Shooter Survey

[AdamHeard]

Hi All,

I saw so many different implementations of flywheels at champs this year, and was curious to hear what worked for a lot of terms.

The information I'm curious about is;

-Shooter Wheel Diameter (inches)
-Compression (inches)
-Travel time in shooter (degrees)

Shooter tread material would also be nice to know.

Please also comment on how much you felt variation in ball density/squishiness affected your shots (although I understand this is purely anecdotal).

[sst.thad]

We used 2 8in wheels side by side from the 2011 KOP. On the same shaft we had a 3lb flywheel with most of the mass at the outer edge.

Our shooter was different because it used a flat plate instead of a curved plate. This meant the wheel had varying compression as the ball traveled through the shooter. At the tangent point the ball had about 2 inches of compression, and the ball shot at a 55 degree angle. Ultimately the ball contacted the shooter for less then 90 degrees.

The main issue with this was that we couldn't shoot very far because the motor had to be at 70% speed in order to shoot the ball from the key. But the entire system was very accurate, and was not affected by ball density at all. It was much more affected by how sticky the ball was, but this was only a problem in our shop when we wore out the surface on all our balls. We were only affected once by ball density, and that was our last match at worlds, where we had a ball that was as hard as a rock. Because of our 2 inches of compression, we couldn't get the ball to compress enough, so it got stuck. But other then that there were no issues with the consistency of our shooter.

Our shooter proved that the entire ball system needed to be well thought out. We had a great shooter, but had trouble actually getting the balls into the narrow gap in the front of our robot. When we had balls they always shot, but we had trouble actually getting the balls.

[jspatz1]

-Shooter Wheel Diameter (inches) = 12 (2 wheels with a center gap)
-Compression (inches) = 1.5
-Travel time in shooter (degrees) = ~60

Shooter tread material would also be nice to know. Hard rubber.

We do not feel ball density effected our accuracy as much as many other teams have indicated. Surface wear was a bigger factor for us. Overall our large diameter and modest compression seemed to give very accurate results without much sensitivity to ball variation.

[CalTran]

Originally Posted by AdamHeard

I saw so many different implementations of flywheels at champs this year, and was curious to hear what worked for a lot of terms.

I believe you got a somewhat close look at ours when you were over in our pit checking out our ball elevator for its spitting capability.

Team 2410 had two different designs this year. Our original design was one a la 1114 and 217 from Aim High (2006). The quad wheel pitching style shooter. It…didn’t exactly work out for our team as it did for those teams.

-Shooter Wheel Diameter (inches)

6 Inches

-Compression (inches)

Somewhere around 4inches or so

-Travel time in shooter (degrees)

Like none. If I had to quantify it, probably somewhere around 10-15degrees of the wheel itself.

Our second shooter, whose information can be found here: [Link to be added when I can find it]
It was a student designed, custom fab whose design looked remarkably similar to Titaniums… minus the lawn mower wheels of course. Each 9” aluminum wheel, 1” od with ~11degree chamfer towards the inside, weighed about 2lbs each, and we were running at 3000rpm.

-Shooter Wheel Diameter (inches)

9 Inches

-Compression (inches)

Variable, though stayed at somewhere between .25 and .75

-Travel time in shooter (degrees)

Originally 65, though we ended up modifying it to I believe somewhere around 68-70ish or so.

Shooter tread material would also be nice to know.

When you have a 2lb wheel moving at 3000rpm, DO NOT use a roll of duct tape as a brake pad. It will shred through 3 layers of duct tape. Residue will be left on your shooter. It will vastly improve the range of your shooter. You will have to drop the power by almost 70% to compensate.

Please also comment on how much you felt variation in ball density/squishiness affected your shots (although I understand this is purely anecdotal).

The first shooter we designed was vastly effected by ball density, namely because of the significant compression we placed on the ball. As soon as we backed off the compression down to only half an inch, then ball variation had basically no effect on our shot.

[KrazyCarl92]

Although we never did get our competition shooter working well due to CAN issues (so we were forced to pursue a defensive role instead...), between our 1st and 2nd regionals we did a lot of work with the practice robot to increase our shooting accuracy from the key to about 90%.

We had a 2 axle shooter with the following qualities:
-6 in. diameter wheels
-2.25 in. compression
-"0" degrees travel in the shooter because it was a 2 axle design rather than a 1 axle design with a hood
-We used the standard KOP wheels from previous years, but turned down the edges on a lathe to a 15 degree angle on each wheel so the ball would sit nicely between the 4 wheels (This dramatically increased our consistency, along with adjusting the compression between the two axles)

I can't speak much to ball variability, as our robot only took one shoot ever in competition with this configuration before CAN brownouts forced a switch to PWM (and ruined our speed control method along with any hopes of accurate shooting). But back home with the practice robot, we tuned our robot to shoot well with the 5 balls we deemed close to competition quality, and saw little shot variation among these 5. About 20 others were FAR softer than any of the balls we ever saw in competition (according to our inbounder).

[BJC]

-two 8" old KoP wheels (gray rubber) spaced about 3" apart

-About 1.5" of compression which tampers to 2.75" at the exit point of the ball.

-Between 120 and 150 degrees of wrap around the gun (variable hood)

-We could deal with both older and newer balls. The only thing that threw us for a loop was brand new out-of-the-box balls.

[AlecS]

Diameter: 4.375", 3" wide, Smooth ABS
Compression: ~2"
Time in Contact: 25-45 degrees, (two position hood).

The wider wheel seemed to have a positive effect on dealing with ball variations, as less pressure is exerted on the balls surface. Having not tested for long times with a narrower wheel, that is only anecdotal.

The smooth ABS, did seem to be a consistency improvement over the previous blue nitrile tread, though at a distance drop, as the ball does slip.

1323 also had success with turning the surface two kit wheels smooth.

[Botwoon]

Team 207:

-Wheel Diameter: 5 inches
-Compression: 1.5 - 2 inches
-Wheel Speed: 4500 RPM
-Travel Angle: ~50 degrees in shooting position, ~80 degrees in feeding position
-Wheel Tread: Silicone

Ball density affected our scoring ability significantly. It usually caused us to miss one or both of our autonomous shots(when we weren't feeding of course). On one particular occasion, one ball went over the top backboard and the other barely cleared the two pointers, in other instances we were able to score both 3-pointers.

[R.C.]

Originally Posted by AlecS

Diameter: 4.375", 3" wide, Smooth ABS
Compression: ~2"
Time in Contact: 25-45 degrees, (two position hood).

The wider wheel seemed to have a positive effect on dealing with ball variations, as less pressure is exerted on the balls surface. Having not tested for long times with a narrower wheel, that is only anecdotal.

The smooth ABS, did seem to be a consistency improvement over the previous blue nitrile tread, though at a distance drop, as the ball does slip.

1323 also had success with turning the surface two kit wheels smooth.

Def, we went with about 1.75-2" Compression.

We had similar setup to 604 but we used a larger wheel. 6" Kop and lathed it down some. It seemed the smoother it got after run time the better we shot!

-RC