[jspatz1]

We are experiencing this wobble in our shaft/bearing/wheel assemblies also, and it is pretty severe. With some experimentation we are confident the problem is with the hex hubs, and is not confined to just the bearings, although they may be contributing. We believe the hex broach is not square/perpendicular, and also possibly not concentric.

To test this we put two plate sprockets, each mounted on their own hex hub, side by side on a spinning hex shaft. Both shafts wobble, sometimes in sync with each other, sometimes opposite of each other. When one is removed and rotated to a different position relative to the other, the wobble with respect to each other changes. This would happen if the hex broach in one or both were not perpendicular.

As a second test we take a wheel assembly with hex hubs and spin it on a bearing-mounted shaft. It wobbles. We note and mark the location of the high points of the wobble. We then put the same wheel on a different shaft and different bearings, and the wobble is identical. This would be the case if the wobble was in the wheel/hub assembly. This same wheel spins true when it is fitted with round bearings, so the wobble is in the hubs, not the wheel.

We also see the hex shafting is not straight. A shaft segment laid on a surface plate will rock in some orientations, and not others.

It is difficult to assess the contribution of each of these factors (bearings. hubs, shaft) but we believe the squareness/concentricity of the hex hubs is the primary problem.

Teams experiencing this problem may want to duplicate these tests and look further at the source of the wobble. In our case it is not just the bearings.