One more '06 robot thread

[Alexa Stott]

Originally Posted by Jeremiah H

We didn't have a shooter, nor did we prototype one, but judging from the things related here and what I observed and learned from talking to people, the vertical-wheel shooters had a flatter trajectory due to backspin, but also were less "reliable" if the shooter wheel did not have time to build back up to its original speed, because the ball would inherently not have the same amount of backspin.

This was actually one of our main concerns, but we fooled around with the programming for the paddles for our shooter so that even if you held the trigger down, the paddles would be slow enough for the shooter wheel to get back up to speed. We also wrote this into our autonomous code.

The vertical wheel also allowed us to shoot from far out without going over the limit.

[Peter Matteson]

Our vertical wheel was driven by our very poor test with horizontal wheels. We had competeing 1 and 2 wheels prototypes with the 1 wheel being the more successful. The one wheel design lent itself to being vertical.
Pete

[Paul Copioli]

For us it was a simple decision. Two major factors come into play when dealing with shooting accuracy (there are many more, but these two applied to this year's challenge):

1. Muzzle velocity - a.k.a. exit velocity
2. The knuckle ball effect - Technical term --> turbulent flow separation

The first item was predetermined for us by the rules.

The second item can be alleviated by spin. A knuckle ball pitcher is most effective when he can get the ball to float (no spin at all). The motion is pretty unpredictable (ever seen a catcher's mitt when catching for a knuckle ball pitcher?) When you place spin on the ball you increase the Reynold's number, thus decreasing the likelihood of flow separation. This also does generate some lift and reduces drag which allows the "flatter curve" effect others have noted.

Once we determined we needed spin, placing them vertically made sense since we didn't want to throw curve balls.

-Paul


Once we determined we needed to spin the ball

[Tim Baird]

We chose vertical wheels for very similar reasons. We also chose them for space constraints because we ended up having two shooters working together in parallel (two balls left our machine with each shot). Two verts just made sense.