Fork type End Defectors & Ball acquisition
 

With fork lift type grippers, what have teams found as most efficient way to grab the ball (against the wall, running into the ball at high speed, small attachments on the forks)?

I noticed that in Florida, team 103 added brushes onto their gripper to help keep the ball from sliding off during pick up.

Anyone else have such ideas or improvements on the standard fork design?

Re: Fork type End Defectors & Ball acquisition
 

Team 1816 runs the ball into a ball/corner and lifts the forks, but to keep the ball on them and prevent it from moving around we bought bicycle handle grips at target and they fit perfectly on the end of our forks. I have seen other teams use tennis balls on the front. If you just add something with a little grip to the front, as soon as the ball is on, it is on until you let it go. Just make sure you don't put too much grip or else you will have trouble releasing the ball for a hurdle.

Re: Fork type End Defectors & Ball acquisition
 

You could add rollers to the end like 71

Re: Fork type End Defectors & Ball acquisition
 

816 had tennis balls at the end.

Re: Fork type End Defectors & Ball acquisition
 

We initially went with tennis balls, but found out that the ball was still rolling out of the side. We've got some sort of modification in the works for Javits, I believe it involves a bit of surgical tubing and zipties.

Re: Fork type End Defectors & Ball acquisition
 

We decided that the ball would come off as we turned the corner, so we added a gripper arm to clamp over the top of the ball. This gives us three point stability. We also added cylinders to the forks so they could open about 30 degrees for easy acquisition of the ball.

When we get the ball - the forks close in from the sides and the gripper comes down from the top. We also have a ball sensor that automatically tells the robot to grab the ball.

I will post a pic when it gets approved.

Re: Fork type End Defectors & Ball acquisition
 

We have a fork type picker upper, and to make it work better we put some PVC side arm things on it, they flop down about 45 degrees when we first lower the lifter, and guide the ball to the center and keep it there, seem to work real well especially when driving towards the end wall when picking up the ball. Hopefully I'll figure out how to get some video off my camera....so you can see them in action...

Re: Fork type End Defectors & Ball acquisition
 

There's a lousy video in the LA regional thread, here's a picture of it with the lifter up, sorry I did not get any with it down, I'll try tomorrow to do that.

The pvc arms just pivot in some short lengths of 1x1x1/16" square tube that's riveted to the top of the lifter. They each have a bolt that fits thru a slot cut in the pvc, limiting travel. Easy to make, seems to work well.

Re: Fork type End Defectors & Ball acquisition
 

IHNTA, IJLS "end defector."

Re: Fork type End Defectors & Ball acquisition
 

We had old strips of toolbox drawer liner material lying around and we added those to the front of our forks and to our gripper. The stuff is lightweight, smooth, and reasonably durable, and it provides a "sticky" (i.e. gripping with very little pressure) behavior without actually being sticky.

Re: Fork type End Defectors & Ball acquisition
 

2077 used plunger and they worked great

Re: Fork type End Defectors & Ball acquisition
 

the brushes on team 103 worked great until we ran them over and smashed their forks.hehe:D


our forks dident have a problem picking up the ball.

Re: Fork type End Defectors & Ball acquisition
 

Here's another picture of our modified fork type ball picker upper, the PVC tubing parts flop down as shown when the fork goes down, and guide the ball in for more reliable lifting. They are held on by those short pieces of square tubing, which are riveted on, and there is a bolt going thru the tubing sideways that fits in slots in the PVC. The slots were very easy to make by just holding the PVC in place, and running a drill in the hole in the square tubing, and slowly turning the PVC, so the drill bit mills the slots.

Re: Fork type End Defectors & Ball acquisition
 

That's probably not something you should be too proud of.

Our forks pick up the ball very easily no matter where we are, provided we can get the ball in between them. It's hard to see the other side of the barrier.

We had some trouble with the balls rolling off to the sides. We fixed that by adding "mantis claws" -- two protrusions over the top of the ball. When we tip our forks back, the protrusions compress the ball a bit and keep it firmly in place. It works great.

Re: Fork type End Defectors & Ball acquisition
 

Yeah... it does work great. We got to watch those mantis claws in action just a few more times in the quarters than we really wanted to. :eek:

Our grippers aren't exactly fork-type (www.youtube.com/dtengineering) but we also found it to be a big problem when we went too far underneath the ball, like we did in Portland.

We swapped the hockey sticks to curve out, not in, and then put a spacer on the gripper pneumatic so it couldn't close all the way in. We also changed the code to give a quarter second delay between closing the sticks and lifting the sticks. This made a huge difference in our ball grasping ability and we were even able to pick it up "on the roll" once or twice in Seattle.