SquidPuppet

I always when guys make that claim about slack. Screw a nut an inch or so onto a naked axle. Is there enough clearance in between the mating threads to wiggle the nut? Plenty. Lots of slop there. Run a second nut down there and jam them together. Now try to wiggle them. Nope. Isn't that why they are called LOCK nuts?

SquidPuppet

No?

sweeks

woodcraft

You're right. I retract my Hmm.

3alarmer 

.
...I never got the impression people were saying you could not compress steel. Only that the force you can muster with a QR lever is orders of magnitude less than the sorts of examples (like the train wheels) you guys are referencing. So the meaningful question is, "Can you compress a hollow steel bike axle with the force you can exert using a cam operated QR lever ?" And I confess I do not know.

The weakest link in the system is doubtless the threading on the QR rod, which is why alloy rod skewers are not recommended for horizontal dropout use. The threading won't hold up to the sort of tensions involved.


But I can honestly say I've not personally experienced much in the way of bearing play/clearance adjustment changes with the compression exerted by my own QR skewers. But I might not have the hand strength to go full force on them at this point because of age and abuse in my hands.

sweeks

Short answer: "YES".
This is demonstrably true.

Steve

Andrew R Stewart 

Regardless of what some might want to believe the axle does shorten when tightened w/ a QR skewer the bearing preload can and often does increase. What actually is going on is the real question although a bit moot as the results are the same. Is it axial compression of is it a bending of the axle?


Axle bending would help support field evidence of only localized pitting along the ball track's circumference being the typical damage spots. Andy

wphamilton

I don't know if I'm more shocked that the question is a can of worms, or that you (or anyone) would open it again

But if I'm following you correctly, bending would change the angle of the axle slightly thus altering the wear pattern. Likely increasing wear. That does seem plausible.

sweeks

I accept that the axle compresses and the skewer stretches, as discussed by Jobst Brandt. As far as I'm concerned the question is settled.

How about the fact that the bearings are loaded from one "side"... that being from above, owing to the weight of the bike and rider. Asymmetric loading fully explains asymmetric wear.
Steve

3alarmer 

.
...I think you guys are over preloading your QR skewers.

sweeks

We're *OVERLOADING* something for sure!
Steve

Andrew R Stewart 

Agreed, but from what the asymmetrical loading comes from is my question. Many years ago I tried to track axle rotational position WRT where the cones were worn. I would mark the axle before removing the rear wheel then see where on the cones was the wear.


I did this on a couple of handfuls of bikes at most over one off season, not a good population I admit. The bikes that I did this with were having complete overhauls already so I thought that extra time in the off season was not wrong (for my boss to support). I didn't come up with any real conclusions IIRC. I do remember that I also didn't find the worn spots to coincide with the top of the bike either. Over the years I rethought this out and sort of came to the present idea, that if axle bending was at play it was impossible for me to also track how it bent WRT the wear on the cones.


I also have considered the aspect of non parallel drop outs. Which is stiffer? The axle or the drops? I have seen many drops "move" with axle tightening. Today this is so often the case with replaceable hangers which don't lay flat against the drop out's seat (but I'm more concerned about the drop out as defined by direct attachment to the stays).


Anyway this is all good, to revisit and expose the younger thinkers to what those before them have discussed many times before. How to revisit these ideas without the scorn of some or the dismissal by others is the trick, sometimes. Andy

sweeks

Amen, Andy!
Steve

Bike Gremlin

In my understanding, a bent axle would break rather quickly. QR force coming in line with the axle, and using a good amount of leverage (relatively little compression with long lever travel), and an axle being hollow, I'd go with the compression, rather than bending. Will try to test it on an axle as soon as I find the time - measuring length and "curve".

Kontact 

The difference between a properly adjusted hub (little loose) and one with zero play is 10-20° turn of the wrench. Axle threads 1mm per turn, so a 15° turn is 1/24 of that millimeter, or .042mm (based on actually doing it with two cone wrenches). That's the amount 100mm would have to compress to use up the slack.

A headtube for a 1" steerer bike is as small as 29.75mm I.D., yet the headset O.D. that is pressed into it is 30.0mm, meaning that parts are expanding/compressing a total of .25mm.

What's more incredible sounding, that a 30mm steel tube could expand .25mm, or a 100mm steel tube could compress .042mm?

To me it is a no brainer that the axle is slightly compressed. QR cams are enormously strong.

sweeks

There are many things that are incredible sounding, yet are true!

Off-topic, I have your icon saddle on my "winter" bike.
Steve

SquidPuppet

Too much preload...

sweeks

Bearing design by M.C. Escher.
Steve

SquidPuppet

Rubik's Bearing

sweeks

That's what they call a "recirculating ball" bearing!
Steve

Kontact 

That's my company. You clearly need another saddle for your "summer" bike, too.

sweeks

LoL... I'd need about 6 of them!
Seriously, that's at the top of my list next time I need to actually buy a saddle. I have a nice assortment!
/hijack!
Steve

Bike Gremlin

Did a test today - using vernier calipers to measure compression of a new front wheel axle with cones and making an improvisation for the forks like in this picture:

(it wasn't inside a hub though, so I could measure the flex as well).

Anyway, I measured almost 0.2 mm compression when locking the QR really tight (as I'd never do on a wheel).
For flex measurement, I used a short piece of steel. Leaned it against a ruler to check for any irregularities - it was fine. Then leaned it along the length of the axle between the two cones - it rested on top of the rolled threads exposed, and I couldn't tell even any bulges, nor flexing to any side. I have a relatively narrow piece of glass on a wooden block - used for knife sharpening. When I find the time, I'll do another test - rolling the axle over the glass (with cones resting on each side) - that should show any curve more precisely.

SquidPuppet

^ Thanks for that.

jack002

I've always thought that the QR affects the bearing preload. I had a '78 Motobecane and with the poor rear axle design I learned how to replace axles often. I soon learned to leave the races a tiny bit loose when building the wheel. Every time the QR took up the slack and made it perfect. I'd think all of you here who build wheels would know that. 0.2mm? I'd believe it.