1950 BRM Type 15 (Pinewood Derby Car Shell)

Summary

Full 3D View

The BRM Type 15 was built to showcase British Racing Motors' supercharged 1.5-litre, supercharged V16, which produced 600 hp--more than any other contemporary engine. The car was very fast, but extremely unreliable, so it was never really competitive in the Formula 1 World Championship series.

BONUS: The car is pictured with show wheels and tires, not legal for racing. Models are included for the show wheels and tires, in case you'd like to use them. (The larger tires obviously are intended for the rear.)

Race Configuration: Use the official wood block that comes with the kit, cut to the shape of the Shaped Block, and the wheels that come with the kit.

Show Configuration: Use the upper holes in the Shaped Block with the 3D-printed show wheels.

What is a "pinewood derby car shell"?

A pinewood derby is an event created by the Boy Scouts many years ago. Each scout is given a pinewood derby kit typically consisting of a block of wood with slots for axles, 4 wheels, and 4 nails to be used as axles. The scout (and his dad, usually) will then carve the block of wood into the shape of a car, paint it and apply stickers, install the wheels on the axles, and then race it at the "derby", which involves a sloped track with a timekeeping apparatus.

An official scout derby will usually require that the parts in the kit be used for cars entered in the derby. Other organizations (including workplaces) often hold derbies, too, and some of them require the use of the parts in the box, including the block of wood.

These "pinewood derby car shells" are intended to be used with an official derby wood block, cut down to size, along with the axles and wheels included in the kit. A printable model of the shaped wood block is provided. You can either use the printed model or use it to accurately cut an official wood block down to size.

Printing

• Body: Requires normal supports on the build plate only. This is a VERY light model, so you may need to use a very high (60%+) fill to bring the weight up high enough to hit 5 ounces, even with tungsten weights. (You can always add weights under the car to hit the 5 oz. limit.)
• Exhaust pipes are pretty easy to print with normal supports.
• The gas cap, windshield and steering wheel are easiest to print with brims.

Post-Printing

Assemble the car using super glue. The seat and windshield are very difficult to get aligned, unfortunately, but I couldn't get the look I was after any other way.

Smoothing

This particular model design can be smoothed pretty well just using sandpaper, if you print it with ABS. If you want to use PLA or you'd like an even smoother surface, you can smooth it with a resin/baby powder mix. You can find videos and guides online that describe the process, but here it is in a nutshell:

• Mix 1 part resin and 2-3 parts baby powder in an opaque container (so that it can be stored without hardening due to UV exposure).
• Using a paintbrush or cotton swab, spread a thin layer of the resin/baby powder mix over the body, wherever you want to smooth print lines and gaps.
• Use a UV flashlight (a cheap one--like the kind used to harden resin finger nail polish, which you can order from Amazon or buy in the pharmacy department of Walmart) to harden the resin.
• Sand the body smooth until there are no thick layers left.
• Repeat over any areas that are still rough.

Other Notes

You can add tungsten weights to the hole in the rear of the body. If you plan well, and use enough infill, you can maximize the weights and end up right at 5 oz.

Patreon/Commercial License

I just do this for fun BUT if you insist on throwing a couple of bucks my way or if you'd like to sell prints of any of my designs, see my Patreon page.