Roller Screw Head Clearance Issue

We built our field today, and we noticed that when the roller is rotated, the heads of the Screws securing the PVC pipe to the ratcheting mechanism hits the plastic pointers used for scoring. This is different from the normal ratcheting effect from the rubber part in the roller mechanism, and requires much more force to clear. Here is a video demonstrating this:

I also made a q&a regarding this issue: Field Specifications- Roller Screws Catching : Robot Events
I’m curious to see if any other teams have had this issue with their fields:

Issues with roller screws
  • Yes, we have had issues with the roller screws hitting the plastic
  • No, we have not had issues with the roller screws hitting the plastic

0 voters


I thought it was designed for this to occur so that once the screwhead is rolled in between the prongs, it stays there. I am also confused at the same time as there is a built in ratcheting mechanism.


As far as I’m aware, this is normal behavior of the rollers, every field I have heard of has had this. I’ve seen it mentioned a few times that this was an intentional design feature, and though I’ve seen no verification that this is true, I can’t imagine that this could have been overlooked when creating these game peices.

But even if this was an intentional effort to make the roller stay put where it’s left, it seems both redundant to the built in ratchet (I have not personally felt the rollers so I can’t speak for how effective the ratchet on its own will be), and a very flawed and generally bad way to add resistance to the roller. I easily see the screws eating away and wearing out the prongs over the course of the season. So I guess robots need to be designed with the worst case resistance in mind for the rollers, similar to in turning point where robots had to be able to hit flags which were much harder to turn than the average flag.

I’m pretty skeptical in general of the longevity of the rollers in general though, considering how violently I expect robots to slam into them in the mad rush to control them once goals are all filled up. Do they feel as if they will last repeated full speed slams by heavy 6m drive robots? I guess time will tell if they have sufficient build quality.


It’s not a glitch, it’s a feature.


We recently held a robotics summer camp where this was somewhat of an issue. At the start, most people trying to spin the rollers including myself found that it was very difficult to get a robot to spin it past the bolt heads. After a few days of the fields being used for practice, autons, and competition they were already worn down enough to be noticeable while driving. I don’t know if it was just us or a design issue. The ratchet mechanism adds very little resistance, akin to having 2 pillow blocks out of alignment on a drivetrain or something similar to that. As for them getting rammed into, that wasn’t much of a problem or if it was, I didn’t notice; however only one person at our camp actually had 6m drive.


At worlds one of the head refs around the spin up field gave me an explanation of how the rollers worked. The screws hitting was intentional as a way to help keep it in a scored position.


As far as I know… I read the instructions and the rubber grip is the main factor that was/is supposed to limit and slow the roller in the game and add difficulty towards the roller movement. I feel that the screws hitting may be unintentional. This is one opinion though, I would like to see what vex’s opinion is on this so we can all aid in design accordingly.

The gdc responded to the q&a posted about this question, and the collision between the screws and the prongs was indeed intentional.


I figured it was intentional but there is no way the prongs are going to last a season. After just a few passes there was a noticable groove in the prongs.


I noticed the same thing where the screw would be caught on the screw. But something else I noticed is that even for the same roller it’s not very consistent for if it gets caught or not. So I wanted to ask wether anyone else has this problem or if it’s just our field setup (if so how chips we possibly fix it) because while it doesn’t matter in a match my autonomous was having issues.

The screws are supposed to hit the plastic to make it easier to turn the rollers accurately. Either add more torque to your roller mech or try to increase the grip of the wheel you may be using

Problem with this is that you “fixing it” on your field means nothing in competition. We recently traveled to a competition where they had brand new field elements and they assembled everything by the book. Everyone had issues with spinning rollers, whether auton or driver. Towards the end of the day things got magically easier. It’s not just the screws, how tight or loose they are, how new the prongs are and if they already have grooves or not, it’s also how much you tighten that rubber piece, how you space the brackets on the perimeter, all of that affects the spinning, the whole thing is a bit strange. What I suggest you do is build it as per instructions with no “fixes” (don’t countersink the screws, don’t make the rubber loose etc…) and build your mechanism for the worst case scenario.

I havent seen too much issue with this. It ends up being a design necessity in the robot, whether it can overcome the screw or not.

That said, sometimes it can be an issue. At one comp, during a skills run, my driver couldn’t turn one roller and ended up ignoring it for most of that run. Not to preen my own feathers, but my roller mechanism is one of the strongest I’ve seen, as have the refs. One of refs maning the skills area came over and tried to turn the roller with his hand, but it was too difficult, so he had to find an alan wrench and completely rebuild that roller. My team and I didn’t end up fighting that skills run because of a broken field, but we did go back to do another run after that.

I think the poll at the top of the thread answers your first question:

And looking a couple of posts above yours will answer your second question:


Thanks for the help and now that our bot uses a better setup for our rollers, and that most fields have been used to the point there is little resistance we’ve been able to get our code to work.

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