Ball Launchers? Ideas?

[Trez]

Originally Posted by seg9585

As a 2006 FRC participant (Aim High) who built a robot using the pitching machine launcher design, I have a few comments about it:

First off, calibrating the wheels ended up being a little more annoying than expected. Even though we used encoders to measure and even out the speed between each wheel, we found the release angle was still inconsistent -- the balls needed to be squeezed by the wheels a bit to get the traction needed to accelerate the ball, and the balls would end up flinging a bit to the right or left depending on which wheel made contact with the ball first and how the ball re-expanded.
For Aim High this wasn't a big deal because the target was relatively large, but with baskets this year we need a lot more precision.

Also, the ball originally came out without spin, so the balls flew like a knuckleball, making scoring unpredictable. We changed the speed of one wheel to add spin, but then had to apply a directional bias since the spin did induce lift on one side of the ball (still better than a knuckleball)!

Lastly, we had to run those large softball wheels with CIM motors to get them spinning fast enough, but when they were on all match it quickly drained our battery. In later matches we had to turn off the spinner during collection periods just to save power, then wait for the wheels to spin up to speed again.

I did see effective single-wheel launchers against a static surface that took out a lot of the multi-wheel variable issues we had, and they seemed to work well.

Why didn't your team just use one motor with some gears to run both wheels?

[Flimsor]

Originally Posted by robostangs548

I have it everyone, I just need to figure out how to get my hands on this! http://www.youtube.com/watch?v=aFl-9W8x-uI

LOL, best design ever. I'm gonna have my team make this but on wheels and as a skunk instead of a seal.

A mechanism that has come up with our team's discussion is a catapult. It would work very well if you can get the programming down, but it may not work with some of our ideas.

[Mark Sheridan]

Originally Posted by davidthefat

This looks cool: http://www.chiefdelphi.com/media/photos/33185

If a team is going to store rotation energy to launch the ball, this is the way to go. Many teams have had some success with this style including me when I was on 766. It generates a lot of backspin, which improves accuracy and creates a shallower bounce of a backboard.

I am really curious what is the limit of accuracy for this design. Shooting a basket is much harder than 2006's game. Hopefully next weekend we will get a prototype running to see if this is practical.

[slijin]

Originally Posted by Trez

Why didn't your team just use one motor with some gears to run both wheels?

Discrepancies in wheel inflation/material necessitated that they offset the speed of one, and consequently introduced a need to change the final shooter direction - at least, that's how I'm reading it. No matter how well you gear it - to say nothing of the difficulty of such a setup - there's going to be enough leeway in the wheels themselves, let alone the leeway given by the gears and sprockets to introduce significant error into the equation.

[davidthefat]

Originally Posted by Mark Sheridan

If a team is going to store rotation energy to launch the ball, this is the way to go. Many teams have had some success with this style including me when I was on 766. It generates a lot of backspin, which improves accuracy and creates a shallower bounce of a backboard.

I am really curious what is the limit of accuracy for this design. Shooting a basket is much harder than 2006's game. Hopefully next weekend we will get a prototype running to see if this is practical.

I am thinking of doing a feeder bot, just grabbing the ball and chucking it all the way across the field is the priority and I think this will be a great mechanism to do it with.

[Apeace]

I heard one great team effort was where one robot chucked balls at another robot and the other just sat at the goal and caught them all while just pouring them into the goal.

Although, this year there are limited balls on the court.

[Flimsor]

Originally Posted by Apeace

I heard one great team effort was where one robot chucked balls at another robot and the other just sat at the goal and caught them all while just pouring them into the goal.

Although, this year there are limited balls on the court.

I have determined that this would be an effective strategy, however it would be very difficult to accomplish unless the robot was programmed in advanced to recognize the loading area for the robot scoring, so planning ahead of time would to have integrated designs would be required.

[Mark Sheridan]

Originally Posted by davidthefat

I am thinking of doing a feeder bot, just grabbing the ball and chucking it all the way across the field is the priority and I think this will be a great mechanism to do it with.

Originally Posted by Apeace

I heard one great team effort was where one robot chucked balls at another robot and the other just sat at the goal and caught them all while just pouring them into the goal.

Although, this year there are limited balls on the court.

Yeah I was thinking that a shooter like that, especially one with an adjustable hood, could possibly be both a scorer and a passer. (like 2006: team 111, 2009: teams 1717, 217, 1114)

Also, look at 217's 2006 robot, they had a sheet that caught balls being thrown at them. It would work by absorbing the thrown ball and funneling it to a storage area.

[Garten Haeska]

Originally Posted by Mark Sheridan

Yeah I was thinking that a shooter like that, especially one with an adjustable hood, could possibly be both a scorer and a passer. (like 2006: team 111, 2009: teams 1717, 217, 1114)

Also, look at 217's 2006 robot, they had a sheet that caught balls being thrown at them. It would work by absorbing the thrown ball and funneling it to a storage area.

So in other words it acts like a Net?

[Grim Tuesday]

This could be very dangerous this year, though, with limited possession rules.

EDIT: This being a funnel/net.

[Mark Sheridan]

Originally Posted by Garten Haeska

So in other words it acts like a Net?

Yep, what was cool about the set up was that balls thrown horizontally at it would not bounce off it. It was very good at absorbing the kinetic energy. I was pretty blown away by it. I don't remember which match I saw it on blue alliance but here is a photo I found.

http://www.chiefdelphi.com/media/photos/24488

[theprgramerdude]

Originally Posted by Sean Raia

I would stray away from that idea. Pneumatics (in my experience) are much better for power than for speed. Maybe use your pneumatics to load a spring?

Power is speed. And pneumatics do not have power, they have huge amounts of force, at the tradeoff of speed. Power = F x V, don't lose the value of a scientific term by colloquially equating it with something entirely different.

[Mike Norton]

This is what we had http://www.chiefdelphi.com/media/photos/23042

What we learn is back spin is very useful to keeping the ball going long distance. Flywheel needs to be heavy. This insures very little speed loss when shooting. We had a pneumatics ball stepper. This made sure the next ball did not drop until the wheel had enough time to be at the right speed. We would shoot 9 balls in 7 second with 80 % score rate. This year is much different you have to arc the ball it is not a straight shot.

[MrForbes]

Team 25 had a pretty nifty shooter in 2006.

I seem to recall that teams that shot the ball with a single wheel that gave it a lot of backspin, did really well.

Of course the backboard messes up that idea a little bit, you have to aim for the sweet spot, a certain height above the basket.

[Sean Raia]

Originally Posted by theprgramerdude

Power is speed. And pneumatics do not have power, they have huge amounts of force, at the tradeoff of speed. Power = F x V, don't lose the value of a scientific term by colloquially equating it with something entirely different.

I dont think ive lost sight of what the equation for power is. It was late at night and i was using laymans terms... He got the idea. But thanks for taking the time to go back to that and tell me what i said incorrectly