Robot Chassis and Drive Train

This entry is part 5 of 6 in the series Autonomous Object Avoiding Robot  

The Treads

Since Tiny Bot uses a differential steering method (drive wheels operate at different speeds/rotation direction to determine heading).   I decided that I wanted to try using a track set.   After an exhaustive search online, I decided on the Pololu 30T tread Set. Since the price was so reasonable, I wasn’t sure what to expect as far as quality. But they have withstood the durability test of my 3 and 6 year-old kids!

I have been very impressed with the durability of these tracks.
I have been very impressed with the durability of these tracks.

To mount the tracks, I used 2 lengths of aluminum angle stock and drilled small holes for the track wheels and large holes to allow for the motor shaft.  To fasten the front wheels and still alow them to spin freely, I used a long 4-40 machine screw and tightened a nut on each side of the aluminum.  Using a threaded bolt for an axle is not ideal but it seems to work fine for this purpose, anyway.

Front wheels are attached by using two 4-40 nuts tightened against the aluminum L-stock
Front wheels are attached by using two 4-40 nuts tightened against the aluminum L-stock

The rear wheels are attached to the motor by hot glue.  The shaft of the motors are flattened so the glue fills in all voids avoiding slippage.

Mounting the Motors

The motors I used were very small gear motors.  I purchased them as part of a lot on Ebay so I’m not sure their origin or torque.  However, they are very powerful for their size and they run at about 100 RPM at 12V.  Pololu has a set similar to them here.

To mount the motors to the chassis, I chose 1/2″ conduit clamps and double-sided foam tape.  The soft plastic of the clamps make them flexible enough to provide some tension when screwed down.  The foam tape also helped keep everything tight.

1/2" conduit clamps and some foam tape make cheap motor mounts.
1/2″ conduit clamps and some foam tape make cheap motor mounts.

Happy building!

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