Making Shoebox Rovers for Racing

The Sojourner rover was 1997's big hit. Who could forget the little rover that could? And who didn't want a rover of their own? Sojourner made rovers very cool. She was so popular that she spun-off two rover toys. One was good looking, wire-controlled, toy that only one motor between its two drive wheels (the other four wheels were just idlers). The rover could drive forwards and backwards, but couldn't turn left or right. Unlike the real Sojourner, this toy was the rover that couldn't.

I met the toy Sojourner rover at the Oregon Star Party (OSP) in 2004 were I was asked to judge OSP's Rover Races (I was demonstrating a wireless rover and was the president of the Boise Robotics Group - The BoRG). After watching contestants steer their rovers by kicking them, I resolved to design a better rover. I've finished designing a simple and affordable rover and this article will teach you how to built the rover. It's my hope that this rover can become the standard for rover races at star parties, Space Day, and Astronomy Day.

Wanna drag?

The shoebox rover uses commonly available materials and requires simple machining. The largest tool you'll need is a drill press. A Dremel or other small handheld electric drill is perfect for cutting holes in the shoebox. The only uncommon tool is a tubing cutter, which you can purchase at your local hobby store.

A Dremel with small drill bit and a tubing cutter

The shoebox rover is built in the following steps.

  1. Convert two battery-powered screwdrivers into the rover drive
  2. Assemble and install the axles
  3. Build the APXS (Alpha Proton X-ray Spectrometer)
  4. Make a set of six wheels
  5. Wire the rover for power
  6. Add the photovoltaic array

Your junk box may already have many of the items needed to build the shoebox rover.

The Rover Bill of Materials

Item

Store

Number

Price

Total

¼”-20 1” Headless setscrew (M71567)

Ace

2

0.30

0.60

1” lamp nipple 1/8 NPT (M64742)

Ace

4

0.40

1.60

Hex locknut (M64615)

Ace

8

0.22

1.76

¾” PVC cap SCH40

Ace

1

0.19

0.19

3/8” Fender Washer (1-1/4”)

Ace

8

0.17

1.36

1/4”-20 Threaded Rod 12” long

Ace

2

2.00

4.00

4” PVC Drain Cap

Home Depot

2

1.25

2.50

3” PVC Drain Cap

Home Depot

4

0.89

3.56

¼” Fender Washer (1-1/4”)

Home Depot

10

0.11

1.10

¼ “ regular washer

Home Depot

1 bag

0.88

0.88

#4-32 nuts and bolts (1/4”, 1/2”, 1”)

Home Depot

3 bags

0.88

2.64

½” by ¾” pine (2 feet long)

Home Depot

1

0.46/ft

0.92

¼” plastic clamps

Home Depot

1 box

1.19

1.19

1/8” thick, 2’ by 4’ hard board

Home Depot

1 sheet

2.65

2.65

Aluminum duct tape

Home Depot

1 roll

3.97

3.97

1-1/4” Galvanized steel pipe straps

Lowes

1 bag

1.43

1.43

Mini roller lever switch (275-0017)

Radio Shack

1

2.69

2.69

Heat Shrink Tubing (278-1627B)

Radio Shack

1 bag

2.59

2.59

Green LED (276-0022)

Radio Shack

1

1.29

1.29

470 ohm ¼ watt resistor (271-1317)

Radio Shack

1

0.99

0.99

12V DC mini buzzer ( 273-055A)

Radio Shack

1

3.29

3.29

#24 (22) AWG wire (278-1222)

Radio Shack

1

4.99

4.99

2 “C” cell battery holder (270-385A)

Radio Shack

1

1.59

1.59

9V battery snap (270-0324)

Radio Shack

1

2.59

2.59

9V battery holder (270-326B)

Radio Shack

1

0.99

0.99

DPDT toggle switch (275-0620)

Radio Shack

1

4.99

4.99

Nylon wire ties (278-1632)

Radio Shack

1 bag

1.79

1.79

#84 rubber bands

Staples

1 bag

0.99

0.99

Silver spray paint

Wal-Mart

1

2.67

2.67

1” diameter wooden dowel

Wal-Mart

1

2.32

2.32

Rubbermaid 6.5 quart plastic shoe box

Wal-Mart

1

1.32

1.32

Black and Decker Alkaline Screwdriver

Wal-Mart

1

7.87

15.74

Broken PS1 hand controller

Neighbor kid

1

0.00

0.00

You can use Sintra in place of the hard board. Sintra is a foamed PVC and is very easy to work with. I used Sintra (since I had it available) in place of hard board for my shoebox rovers. Sintra is available from plastic suppliers and some on-line robot stores.

Modifying the Screwdrivers

In this step you'll shorten the screwdriver cases and add axles for the drive wheels. You'll need a small hacksaw, fine tip straight slot screwdriver, needle nose pliers, hot air gun, and soldering iron to make this modification. Let's get started.

First, make sure the screwdriver is set to POWER, and not MANUAL. In MANUAL, the drive train is locked and the motor doesn't turn.

Note: Be careful that the gears don't fall out (it's easy, but slightly greasy, to replace them)