Uncertainty bearing in V groove

[S1MPL3]

I have the following case:

A camroller that is preloaded by leafspring into a V groove on a disc of circa 150 mm diameter that can rotate. The precision is key in this case and there is chosen for a camroller instead of ball because of the possibility to use rolling friction instead of sliding friction. Because the friction has a negative influence on the ability to let the disc center itself due to the preload on the camroller into the V groove.

The question is regarding the clearance and the precision of the camroller. According to the specification of the camroller it has an internal clearance of 20 micrometer.
But due to the preload and the innerring is pressed into the outerring and makes contact.

Questions I have:
- What is the effective uncertainty tangential to the disk when the force stays constant (The bearing is centered down into the groove).
In my thaughts down to the mechanical hysterises and i can ignore the clearance because of the constant preload.? Correct?
- What tangential disterbance force would actuate the axis over the innerring?
May i assume this situation as mass on slope like the basic friction test?

 

[MikeHalloran]

The camroller may be a suboptimal choice in this instance because of the radial clearance within it. With everything seated, you've effectively got a 'valley' at the inside surface of the camroller's outer race, and a cylinder (either the needle radius or the radius of the outermost locus of the needles' periphery) pressing into the valley, and easily lifted by a tangential force.

You'd probably be better off with simple tapered shotpin.

Then you've got a similar uncertainty associated with the index wheel's bearings, so maybe you need two shotpins.

I'm curious what you're trying to do that requires that kind of accuracy.

Mike Halloran
Pembroke Pines, FL, USA

 

[S1MPL3]

The exact purpose of the solution i can not tell. But this part of a bigger solution, where the amount of positions is predefined/limited with a high repeatability demand. To meet this demand a kinematic solution is preferable instead of an active controller.

A tapered shotpin needs a sleeve bearings where is at least the same amount of clearance. But a ball fixed to the leafspring would prevent the clearance.
Despite this is my back-up solutions, because this will work as proven in the past. But the amount of friction is based on a sliding friction instead of a rolling friction.

I agree with the valley where you push, for example a 3.99 mm axis in to a 4.01mm disc, there is an internal clearance of 20 mu. But by pressing the the axis hard down in the valley with preload F, the positions predefined, the axis is down into the valley fo the outerdisc.

I would like to exactly express the tangential force is needed to move the axis 1 mu sideways with the preload F on top. Should i see this as a simple mass on hill. From thereout i can determine of this clearance is relevant.

 

[MikeHalloran]

Yes, I think it's a trig problem.


Mike Halloran
Pembroke Pines, FL, USA