What force does a quick release skewer create?

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mattheus
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Re: What force does a quick release skewer create?

Post by mattheus »

Jdsk wrote: 7 Oct 2021, 3:28pm
There are many situations in which gravitational measures of force work well, mostly of course where weight is important. I wouldn't choose to use them but I can see why others would. But weight doesn't play any rôle in this problem...
I did my physics degree entirely in metric. I'm pretty happy with torque, pressure, energy etc.
/background


This thread is the first time I've found out what a "kgf" is. I can see some practical uses:

I know that by standing on the end of a spanner, the most force I can exert is X kgf (where X is my mass in kgm which luckily I know !).
By pulling up I can exert slightly more - but not much.
Jdsk
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Re: What force does a quick release skewer create?

Post by Jdsk »

mattheus wrote: 7 Oct 2021, 4:02pm
Jdsk wrote: 7 Oct 2021, 3:28pm There are many situations in which gravitational measures of force work well, mostly of course where weight is important. I wouldn't choose to use them but I can see why others would. But weight doesn't play any rôle in this problem...
I did my physics degree entirely in metric. I'm pretty happy with torque, pressure, energy etc.

This thread is the first time I've found out what a "kgf" is. I can see some practical uses:

I know that by standing on the end of a spanner, the most force I can exert is X kgf (where X is my mass in kgm which luckily I know !).
By pulling up I can exert slightly more - but not much.
And a factor of 10 isn't too hard to remember!

: - )

Jonathan
MikeF
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Re: What force does a quick release skewer create?

Post by MikeF »

mattheus wrote: 7 Oct 2021, 4:02pm
I did my physics degree entirely in metric. I'm pretty happy with torque, pressure, energy etc.
/background


Ah a youngster. I didn't do physics to degree level but we had to learn physics using imperial and metric simultaneously. Questions could be either units. And the metric system was cgs not the more recent mKs. :roll: But torque, pressure and energy can be in any unit.
Factors of 10 are not common place in imperial units so the chance of decimal point being misplaced were not great! :wink:
"It takes a genius to spot the obvious" - my old physics master.
I don't peddle bikes.
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andrew_s
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Re: What force does a quick release skewer create?

Post by andrew_s »

Jdsk wrote: 7 Oct 2021, 3:28pm There are many situations in which gravitational measures of force work well, mostly of course where weight is important. I wouldn't choose to use them but I can see why others would. But weight doesn't play any rôle in this problem...

Jonathan

PS: It's about the weight of an apple! : -)
Is that apple a Cox or a Bramley?

When, as in this case, a good part of the question is how hard to pull/push on the end of a lever, of course weight comes into it.
Lifting things of known weight is how your muscles get calibrated.
If you follow Shimano's recommendations, and tighten your cassette lockring to 40 Nm, in the absence of a torque wrench (which those of us brought up on steel bikes commonly don't have), you look at the spanner (25 cm), do a little mental arithmetic, and say "pull hard enough to lift 16 kg" (or 35 lb if you are an imperial dinosaur).
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andrew_s
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Re: What force does a quick release skewer create?

Post by andrew_s »

MikeF wrote: 8 Oct 2021, 8:26pm Ah a youngster. I didn't do physics to degree level but we had to learn physics using imperial and metric simultaneously.
Factors of 10 are not common place in imperial units so the chance of decimal point being misplaced were not great! :wink:
Since you would also have performed your calculations on a slide rule, you should have been well used to keeping track of the decimal point :)
nirakaro
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Re: What force does a quick release skewer create?

Post by nirakaro »

andrew_s wrote: 9 Oct 2021, 12:17pm If you follow Shimano's recommendations, and tighten your cassette lockring to 40 Nm, in the absence of a torque wrench (which those of us brought up on steel bikes commonly don't have), you look at the spanner (25 cm), do a little mental arithmetic, and say "pull hard enough to lift 16 kg" (or 35 lb if you are an imperial dinosaur).
Returning to the original question, how would you apply that to a quick-release skewer? Alternatively, how would Mr. Shimano have you apply a torque wrench to a QR skewer?

40Nm, incidentally, seems a huge torque to apply to a cassette lockring, unless it's for a serious athlete. I've always done mine up to finger-tight-plus-a-little-bit, and never had a problem.
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andrew_s
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Re: What force does a quick release skewer create?

Post by andrew_s »

nirakaro wrote: 9 Oct 2021, 12:30pm
andrew_s wrote: 9 Oct 2021, 12:17pm If you follow Shimano's recommendations, and tighten your cassette lockring to 40 Nm, in the absence of a torque wrench (which those of us brought up on steel bikes commonly don't have), you look at the spanner (25 cm), do a little mental arithmetic, and say "pull hard enough to lift 16 kg" (or 35 lb if you are an imperial dinosaur).
Returning to the original question, how would you apply that to a quick-release skewer? Alternatively, how would Mr. Shimano have you apply a torque wrench to a QR skewer?

40Nm, incidentally, seems a huge torque to apply to a cassette lockring, unless it's for a serious athlete. I've always done mine up to finger-tight-plus-a-little-bit, and never had a problem.
You apply a torque to the QR by making the same calculations as I did. It's only a rough indication of how tight is suitable, as indicated by the fairly wide range originally quoted.

As for 40 Nm for a lockring, that's what Mr Shimano prints on them.
It's tighter than I would use too (I judge by the number of clicks on the ribbing), but I use a steel freehub body, so the fact that the load on the freehub body isn't properly shared between the individual sprockets doesn't matter all that much.
If you use an aluminium freehub body, and don't torque up the lockring fully, you'll find that the edges of the sprocket splines get embedded into the edges of the freehub body splines, and it's difficult to get the cassette off even after the lockring is removed.
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Keezx
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Re: What force does a quick release skewer create?

Post by Keezx »

andrew_s wrote: 9 Oct 2021, 1:11pm
It's tighter than I would use too (I judge by the number of clicks on the ribbing), but I use a steel freehub body, so the fact that the load on the freehub body isn't properly shared between the individual sprockets doesn't matter all that much.
If you use an aluminium freehub body, and don't torque up the lockring fully, you'll find that the edges of the sprocket splines get embedded into the edges of the freehub body splines, and it's difficult to get the cassette off even after the lockring is removed.
Good demonstration why Campagnolo changed the freehub design around 1996 when 9 speed became the new standaard....
Ontopic:
The force a skewer creates is a direct derivate from the elongation of the skewer axle and also from the material of the axle.
Which proves that a design of a steel skewer should niet be copied to fabricate a titanium skewer, the last one needs much more elongation to create the same clamping force due to the lower E-modulus....
ChrisP100
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Re: What force does a quick release skewer create?

Post by ChrisP100 »

With QRF's I always just position the lever in line with the spindle and rotate to the preferred final position (in my case, front wheel lever half way between fork and mudguard stay, rear lever equally inside the rear triangle), rotate the opposing nut until it just starts to tighten the spindle in the dropouts, add around 1/2 a turn, then lock the lever.

Absolutely no idea what the force is, but I've never had an issue with a spindle or cam/pin breaking, and I've never lost a wheel.
Jdsk
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Re: What force does a quick release skewer create?

Post by Jdsk »

nirakaro wrote: 9 Oct 2021, 12:30pm
andrew_s wrote: 9 Oct 2021, 12:17pm If you follow Shimano's recommendations, and tighten your cassette lockring to 40 Nm, in the absence of a torque wrench (which those of us brought up on steel bikes commonly don't have), you look at the spanner (25 cm), do a little mental arithmetic, and say "pull hard enough to lift 16 kg" (or 35 lb if you are an imperial dinosaur).
Returning to the original question, how would you apply that to a quick-release skewer? Alternatively, how would Mr. Shimano have you apply a torque wrench to a QR skewer?
I've never seen anyone measure the torque or use a calibrated tool. Or any Shimano document describing it.

Jonathan
Jdsk
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Re: What force does a quick release skewer create?

Post by Jdsk »

ChrisP100 wrote: 11 Oct 2021, 2:34pm With QRF's I always just position the lever in line with the spindle and rotate to the preferred final position (in my case, front wheel lever half way between fork and mudguard stay, rear lever equally inside the rear triangle), rotate the opposing nut until it just starts to tighten the spindle in the dropouts, add around 1/2 a turn, then lock the lever.
Similar, but I adjust the knob on the other side until the clamping force on the lever feels right. That usually takes a few attempts, but if I did it more often I might get it right first time.

Jonathan
MikeF
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Re: What force does a quick release skewer create?

Post by MikeF »

andrew_s wrote: 9 Oct 2021, 12:19pm
MikeF wrote: 8 Oct 2021, 8:26pm Ah a youngster. I didn't do physics to degree level but we had to learn physics using imperial and metric simultaneously.
Factors of 10 are not common place in imperial units so the chance of decimal point being misplaced were not great! :wink:
Since you would also have performed your calculations on a slide rule, you should have been well used to keeping track of the decimal point :)
Slide rules weren't used. Logarithms probably as far as I recall.
"It takes a genius to spot the obvious" - my old physics master.
I don't peddle bikes.
Manc33
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Re: What force does a quick release skewer create?

Post by Manc33 »

The advice is "until the QR lever hurts your hand when you press it" :lol:

OK who's pressing it...
We'll always be together, together on electric bikes.
Jdsk
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Re: What force does a quick release skewer create?

Post by Jdsk »

More impossible units of force over here:
viewtopic.php?p=1646292#p1646292

Jonathan
the snail
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Re: What force does a quick release skewer create?

Post by the snail »

Manc33 wrote: 12 Oct 2021, 10:32pm The advice is "until the QR lever hurts your hand when you press it" :lol:

OK who's pressing it...
That's not what Shimano say. They advise you to tighten the nut so that the lever engages when it is parallel to the axle. That doesn't require a lot of pressure to close it (in line with the 5Nm you quote, although I don't think you would measure it). I think maybe you are overthinking this!
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