Slot in 4" Omni?

What is the official intent of the slots in the newer 4" omni (HS compatible)? I have seen it used for locking to small axles, but nothing appears to fit in there just right.

Seems obvious that it is there with some specific intent as it does not look like it was needed for the mold…

Maybe for the piece on the right? My school is using the older omniwheels that don’t have the slots so I’m not entirely sure.

people like to put lock bars on each side of the omni with standoffs connecting the two sides. I’m guessing the slot allows for a better clearance when such methods are used

As far as I know it is for lock bars, but it also helps tighten collars that are right next to the wheel. Our old wheels all have the metal inserts, which are thinner than the old plastic ones, which makes putting collars rn to them a pain.

Do the new omnis fit standoffs in between the curved plastic parts that connect to the tires? I use the lock bars on the old omnis and I can’t fit a standoff in between the two lockbars.

Yes I think it might primarily be to aid in tightening shaft collars

I considered adding some kind of lock bar to the wheels to aid in encoder precision but nothing quite fit correctly and the slight twist caused the shaft to bind completely. If someone has pictures to share of a good locked wheel I would really appreciate it!

Pic by George Gillard


I’ve never seen new omnis, but I’d figure they’re either equally as easy or easier to bar lock.

Kind of sad to see that this technique of using bar lock to reduce slop is now almost a lost art.
It used to be very common… especially during Toss Up.

But that said, not every situation will require to add in the bar lock.
During Toss Up, robots needed to go over the big bump, and the sustained impact can be quite damaging to the shaft and the wheels as well.

The slot size is not wide enough for the lockbar or any other vex part I could think of…

We found at least one use for the slot - it makes it easier to assist removal of the inserts with a flat screwdriver:


The slots are ideally located for lockbars, but they just don’t quite fit them without modifying either the lockbar or the wheel (hence the original post). They do seem to fit white spacers on screws going through the wheels from sprockets/gears/lockbars.

Thanks! Looks pretty good.