Casting a 1:24 Scale Model of Riding Bean’s Buff the Roadbuster, Part 2

Continuing our story from Part 1, the next step was to cast the wheels.

Since my 3D printer didn’t have high enough resolution to handle the fine details of the tires, I shipped off the 3D files to Shapeways for printing in resin. I also printed the rear spoiler because it was only a few bucks extra and would require less cleanup than printing it at home.

Cleanup on these parts required soaking them in soapy water to remove leftover support wax, and very gentle sanding with an Air Eraser (an airbrush accessory) using baking soda as the abrasive.

Figuring out the right way to cast the wheels turned out to be more difficult than I expected. After a handful of different attempts, I stumbled upon using foil tape (basically, aluminum foil with adhesive on one side) to separate the two halves at the inner edge of the tire.

Base, with holes for the axles.

Foil tape (adhesive up) separates the two halves.

Silicone applied to the tread and fine details of the hub with a brush, to ensure coverage.

First half has keys cut into it. Note how the crinkled foil also provides a good mating surface for the second part of the mold. Small screws were hot-glued to the rim to make sprues to allow air bubbles to escape.

When mixing small amounts of resin, using syringes helps you get the quantities exact. You can reuse them, just make sure you can tell which syringe is for part A and which for part B.

Casting success rate is about 90%. I have the mold slightly tilted (sprues higher) during the pour to help the air go in the right direction. Then I lay it flat and add a little more plastic.

The spoiler was made with a similar technique, using the foil to make a seam that makes it easy to get the part out of the mold.

Since I had some time while Shapeways was making the parts, I decided to improve the body model by adding some details and sharpening up the lines. I used Kneadatite epoxy putty as filler material in a lot of places.

Then I trimmed the new spoiler part and attached it to the body with UV-cure resin. This is the stuff that comes with a blue UV LED that will instantly turn the liquid resin solid; you just apply it, get the parts into the correct position, and shine the light on them to lock them together. It files and sands nicely, which also makes it a perfect filler material for fixing small imperfections in the casts (like the one in the spoiler).

Here’s the original casting and the new one, side by side:

My next challenge will be painting the model. If there is no part 3 to this build report, you may assume it is because the results were horrific.