Screws On Roller Hit

My team is assembling the Spin Up field and the screws on the rollers hit the prongs that tell you which side is up. Is it supposed to do this or is something wrong?

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At Vex Worlds I got to go up close to the field they had and a Head Ref showed me how they worked and they intentionally do that as a way to kind of lock it in one of the two states.


Yikes, I can see those prongs breaking off/wearing down with repeated use as the screw contacts the prong over, and over again. Hopefully this doesn’t evolve into a problem later in the season.


That’s not the only lock, they have a soft ratchet like mechanism that uses some rubber to make it harder to spin.


Are the rollers supposed to spin both directions, or just one? My idea of a ratchet is that it is only able to rotate one direction, but when we set ours up, it spins both ways albeit with quite a bit of resistance. Did we set ours up wrong, or are they supposed to do that?

Yes, they can spin either direction, and yes, they are relatively hard to turn.


One more thing to note, the screws on the roller + rubber ratchets were inconsistent. The amount of roller resistance actually varies from field to field.

At mall sig we used our auton at several fields (practice fields , qualifications matches).

Sometimes our auton would turn the rollers, sometimes it wouldn’t. This was due to the varying amount of resistance on the rollers of the different fields.

When designing your roller mech, I would recommend taking this inconsistency into account and designing a mechanism that would work for both high-friction and low-friction rollers.


There was discussion about this at the EP Summit. When assembling the rollers there is a rubber disk that is used to slow the spin. It should be just tight enough that you can’t flick spin the disk with a finger.

Problem is people (like me) that tighten everything on a field to make sure it never comes apart. This means the rubber disk is compressed and becomes wider. This means more surface contact with the roller and makes it much harder for a robot to move it.


Sounds like they should be shipping torque measuring devices to be able to tighten within a specified range.

Or work to have a design that works independent of screw tightening amount…


Going to say that most people assembling the rollers have fingers.

Insert and tighten screw.

Flick disk with finger. Does it spin? Yes, tighten to the point it just doesn’t spin.

No? Loosen until it will spin with a flick then just tighten a small amount.

It’s like finger tight for nuts. :slight_smile:


Do you have a source on that? Build instructions don’t say anything about how much to tighten that screw:

I’m curious how much of an effect the tightness of that screw has on roller resistance vs. other factors (such as wear over time). I guess the idea is that with the screw tighter, the rubber nub deflects more towards the gear, thus pushing into it harder?

Looks like those screws ought to be accessible when the roller is fully assembled, maybe I’ll play around with our field next week and see how much of a difference it makes.


Yep, it deforms it and pushes harder on the roller.

There was no printed / written guidelines. There was a field set up at the EP summit. I spun their rollers and they moved pretty easy but were “sticky”. I asked what the deal was between mine that spin with much force vs the ones there. That was the explanation I got. I’ll incant @VEX_GDC and maybe they can add something in the next manual update.


Having sensor based roller scoring in your autonomous routines would also help with this.

Using an optical sensor or a vision sensor, have your robot spin the roller until the sensor reaches the right values to indicate the roller has been scored correctly.


Our coach shaved down all of the prongs because he thought that it was a problem with the manufacturing. Guess not.


Where do you think the resistance primarily came from? Is it the screws hitting the rollers? Or is it the rubber disk?

Thoreticlcy would it make sense that while waitting for the match to start to try to loosen the rollers by spining them? Do you think that would make a diffrence?

Cursed images please.


I mean It was going to happen from use over time anyway.

our ep countersunk the screws into the rollers


I will try when he comes back from vacation.

So I understand that the screws hitting is intentionally, however, our field is already showing signs of damage.

This after less than 2 months of use from 1 robot. Each of the rollers has probably only been spun a couple hundred of times. This might seem like a lot, but a roller could be spun thousands of times of the course of a season. I can only imagine how much worse this will after multiple tournaments and months of practice from multiple robots.

I am concerned about these parts getting more worn down and causing a huge amount of inconsistency. I wouldn’t be shocked if the screws didn’t hit at all by worlds due to continued use.


I am less concern - our tournament fields are use just for that :slight_smile: So 48 team tournament, 3 fields, and 3:30 match cycle (our usual goal) will have 74 qualifying matches - roughly 25 matches per field. We have two separate skills fields - for those will see total 288 runs. I expect to see the most beat up fields be the practice fields - there hard to tell load on rollers.

We will run 7 qualifiers this season, and two championships. As season progresses, we will bring more game sets.

I think we will be ok.

(to be clear, field wear through the season will be universal - so design for what you think benefits your team most - design most resistant roller or least resistant? Design to check for color orientation - or use human visual feedback? )