As of right now my team and I are pretty settled on the idea of fielding robot. At our states competition, the successful robots in the high school division had one thing in common: a fast base. Many of these robots were astonishingly fast and being able to pick up as many balls as we can is definitely an advantage in the game. The thing is, I can’t build a fast base.
My robot is about 14 pounds and the maximum sprocket ratio I can get with my chained base is 1 to 1. I would try to put some gears but none of the combinations mesh together perfectly and otherwise the robot has like no torque.
I need some advice from high school students. For example, how many pounds is your robot? and what is your gear/torque ratio.
Also, do you guys have any tips for chain. Every match I always see a piece of chain, and it seems to turn out be ours. I just needed my construction to be robust.
I’ve had more success with chain on our drivetrain than anything. The only axis you really need to worry about when lining up is the position of the sprocket relative to the axle, and spacers make it pretty easy to make sure both sprockets are in line. We are around 18 pounds with 2.75" wheels running 3:1 externally with 6 motors. I haven’t had any problems with stalling yet, and can move around pretty fast. The hardest part of a fast drivetrain is eliminating friction. Make sure that every axle will spin for a good 10 seconds with a wheel on it after you spin it. Make sure all of your bearing blocks are tightened and in line, and make sure your axles aren’t bent.
If your chain is in that irritating spot where its either too tight or too loose, make it loose, then use spacers on screws to tighten it. Sort of like this: http://i.imgur.com/TK9lSvhh.png
Wow… Tiny picture.
It does add friction to a minor degree, but if the spacer is able to roll freely, then it doesn’t add any more friction than a freewheeling sprocket. Generally chain isn’t the best choice for frictionless systems anyway, it takes so much extra work to make it perfect.
Well generally if the chain is properly tensioned, then it shouldn’t snap. Just check all the links once and a while to make sure they aren’t coming loose. I have had chains trying to power something that couldn’t be moved (engineering error :P) instead of breaking they simply jumped and skipped on the sprocket. (Of course this can happen is they are simply overly loose)
I’ guess I’m assuming you’re using high strength chain?
My robot weighs around 18 pounds (I’m guessing, as we don’t have a scale to use) and it has high speed motors geared together to power one axle, which powers a 4" omni wheel, which is then chained to a shaft encoded and another omni wheel. I haven’t had any issues with chain snappage.
