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Originally Posted by Matt Adams
I would fight to the tooth (with numbers of course!) that you can not have a robot that is both competitively fast and competitively strong using only one pair of drill motors or the chips without a mulit-ratio transmission.
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That statement depends very highly on the game that you are playing. For example, last year you did not need to have pushing power if you weren't solely a ramp dominator. Take team 25, one speed, 4 motors, 12.5ft/s. All you need to move someone off of something, top of the ramp for example, is momentum (p=mv). No where in the formula for liner momentum is torque taken into account. Then you could also argue that team 25 was a strong robot for defense because of thier brake system. Or like any other robot with a high coef. of static friction, you can just turn sideways for defending a stack, or in previous years a goal. A 4 motor drive geared correctly for one speed can always be competitive.
Take last year for example, FIRST made it a little easier on everyone by making the ramp top out of hdpe so that way everyone would have a fair fighting chance for it at the end of the match. In most cases a fast robot could charge the ramp at the last few seconds and push down a stronger robot with thier momentum,which lead other teams to develope a method to keep thier robot attached to the hdpe by means other than just a drive system. Innovative new ideas can beat widely spread old ideas.
When picking your drive and wether or not your team wants to shift gears, analize the game first and then decide wether or not you actually need to shift to accomplish all the things you want to do in the game. If you can think of more reasons not to shift gears and concentrate somewhere else on an arm or such, then you should probably put a 2 speed tranny off to the side untill needed. If need the most pushing power or the most speed to accomplish your goal, then concentrate in there if you do not have the resources to make a shifting tranny. If you make a list of things you want your robot to do and high mobility is on the list, then I would suggest investing time in a swerve/crab drive rather than a 2 speed 1 dirrection drive.
One thing to keep in mind for everyone designing your multispeed tranny's: the shifting mechanisms can wear down to the point where they become unshiftable. You may want to keep that in mind with some methods so that if you are forced to lock it into one speed, you'll still be able to be competitive in that speed. Meaning don't set a goal of your robots high speed to go as fast as possible without tripping breakers, but then also try to be fast enough where you can be competitive if need be to lock into low gear. For that reason you also may want to make your multispeed tranny have 4 motors, since in many cases adding in another motor will only require 1 or 2 extra gears and so the power added is well worth it. You can also design it so if need be, you can add a motor or easily take out a motor if you decide to use it for a mechanism or if you just can't make weight. Just some of my thoughts on the subject...