Shooter Issue

[EagleEngineer]

So we finally are getting close to getting our robot complete, but we decided to test our shooter. We are running a linear shooter with 2, 4 7/8 in Orange Banebot wheels using 2 RS550's. The first wheel is on a 4:1 reduction, while the second wheel (final wheel that touches the Frisbee) is on 1:1 (via versa gearbox). We had 3/8 of an inch of compression. We tested the shooter and it shot about 12 frisbees (around 20-30 feet), and then the second wheel's orange tread bursted off. (basically the rubber tread popped off the wheel). We tested it again (with a new wheel), and the same thing happened after around another 12 shots. Why do you think the tread is popping off? is it the excessive speed of the second wheel... or the excessive amount of compression?

[BJT]

If I read this right, you have a 4 7/8 inch wheel on a 1:1 rs550. the tread didn't fly off, it achieved warp speed and is in the next galaxy.

Or its really late and I missed something.

[EagleEngineer]

If I read this right, you have a 4 7/8 inch wheel on a 1:1 rs550. the tread didn't fly off, it achieved warp speed and is in the next galaxy.

Or its really late and I missed something.

no your right. its a 4 7/8 wheel on a 1:1.

[Mr V]

Centrifugal force is causing the rubber to expand due to the high speed. You could try one of the Blue compound ones or slowing it down.

[ablatner]

Your shooter is definitely way too fast. With a 1:1 ratio off a 20,000 rpm 550 using a 4.875" diameter wheel, you end up with a 425 ft/s tangential velocity (http://www.wolframalpha.com/input/?i=20000rpm*1min%2F60s*pi*4.875in%2Frev*1ft%2F12in ). That's 290mph, and there's no way your shooter is accelerating the frisbees to even close that speed. It would be much better to slow it down and increase the torque. Because of the extra torque, the speed will drop less as you shoot, and your shooter will more effectively accelerate the frisbees.

[Johnny]

I'm sorry but i lol'd after reading this post. If you really wanted to run your wheel that fast (can't really imagine why) i would try using wheels with fastened tread (pop rivets, machine screws). Those type of wheels might be able to survive those kind of velocities.

Honestly, our team has tested the wheels and have figured that 5000rpm is the absolute max you would want to spin with a 4 inch diameter wheel with similar torque to that of a cim motor (350 oz/in i think). Keep in mind that changing the diameter of your shooter wheel DRASTICALLY changes the velocity. You can achieve similar results to what you have mentioned with a 8 inch wheel spinning at say 2500 rpms (i didn't actually do the math). Find a physics teacher and have them show you how to calculate these things. Your effort will be rewarded with full court 3 point shots :D

[Andrew Lawrence]

Centrifugal force is causing the rubber to expand due to the high speed. You could try one of the Blue compound ones or slowing it down.

Sorry if this seems kinda out there, but it's Centripetal Force that causes the rubber to move outwards tangent to the direction of rotation. Centrifugal Force does not exist. :)

[cdizzle]

Sorry if this seems kinda out there, but it's Centripetal Force that causes the rubber to move outwards tangent to the direction of rotation. Centrifugal Force does not exist. :)

Sorry if THIS seems kinda out there, but it is actually Inertia that causes rubber to move outward, Centripetal Force pushes inwards.

[Alan Anderson]

Sorry if this seems kinda out there, but it's Centripetal Force that causes the rubber to move outwards tangent to the direction of rotation. Centrifugal Force does not exist. :)

If you look at it from the point of view of the non-spinning outside world, Centripetal Force causes the edge of the wheel hub to move "inwards" away from the rubber, which tries to continue in a straight line.

If you look at it from the point of view of the spinning wheel, Centrifugal Force is real and strong.

http://www.youtube.com/watch?v=-LDxOSz80pI

http://xkcd.com/123/