Re: Ball posession: Roller (ball magnet) or vacuum?
 

I didn't have much to do with the programming, but I think our programmer found some code to start from and made it perform better with tweaks of his own.

Re: Ball posession: Roller (ball magnet) or vacuum?
 

Kiwi is a nickname for something properly called a "Killough" drive platform, named for its inventor. I think it was first described in the literature in the late 1990s.

An early application in FRC essentially didn't have any fancy computer software making it work. The driver used three joysticks, arranged in the same orientation as the wheels, and connected with a Y-shaped yoke, to directly control motor power.

Re: Ball posession: Roller (ball magnet) or vacuum?
 

Along with this thread... I have to wonder how many teams have two bars incorporated into their design? We do, but I have seen many other robots use the concept with only one.

Re: Ball posession: Roller (ball magnet) or vacuum?
 

If 148, 217, 1114, 1868, etc. are any indication, two well placed bars beat one bar any day of the week. I've seen a few 1551 type "underrollers" or "split rollers" (3125 has one like it) that work alright, but nothing beats an IFI magnet.

Re: Ball posession: Roller (ball magnet) or vacuum?
 

For those of us who don't know the jargon, what's an "IFI magnet" ?


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Re: Ball posession: Roller (ball magnet) or vacuum?
 

Double roller (or roller and stop) that 1114 / 217 / 148 / 254 seem to be using. I guess I started calling it that since they're all part of Team IFI.

Re: Ball posession: Roller (ball magnet) or vacuum?
 

Team 818 uses carpet tape. Yes there are some legal brands still!

Re: Ball posession: Roller (ball magnet) or vacuum?
 

by "bar" do you mean "roller"?

What's the conventional wisdom on what constitutes "well placed"?

Should the upper bar be forward or aft of the lower bar? And should one bar be above the center of the ball and the other below it?


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Re: Ball posession: Roller (ball magnet) or vacuum?
 

I dont know what the perfect placement would be, but we have two bars that are parallel. The bottom bar is free spinning and there for the purpose of keeping the ball from being sucked under the robot by the top roller. The top roller (we have a fisher-price powering ours) is powered and has some kind of friction producing material on it. I saw many robots at the NASA/VCU with modified pool noodles, while we use friction tape... the same stuff on stairways.

The combination of the two almost pinches the ball, while the free-spinning bottom roller keeps it from picking the ball up.

Re: Ball posession: Roller (ball magnet) or vacuum?
 

1717 uses a sort of a claw to pinch the ball.

Re: Ball posession: Roller (ball magnet) or vacuum?
 

We used a single horizontal roller. It wasn't very effective (lost ball if driving more than half speed backward, and slowed our forward and turning speed) and we're looking to improve on it during off season.

Re: Ball posession: Roller (ball magnet) or vacuum?
 

You can add team 33 to this list.
All during Troy we were tweaking ours so it would stop picking up the ball super slight amounts off the ground. Penelties resulting from this over the course of the quals actully resulted in us just missing 1st seed and breaking up the 469 / 217 combo (we came in a very close second).

By elims we had it working very well. However, by states this weekend you can be sure we will be working even better!

Re: Ball posession: Roller (ball magnet) or vacuum?
 

Is the bottom bar directly below the top one, or is it set back a bit?

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Re: Ball posession: Roller (ball magnet) or vacuum?
 

The ball can only penetrate the vertical plane of the frame perimeter by 3 inches (Rule G46), and no part of the robot may extend beyond the frame perimeter for more than 2 seconds (Rule G30). It's hard to visualize a "claw" that could grasp the 3 inches of the ball that is inside the frame perimeter... unless the "claw" has powered rollers or a vacuum or some adhesive.


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Re: Ball posession: Roller (ball magnet) or vacuum?
 

It's certainly possible for a claw to grip a ball without grabbing more than 50% around a ball. http://www.chiefdelphi.com/media/photos/29535