gugie 

I bought one of those for a shop I managed in the early 80's. It was around a grand to purchase, as I recall. Available new today for $4500. It's one of those things I'd love to have, but will probably never purchase unless I win the lottery.

gugie 

Most of the big wheelbuilders in town (well, at least two that I know) use the Morizumi spoke machine. At $2900, it seems like a steal.

unworthy1

a rolled thread also (very slightly) increases the diameter of the final threaded portion compared to the original diameter of the stock (in this case a tube) since the process forces metal both UP (in the tread crests) and DOWN (in the thread roots). Not sure if that small difference would require slightly undersized steerer tubes (or lathe-turning them down) or if that could make crown fitting a problem and in either case if that could be a deal-killer.

clasher

See if they do tours!

Jeff Wills

Aside from other differences, I think a rolled thread would leave the threads slightly proud of the rest of the steerer tube. (Measure the diameter of a spoke on the shaft and at the threads to see what I mean.) That would require a slightly different inside diameter of the upper cup for the headset to fit.

All the threaded fork steerers I've worked on have had cut threads, and, BITD, we would cut a few more threads on a replacement fork if we didn't have one that fit.

gugie 

That's what I remember as well.

Was it Ten Speed Drive that started prepping their frames in the US prior to shipment to dealers? Before they started doing that I remember you always had to face and chase the bearing surfaces, and sometimes cut the steerers to length. They'd also do an alignment on a flat table.

SteelCharlie

Nope! Incredibly high precision high tensile strength parts can be roll threaded easier than threads cut. Aircraft spec Ti bolts are commonly rolled as are to the best of my knowledge ALL aircraft bolts. Cut threads introduce a stress riser at the thread/body join.
Steering tubes are quite different and I can't imagine why any company would invest in rolling threads on them when cutting machinery would produce perfectly satisfactory results at a way small fraction of the cost.

Kontact 

Because cutting dies wear out much faster than roll dies?

Ghrumpy

DT use 18/10 stainless according to their web site.

Kontact 

Which is a very mild, barely magnetic steel. You can do the same job with piano wire half the gauge.

dddd

Ahh, but wouldn't the thinner wire be much more elastic, requiring higher spoke count to achieve same wheel stiffness and side-loading limits?


They can get some stiffnes back by doing away with the J-bend, and I wonder if today's 1.5mm spokes are processed/worked to much higher tensile load capacity than the thicker ones? I recall that HED instructed me to use 150kg with the 1.5mm spokes (I encountered nipple-seating issues a bit short of that level of tension iir).

Kontact 

A guy in the late '70s made wheels with piano wire. They worked well and were quite light, but they needed bales in the hub because the wire was too thin to use with nipples. But tension is tension, and that's all a spoke needs to provide.

They are probably also not kind to fingers.

dddd

There are two "modes" of wheel stiffness. There is firstly the small-deflection mode, where the elasticity of the spoke's net load path on both sides of the wheel contribute to the rim's lateral support. Note that the "elasticity of the spoke's net load path" includes the spoke count variable as well as the spoke's dimensions and head configuration (straight or bent) and the hub flange structure as well.

There is also a higher degree of rim loading and deflection where some of the spokes on one side begin to lose all tension, where the stiffness of the wheel is seen to suddenly drop off, and where higher initial spoke tension (pre-load) can extend this deflection point of the rim where that onset of zero tension and reduced rim stability begins.
But in both modes, at any degree of rim loading, bigger spoke diameter contributes to increased wheel stiffness as seen at the rim, and vice-versa.

Kontact 

I disagree. Spokes work 100% by tension and aren't even anchored to the rim. All they do is pull, and that pull never goes to zero tension.

Ghrumpy

Agree. The only things that will cause a properly tensioned spoke to reach zero tension is a rim failure, whether a dent, a crack, or a rim collapse, or a hub flange failure.

I suppose it's theoretically possible that a high-enough sudden load could unload a single spoke enough to cause it to lose tension but I've never seen nor experienced such a load that did not cause the rest of the structure to fail catastrophically. I can't even imagine a scenario where a load like that would not cause the rider to lose control whether the wheel failed or not.

dddd

Of course spokes work through tension, I never suggested otherwise. But a spoke is also a tension spring, it is not rigid, it has a defined spring rate dependent on it's dimensions (why we and our spoke length calculators calculate final spoke length with some consideration of the spoke gage).

How could one conclude that the elasticity of the spokes would not affect the stiffness of the wheel?

When a wheel sustains load, it flexes, and the spokes flex (elongate elastically) when this occurs as well.
So it goes without saying that making the spokes less elastic will reduce the flexibility at the rim as the built wheel sustains a varying load.
It's the same reason why different numbers of spokes affect wheel stiffness, and is one reason why straight-pull spokes have allowed today's wheels to achieve their stiffness with fewer numbers of spokes.

The benefit of higher spoke tension is that the rim can be deflected further before any spokes reach a point of zero tension, and thus of those critical few spokes no longer responding to increasing rim load with any further change of their tension. Higher tension does almost nothing for wheel stiffness up to this point of loading, other than present a straighter load path where the spokes may be crossed.

It sounds as if you are assuming that a spoke sees no change in tension in response to loading applied to the built wheel's rim. But spokes do see changing tension and elongation from even very small loads applied at the rim, easily verified by plucking a spoke, then pushing sideways at the rim and plucking it again. This is how I sometimes achieve higher final tension in the truing stand, when nipples may otherwise begin to gall an eyelet-less rim, or when a used wheel has corrosion issues at the nipples.

dddd

You are partially correct that, assuming a properly-built wheel in normal use, no spokes fully de-tension.
I did not suggest that it does, only that a wheel's load limit can be improved by increased tension up to a point, and only for the point of validating part of what Kontact had previously argued.


But my original and main point was that spoke thickness affects the stiffness of the wheel at all times, from the smallest loading up to and perhaps measurably beyond the point of when some spokes begin to see complete detensioning.
In fact every part of the wheel structure affects this stiffness, even the way that the spoke flanges are braced together by the center of the hubshell and the way that the ends of the spokes are held in a most rigid curcular array relative to each other and to the rest of the hubshell.
In short, any part of the wheel that sees a change in force/stress (such as the spoke tension does) in response to wheel loading affects the stiffness of the wheel in any direction as measured at the rim.

Kontact 

You're not stating a reason that a thick spoke is going to do anything differently than a thin one at the same tension.

dddd

I was assuming that everyone here would understand that a thicker spoke has a higher longitudinal spring rate in response to changes in tension force/stress, and thus a thicker spoke is a stiffer spoke.


But again, it sounds like you are still assuming that spoke tension doesn't change in response to even small changes in the wheel's loading. Is that your assumption?

exmechanic89

FWIW - which is clearly not much, lol - I've always thought steerer threads were cut. Always seemed like the most logical way to do it to me.

Kontact 

I don't know if the bolded actually makes any sense or are just words you're putting together.


It is also an assumption on your part that a spring rate has anything to do with "stiffness". And you aren't defining what sort of stiffness. Stiffness is a word generally applied to lateral bending, not tensile strength. Are you talking about the spoke or the wheel? Spokes don't benefit from stiffness - they are hinged top and bottom.

But tension is tension. The amount of force to put a thin spoke to 100 kgf is identical to the amount to tension a thick spoke to 100 kgf.

gugie 

Stiffness? Modulus of elasticity, ie, Young's Modulus. For pretty much all steels, it's around 30M PSI. Doesn't matter what alloy you use.

dddd

Every part of a structure has a resistance to deformation, whether it is in bending, in shear, in compression, in torsion or in tension. Once the part has it's dimensions and material defined, it can be said to have a spring rate along whatever critical direction that the expected loading will be applied.
In the case of spokes, obviously this will be tension force along the length of the spoke, and the stiffness or spring rate of the spoke will be proportional to the cross-sectional area of the spoke (and inversely proportional to the spoke's length).
Any vertical or lateral force applied to the rim of a built wheel will cause a change in the individual spoke's tensions that will alter their lengths and allow the rim to move relative to the hub. This is wheel flex, which can never be eliminated but which is reduced as the spokes become thicker (or more plentiful) and thus more resistant to changes in length.
Stiffer rims could be said to accomplish the same effect by spreading the localized loading near the contact patch out over a larger arc along the rim, and thus over a larger number of spokes, which in total represents a larger net cross-sectional area of spokes within the (larger) peak deflection zone.

Kontact 

If anything, thinner spokes are more elastic at a given tension, not less.

jetboy 

I got to call this one for dddd. but anyway; we can agree that fork steerers threads are cut?

next: Mag wheels.