Do it yourself slot car tires......any ideas?

Yo Fred!  I am working on a how-to article on tire making to go in the "Books" section of this site.

I have been experimenting with many different sizes and compounds, with little concern for appearance.  I have gotten great advice from folks on this site & at other sites!

Whatever compound you use, you probably want one that is a 2-part chemistry (polymer & cure agent mixed together in a specific ratio, just before you use it).  The compound should also be advertised as "pourable".  The thinner, the better, generally less than 10,000 cps as mixed.  You can work with thicker materials, but it can be a huge pain to get it to fill the mold properly.  You may need a vacuum pump to get air bubbles out of the compound after you mix it.  This is not required for the really thin materials.

It sounds like tire color is important to you, so you need to pick a material that can be made black without too much difficulty.  MicroMark TCR with black pigment might work for you.  I have used black urethane compounds from Forsch Polymers with some success.  I have also added HP LaserJet toner to light-colored silicone compounds, and gotten a reasonable shade of dark gray.

Aluminum molds are nice, but then you have to fool with mold release compounds.  PTFE makes a very nice mold, with no release problems.  It is available in sheet-form, so you can make multiple rows of holes, and scrape off the excess goop after you fill them.  You will need some sort of mandrel in the middle of your mold too.  Once again, PTFE, Delrin, and similar plastics work well here.  Metals and acrylic plastics require the use of mold release agents.

The simplest molds I have made have been for A/FX rear tires.  This rim diameter is 0.27", so a 1/4" PTFE rod makes a great mandrel, no cutting required.  I would start by drilling a 1/4" hole through my 1/2" thick PTFE sheet, then using a 27/64" (or larger if you like) end mill, I would mill a concentric hole, 0.21" deep. 

Put the mandrel in the hole, push it down flush with the top of the mold, fill with goop, scrape off the excess, and wait for it to dry.

This leaves you with a cylinder with "sharp" edges.  If you want rounded edges, then you need to modify the end mill, or use a different technique to cut the hole.  You will always have at least one sharp edge unless you use a two-part mold, or use some other technique to round off the edge on the top of the mold.

Good Luck!

Joe

(PTFE Tire Mold, before I realized that the mandrels should be pushed in flush with the top surface of the mold, and before I started using 2-part silicone)

It seems like all the 2-part mold guys, primarily body casters, use pressure pots to force their materials into the mold.  I suppose the same could be done with two-part tire molds.  I suspect that the tires in Fred's photo might be made that way.

Thanks Serge!!!!