured.jpg"]
