Hi all,
I’ve got a question for teams using plastic rollers on their grabbers (I’ll use the Robowranglers as an example: ](http://www.chiefdelphi.com/media/photos/27533) ). How much room do you leave between your top roller and the bottom roller? In other words, how much do you compress the tube when you pull it in to keep it stable? Just curious. Sorry if there’s already a thread on this somewhere that I missed.
Thanks! :]
I designed the end effector for the HOT Team (67) to be adjustable to compensate for variation in ringer inflation, but we did not have to adjust the distance between roller all weekend at GLR.
We have our belts positioned 5-5.5" apart.
If you want you can see pictures of it on our website.
http://www2.huronvalley.k12.mi.us/schools/mhs/activity/hot_team/HOTPhotoAlbum/2007Photos/index.html
We did extensive research on this subject and built a total of 3 different “suckers” before we got it right.
Center to center, the perfect distance was 9" - but we used 3" wheels so the compression was 6." This may sound tight, but the rubber wheels we used were able to “suck” the tube through the narrow opening.
But the primary griping force wasn’t in the wheels at all, it was in the belts that drove them. The belts were arranged in a “V” configuration, so that as the tube was drawn in the compression became even greater. The belts act like rubber bands, squeezing the tube.
It is impossible to remove an inflated tube without running the motors.
http://img.photobucket.com/albums/v519/spinmunky/Robotics%20stuff/100_1064.jpg
(rubber wheels not shown)
That’s gorgeous! Thanks for the info and the photos. I’ve been looking up videos of roller grabbers in action and it looks like everyone uses lots of compression.
Hey… isn’t that against the rules? 
http://www.chiefdelphi.com/media/photos/27496
^ 868’s kicker wheel. A little different, but the same principle.
We compress the tubes probably 1.5", but I can’t remember exactly how much. We do have trouble picking up fairly underinflated tubes, but I don’t recall us ever encountering a tube in a match that we couldn’t pick up, only on the practice field.
It is. I’m not sure if 100 has competed yet, but if they haven’t, they better find a way to remove them or they will fail inspection.
Calm down everyone; He doesn’t literally mean impossible.
The glove motors can be back driven by hand, therefore pulling a tube straight out will allow the tube to come out. Since this kind of pull probably won’t happen in a match, the tube must be pretty secure during gameplay.
How is it impossible to remove without running the motors?
It may be difficult during a match cause of compression factors which is indeed a good thing when trying to hold onto a tube, but when I can pull a tube out of that gripper fairly easily because of an open gripper design, it’s not impossible.
I would like to know where " impossible to remove an inflated tube without running the motors" logic comes from.
Okay!!! maybe I exaggerated, I’m kind of a weakling (
)
As was said earlier, the globes back-drive and the tube comes out. You can do it but its difficult.
What I should have said was “It is impossible to remove an inflated tube without turning the motors.”