Ball Launchers? Ideas?
 

Hey there. Today we discussed various launchers.
Spring Loaded
Throwing Arm
Pnuematics?

Any ideas? Pro/Cons?

Thanks!
Thomas 1939

Re: Ball Launchers? Ideas?
 

I want to see the animation robot with the plunger to pick up balls and the boots that spin to kick them. Could you do that please. It would be very awesome. :D

Re: Ball Launchers? Ideas?
 

I'm actually thinking of a conveyor belt going from an intake roller all the way up to 2 wheels that spin like pitching machine wheels to launch the ball. 45 degree angle for maximum distance, adjustable speed on the wheels for height.

Re: Ball Launchers? Ideas?
 

A con is reload time. It takes all of those systems time to reset for the next shot.

I was actually thinking of a similar system to this. There is no reload time on the shooter so shots can be fired quite quickly.

Re: Ball Launchers? Ideas?
 

Something similar to this, but "tank treads" instead of wheels

Re: Ball Launchers? Ideas?
 

Ive worked out an equation for trajectory that will hit an exact point (middle of hoop) based on a fixed theta (angle of launcher) and a variable velocity (wheel or spinning boot speed)

Its still the FIRST day of this build season so we will have to see

Re: Ball Launchers? Ideas?
 

So the rules dont have a maximum "Muzzle Velocity" :D hmmmmmmm

Re: Ball Launchers? Ideas?
 

We actually discussed the tank tread idea as well, but one of our mentors brought up a really good point. How many commercial pitching or throwing machines do you see with tank treads? With a foam ball especially, the shortest amount of time that the ball can be in contact with the wheels will not only benefit the condition of the balls (if the belts spin at different speeds at all, the ball spins and it could do some damage to game pieces), but also will help with size, weight, and ease of construction of the mechanism.

Re: Ball Launchers? Ideas?
 

Check out 1771 on FRC Designs Gripper page (See Link Below). This arm used a suction system to grab the ball and then used a device to launch the ball.

http://frc-designs.com/html/grippers.html

Matt

Re: Ball Launchers? Ideas?
 

I wish FRC Designs had some stuff from '06...

Re: Ball Launchers? Ideas?
 

Yup, it was a big funnel with an impeller for suction, then 4 pneumatic cylinders that shot it out.

We also used 2 smaller suction cups in 2010 for the soccer balls. Although we got through 1 regional with them, we quickly switched to a roller design before championships. The problem with the soccer balls (and probably these foam basketballs) is that it isn't an even surface, so it was hard for the suction cups to get and keep suction on.

Re: Ball Launchers? Ideas?
 

At first we considered a crossbow kind of idea, but now we're moving onto something a little bit more akin to some of the winners from '06.

Re: Ball Launchers? Ideas?
 

I would steer a bit away from 2006 mechanisms. Those mechanisms had a maximum muzle velocity, and they shot through a hole in the wall, not a hoop with a backboard.

The concept seems fine, but those designs need major mods to make them work with this game.

Re: Ball Launchers? Ideas?
 

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.

Re: Ball Launchers? Ideas?
 

We're looking into programming the Kinect to help control an aim-able barrel, depending on distance from the hoop and which hoop we're aiming for.

Re: Ball Launchers? Ideas?
 

Quite a noble task! My team is thinking of staying away from Kinect, I'm not entirely comfortable, and I think that for autonomous, there is no better controller than a vision and ultrasonic sensor with a processor on board. We'll see about our main robot design.

Re: Ball Launchers? Ideas?
 

That's sweet. But I want the boots on a kicker / launcher of some kind.

Re: Ball Launchers? Ideas?
 

Careful about saying that there is no reload time. In 2006 our shooter would have to get back up to speed after shooting only a couple balls. You lose a lot of energy when you shoot a ball.

Re: Ball Launchers? Ideas?
 

This is true, but at the most you are only going to be shooting 3 balls at a time.

Unless you have a really well coordinated alliance partner to line them infront of you, then push them into your intake as you shoot... :p

Re: Ball Launchers? Ideas?
 

What powered your shooter a CIM?

Re: Ball Launchers? Ideas?
 

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

Re: Ball Launchers? Ideas?
 

Our team was starting to think about a pnuematic piston that shot-puts the ball through a barrel at the target.

Any suggestions?

Re: Ball Launchers? Ideas?
 

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?

Re: Ball Launchers? Ideas?
 

Use smaller diameter cylinders they travel faster. We used them in breakaway with success. The important part was speed not necessarily mass behind the strike. KE = 1/2MV^2 I guess.

Re: Ball Launchers? Ideas?
 

Maybe I'm just a little slow in the head after the flow of information today, but why didn't you set up the robot so you could have identical gears underneath the wheels that would allow them to turn at the same rate?

Re: Ball Launchers? Ideas?
 

I think our ball launcher should have the wheels spinning around 80mph. But that's a rough estimate we'll see what actually happens.

Re: Ball Launchers? Ideas?
 

Can you clarify that? Rotational speed typically isnt measured in mph.

Re: Ball Launchers? Ideas?
 

What is 80 mph converted to rpm? Or are you planing on shooting your wheels at a speed of 80mph.

Re: Ball Launchers? Ideas?
 

Well I estimated what the cim speed would be because I have no idea. I converted it in to mph to make it more easily recognized. But Yeah I have absolutely no idea how fast a cim would actually be spinning but. I took the diameter of the wheel in ft, .5, multiplied it by pi. multiplied it by rpm which I just put in 4500 because I have no idea. Oh yeah the Cim motor would be directly connected to the shaft through the wheels. Then I divided by 60 to give me ft per second. and converted it to mph.

Does any one have any rough ideas as to how fast a cim motor would be spinning under a load of a 6in wheel that is free spinning?

Re: Ball Launchers? Ideas?
 

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

Re: Ball Launchers? Ideas?
 

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

Re: Ball Launchers? Ideas?
 

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.

Re: Ball Launchers? Ideas?
 

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.

Re: Ball Launchers? Ideas?
 

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.

Re: Ball Launchers? Ideas?
 

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.

Re: Ball Launchers? Ideas?
 

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.

Re: Ball Launchers? Ideas?
 

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.

Re: Ball Launchers? Ideas?
 

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.

Re: Ball Launchers? Ideas?
 

So in other words it acts like a Net?

Re: Ball Launchers? Ideas?
 

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

EDIT: This being a funnel/net.

Re: Ball Launchers? Ideas?
 

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

Re: Ball Launchers? Ideas?
 

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.

Re: Ball Launchers? Ideas?
 

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.

Re: Ball Launchers? Ideas?
 

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.

Re: Ball Launchers? Ideas?
 

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 :p

Re: Ball Launchers? Ideas?
 

So what people really should be looking at is the shooting motion of basketball players and see if you design a mechanism imitating their motion.

Re: Ball Launchers? Ideas?
 

I hope teams, when designing, think of how humans throw a basketball. They don't launch it at the square of the backboard, they try to arc their shot.

Think of how your rotational velocity of your pitchers, pitch of the launcher, and distance from the hoop go into arcing the ball instead of launching it.

Re: Ball Launchers? Ideas?
 

This Thread has absolutely EXPLODED. Its great to see so many people thinking about this.

My two cents.

Speed. Both in terms of muzzle velocity and reload time.
A variable initial velocity is a great idea.
Very important.

Accuracy/Consistency. With wheels you run into the issue of spin (which
can be tweaked to even remove air resistance from the equation). Deformation is also a big problem because that compressed force will make the ball wobble when fired. (Although nominal, i need to look further into this)

Range. Simple enough. Must be consistent and long enough to provide for as many scoring opportunities.

Now. If you can set the launcher to 45 degrees and leave it there it makes the equation for finding the velocity to shoot an optimum parabola. And you can limit the number and size of moving parts with a fixed angle shooter.

(Hint Hint, Programmers this is way easier than solving an equation with both V and theta in it)

Thanks for reading!

Thomas 1939

Re: Ball Launchers? Ideas?
 

I think that using the human method is fine for humans, but since the robot isn't human, teams might need to play around with different methods and see what can be done successfully with the fewest degrees of freedom. In 2006, like I said, teams that used a single wheel shooter that gave the ball a lot of backspin were successful. Think about how it works, and what's required to do it.

edit: also look at the teams that were successful in 2009, although the number of balls was different, there were a lot of teams that scored consistently by getting right next to the target and dumping the balls in

Re: Ball Launchers? Ideas?
 

The target in 2006 was like throwing a dart at the wall. This year your aiming for a floating hole in the ground. What worked back then probably won't work as well now.

Re: Ball Launchers? Ideas?
 

I don't know about that, I got to hang out with the Falcons (team 842) yesterday, and we seemed to have more success getting the ball in using the backboard and backspin, than we did lobbing it.

But it's still pretty early in the season, hopefully we'll see some youtube action this week that will astound us all

Re: Ball Launchers? Ideas?
 

quick question: how are teams going to work with the weird height requirements?
the absolute height must not exceed 84 in
any appendage may not extend more than 14 in. beyond the frame perimeter

i can't seem to think how this works

Re: Ball Launchers? Ideas?
 

Horizontally, 14 inches, vertically, cannot exceed 84"

Re: Ball Launchers? Ideas?
 

OHHHHHHHHHHHHHHHHHHHHHH i feel so dumb now lol
man- i always over complicate things

Re: Ball Launchers? Ideas?
 

The biggest issue with the shooter fixed at 45 degrees would be if you are really close. The proximity would make it impossible to score in the top basket or even the middle depending on the size of your robot.

Re: Ball Launchers? Ideas?
 

At a glace, it appears this year's shot arc is going to be very different from 2006. I have been joking with my team that its going to be like kareem abdul jabbar's sky hook. The ball will have an early release (higher angle on the the ball's initial trajectory) and using the robot's frame perimeter and height to prevent the shot from being blocked.

I am really nervous about how large the backboard sweet spot will be.

Does anyone feel accuracy will be more important than frequency of shots made? My team was thinking that missing the shot and failing to rebound will give the opponents possession of another ball and a scoring advantage.

Re: Ball Launchers? Ideas?
 

Well if the balanced bridges can be worth 40 points in elimination rounds, I think they expect a decent number of shots to be made, so I wouldn't expect and amazing amount of ductility with making shots. But I have yet to test anything.

Re: Ball Launchers? Ideas?
 

I think arm styles are certainly worth of note and it looks like 1875 has one up and running: http://www.chiefdelphi.com/forums/sh...highlight=1875

1523 MARS had a "pitching style" arm in 2006 that (I believe) used a cam and spring set up. Their shots were extremely consistent but may not have had the ability to easily change trajectory.

Re: Ball Launchers? Ideas?
 

I guess I am thinking of where the point deferential will come from. I guess this will be steering a little off topic. If both alliances get the 40 points, then autonomous/hybrid and shooting baskets will decide the match.

I guess I am wondering how much of a disadvantage a missed shot would be. Suppose if team A that can only make 50 percent of the shots at the 3 point hoop and team B that can make 100 percent at the 2 point hoop. Then if 6 shots were made by both teams. Then the total would be Team A 9 points and Team B 12 points. Team B would also have opportunity to recover some of the missed shots of team A. This is an over-simplified example.