Consistent shooter

[rkbot]

Team 2014 can shoot from beyond 18 feet. At GTRE they had an extra volunteer to stand further back because we could launch the balls so far. We went to a full practice field just before the end of build season putting out springs to the second highest setting and made a moving 10 pt goal shot from about 45 feet. We do have massive power draw from out batteries as we run 2 rs 775s for our reload and also have a 6 cim drive. During our first matches it guys were telling us our voltage dropped to 4 volts and even under 4 once.
One problem we have run into though is the fact the the inflation of the balls can be different. if we use the harder balls on the field we usually shoot to high because the ball doesn't absorb as much energy.

[RonnieS]

Team 314 is using a "spear gun" tubing catapult and we find it effective for about 700-900 shots before we have to replace it which when done is cut to correct length then tested with scale to make sure of the same force. We have changed it 3 times through build season and our first district this weekend which was kettering. I dont know what all of you consider accurate or a "good" launcher but if you want to judge go to youtube and FIRSTinmichigan and you will find archived matches. Ill leave this one up to you guys to decide.

[Ether]

Teams with wheeled shooters:

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

[AustinH]

Speaking of adventures in consistency...

We couldn't for the life of us figure out why we had about a 75% accuracy rate in autonomous mode on the field as opposed to near 100% on the practice field. We controlled for starting position, angle, battery voltage, air pressure, etc. We even added a sizable delay between our "charge" forward and when our catapult fired in order to let the ball fully settle.

One of our four batteries had a terminal lug that was perpendicular to the rest. As a result, the battery power cable protruded *ever so slightly* into the catapult bucket, preventing the ball from seating properly in the bucket. Thus, every few matches (namely when the aforementioned battery was installed), we would miss our auto shot.

Needless to say, the fix was applied the moment we got back and is ready for Mount Vernon this weekend.

[Kevin Leonard]

From what I've seen of matches thus far this season, a high-pivot catapult with springs resistant to wear seems the most consistent.

We have a low-pivot catapult, and from our testing, we've discovered a few different things affect the variability of our shot (some controllable, some not).

• Where the ball seats itself in the catapult
• How far we pull the catapult back
• The thickness of our catcher panels (we generally shoot with our side-panels for catching retracted. This helps to:
  a)center the ball, and
  b)avoid breaking our catchers when they are under defense. They are filled with a padding to help deaden the ball when we catch, but the padding slides down our catchers over time, changing the effect of the catchers)
• Ball Inflation and Ball Condition-
  This is a very small effect, but it can change our accuracy if we're shooting from either end of our sweetspot. If the zipper of the ball sits right on one of the two prongs of the catapult, it can also change our shot.
  
  Our springs were custom made to be extremely resistant to wear. So even after hours and hours of drive practice, we still shoot very well.

[Andrew Schreiber]

Originally Posted by 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?

We found small clamps actuating into position when the ball is in the cradle helped eliminate almost 100% of the settle time.

[Mark Sheridan]

Originally Posted by Andrew Schreiber

We found small clamps actuating into position when the ball is in the cradle helped eliminate almost 100% of the settle time.

I second this, we just made a very crude one and it does wonders to the settling time.

[woudie]

In my teams shooter we incorporated a wheeled shooter along with a pneumatic launcher, the way it works is that when the pneumatic launcher is engaged it lifts the ball right into the rectangular formation of rotating wheels and gets shot out of it, the distance is controlled by the drivers, who control the rpm of the wheels. We ended up winning the innovation in design award at gtrw for it.

[Answer42]

Originally Posted by rkbot

During our first matches it guys were telling us our voltage dropped to 4 volts and even under 4 once.

Under 4? I would expect the radio to reboot way before that. You guys have any brownout/ main breakout problems?

[Tim Lehmann4967]

4967 has a extremely accurate and consistent shooter, but we need to be about a foot away from the front of the low goal. We missed 5 shots total during the Gull Lake Regional. 33 has a very powerful springloaded shooter, but it is very easy to push them out of shooting alignment due to their use of omni-wheels.

[Deke]

I'm not sure about wheeled or linear shooters, but we have done a lot of prototyping catapult shooters. It's all about holding the ball consistently. High pivot, low pivot, springs, pneumatics, close shoot, distance shot does not matter. Can it position the ball the same everytime?

[IronicDeadBird]

Originally Posted by Ether

Teams with wheeled shooters:

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

Are you talking about making a shot with one angle from one point as being the same. Or are you talking about getting the ball to target consistently?

[Ether]

Originally Posted by IronicDeadBird

Are you talking about making a shot with one angle from one point as being the same. Or are you talking about getting the ball to target consistently?

The former.

[IronicDeadBird]

Originally Posted by Ether

The former.

I will ask the team I work with (1339) I don't believe we tested different ball size but I will ask and see if we have any information at all on it. Another team that might have the info is Robotknights they have a pretty intense wheeled shooter so if I can get a hold of them I'll see if I can find anything out.

[Mike Norton]

How about 100% in auto mode. 14-0 at WPI and 18-0 at Bryant. We use surgical tubing cross bow style.

We use extrude aluminum 1"x1" as the launcher with two rollers at the very top. This give the ball a slight backward spin to keep it floating.