Soap Box Derby Cart




About: Ship builder professionally, scout leader for fun

This a simple soap box cart that my son and I built for my 9year old daughter so she could enter the Trowbridge Carnival Soap Box derby

Step 1: Basic Frame

We used planed softwood, 2.1m x 74mm x 18mm for the frame and 2.1m x 50mm x 18mm for the front axle.  The king pins for the steering will be M10 x 100mm bolts

The cross brace at the front is 400mm as is the the brace that forms the "radiator" whilst the rear is at 600mm

The wooden pole is from a beach wind break and is used to estimate where the driver will be sitting.

The body frame work is made using 25mm x 25mm softwood and its size was based on my 9yr old

Step 2: Bodywork

Cheap, fine plywood.
In order to minimise waste and keep costs down the frame was wrapped in craft paper. We used this to calculate how much ply was needed. 
The paper also formed the templates for each panel

The wheels, again just as a guide

The grill, seat and floor are made from pieces of chipboard I had lying around in my shed, you might also notice that the dumb irons at have been shortened.  I thought this improved the proportions of the cart.

Step 3: Steering

After much experimentation the steering system finally consists of:

1. Steering wheel from an old games console
2. Steering column made of tubular clothes rail
3. A bicycle front crank
4. two 15mm brass plumbing equal T pieces
and a couple of go-kart track rods bought from e-bay

In one picture you can see we used the bike chain to check we had the frame, king pins and steering square.

The tube was cut in half and a another piece found to fit snugly inside. the was clamped using U bolts so that we created a rudimentary collapsible steering column. One end bolted to the steering wheel and the other welded to the bike crank.
Ultimately the crank was drilled  to allow the track rods to be fitted, creating in effect a Pitman arm.

Step 4: Finishing

Simple brakes were added the act directly on the rear wheels, some lights, a horn and some wings for the front wheels.

The whole thing then finished off with green and yellow paint.  The racing numbers are created using white sticky back plastic and red insulating tape for the No 7.



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    14 Discussions

    GarethMorrisJack The maker3

    Reply 2 years ago

    I've used 2 methods:
    i. a simple push operated bar that acts on both rear wheels, a simple pivoted pedal connecting to a bar acting on the front of the rear wheels.
    ii The second method was bike brakes, a wooden batten fixed in front of the rear wheels cable operated in the same way as on a bike. The brake lever mounted to the cart body. If you use a go cart steering yoke then the lever may fit straight on to the yoke.

    GarethMorrisJack The Maker2

    Reply 2 years ago

    it would possible, although I think an electric motor would probably be the best choice.


    3 years ago on Step 4

    Beautiful! Thanks so much for the plentiful and super clear photos, especially the close-ups of the steering arrangement. Makes this really doable!


    4 years ago

    just wanted to drop a comment to thankyou for a great 'ible. followed it pretty closely (albeit with a few personalised tweaks) and it bagged me a trophy in a recent event. good stuff and keep them coming

    244 Jake

    5 years ago

    Gee in about 1960, I made my down hill run in derby, in those days in Tampa Florida we had to use standard tire / wheels, that derby guys idea on brakes. And a straight front and rear axles.
    Your project does bring back some good images of family and friends.

    Thanks and best of luck!

    Big Jake


    5 years ago

    You sir are a man among men it did my heart good to see you (and daughters) project kudos to you
    (From a dad of two grown girls)


    5 years ago

    Looks good!!! We just went past Derby Downs here in Akron this part weekend.... Hope to see you there next year!!!

    chuck the canuck

    5 years ago

    growing up I always wanted a soap box but there were no derbies near me. now the city I live in started derbies. looks like I will have to recruit a neighbor kid to drive so I can make one