Pololu Zumo Chassis Kit (No Motors)

The Pololu Zumo chassis is a small, tracked robot platform that is less than 10 cm on each side, allowing it to qualify for Mini Sumo competitions.

The chassis is composed of black ABS and features a compartment for four AA batteries and sockets for two micro metal gearmotors. It ships as a kit with two silicone tracks, two drive and two idler sprockets, a 1/16″ acrylic mounting plate, and mounting hardware (Motors and batteries are not included).

The battery compartment terminals protrude through the chassis and can be accessed from the top side. A black acrylic plate is included with the chassis. This plate holds the motors in place and can be used for mounting your electronics, such as your microcontroller, motor drivers and sensors.

The drive system consists of two black silicone tracks, one on each side, that are each supported by a freely spinning idler sprocket and a motor-driven drive sprocket (see the Motors section below for more information on how to select appropriate motors for your robot).

Assembly instructions are available in the user’s guide.

Motors (not included)

The Zumo chassis uses two motors, one for each tread. The ideal motors for your robot depend on your desired torque, speed, and current draw, so motors are not included with the chassis.

We generally recommend using high-power (HP or HPCB, which have long-life carbon brushes) versions of our micro metal gearmotors since the tracks require a decent amount of torque to move effectively; higher gear ratios of the non-HP motors might work if you want lower current draw, but they will be slower and offer less control.

Specifically, we primarily recommend the Pololu 50:1, 75:1, or 100:1 HP or HPCB motors for use with this chassis. The following table summarizes the key specifications of these three gearmotors. The first four columns are specifications of the motors themselves, while the last column is the measured top speed of a Zumo chassis loaded to a weight of 500 g and driven with these motors. Note that the specifications are for 6V operation, which is approximately the voltage you would get with four alkaline batteries; four NiMH AA cells will typically provide less than 5V.

Micro Metal Gearmotor	Free-Run Speed @ 6V	Stall Torque @ 6V	Stall Current @ 6V	Top Zumo Speed @ 6V and 500g
100:1 HP or 100:1 HPCB	320 RPM	30 oz·in	1600 mA	20 in/s (50 cm/s)
75:1 HP or 75:1 HPCB	400 RPM	22 oz·in	1600 mA	25 in/s (65 cm/s)
50:1 HP or 50:1 HPCB	625 RPM	15 oz·in	1600 mA	40 in/s (100 cm/s)

Electronics (not included)

You can add your own motor drivers, sensors, and programmable controllers to this chassis, or you can get one of our more complete Zumo robots, which include electronics designed specifically for the Zumo chassis.

If your goal is to make a robot based around a controller other than an Arduino, we recommend the DRV8833 motor driver carrier for use with this chassis.

Batteries (not included)

This chassis works with four AA batteries. We recommend using rechargeable AA NiMH cells, which results in a nominal voltage of 4.8V (1.2 V per cell).

When the batteries are fully charged, they will be well above 5V, and when they are almost spent, they will be well below 5V. As such, you might consider using a step-up/step-down voltage regulator to power your logic, since this will hold your logic voltage steady at 5V, no matter if your battery voltage is above or below 5V. You can also use alkaline cells, which would nominally give you 6V, but that voltage would drop depending on the load.

Basic sumo blade (not included)

We carry a basic stainless steel sumo blade that can be mounted to the front of the Zumo chassis. With this blade, the Zumo chassis can push around objects, such as other MiniSumo robots. You can also use the design file for this basic blade as the starting point for a custom sumo blade.

Dimensions

Fully assembled, the Zumo chassis is 98mm wide, 86mm long, and 39mm high, with approximately 5mm of ground clearance.

Since each side is smaller than 10 cm, this chassis meets Mini-Sumo size requirements. The front screws used to mount the acrylic plate to the chassis can also be used to mount a front scoop that can extend up to 14 mm before exceeding the Mini Sumo limits. The assembled Zumo chassis weighs approximately 210 g with motors and batteries.

Resources

• User guide
• Design file
• 3D Model
• Tuning tips