Adventures in Mold Making Part I
I’m planning to do some fairly sophisticated sensors, but that’s a topic for another day, and likely after the games as I likely have to run a temporary brain for this competition as time is too tight to get a PCB turn.
Delrin is a really nice material to work with on a hobby mill and lathe, and it was relatively easy if somewhat time consuming to bore out the 25mm diameter hole for the robot.Smooth-On Reoflex 30. Other people have used various Reoflex durometers for sumo robot tires as well. Feeling in a spendy mood, I also decided to buy some blue pigment.
Excitedly, at the end of the work day I got home with the polyurethane in it’s shiny box, which I’d bought over lunch hour, and prepared the mold. After collecting all the things I would need to cast my tires, I found that the really Old AIrbrus lying around wouldn’t spray the mold release agent anymore, so I cheated and used a brush instead. After waiting for the mold release to dry, I clamped the mold pieces together, popped in a wheel, and started mixing some polyurethane.
A word of caution when using pigment for polyurethane, however: The “SoStrong” pigment.. Is, just as the name would imply, oddly, So Strong. I used a few drops, which was a few drops too many. The end result was a very dark mix. But, as this is a prototype tire that I plan to rip appart to test strength, I wasn’t too concerned.
Now the tire is sitting in the mold. With a 16 hour de-molding time, It should be ready tomorrow roughly around lunch… We shall see how it turned out then.
For now, here are some other links you may find useful with regards to polyurethane sumo tires:
- Jon Hyland’s Seeker3 Sumo - He has some very good pictures of his awesome robots, including some more details on molds
- Dave Hyland’s “Making Marauder’s Tires” - Jon’s brother has more good details on casting polyurethane
- WCRG’s Molding Tires