Overview
This set contains components for adding a tracked drive system to a small robot or vehicle. It consists of:
- Two silicone tracks
- Two ABS drive sprockets
- Two ABS idler sprockets
- Two M3 shoulder bolts with a 5mm threaded portion
- Two M3 shoulder bolts with a 12mm threaded portion
- Two washers and M3 nuts
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We make the sprockets in three different colors (black, red, and white) and the tracks in two different lengths (22 teeth and 30 teeth), which allows us to offer a total of six different track set combinations:
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Pololu 30T track set with red sprockets mounted on a 3D-printed chassis. |
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Side view of Pololu 30T track set with white sprockets mounted on a 3D-printed chassis. |
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- 22T tracks with black sprockets
- 22T tracks with red sprockets
- 22T tracks with white sprockets
- 30T tracks with black sprockets
- 30T tracks with red sprockets
- 30T tracks with white sprockets
Additionally, we offer the red sprockets and white sprockets by themselves (without tracks or fasteners) for use as replacements for the black sprockets included with our Zumo robots.
The flexible one-piece silicone tracks are available in two lengths, with either 22 teeth or 30 teeth that are designed to mesh with the drive and idler sprockets. The 22T set, with an overall length under 90 mm, is short enough to be used as the drive system for a mini-sumo robot (for example, our Zumo chassis and Zumo 32U4 robot).
The drive sprockets are designed to press-fit securely on the output shafts of our micro metal gearmotors, 15.5D mm metal gearmotors, and mini plastic gearmotors with 3mm D-shaft outputs. On our Zumo robots, these gearmotors are intended to be mounted with the raised lip on one side of the drive sprocket facing away from the motor, but if you are not using a Zumo chassis, you can insert the drive sprockets onto the 3mm D-shafts in either orientation.
Both the extended and non-extended versions of our micro metal gearmotor brackets work with these hubs.
Although the drive sprockets are similar to the hubs used in the Pololu 42×19mm wheels, they are not as wide, so they do not physically support the whole tire.
A pair of idler sprockets is also included in the set; these are very similar to the drive sprockets, with the main difference being 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 blue component labeled “ROBOT CHASSIS” represents a bracket or piece of a robot chassis that the sprocket is being mounted to, and is not a part included in the set.) Our nylon spacers with 3.3 mm inner diameters can be used to offset the sprockets from a flat mounting surface.
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Exploded view diagram showing an idler sprocket and its mounting hardware. |
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We include two pairs of shoulder bolts with the kit, one with a 5mm threaded portion and one a 12mm threaded portion, so you can pick the pair that is appropriate for your application. You will only use two of the four included shoulder bolts.
Details for item #3031
This track set comes with red sprockets and 22T tracks.
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Pololu 22T Track Set – Red. |
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Dimensions
A dimension diagram containing the sprockets, tracks, and bolts is available here (618k pdf). Several key dimensions are highlighted below:
- Sprocket diameter: 35 mm (1.38″)
- Diameter with track: approx. 39 mm (1.54″)
- Track width: 14.6 mm (0.57″)
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 48 mm for the 22T tracks and 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.
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Sprocket spacing diagram for the Pololu 22Tand 30T track sets. |
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These track sets are similar to our original 22T and 30T track sets, except they replace the old sprockets with newer, spoked versions. This spoked design removes material from several areas near the central hub of the sprocket, which has the advantage of allowing the drive sprocket to be more easily removed from the D-shaft of the motor while still remaining firmly fixed after being press-fit into place.
