Let's Make Robots!

Need advice about tracks

Hi all !

I am currently working on a tracked robot (electronics is finished, starting mechanics).

The tracks I am planning to build look like that :

I will you use the "pattern" described on many projects on LMR (the one using bicylcle chain, nuts...).

My question is : how much important is the choice of the wheel that will be connected to the motor ? I had planned to fix the motor on the wheel "A" on the picture but I am wondering if this is a smart choice. Because the belt will be driven by friction, would it be more efficient if the driven wheel was one of the bottom (B or C) (which will be in contact with the floor by "gravity" ;).

Thank you  ! :)

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Chris the Carpenter's picture

All that is assuming that "A" is the back of the robot.  If your picture moved, the robot would be going from left to right on the screen with "D" being the nose of the robot.

LordGG's picture

Hi Chris,

Yes, you figured it out well, A will be the back, D the noze :)

Thank you, since you both agree on A and that it is the easiest way for me, I will go for A !

Chris the Carpenter's picture

I would also say A or B (Probably A) for the fact that, during normal operation (forward) that drive wheel is "pulling" the track. Now, I suppose that because the track is a circle, any wheel would be "pulling" depending on how you look at it, but because the track is never going to be 100% tensioned, there will always be a taught side and a slack side. It makes sense to me to put the slack side on the top and the tight side down where the work is being done.

OddBot's picture

In your drawing, A or D are the best wheels to connect to your motor because there is more surface area between the wheel and the track (the track wraps around a larger portion of the wheels circumference).

If you were to drive wheels B or C then most of the time they would not grip the tread sufficiently and skid. This would mean your robot goes nowhere while it spins it's wheels.

With tracks you need maximum grip between your drive wheel and the tread.

LordGG's picture

Hello OddBot,

Thank you for this accurate answer :)