This track set includes a pair of 30-tooth silicone tracks, two drive sprockets measuring 35 mm in diameter, and two matching idler sprockets along with mounting hardware. The drive sprockets are designed to work with 3mm D-shafts, such as those on our mini metal gearmotors.

This set contains components that are great for adding a tracked drive system to a small robot or vehicle. It consists of:

• Two silicone tracks
• Two drive sprockets
• Two idler sprockets
• Two shoulder bolts, washers, and nuts

The flexible one-piece silicone tracks are designed to mesh with the drive and idler sprockets. The 30T set, with an overall distance between centres of 85mm, is short enough to be used as the drive system for a mini-sumo robot.

The drive sprockets are designed to press-fit securely on the output shafts of geared motors with a 3mm diameter 'D' shaft such as our Solarbotics mini metal gear motors. These gearmotors are intended to be mounted onto the side of the hub with the protruding teeth. The output shaft will slide into the socket easily at first but will achieve a snug fit when pressed through to the other edge of the hub. When the drive shaft is too short,  they will have to be mounted onto the other side of the sprocket where the fit is tighter. 

Although the drive sprockets are identical to the hubs used in the Pololu 42×19mm wheels, they will not work reliably with the quadrature encoder associated with those wheels. The tracks do not block enough ambient light around the teeth of the sprocket, so the encoders will be unable to achieve a good contrast between black and white unless you take special measures to shield them.

A pair of idler sprockets is also included in the set; these are identical to the drive sprockets, except that they are designed to spin freely instead of attaching to a motor shaft. They can be mounted with the provided shoulder bolts as shown in the diagram below. (The red block represents a bracket or chassis that the sprocket is being mounted to, and is not a part included in the set.) Nylon spacers can be used to offset the sprockets from a flat mounting surface.

Dimensions

• Sprocket diameter: 1.38" (35 mm)
• Diameter with track: approx. 1.54" (39 mm)
• Track width: 0.57" (14.6 mm)

A dimensioned drawing of the sprockets and the shoulder bolts included in this set can be seen above. The threaded portion of the shoulder bolts can be cut to the desired length.

The ideal spacing between the centers of the two sprockets is about 85 mm for the 30T tracks. Because the tracks are elastic, they will maintain tension even if you do not precisely match this distance. However, if the spacing is too short, they will be loose and more likely to slip off; if the spacing is too long, additional strain will be placed on the sprocket shafts, and the motor might not be able to turn as well.