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Friday, January 2, 2009

When a droid SLAMS on his brakes

Ok, mystery solved. I took apart R2's drive system and foot shells to give him a wheel alignment. And I did discover that one leg was an inch or two lower than the other so I modified the one mount.

The next step was to drive the droid on the driveway (without dome or foot shells) and see if the skid marks from the wheels still appear on the driveway. I can watch the process easier without the foot shells. And sure enough new skid marks appeared on the driveway. But this time I was able to pinpoint when and why. They happened when I let off on the throttle and the speed controller applied it's version of brakes to the droid motors. And just like in a car, when your droid "slams on the brakes", skid marks will appear on the driveway. Got me thinking .... maybe if I rewired R2 to 24 volts, I could squeal the tires during acceleration and produce skid marks that way.

So the mystery of why there's skid marks on the driveway is solved. AND the wheels are better aligned. Now to balance the foot shells better. I got some good information from Marc B regarding my foot shell alignment so I'm thinking about a few alternatives I now have.


Cori said...

Is there any potential (no pun intended) to control the acceleration and decceleration ramps on your speed control?

There is some R/C logic on the market for model turbines to prevent compressor stall using ramp angles, maybe your radio already has it?

Jim Quinlan said...

Thanks for the feedback Cori. Actually there probably is a way to control the speed control with my setup but I think these default settings will be ok. I tested my droid on the driveway which is on a hill and actually the skid marks happened going downhill. I'm glad that the droid has the capability to stop when you remove the throttle for safety reasons. In case a little kid runs in front of the droid in motion, I want it to stop asap. And R2 makes it appear as a pretty smooth stop considering the tires dragged a little. It's not jerky.