See thread404-513773: Radial Run Out Stack up for a previous attempt on the OP question.

My follow-up to the last post is: the circle described by the rolling elements define the axis of rotation, that is the bearing surface of the inner race.

The only bearing runout that affects the hub will be from the moving part of the bearing, and that runout is from the bearing surface of the outer race to the bearing OD.

The fit between the outer race and the hub can be adjusted to maximize or minimize or be in between; there are similar adjustment offset bushings used to change alignment by rotating the bushing.

3DDave do you have an example of a stack up where the bearing , bore, hub GD&T is considered ?

Where are you measuring the runout? I'm struggling to see how lateral runout is at all significant for a wheel given that its most important interface is to a wobbly black thing that is more or less round.

Typically in automotive tolerance stacks are run on statistical packages that account for the distribution of the tolerance rather than just assuming the distribution is just normal or just uniform. I don't think they are incredibly sophisticated, they just Monte Carlo it.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

Thanks GregLocock.


There is a circular run out tolerance call out, of 0.02mm on the face where the dial indicator is shown. I know that bore position tolerance , perpendicularity and other will affect the wobble of this face, but not sure how to compute the stack up. Seems like it would be a fairly common activity for suspension engineers, but I am not finding any examples, besides 2D linear stack up, like this belt tensioner example :

https://www.wasyresearch.com/2d-tolerance-stack-up...

I was told a loop analysis would allow me to find the worst case wobble resulting from the assembly GD&T stack up. But as in the linked example, it doesn't seem to account for the axis of rotation being angled.

so your biggest contributor to wobble is the radial clearance on each bearing. Since we switched to hub units which are preloaded this is not an issue. Otherwise it is perpendicularity of the hub face to the bore axis, or misalignment of the bearings.

If you want me to put any effort into this you'd best post a proper drawing.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

Quote (umatrix)

But as in the linked example, it doesn't seem to account for the axis of rotation being angled

That's because the axis of rotation being angled doesn't contribute to runout (ie.. it doesn't cause wobble).

Think about it. If the bearings/hub/entire assembly is perfectly manufactured such that runout is zero, but the angle of rotation is angled relative to the axis of the dial indicator, the dial indicator is going to read perfect zeros. The point where the dial indicator contacts the surface being measured does not move.

The only way the dial indicator can read anything other than zero are:

A) the surface being measured moves normal to the axis of rotation. Causes for this in the real world could be errors in flatness of the face, errors in perpendicularity between the face and the axis of rotation, or axial play/runout in the assembly due to bearing problems or insufficient axial preload.

B) the axis of rotation itself is precessing about some other point or axis. Causes for this in the real world are pretty much confined to radial runout in bearings, which for the case of tapered roller bearings are also the result of insufficient preload.

I really just wanted an example(textbook, website or other resources)for performing a stack up for worst case run out. Getting into these details is too difficult with being able to post the actual print.

Well... you aren't going to find one that's exactly like your real part.

You need to calculate the maximum deviation of the axis of rotation (which it seems you have already done) and then use geometry to calculate how that affects the position of the measured point on the rotating face based on maximum axis deviation from nominal plus position changes due to imperfect features.