Sawppy the Rover’s Wheel on a Stick

Early on in development of Sawppy‘s wheel and steering knuckle mechanism, it was useful to do a quick physical test to make sure nothing silly was overlooked in digital design. The rover has six wheels, but we only need one to start. Introducing the Wheel on a Stick!

This test rig lets us put load on the wheel steering subsystem in a way that’s much closer to how the rover will work. By holding the aluminum extrusion and pushing it in various directions, we could get an idea how this subsystem will react with more confidence than we would if we were just pushing on the individual pieces with our hands.

And once the basic mechanical pieces were proven to work, servo motors were installed to test how it all moves. Reading servo spec sheet is one thing, actually seeing it move in person and feeling the actuator forces should be quite a confidence builder. Or it would be, if the servos had any traction.

Both drive axle and steering joints had their bearings and 8mm steel shafts here, but they did not yet have slots for retainer clips and more importantly, they did not have detents for set screws. As a result the couplers didn’t grab very tightly. All we could tell is that these LewanSoul LX-16A serial bus servo motors are stronger than our shaft coupler’s grip, which isn’t very much.

We could still go without the retainer clips for a bit, but before we can verify we have enough motor strength for a rover, we need to put in those detents and set screws.

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