Schwinn me

Without something like this we will never get to the bottom of this axle compression issue. A test that cannot be duplicated with precision is worthless.
https://www.com-ten.com/images/super/ST1-vert.gif

Lakerat

When I was a young automotive machinist, my mentor performed a demonstration of the flexibility of metal, in this case, cast iron. He set an inside micrometer with just the right tension that it would barely "hang" inside the top of a cylinder bore. Then he squeezed the cylinder with his hand or both hands perpendicular to micrometer and the micrometer would drop to the bottom of the cylinder to be caught by a rag.

sweeks

Beautiful example!
Steve

EDIT: Some will say it's because he jiggled the cylinder. <_<

sweeks

I looked into load cells for the heck of it... way too expensive. But I think I could make an improvement on my previous try. Here's the idea:
1) Use the same set-up to measure the apparent decrease in axle length in the vise.
2) Place cylinders over the axle stub ends to limit the compressive loading to the locknut/cone assemblies and the axle between them and measure the apparent decrease in length.
Prediction: The length change will be slightly less when load is applied to the locknuts, reflecting the shorter length of axle being compressed. This may be too small a change to measure.
Problems: The big one is tightening the vise the same amount both times; I suppose I could put a torque wrench on it. It might be possible to get the dial gauge closer to the axle and certainly more parallel!
The other issues (plate "flex", vise friction, etc.) would pretty much cancel out. There is no significant "slop" in the arrangement because the axle is under *slight* compression to start.
Anyway, that would be the best I could do.

FIFY
Steve

Schwinn me

I like the way you think

If your bench vice is anything like the two I have, I wouldn't trust them for accurate anything. Good for clamping and holding things and that's it. Slop in the screw and where the vice jaws slide causes intermittent binding that would make it impossible to be sure I could duplicate pressures from one clamping session to the next. Even if you could ensure a "reasonable" duplication of pressure, without knowing how much pressure you are actually applying and if that pressure is equal or close to what a QR would apply. It would give us erroneous results. Unfortunately I think we hit a dead end unless someone has access to the kind of equipment we need.

I have a pretty good hydraulic press, If I can think of a way of measuring pressure on the cheap, it might be of use to us.

McBTC

Yup... the change in tension of the upper spokes is <4% of that undergone by the lower spokes. So, you are right: we could say--e.g., the axle hangs 'hangs' because it seems logical since the tension increases but that would be an erroneous conclusion given the far greater change in the tension on the lower spokes, which become shorter due to compression but are still rigid enough to support the weight of the bike like a column because they're still under tension.

Bike Gremlin

Exactly. It is the amount of (lower) spoke tension that limits the maximal static load, not the amount of tension increase of upper spokes that limits it - since they (practically) don't gain any tension. A wheel collapses when a spoke looses tension, not when a spoke gets so much tension it breaks from it - they break from direct impact damage, or fatigue.

wphamilton

You don't need to measure pressure, if you can measure compression on the axle and movement of the nut on the axle at the same time.

maddog34

try a better "ear"... like a seiko quartz guitar tuner... the top spokes change tension, but the change is not to just one spoke, it is spread in a diminishing pattern, working outward from the topmost spoke.... and the more horizontal spokes will bend slightly, since the tension induced friction at the j bend is usually higher than the force required to swing the spoke at the hub.

maddog34

Plus one.

and bench vise jaws move all over when imparting load.... rather crude, but effective tools, bench vises... i have four of them, presently.

Schwinn me

I don't see how that can be done at the same time.

wphamilton

Use two devices.

McBTC

I do not think sophisticated equipment is required. A nut that is screwed down with enough force to prevent the axle from dropping out of the dropouts is pretty easily accomplished without having to deform the axle in the process (just like locking a nut in place by backing it up with another nut doesn't take so much force as to deform the threads). A Quick Release is nothing more than adding a lever and a cam to a nut (resulting in an action which has been compared to putting a chock behind a wheel to keep the truck from moving).

sweeks

>sigh< Where do we start?
Steve

davidad

Lets do this the other way. When you tighten a bolt it stretches. In the refinery we had vey high flanges with 3and 1/2" bolts holding them together. We had a device that allowed us to stretch 4 bolts at a time with 12500 pounds of hydraulic pressure that allowed us to rotate the bolt by hand. When the pressure was released the bolts were tight and unmovable and held back over 2500 pounds of product pressure.


If we could stretch them a like pressure would compress them.

Bike Gremlin

Even better - try reading the paper - or just see the graph showing tension change as a wheel revolves under pedalling load (pulling spokes). Do you see any flaws to that? Without pedalling load, the increased load of the non-bottom spoke would be (closer to) zero.

McBTC

I think that >10,000 PSI converts to >1200 ft-lbs of torque...

maddog34

i read it... twice, just for laughs.

you assume much, but know little.

hub shifts, tension shifts.

QR forces everything to shift on axis of pressure...

the threads( both inner and outer)are the weak link.

the threads bend, or FLEX... the inner threads are part of the axle... the cones and jam nuts are part of the axle ASSEMBLY....... to simplify for public consumption, "The Axle FLEXS".

sweeks

There; fixed it for you I did.

Bike Gremlin

Provided one experiment (a measured one), one you can do at home (that you disputed by my bad hearing) and one book that has been accepted as correct and good one - but you still don't seem convinced. It is possible we could all be wrong, but your arguments are not convincing enough to convince me, just like mine aren't convincing you obviously.

maddog34

did you do the guitar tuner test?

no? i did.

done.

Bike Gremlin

Don't have refined equipment. Can you measure spoke frequency of a single spoke on a statically loaded wheel as you position it at 12, 1.5, 3, 4.5 and 6 o' clock and let me know? The frequency change at 6 o'clock should be by far larger than any other position frequency change.

Also note the number of spokes on that side of the rim. The total increase in tension will not be close to the decrease in tension of the bottom spoke(s). Using the same load, of course, and making sure it is vertical, not sideways applied. Also, either use the same spoke, turning the wheel, or first check whether all the spokes on that side have uniform enough tension. Plucking each (position) 3 times, to eliminate any measuring mistakes.

Absolute tension (change) can then be calculated if spokes are of known material (steel?), length and thickness.

McBTC

You're definitely onto the flaw in the logic of the 'hang' theory. If we imagine a single piece of rope perpendicular to the ground instead of spokes above and below a hub we'd really have the intuition of 'hangers' fuming when we don't agree with their logic. Nevertheless, if we draw the rope taut, and attach a weight in the middle, if the change in tension on the portion of the rope below the weight is greater than the portion above the weight, the logical conclusion is that the portion below the weight is supporting the most of the weight just as we would conclude that a solid column -- like a wood spoke on a wagon wheel -- was supporting all of the weight.

maddog34

go read a book.

Bike Gremlin

Have read, several. Found no flaws in author's logic, but have in yours, I believe you are incorrect and there is a simple way, since you have the tools, to see for yourself, don't take my word (or authors') for it.