V-Wheels bearings bad, slightly eccentric? FIXED

X-Carve
1

UPDATE:
After swapping around bearings v-wheels washers and bolts I was able to get all but 2 wheels to turn smoothly when tight. There is definitely some error stack up type of thing going on here.
Last 2: I took a 90 degree carving chisel and gently cleaned the inside corner bottom and edges of the v-wheel pockets. After removing a couple of very small bumps I was able to get everything to turn reasonably well.

Made my first cut last week and everything looks great! +/- .02" on xy circle and rectangle dimensions.
Yay!

Original Post:
I seem to have gotten a bad batch of bearings, out of 16 v-wheel only 6 of them turned freely out of the box,

First 6: worked well.
Next two:: the bearings were not fully/evenly seated in the delrin. Pressed them in, no problem.
Two more: I was able to get 2 more wheels working nicely after swapping bearings around…
Last 6: I pulled all the bearings and put them on some long 5mm bolts.

I found that after tightening the shaft the bearings all still spun nicely.
put them back in the delrin, as soon as the shaft tightened, no spin.
swapped washers. not change.
back on the bolt, tightened the shaft, still spin nicely. a mystery.

then, I pinched the OD of several bearings while spinning the shaft. I could feel the outsides of the bearings wiggling.against each other as the shaft spun, as if the bearing were slightly eccentric

I think maybe the tight ID delrin is forcing the slightly off center bearings to put too much pressure on the hub and is preventing the bearings from spinning around the race and instead force the hub to spin around the shaft.

please help?

2

It may not be the bearings but the spacers between the bearings and the rib in the center if the wheel rim. If the center rib is thicker than it is suppose to be then when you tighten the center bolt you squeeze the inside race against the outside race. This causes the binding you are seeing.
Try this lay a washer in a thick piece of paper and out a paper washer. Now put the metal washer and the paper washer in the wheel with the problem. tighten and see if the wheel now turns freely. If still a little tight cut another paper washer using thinner paper and put 2 paper washers and the metal washer. test again.
If wheel spins freely you have a wheel with a thick center rib.

When I measured all of the wheels I received I found that about half had center ribs that were thicker than specs called for.

Dave
Ariel, WA

3

Definitely some sort of interaction with the delrin v-wheels, I’ve added several metal and fiber washer combinations. I’m investing in some washer and shaft shims next.