Modifications to FIRST Gray Wheels for Better Consistency

[philso]

Originally Posted by thefro526

2) Make sure the balls are entering the shooter consistently. Some systems I've seen have allowed the ball to move around left to right before hitting the shooter wheels. In a perfect world, the ball enters on the same center as your shooter wheels 100% of the time.

We padded the side walls on either side of the ball from before it gets fed into the shooter all the way out. We originally had about 3/8 inch on either side.

Our original "hood" was a 1 1/2 inch wide piece of hardwood cut on a bandsaw to get the required curve. At Alamo, we discovered that the cut was not perpendicular to the wood, causing a tilt to one side when the ball was launched. We were able to straighten it out with several layers of duct tape on one side. Our new hood is adjustable for tilt, compression and curvature.

We may have had some inconsistency when the wheels were not rigidly attached to the shaft. We are using two of the 8 inch gray wheels on AndyMark hubs and a 1/2 inch smooth (no keyway) shaft. We drilled and tapped the hubs for two set screws each. We also drilled into the shaft, through the set screw holes, so that the sets screws have more "bite". Sometimes the set screws loosen and the wheels will wobble on the shaft even though they do not spin.

Using an encoder to enforce a constant speed on the wheel will help, if you are not already doing so. Also, allow time for the wheel to come back up to speed. I have seen several instances where one of the top teams fires off several shots in rapid succession and the later ones all fall short, by more and more.

Probably the most important thing is to make sure your test method is consistent. We were able to see variations in the trajectory of the ball as it left the shooter by holding up a yardstick and comparing the trajectories of a series of shots.