sweeks

Here are some images to help you understand. I didn't have a cup-and-cone hub handy, so I've used a dynohub that's not built into a wheel. This is a cartridge bearing hub, so you'll have to imagine the locknuts and threaded axle.

The first image shows an overview of the hub held in a homemade wheel bearing adjustment fixture. The Q-R is tight.

The second image shows the Q-R nut in contact with the axle stub, *not* the locknut. Consequently, were this a cup/cone assembly, it would be *unloaded*. According the the "thread-yield" hypothesis, putting this hub into a frame and tightening the Q-R would result in the bearing getting tighter. True, it would only be half the decrease in clearance expected with *both* cup/cone assemblies, but this would probably still be detectable.

The third image shows the cam end of the Q-R; the hub's locknut is against the fixture and, therefore, under compression.

The last image shows the fixture. It's just a piece of angle-iron with an extra bit silver-soldered on to make it about as thick as a dropout.

I've adjusted many wheel bearings with this fixture, and the bearings do get loose when I take the Q-R off, but then go back to proper adjustment when installed in the bike. The beauty of this fixture is that I can adjust the bearings without releasing the Q-R, making the adjustment go more quickly with no surprises when the wheel goes back on the bike.

Hope this helps!
Steve

wphamilton

Non-parallel forces, or variations in the material, will lead to un-equal compression which seems to me to be identical to a small flex. So some amount is inevitable. Where does the torque needed to bend the axle more than that slight amount come from though? It's still all a form of compression.

70sSanO

Back on post #118 I merely said that Park states that hollow axles flex. Per Park...

"Quick release hubs have hollow axles that flex slightly when the quick release is closed."

It just seemed to me at the time that if the people that manufacture tools, and provide step by step instructions that are used by thousands of mechanics, who am I to disagree. I mean it's not like anyone else on this forum has that level of expertise or influence.

John

unterhausen

I thought someone did the book compression calc and found out it was about what is needed? I feel like that when you have the cone and locknut properly adjusted, they really aren't going to move. The way a threaded joint works, there is material under significant compression, and once that is defeated, the joint comes loose. But I don't see that happening in a properly adjusted cone/locknut.

Doug64

That is exactly the method I use to adjust the cones. I think I learned the technique from Parks's Blue Book.

maddog34

FLEX... 1)to bend slightly
...........2) to CONTRACT.

just sayin'.....

also... there are people here that have made many tools...both production, and custom.

as to WHERE park gets the designs and specifications for most of their tools... look to the manufacturers of the parts, and the suppliers of their tools.... with a dose of input from greasy underpaid mechanics scattered around the world, looking to make the Park tools work better, and bold enough to question Park's judgment, then weld/cut/grind the shiny new Park tool to fit/function in an improved fashion..... And Park has designed a few from scratch, too, i'd imagine...

sweeks

Yes! And it's also the same as the method described on Park's DIY site, except that they show the wheel attached to the *outside* of a rear dropout. I don't remember where I got the idea to make a fixture, but it wasn't my idea!
Steve

Schwinn me

So far no conclusive proof axles compress with QR pressure, at least not enough worth mentioning. All I see is one experiment that appears its only purpose is to come to a predetermined conclusion. Missing critical data points are made up for with sarcasm and that has to be taken as a form of deception.

wphamilton

If someone wants to see how much the nut moves relative to the axle, just look at the edge of the nut and the next thread before and after tightening with the QR. Use a macro lens or a smartphone and magnifier, and you should easily be able to see a change of a fractional mm.

70sSanO

Tell me you just didn't google flex and got a definition of contracting a muscle to flex a joint and are applying it here.

John

wphamilton

Or, if you don't like taking a picture of the nut, construct a caliper from a 1-meter stick by attaching a pivot arm 1 cm from one end, 10 cm in length (assuming we're measuring differences from a 100 mm length). The end of the meter stick will sweep 90x the distance the short end (90.68 times in the case of a 0.1mm change, if my trig is right). Someone should be able to measure 9mm, if he's careful about keeping the rig positioned.

Or, strap a laser pointer on a shorter stick and shine it on a distant wall. Strap one on the other end of the axle as a reference point. Point being we can measure small quantities using some imagination, without special equipment. What we give up is precision, but high precision is not all that important on this one, IMO.

McBTC

The common understanding and it's not hard to believe is that a spoke is stretched and compressed over and over but I think the question is... how much are we talking about? It wouldn't take much to make a spoke, for example, feel slack or taut.

Bike Gremlin

To be (more) precise, a spoke is stretched (tensioned) and less stretched (lower tension). If it gets to compress (i.e. loose all the tension), a wheel can collapse.

sweeks

I assume you are referring to my "basement science". I'm waiting for *your* contribution.
There are at least three engineers on this thread who appear to support the axle compression hypothesis, to say nothing of Jobst Brandt. As for sarcasm, I've been on the receiving end rather more than the reverse.

I'm going to go out on a limb here and predict that if any movement is observed, it will not be of the necessary magnitude to explain the observed bearing clearance change.
Steve

Falcon3

I love this thread. 3 pages of discussion that hasn't broken down into too much of name-calling.

Anecdotally, I have never gotten the famed hub compression to make a difference in my bearing tunings. I tighten the locknut so there's a tiny bit of play then compress the QR into the axle and there's still a tiny bit of play. I adjust locknut so the wheel turns smoothly with no perceptible play (maybe 1/16 of a turn on the cone) and tighten QR, and the wheel will spin forever, with no noticeable binding.

Am I ruining hubs? Maybe. Am I bad at adjusting hubs to closer than 1/16 of a turn on the cone? Yes. Will I change my methods as a result of this thread? Probably not.

70sSanO

In hindsight it is probably not possible to determine if there is a slight amount of material that is compressed, or a slight amount of flexing (bending), or a slight amount of give in the threaded area due to tolerances without a special fixture and very precise measuring equipment.

I highly doubt anyone including Park or Jobst Brandt or Sheldon Brown had done any experiment prior to adopting the use of compress or flex and the adoption of whatever word has no relation to the actual phenomenon that has spanned these pages.

John

wphamilton

.1 mm is about 1/10th of a turn isn't it? (24 tpi nuts). It's hard to imagine the nut being forced 1/10th of a thread down without shearing something, but some fraction of that maybe.

sweeks

I hope nobody is shearing anything! I just meant that once the cone and locknut are jammed together there's not likely to be 0.10mm of movement. That's my *hypothesis*... it remains to be demonstrated.
Steve

McBTC

True, a lower spoke is compressed when the axle is "standing" on it, although the lower spoke is still under tension and therefore, still taut.

maddog34

glad you posted this... i leave a touch of play in my hubs... been doing so since i bought my DA hubs in 1983... 20,000 + miles on them now... smooth as butter.

maddog34

NOW... what occurs to the bearing clearance WHEN THE WHEEL IS UNDER LOAD of a rider?

It loosens slightly due to hub bearing CUP, and bearing BALL distortion.

maddog34

excluding solid, ridged, fixed, non-adjustable, spoked wheels.... spoked wheels hang from the upper spokes, and the rim slightly ovals.... add torque by pedalling/opening a throttle, and the rim goes slightly egg shape.

lower(bottom) spokes' tension are relieved slightly by the increase in tension experienced by the upper spokes when just rolling along.

tension change experienced by spokes increases when less spokes are present... low spoke count wheels require more care.

Now... what would BRAKING FORCES do to spoke tension, and rim shape?

disc and rim brake induced rim distortion will be different, btw.

Bike Gremlin

I can recommend reading Bicycle Wheel - by Jobst Brandt - it explains nicely the fact - tried and tested - that the wheel doesn't hang from the upper spokes, as I too had believed, and that the upper spokes don't gain tension when the wheel is loaded by rider's weight. This paper also tests and demonstrates that:

https://people.duke.edu/~hpgavin/pape...heel-Paper.pdf

For all I know, someone correct me if I'm wrong:
Disc brakes produce effect similar to the pedalling - just in reverse direction. So the leading spokes are tensioned, while the trailing ones are de-tensioned.

Rim brakes don't have that effect. They make the front half of the wheel's spokes a bit looser, while slightly tightening the rear half of the spokes.

maddog34

so... the bottom spokes lose tension... that force is transfered to.... the top spokes.

the top spokes carry the radial load imparted to the rim, since the bottom spokes... LOSE TENSION

spokes are not very good columns

and the egg IS the chicken.... ;-)

i love a good debate.
in a recent school bond discussion before the vote, i took on the role of dissenter, just to flesh out the "over the fence" questions and complaints of my fellow taxpayers... i had always intended to vote yes, but many were planning to vote no on that bond issue.

I took no end of heat for dissenting.... didn't care one bit... the views and questions needed addressed. The bond measure passed by a hefty margin.... polling was neck and neck two weeks prior to the vote.

and the force transferred to a wheel loaded with a bike and rider simple can not vanish. The TOP spokes carry an increase in tension load imparted by gravity. PERIOD.

i bought Brandt's book many years ago, now... read it cover to cover... and i yelled "BS" more than once while reading that first chapter.... paid 48 cents for it... virtually brand new copy, too... i love half price day at the thrift store... i had it out about two weeks ago... wanted to see what to do about a rim that had the holes opposite to most others... ended up lacing it opposite to the normal way... first spoke to the right of the valve stem hole, etc.... my choice, since that was apparently not addressed in "The Bicycle Wheel", that i could find, anyways... might be there... too busy to look further... it's spring!


loads can NOT vanish.... they are TRANSFERRED.

build up a wheel with 8 spokes, radially laced... retest... see what happens to the spoke strain then.

what fails in a bike wheel's spokes? the nipples, and the spokes... HOW do they fail? TOO MUCH TENSION IMPARTED BY LOADS.... and failure under load due to wear or damage... they don't bend in half... they tear apart... from too much tension, eh?

i have never seen a bike spoke fail from too little tension on it... sure seen a lot torn in half, though.... same for nipple failures...

Bike Gremlin

Tire is pressed at ground contact point. It's force pulling the wheel outwards is diminished at contact point, while it's inward pushing force (from pressure) remains the same all around. The reduced pulling force causes less spoke tension in the down spoke or two. The spokes next to the lowest one/two get a little bit of extra tension, but not as much as it is lost due to tyre's lowered "pull". It is explained, tested and confirmed.

In the previous post I provided the name of the book that explains it, as well as a link to a PDF on-line file that experiments with it.

You can easily test it yourself. Pluck the top spokes. Load the wheel and pluck them again. Does the sound change? Neither does the tension.

It's good to always question things, but one must also consider a possibility of being wrong themselves, usually by missing an important factor that plays a part. I was also certain the wheel hangs from the top spokes, it was "only logical!" "PERIOD", as you put it.