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View Full Version : Do I need thrust washers inside snap rings?



jwatte
05-15-2017, 11:58 PM
So, I'm re-designing the Money Pit suspension, using oilite bushings instead of ball bearings.

The axle is 303 stainless, and pressed through precision holes in the aluminum bracket that holds it out the outside; the bushings are between the moving bracket on the inside and the axle, as well as between the inner moving part and the sides of the bracket (flange.)

See picture:

https://watte.net/snap-ring-axle.jpg


The question for you mechanical engineers (that means YOU, tician!) is:

Do I need a (thrust?) washer between the snap ring and the outside bracket?

My inclination is "no" because the axle "ought to" not move sideways too much within the bracket, because the bushing insulates it from movement of the inner part. The force between the bracket hole and the axle "ought" to be enough. (6061 T6 aluminum versus 303 SS.)

And, worst case, if the axle moves enough that the snap ring catches the side of the bracket, again, it'll just jam against the aluminum and lock the axle in place, which is perfectly fine. In fact, I might even epoxy or super glue it to the outer bracket just for funsies :-) (or I might not.)

But, being a neophyte in snap ring application, am I missing something?

(Old Money Pit used a shaft collar with a set screw into a milled flat, and the axle interface was ball bearings -- overkill, as they say :-)

tician
05-16-2017, 12:41 AM
So, basically, the shaft is unable to be reliably press-fit into the outer bracket and you added the snap ring(s) for insurance? Probably don't need any plain spacers/washers unless you want to prevent the snap ring marring the surface of the outer bracket when the shaft slides axially.

Brooks
05-16-2017, 05:11 AM
The axle will "work" against the outer flange, won't it? Since you already have them, a second set of flanged bearings, shoulder-out, will let the axle float, remaining captured by the snap-ring riding against the outer bearings' flanges.

jwatte
05-16-2017, 10:28 AM
the shaft is unable to be reliably press-fit into the outer bracket and you added the snap ring(s) for insurance?

Well, aluminum is softer than steel, so that would be the main reason the axle would float sideways. I don't care about surface marring, and in fact, if the axle slips, and if the snap ring catches on the side, that'd be perfectly fine by me!


a second set of flanged bearings, shoulder-out, will let the axle float

Hmm. I'd rather just make the axle by default friction fit, and use the snap rings for insurance. I think floating the axle both ways is, again, overkill :-)