Revised ball holder

[Michael Kapp]

I'm actually more inclined towards two horizontal rollers because they will make contact and grab the ball almost instantaneously. I can explain this more in depth later.

That does seem to be a good possibility, and I think that the best way to implement it would be to place the bottom roller quite close to the ground and have the kicker kick in between the top and bottom rollers.

One thing that I am not sure of is the directionality of the bottom roller. I know that other teams have successfully used the bottom roller spinning in the opposite direction, and this sounds like it would require a firm grip on the ball by the two rollers in order to work. On the other hand, spinning them both in the same direction would increase the angular momentum of the ball so that it spins, slipping on the carpet (thus reducing ball-carpet friction by reverting to kinetic friction instead of static, allowing the ball to roll with the robot more easily.)

[Sunny]

\That does seem to be a good possibility, and I think that the best way to implement it would be to place the bottom roller quite close to the ground and have the kicker kick in between the top and bottom rollers.

One thing that I am not sure of is the directionality of the bottom roller. I know that other teams have successfully used the bottom roller spinning in the opposite direction, and this sounds like it would require a firm grip on the ball by the two rollers in order to work. On the other hand, spinning them both in the same direction would increase the angular momentum of the ball so that it spins, slipping on the carpet (thus reducing ball-carpet friction by reverting to kinetic friction instead of static, allowing the ball to roll with the robot more easily.)

We've already been down this road and I don't want to spend a hellalong time prototyping a slipping roller again. The main issue with having the spining roller is that when we back up/turn, the ball will want to remain static, so we have issues of the ball not spinning as fast the backward movement of the robot or the ball getting jammed on one side of the roller system.

Having two rollers (or one roller and one static bar) will be more helpful in pinching the ball and maintaining a constant, firm grip over the ball. A grip that will ensures that the ball stays with the robot no matter which direction the robot is moving in.

[freds]

Lets try and find some video from last weeks regionals of the robots that used this design and see how they performed.

One potential issue is lifting the ball off the ground in this 'pinching' situation.

[Sunny]

217 played at FLR this past weekend and they won. So...I don't have any video of that. I'll do some hunting and post back my findings.

EDIT: 217 will be playing at the Cass Tech event this week. The link below has a link to the webcast. I'll definitely be watching.

http://firstwiki.net/index.php/2010_Webcasts

[Sunny]

I found a vid. for 217: http://www.facebook.com/video/video.php ... 754&ref=mf

I like the blue alliance could only score two simply because they were starved for balls. You can see 217's bottom roller, but they definitely have control over the ball. I can see that they've dropped the bottom roller always all of the way down to the ground. I'm not entirely sure if that is some how better, but we'll see Thursday.

I also found a vid of 1717's hanger. It looks like a some sort of rack and pinion or even a custom pneumo system....but I have *no* idea besides that.

http://www.youtube.com/watch?v=H-e7_Cyp8iA

[freds]

I could not really see anything about 1717, other than some neat lifting mechanism.

I could not see anything in the myspace video, too small for my eyes.

Lets keep looking!!!

[Sunny]

I could not really see anything about 1717, other than some neat lifting mechanism.

I could not see anything in the myspace video, too small for my eyes.

Lets keep looking!!!

There's not gonna be much in these videos except watching these robots do their work. I think the design is up on facebook somewhere, I'll do a little digging tonight and see what I can find.

And, I just posted 1717's match so people could see the lifting mech.

[Tanner]

http://www.chiefdelphi.com/forums/showt ... post935411

[freds]

One solution to sense when a ball is in, pinched far enough is to create a lightweight piece of metal across the front, behind the roller on a hinge at the top so as the ball comes in, it pushes the hinged metal back and the piece of metal makes contact on a limit switch. This would cover the whole front end.

[freds]

So we had some success today. Great!

I got a second vac converted today. Much easier the second time and used parts only vs buying a complete vac. Just think like cars, dual exhaust, we could have dual vacs.

Back to the pincher. Tanner mention the use of a encoder to tell when the roller stops and there to turn the motor off. Also mentioned having to add a back plate to prevent 3" overpinching. That would work, but what if we went back to my idea of some narrow hinged plate across the front just behind the roller at the right position, so the ball would hit it and with a properly adjusted switch, shut the roller off. We should not need the backplate then and not worry about over pinching.

I heard we will need a curved kicker.................If this is the case, someone needs to be autocadding one.......I could take a detailed drawing by Swift Atlanta and see what the possibilities are.....I was there this morning getting the motor cutoff an orginal Makita vac assy. The design would have to be pretty perfect.