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Originally Posted by [527]phil
team 1114 had a motorized cart last year, since we're getting different motors this year i suggest using the old drill motors with the helical gearboxes, i don't think anymore gearing is required after that, just attach the wheels directly to the gearbox, it seemed to work for them
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That cart was my little baby. It was an offseason project to determine weather a CVT was viable. As it turns out it was. It used 1 drill motor with the planetary gearbox, and a set of variable diameter pulleys from
www.hi-lo.com
They worked by having 2 pulleys that expand and contract. One is spring loaded, while the other one has a handwheel that turns to vary the pulleys diameter.
It worked out quite well for our application, and achieved a speed of 2tf/s in the low end of the CVT and about 8ft/s at the high end. I also played around with the sprocket ratios on the wheel to make it go faster for racing around the halls at school.
I don't think the variable diameter pully system is the way to go for FIRST robots. the system is
1. bulky
2. heavier than many 2-speed designs
3. harder to control than a 2-speed, since you need to have a motor and a potentiometer to change the gear ratios. For our application, we just turned the knob on the bottom manually.
4. Although we never experienced any slippage in the pulleys, the chance exists under high loads.
All in all, building a cart can be a good offseason project, and can be a good test platform for new designs. Or you can just put a sound system in and make it look cool, either way, carts are cool.