842's Ball Sucker

[sdcantrell56]

Originally Posted by Tom Line

I know you've given up on the rollers, but let me give you a hint anyway as to what some teams figured out.

It's a whole lot easier to "wedge" the ball into 2 rollers so that it's actually held rather than trying to roll it backwards. Rolling it backwards depends on a lot of variables, especially the relative friction between your rollers, the ball, and the carpet. As long as the ball isn't off the ground when it's "wedged", you're fine.

Take a look at robowranglers video to understand better what I mean. Notice when they mistakenly drive up the ramp the ball comes off the floor? They're not spinning the ball - they've got it wedged.

I hate to say it but I am under the impression that 148/217 is probably carrying the ball by a very small amount most of the time. In order to truly have the ball wedged like that the ball would need to come off the floor a small amount. I have also heard from some people who have prototyped these systems who echo the same findings. If they are not carrying then I'm truly impressed but otherwise teams should be very careful when creating these pinching systems.

[Paul Copioli]

Originally Posted by sdcantrell56

I hate to say it but I am under the impression that 148/217 is probably carrying the ball by a very small amount most of the time. In order to truly have the ball wedged like that the ball would need to come off the floor a small amount. I have also heard from some people who have prototyped these systems who echo the same findings. If they are not carrying then I'm truly impressed but otherwise teams should be very careful when creating these pinching systems.

The referees at Finger Lakes were on their hands and knees checking out our system. They even pulled us (and 188) to the practice field to prove it to them. When we proved that the ball never leaves the ground when driving around the flat part of the field, they agreed.

We never got a penalty for carrying the entire regional. Even in the finals when we were the front zone scorer, the refs at both goals were always watching our robot to make sure we never lifted the ball. again, no penalties.

It is possible, but is very difficult to do. After each match we had to check the geometry because if it changes just slightly, you won't grab the ball.

And how we go up the scoring ramp without lifting the ball is our little secret...

[Pat Major]

At Kettering two teams had the two bar system and when they put their front wheels on the ¾ inch plywood at the base of the bump they were both carrying the ball. A piece of paper was slid under the ball. Both teams agreed that they were indeed carrying the ball at that point and had to avoid that area when they had a ball or risk a penalty. They were also carrying the ball if the front of the robot went into the goal and there was no floor left under the ball. They solve this issue by not driving into the goals.

[Karthik]

Originally Posted by Pat Major

At Kettering two teams had the two bar system and when they put their front wheels on the ¾ inch plywood at the base of the bump they were both carrying the ball. A piece of paper was slid under the ball. Both teams agreed that they were indeed carrying the ball at that point and had to avoid that area when they had a ball or risk a penalty. They were also carrying the ball if the front of the robot went into the goal and there was no floor left under the ball. They solve this issue by not driving into the goals.

I'll give away the simple solution for teams using the "pinching" method of grabbing the ball who happen to lift the ball in the manner that Pat described; Put your roller system on a pivot and spring load it down. We have done that and it ensures that our ball always stays on the ground, even when our back wheels are on the carpet and the ball is on the plywood lip in front of the bump.

Now, teams like 188 and 217 in Rochester had pinching rollers, which weren't spring loaded, but they managed to keep the ball on the ground with no difficulties. This just goes to show that there are multiple ways to solve this problem.

[RMS11]

Originally Posted by Karthik

I'll give away the simple solution for teams using the "pinching" method of grabbing the ball who happen to lift the ball in the manner that Pat described; Put your roller system on a pivot and spring load it down. We have done that and it ensures that our ball always stays on the ground, even when our back wheels are on the carpet and the ball is on the plywood lip in front of the bump.

Now, teams like 188 and 217 in Rochester had pinching rollers, which weren't spring loaded, but they managed to keep the ball on the ground with no difficulties. This just goes to show that there are multiple ways to solve this problem.

One question about your duel rollers. Are they both motorized or is one just there to stop the ball from jumping the robot and going too deep into the bot?

[Karthik]

Originally Posted by RMS11

One question about your duel rollers. Are they both motorized or is one just there to stop the ball from jumping the robot and going too deep into the bot?

The top roller is motorized, while the bottom part of the system is just a passive steel bar wrapped in rubber.

[sdcantrell56]

Originally Posted by Paul Copioli

The referees at Finger Lakes were on their hands and knees checking out our system. They even pulled us (and 188) to the practice field to prove it to them. When we proved that the ball never leaves the ground when driving around the flat part of the field, they agreed.

We never got a penalty for carrying the entire regional. Even in the finals when we were the front zone scorer, the refs at both goals were always watching our robot to make sure we never lifted the ball. again, no penalties.

It is possible, but is very difficult to do. After each match we had to check the geometry because if it changes just slightly, you won't grab the ball.

And how we go up the scoring ramp without lifting the ball is our little secret...

Thanks for clarifying this paul. My initial thoughts were that you had to be carrying to get a grip like that but in the back of my mind I figured you guys weren't willfully playing the system. I guess I might be protoyping a pinching roller here in a bit although Im quite a fan of the vacuum systems as well. It just goes to show theres definitely multiple ways to handle the possession of the ball this year.