Consistent shooter

[Abhishek R]

Originally Posted by MysterE

So, how would one add consistency in ball placement to a catapult based system?

Make sure the ball is sitting in the exact same position every time. Any discrepancies will cause variation in flight path. Engineer the catapult so it cradles the ball better.

EDIT: We actually added a bar to the back of the catapult to somewhat simulate a curved shooter to hold the ball better.

[Brandon_L]

We've been nailing 10pt shots from around the 18ft mark consistently with a spring launcher. Battery drain only effects our reload time. What kind of data are you looking for, specifically?

[Jeffrafa]

Originally Posted by Ether

and near the bottom of the list would be a) motor-powered kickers and b) motor-powered wheel shooters.

The sample size for wheeled shooters seems to be pretty small this year. We have a wheeled shooter consisting of 2 8" Colson wheels in a vertical orientation, shooting from fairly low. Each has independent closed-loop pwm control, to make sure the speed is consistent no matter the battery state (on the practice field we are making the same auto shot for a battery just used in a match as a fresh one). Also having the wheels above and below the ball lets us control the amount of back/top spin the ball has (currently tuned for backspin, although the effects of top spin on the ball trajectory are interesting and not quite intuitive - I am fairly confident we could increase our sweet spot range with top spin, but only the longest shot distance would improve. We have only done enough testing to demonstrate the spin effects I calculated, but not enough to justify a change.)

So far in our 1st day of qualifying matches we are 8/10 in auto mode (shooting from behind the white line), and have the 2nd highest cumulative auto score in our district (2nd to a 2-ball auto, but not by a lot). The 2 misses could likely be attributed to human error, as auto wheel speed was being read from an analog knob on the drivers station, now it's a set calibrated value.

Scoring high in teleop has not been as consistent as auto, but I am confident that will improve with more driver practice. We will see how things pan out in day 2 of this district, and at our second district in 2 weeks.

[Ether]

Originally Posted by Jeffrafa

on the practice field we are making the same auto shot for a battery just used in a match as a fresh one

What about ball inflation?

Have you tried making the exact same shot with a slightly overinflated ball and a slightly underinflated one?

[Ether]

Originally Posted by Jeffrafa

We have only done enough testing to demonstrate the spin effects I calculated...

Could you explain what calculations you did, and what testing you did to confirm those calculations?

[Gregor]

Originally Posted by dodar

I dont think 1114 is a wheeled shooter.

And to what would you base this assumption?

[dodar]

Originally Posted by Gregor

And to what would you base this assumption?

On that when you watch them in their matches it looks like they have a pneumatic puncher.

[Gregor]

Originally Posted by dodar

On that when you watch them in their matches it looks like they have a pneumatic puncher.

[dodar]

That definitely looks like a gatherer to me.

[Gregor]

Originally Posted by dodar

That definitely looks like a gatherer to me.

The red and white roller is their intake. I wonder what the two black wheels do...

[NickTosta]

Originally Posted by Gregor

(image)

I see two pneumatic cylinders directly behind the ball. Granted, it's hard to say exactly what they're for, but they appear to be positioned correctly to "punch" the ball.

edit: To be honest, it looks like those small cylinders punch the ball into the black rollers. So, it's probably both.

[mman1506]

Originally Posted by NickTosta

I see two pneumatic cylinders directly behind the ball. Granted, it's hard to say exactly what they're for, but they appear to be positioned correctly to "punch" the ball.

edit: To be honest, it looks like those small cylinders punch the ball into the black rollers. So, it's probably both.

We talked to them, it's a combination of wheeled and pneumatic but a the majority of the work is done by the wheels.

[Duncan Macdonald]

Alright, lets get this thread back on track....

I agree with Ether's original rough sorting of shooter types. Additionally, waiting for the ball to settle in your shooter varies by design (SS style being the best I've seen) and effects your in game shot percentage by giving defences extra time to close in.

For teams using surgical tubing, what have you done to improve consistency? I built a surgical tubing catapult in 2008 and it was never exactly the same between matches. This didn't matter much when throwing a ball over a bar. Does the variation come into play when aiming for a goal?

[who716]

We were shooting from 8-11 feet not very accurately with a motor driven catapult at 100% power today we I bagged for our slotted time we are allowed and lowers the speed to 84% and now we are shooting at about 98% from three feet off the wall( just behind the low goal) we use 100% speed to shoot over truss

[Pretzel]

Originally Posted by Duncan Macdonald

For teams using surgical tubing, what have you done to improve consistency? I built a surgical tubing catapult in 2008 and it was never exactly the same between matches. This didn't matter much when throwing a ball over a bar. Does the variation come into play when aiming for a goal?

Our team didn't end up using surgical tubing but I had thought up a way early in the season to ensure consistency between matches with surgical tubing.

If you wind up the surgical tubing on two drums, then unwind it just enough to attach it to the plunger or whatever it was propelling, you could then add a load sensor to the surgical tubing or the motor such that it measured the amount of tension in the tubing. Using two motors (Bag motors would would fine for this) you can have software that causes the drums the tubing is wound on to tighten or loosen the tubing depending on how far you want to shoot and how much the tubing has stretched. This keeps the tubing at the same tension for every match and also allows for lower powers settings in order to pass or shoot from a different distance.