Shaft Collar Issues

Hi, our team has been complaining about the unreliability of shaft collars. We are wondering how other teams deal with this. In our testing, we noticed that no matter how tightly we tighten the shaft collars, they begin to slide on the shaft gradually, and after a few days of testing, they cause our lift to be at an angle, as the c-channels we connected by shaft colllars have slid. The shaft collar screws don’t have a good grip, strip easily, and are overall low quality. How do other teams deal with this? Would you recommend using Rubber/Clamping shaft collars instead? Also, I have heard mentions of “high-strength shaft collars” on the Vex forum, but I can’t find them on the Vex store. Do those exist?

Thanks

Use blue locktite. Also, the extra shaft collar screws VEX sells online are higher quality than the ones that come with the shaft collars, which is really stupid.

The set screws you use to tighten the lock collars have little cups in their ends. Any set screw will eventually end up with flattened cups, which behave as you describe. Take a look at ALL your setscrews and throw out the ones that are flat. Then, replace them with better ones. I’ve used these for years: 18-8 Stainless Steel Cup-Point Set Screw 8-32 Thread, 3/16" Long (https://www.mcmaster.com/#92311a189/=1alkz0y). The cost is $4.51 for 100 screws.

We do what Rick said. Also, for explanation: “High Strength Shaft Collars” are for High Strength shaft, which is 1/4" square instead of 1/8" square. Here is the VEX Robotics page for HS shaft: https://www.vexrobotics.com/hs-hardware.html

A high strength lock bar (keeps you from stripping or breaking HS Gears) is also available from Robosource.net VEX only makes regular lock bars.

If VEX only makes regular lock bars, then the HS lock bars are not a VEX component and I assume they would be functional, isn’t this illegal?

This is a simple modification of a VEX legal part. It’s like selling VEX parts which you have anodized, or C-channel you’ve sliced longwise.

In this case, Robosource is simply broaching a larger hole in a lockbar they bought from VEX. Since you could do that yourself, it’s legal to sell, or buy, or use.

Ok, I didn’t know that they were modified VEX parts, I assumed they were made that way.

We just use normal screws instead of set screws…

We are rebuilding many parts of our robot. Would it be wise to use clamping shaft collars or rubber shaft collars, or just stick with the original shaft collars?

We used clamping shaft collars when we rebuilt our drive and they have worked very well, not loosened or moved. Even thought they are 2x as big as regular shaft collars, I would recommend using them.

Sometimes we have to cut a little divot into our axles which helps the screw stay in place.

+1 to this. Makes it really hard to get them loose but isn’t that the point?

Using a rubber shaft collar in addition to the set screw variety is another way to help keep them in place. But sometimes you don’t have the room.

We have started replacing the set screws with regular screws anywhere we can as long as the screw head doesn’t interfere with anything.