pic: Team 306's (maybe) roller system.

Our current roller ball pickup system for our '06 robot is somewhat sloppy, so andrew and I have started designing plates to fix it. This is my submission.

The front roller (powered by Minibike) is mounted 6.5" off of the ground, and it is 2" in diameter, it is made of turned aluminum tubing, and spins at appprox. 2-3000 rpm. The back roller(powered by FP) is made our of 3" PVC and spins at the output speed of the FP transmission.

In my opinion, that is too more than enough power for a roller intake system (assuming balls roughly the same size and weight there were in previous games). You are allocating two of the stronger motors you are allowed, not only to a single task, but a task that can typically be acheived with much less power. We used a single mini-bike in 06, and it worked fine (our hopper did jam on occasion though, but the intake had little to do with that). We probably could (and should) have used even a lesser motor (as the minibike could, on a full battery, actually launch the balls out of the top of the robot), and allocated the shooter the 2nd minibike motor.

This is just a rebuild of our 2006 roller system. The rear motor helps to facilitate easy ball flow out of the hopper.

The independant control of the rollers is an important part of our ball feeding system. Without it our 'bot would bind up a whole lot more than it does. The fact that we have the mini-bike motor as the sole drive for the front roller is just because it was left over, and would do the job well. It also allows us to shoot balls into the corner goal from 5-10 feet away.

We used 1 minibike motor to shoot the balls and they went about 45 feet at max speed. We used the other minibike motor for our intake and it could throw the balls out of the robot before we finished it also.

3000 rpm is awfully fast. That means you’re actually gearing the big CIM up. I’m not so sure you want to do this, as you run the risk of either stalling the rollers, or depending on the hopper on your robot, shooting the balls right out of the top.

Secondly, adding that second roller creates a choke point. Your first roller may be running at 3000 rpm, but the second roller is running at a mere fraction of that. The speed of the second roller is the limiting factor, and you’ll never be able to utilize the higher rpm front roller to pick up balls faster if they all jam when they hit the slow roller.

Our pickup was somewhere around ~1000 rpm, and we could drive full speed into a line of balls and pick up all of them without having them feed too slowly into the robot, and jam.

The speed of the front roller is for scoring the balls more than picking them up, as it allows us to shoot the balls across the floor. The back roller stops the balls from shooting out of the top of our hopper when we pick them up, and acts as our stirring mechanism so our hopper doesn’t jam often. The Minibike motor has enough torque that unless something is terribly out of line, it won’t stall out (or hasn’t stalled out in the past).

The back roller doesn’t limit us to the point that we jam as we pick up, and we can run at full speed into a line of balls and pick them all up as well.

This design has already been implemented, and has worked Pretty well for the entire 2006 season, so the most obvious design flaws have already been remedied, This is mostly to make the robot look pretty. :smiley:

Ah, ok. I wasn’t sure if the second roller is needed to push the balls up into the hopper, or does what you described.

Just remember that according to the 2006 rules a low goal scorer like this still has to follow the 12 m/s speed rule.

What competition are you building this for or are you just doing it for fun?

This is the design from our 2006 robot. Right now we have two separate plates holding the different motors, and all we are doing is changing it to a single plate to give it rigidity, the ball travels 10-12 m/s when exiting our robot.