Team 2363 double wheeled shooter prototype

[ToddF]

Video here: http://www.youtube.com/watch?v=neqyzZ1SM2w

We hooked up the drive motor two ways. First, the CIMple box output shaft directly drove the the wheels. This produced shots similar to those from the single wheeled prototype. (http://www.chiefdelphi.com/forums/sh...hreadid=100266) Then we used chain driven sprockets to speed the output. This produced the shots in the video.

We didn't make any baskets because pointing the shooter directly at the backboard caused the shots to bounce off before they reached the apex of the trajectory arc. Our room doesn't have the headroom for us to tilt the shooter back far enough to arc the shots into the hoop. The shooter was ~16 feet from the backboard.

Some numbers...
when direct driven by the CIMple box:
- CIM motor free speed 5310 RPM
- CIMple gbx reduction 4.67:1
- pitching wheel speed 1137 PM
- pitching wheel tangential speed 39.7 ft/sec
- ball center speed 39.7 ft/sec

with sprockets driving the wheels:
- CIM motor free speed 5310 RPM
- CIMple gbx reduction 4.67:1
- gbx output shaft speed 1137 PM
- chain drive speed multiplier = 40 teeth/15 teeth = 2.67
- pitching wheel speed 3032 RPM
- pitching wheel tangential speed 105.9 ft/sec
- ball center speed 105.9 ft/sec

Calculations assume:
- motor running at free speed (not true because of inefficiencies in the transmission)
- ball leaves the pitching wheel traveling at the tangential speed of the wheel (may or may not be true depending on the friction between the wheel and ball)

Ideal calculations give a good rule of thumb for comparing various transmission designs. We would have saved ourselves a ton of time if we only had a shaft coupler to direct connect the CIM output shaft to the wheel shaft.

Next we'll hook up a motor controller to see how reducing the motor speed affects the shots. We may also go outside to see how far we can make baskets, at full motor power, given adequate headroom. Then, it's on to the catapult prototype.

[Ernst]

That looks really good, but I have few questions.

1. How much is the ball compressed?

2. Does the ball have much spin in any direction?

[MrForbes]

Interesting to see the ball bouncing off the backboard....we sort of predicted that by throwing a ball at the wall, using no spin, topspin, and backspin. The backspin technique made the ball bounce down, in the direction of the basket. So our shooter prototype is a single wheel, below a flat plate. It seems to work well if the wheel is spun up over 3000 rpm

http://www.youtube.com/watch?v=jeLe2WWemWA

To do this, we borrowed a custom made Fisher Price gearbox from a previous robot, and tried it. The ball didn't shoot very far the first time we tried it, so we moved the gears in it around to get less gear reduction, so the wheel would spin faster. That did the trick.

We're thinking that using just the first gear from the 2012 FP gearbox, and the 2012 FP motor with it's 19 tooth gear, will work well. Making a gearbox like this kind of requires a lathe, and the ability to accurately make some holes in thick sheet aluminum, but it's relatively easy as far as building gearboxes goes.

[Andrew Zeller]

My team has also discovered that a single spinning wheel with a curved plate is quite effective. Check out the video:

http://www.youtube.com/watch?v=Hb73f...1&feature=plcp

[Eminent Waffle]

I think you can easily put back spin on a two wheeled design,all you need to do is fiddle with the gearing so that the top wheel spins slightly slower. Applying back spin should increase the accuracy as well as cause it to roll down into the basket. As the ball spins through the air it helps to stabalize its flight thus causing it to travel in a straighter line.

[Ludicium]

Not to give away team secrets but id like you to watch this video.

http://www.youtube.com/watch?v=IU8eh...eature=related

TEASER #Small spacing + &%^@*@&# + &!@#$& *&#@!% = #$^@ = profit#

[wilsonmw04]

Originally Posted by ToddF

Video here: http://www.youtube.com/watch?v=neqyzZ1SM2w
Next we'll hook up a motor controller to see how reducing the motor speed affects the shots. We may also go outside to see how far we can make baskets, at full motor power, given adequate headroom. Then, it's on to the catapult prototype.

We have a similar set up. we played around with power control as well. We found that at 100% we could get the range to make 1/2 court shots inconsistently. with reduced speed, the 8-15 ft shot were much more consistent than when we tried to power them in. angle and "touch" are going to win over high speed this year.