Hello, my team is working on building a new intake on our robot for an off-season event, it is a four bar mechanism with 3 sets of Veras rollers that were assembled similar to the example on Vex’s website, however we have noticed a problem where the shoulder bolts, that go through a bearing and into the VersaRollers at each end, tend to back out if not tightened a bunch, but when they are tight enough to not back out they create a lot of friction and the Falcon 500 that we use to power the rollers tends to stall. Has anyone encountered similar issues, or have any ideas on how we could solve this issue? Any help would be greatly appreciated.
We had similar problems in 2017 the last time we tried to use shoulder bolts in rollers. Our only solution was red loctite, which made it a royal pain to maintain.
Ever since, we’ve preferred dead-axle rollers, where the bearings are in the rollers (rather than the side plates) and the hex shaft doesn’t rotate.
We used shoulder bolts on our intake this year, and initially had the same issue you experienced. We solved this by getting longer shoulder bolts that dont compress the bearing at all, instead tightening the shoulder against the shaft. We also got shoulder bolt shims to remove play from the system, but not so much that it would compress the bearing.
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Never experienced the screws backing out on our VersaRoller setups of 2019/2020/2021, though we virtually always used the plug inserts rather than an axle going all the way through. Not sure which of those approaches you’re doing.
Like @nuclearnerd, we’ve switched to dead axle rollers for 2022 and have been very happy with them. Only had to replace one all season, and it was the floor pickup one that got beaten in.
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In theory, tightening the shoulder bolt should only act to clamp the inner race to the threaded insert more tightly. Since the inner race of the bearing is supposed to be spinning with the roller itself, clamping it tightly should not create any binding. But, clearly, there is some binding or friction coming from somewhere that gets worse when you clamp it down tight.
Looking at the example that VEX has posted, I’m not sure I understand the purpose of the hex spacer between the bearing and the threaded insert:
If that is there to try to create a gap to prevent the outer flange of the threaded insert from rubbing on the outer race of the bearing, then it seems like you would have been better off using some washers that were the right size for the threaded portion of the shoulder bolt instead of a hex spacer. If the purpose of the hex spacer to take out some slop in the system because the shoulder is actually longer than the bore of the bearing, then maybe you can live with that slop.
In either case, I would look at removing that hex spacer. This is something that you should be able to test on a spare versaroller assembly on the bench. If that hex spacer is the problem, then you should be able to replicate the binding on the bench by tightening down the clamp group and seeing what rubs.
However, if you are able to tighten the clamp group on the bench and nothing binds, then it is possible that the bearings themselves are binding because of some alignment issue in the plates they are mounted in. In either case, the bench test should help you sort out where the binding is coming from and, hopefully how to eliminate it.
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We replaced the hex spacer with some properly sized washers and it didn’t really help the issue, but misalignment of the bearing could be the issue as the whole assembly is quite flexible, so the bench test is a great idea and should definitely help us troubleshoot that, thanks a ton for the suggestion.
Do both shoulder bolts loosen, or just one side primarily? If the latter scenario, have you tried a left-hand threaded shoulder bolt?
They don’t typically work well in right hand female threads 
Although if you manage to fully torque one in, I imagine it’s never going to loosen.
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One side does seem to loosen more than the other but both do end up loosening, I think because of the vibrations, and I don’t believe that vex sells left hand thread shafts for the Versa rollers, but thanks for the suggestion anyway.
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