Ball Collecting Robots

[sanddrag]

For this past game of Zone Zeal, many teams had nicely functioning ball collectors/shooters. We tried to have a spinning wheel that shoots the ball up a short precisely formed ramp. The ball never really made it and higher than a foot above the ramp so we scrapped the ball shooter.

I am particularlty interested in designs of collection devices and and insertion devices, conveyors, lifting and dumping bins, shooters, etc. If your team had any of these things especially a collector and lifting bin, please give me some specific details on the design and construction.

We would really like to implement the use of balls in 2003 if the game permits. Any help is greatly appreciated. Thanks.

[Clark Gilbert]

We the TechnoKats had a ball shooter w/ basket dumping combonation...



As you can see in that wheel all we did was us one of our motor mounts designed the previous season and connected it to a skyway wheel that shot the ball up a small ramp (u can see the bottom of one of the metal ramps)



In that picture u can see 2 sets of ramps...we actually made 2 seperate ball shooters that could be switched before a match depending where we thought we wanted to start (that way the wheel was up against the wall), but if i remember correct we only ended up using the red one because it took way too long to line everything up and get the balls to go into the basket. If i remember right we didnt get it down till about the 2nd regional, and it seemed to work it's best at Nationals.

5mb video of ball collecting

I dont really like the accuracy of the robot collecting the balls in that video, but it gives u the overall idea of how it works.

[Joel J]

Our ball collection method is rather simplistic. Two cylindrically shaped pieces of wood, rollers, (one at the front and one at the back of the robot's "basket") are connected by "threads" of polycord. Attached to the aft roller is an atwood motor with a 2:1 (?) gear reduction and an additional "software reduction" of 50%. The rollers grab the balls (3 columns) and stops spinning when the basket is filled. Not the most technical description, but my forte isn't mechanical engineering. Ball pickup demonstration at this URL: http://rage173.org/bpvid.html. Ball dump demonstration at this URL: http://rage173.org/Vidbin.html. More pictures at this URL: http://rage173.org/gallery.php

[sanddrag]

ABSOLUTELY GENOIUS!!!! Both of them!!

Clark,
What is the purpose of all the chain and belt reductions? That drill/fisherprice combo is only driving the spining wheel right? Also, did the wheel have enough rotational inertia to keep spining after a ball was chucked at it? Last, you wouldn't have those videos in a WMP compatible format would you? Or at least some more pictures or description of the baskit dumping rigging....

Joel,
How exactly is the basket raised up to goal top level? The videos and pictures are wonderful but if you had a little more explanation on that part of it that would be great. Also, what is that surgical tubing used for?


Last, where do you get this polycord stuff? Looks pretty neat.

If anyone can answer the questions, give it a shot.
All your help is greatly appreciated. Let's see some more...

[Rob Colatutto]

my advice is....if you are going to be a ball handler, you have to be amazing with it. you should be able to pick up every ball qucikly and get them into the goal in some way that will make you noticed, a perfect example would be team 224, or 121, or buzz robotics

[Joel J]

Originally posted by Nataku
my advice is....if you are going to be a ball handler, you have to be amazing with it. you should be able to pick up every ball qucikly and get them into the goal in some way that will make you noticed, a perfect example would be team 224, or 121, or buzz robotics

Heh... you shouldn't say something like that, unless you mention team 95, the grand daddy of ball pickup robots. I am pretty sure everyone noticed them.

[Jeff Waegelin]

We didn't do balls this year, but I have great respect for those teams that managed to come up with a good ball handler.

[Clark Gilbert]

Where to start, where to start.....

What is the purpose of all the chain and belt reductions? All the orange cord (is this what u are talking about?) was used to bring in balls towards the shooter wheel...i wish i could say it worked perfect, but it was far from even though it helped some.

That drill/fisherprice combo is only driving the spining wheel right? The drill fisherprice combo actually got modified down to just the drill (opps, forgot to mention that) and the drill powered the orange cord and the wheel.

Also, did the wheel have enough rotational inertia to keep spining after a ball was chucked at it? Yah, we tested adding weights and stuff to the wheel, but the normal wheel and the drill motor worked just fine, if we got the balls to go in nice and straight it could shoot them through pretty fast w/o slowing the wheel down. (kind of had to see that to believe it)

Last, you wouldn't have those videos in a WMP compatible format would you? No, but i wish i did, especially since the ball collection in that video is pretty crappy...Anyone have any video from Nationals or Motorola Midwest Regional of us collecting balls?

[sanddrag]

What I was referring to as chains and belts were actually, all the chains, belts, and sprockets I see in the first picture you posted. Are these just to get the motor power to be split between the orange cords and the spinning wheel?

Also, could you give me a diameter on that spinning wheel and the rpm it was usually run at? That would be really great. Thanks.

[Joel J]

How exactly is the basket raised up to goal top level?

There are two pivot points... One is located where the basket meets the arm and the other where the arm meets the metal thing that attaches it to the base. Powered by a drill motor (brakes on) with [Edit: some major gear reduction], the arm-base pivot allows the arm to go forward and back to become parallel to the goal. Powered by two globe (?) motors, the basket-arm pivot allows the basket to go down and up to become parallel with the floor. In the end, you have the arm aligned with the goal, and the basket at a position where gravity does some of the work in dumping the balls. Oh... to dump, the arm operator drops the bar at the back of the basket, which holds the balls in, and holds the trigger button on his joystick, as though he is picking up the balls. If you need something more detailed than this, you'll have to ask Steve.

...what is that surgical tubing used for?

The surgical tubing functions as a brace for the basket. When the basket is filled with balls, gravity tends to pull it towards the floor. This forces our arm driver to constantly reach a compromise. This wasn't acceptable because we wanted the arm driver to worry about dumping the balls, not holding the basket up there.

...where do you get this polycord stuff?

I think the mechanical people got it from the small parts catalogue.

[Jeff Rodriguez]

Originally posted by sanddrag
How exactly is the basket raised up to goal top level? The videos and pictures are wonderful but if you had a little more explanation on that part of it that would be great. Also, what is that surgical tubing used for?


Last, where do you get this polycord stuff? Looks pretty neat.

If anyone can answer the questions, give it a shot.
All your help is greatly appreciated. Let's see some more...

The basket is raised up to the goal-top level by the 'arm'. There is a pivot where the wrist is attached to the arm and a pivot at the base of the arm near the base. The picture should help. The 'wrist joint' is powered by 2 globe motors, and the 'shoulder' is a drill motor. In previous years we used the fisher price but they don't have those anymore.

The surgical tubing on the side of the arm is a counter balance. It pulls the wrist back to help balance the weight of the balls when they're in the basket.

The poly cord is in small parts i belive. I've never really looked at where we got it, but i know its in some legal catalog.

and if you want to see more video i have alot. just IM me or PM me or e-mail me i don't care. just ask.

[Andy A.]

Making a fast ball pick up device, thats the easy part.

Finding enough weight after the dust settles to make a half way decent drive train, goal claw, brake, etc. thats another story.

Anyways, 95 used a series of rollers on the front end of the bot, that rotated inwards at very high rpm. They were powered by two FP motors, and at full speed ran about 1400 rpm. Rollers rotate in, balls get sucked in. Balls get sucked in, balls go into hopper. Balls sit in hopper till dumped. Hopper dumps, balls go in, and the people rejoice. Yea.

Goal is then stolen from us, because we have no torque.

Thats pretty much how it went for us. The moral is, don't specalize the 'bot to the point that you can no longer do anything else. There were plenty of other ball collectors, that while they couldn't pick up as many balls or pick them up as fast as we could, could more reliably hold onto the ones they did score. I could give you terribly detailed info on our ball sucker, but it wouldn't do a whole lot of good, because it would be so difficult to use for anything else.

[sanddrag]

I've thought of two things to lift a hopper or basket or whatever you call it. What if you had a winch drum attatched to the window motors. Those things go slow and cannot be backdriven. There would be a steel cable attatched to the winch drum on one end and attatched to the basket on the other end with a pulley to change the direction somewhere in between. So, when you wind up the cable, the basket would be pulled upward. You could replace the cable and winch with a chain and sprocket I suppose. Whichever way you make it, you could have two of these mechanisms pulling up the basket. The basket would have to slide on some sort of track - perhaps telescoping.

Another thing I thought of was something like a screw drive. Have a really big bolt thing spun by a motor and have part of the basket be like a really big nut. Has anyone done this? Would it work?

Or what about a scissor lift operated by the optional 18" stroke pneumatic cylinders or some other means?

Also, how does your everyday forklift go up so high in such a small package?

We are really getting somewhere. Lets build on these ideas. Go!!!

[Ricky Q.]

I'm at school right now so I don't have pics avalible, but I can add those later......

Our goal was to collect alot of balls in minimal time, dump, and then do it again.....Which we accomplished with our rollers.

Basically we had 8 pieces of PVC connected with belts, and they then had plastic tubing wrapped around them, we had it connected on the drill motors, the balls went up through the rollers into our basket and basket goes up, dump into goal and back down....We could collect 10 balls in about 9 seconds and averaged 2 dumps a match, our best match had 3 dumps and 28 balls in the goal.

Our main problem during construction of the system was the basket, we first wanted a PVC basket to be able to hold more balls, but we had trouble finding ways to lift it, so we went with a basic aluminum basket raised by string on tracks

Its kinda hard to see without pics...Ill add some when I get home...

[ChrisH]

Originally posted by sanddrag
I've thought of two things to lift a hopper or basket or whatever you call it. What if you had a winch drum attatched to the window motors. Those things go slow and cannot be backdriven. There would be a steel cable attatched to the winch drum on one end and attatched to the basket on the other end with a pulley to change the direction somewhere in between. So, when you wind up the cable, the basket would be pulled upward. You could replace the cable and winch with a chain and sprocket I suppose. Whichever way you make it, you could have two of these mechanisms pulling up the basket. The basket would have to slide on some sort of track - perhaps telescoping.

Another thing I thought of was something like a screw drive. Have a really big bolt thing spun by a motor and have part of the basket be like a really big nut. Has anyone done this? Would it work?

Or what about a scissor lift operated by the optional 18" stroke pneumatic cylinders or some other means?

Also, how does your everyday forklift go up so high in such a small package?

We are really getting somewhere. Lets build on these ideas. Go!!!

Actually, the FP motor/gearbox makes a really good winch. For ideas on telescoping you might want to check out my White Paper on lift mechanisms.

I won't say "don't do a scissors" but I don't recommend it. The scissors lift is a very subtle problem. It looks easy, but as you get into it it gets really ugly. It also has limited utility as your load must stay centered, and they tend to be heavy.

A four bar linkage is much more practical. One of these days I might even rework that portion of the White Paper, but I've got enough on my plate at the moment.

Since you're in Southern California you might want to come to the SCRRF workshops. I will probably be doing a reprise of my Lift presentation. I'd love to have someone in there who has been thinking about the problem before hand. I might even leak the results of my four bar work a little early. That is before posting it here, which depends on whether we need it this year or not.