Spoke Tensionometer
Re: Spoke Tensionometer
In a thought experiment it would be possible to screw half the nipples on one half of the wheels fully down then tension the other half so all spokes were the same tension. This would produce an evenly tensioned wheel that was eccentric. Thus showing that even tension does not equate to a theoretically perfect wheel.
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J Bro
J Bro
Re: Spoke Tensionometer
Yes, my rear wheel has a 36h SA 3sp, and no doubt the bike as originally fitted with a Miche small-flange 28h there would be plenty room.rogerzilla wrote: ↑30 Oct 2022, 5:26pm I can get the Park one into a x2 406 wheel. May be a smaller-diameter hub, though.
Mick F. Cornwall
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Re: Spoke Tensionometer
By "eccentric" do you mean "dished"?jb wrote: ↑30 Oct 2022, 6:02pm In a thought experiment it would be possible to screw half the nipples on one half of the wheels fully down then tension the other half so all spokes were the same tension. This would produce an evenly tensioned wheel that was eccentric. Thus showing that even tension does not equate to a theoretically perfect wheel.
"It takes a genius to spot the obvious" - my old physics master.
I don't peddle bikes.
I don't peddle bikes.
Re: Spoke Tensionometer
No, I mean off centre like a circus bike.MikeF wrote: ↑31 Oct 2022, 1:44pmBy "eccentric" do you mean "dished"?jb wrote: ↑30 Oct 2022, 6:02pm In a thought experiment it would be possible to screw half the nipples on one half of the wheels fully down then tension the other half so all spokes were the same tension. This would produce an evenly tensioned wheel that was eccentric. Thus showing that even tension does not equate to a theoretically perfect wheel.
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J Bro
J Bro
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Re: Spoke Tensionometer
Hm. I'm not sure about your thought process. A rim is off centre of a symmetrical hub if the spokes are not the same tension on each side.
"It takes a genius to spot the obvious" - my old physics master.
I don't peddle bikes.
I don't peddle bikes.
Re: Spoke Tensionometer
I'm not talking about the dish, I mean that even though its possible to have all the spokes at exactly the same tension it does not automatically follow that the wheel will be true (assuming a perfect rim)
Like wise, a non dished wheel could have a lateral swash or side to side movement and still have equally tensioned spokes. For a wheel to be true it needs equal tensioning 'and' spokes of exactly equal lengths (& a perfect rim), which is the tricky bit for a hand built wheel as even when starting off with all the nipples screwed to the point were the thread disappears errors will creep in which have to be corrected.
Dishing simply adds an unnecessary complication for the purpose of the thought experiment.
Last edited by jb on 31 Oct 2022, 2:42pm, edited 1 time in total.
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J Bro
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Re: Spoke Tensionometer
I thought the same - but then realised jb was talking about radial eccentricity, where both left and right spokes would be shorter over half of the circumference, such that the hub would no longer be centred radially in the rim.
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Re: Spoke Tensionometer
You have to build some Brompton wheels like that, as the standard el cheapo front hub is often drilled off-centre.
The wheel ends up concentric to the axle but not to the hub shell. It looks wobbly but runs ok.
The wheel ends up concentric to the axle but not to the hub shell. It looks wobbly but runs ok.
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Re: Spoke Tensionometer
Thanks. Hard to see what was meant. I think most people building a rim would ensure it is radially and laterally true. I do, but I'm not a professional wheel builder; my wheels seem to be fine for my use.Airsporter1st wrote: ↑31 Oct 2022, 2:41pmI thought the same - but then realised jb was talking about radial eccentricity, where both left and right spokes would be shorter over half of the circumference, such that the hub would no longer be centred radially in the rim.
Assuming a perfect rim, then each spoke should have the same tension (on each side) and emit the same note. That requires a tension and frequency meter. I don't have a tension meter and just rely on a radial true rim (as near as I can make it) and equal sound of the
spokes from each side as far as possible.
"It takes a genius to spot the obvious" - my old physics master.
I don't peddle bikes.
I don't peddle bikes.
Re: Spoke Tensionometer
i took a punt on a £16 tool more of a test rather than a necessity.
The front wheel - radial both sides - the tool worked admirably.
The rear, only 50% as it wouldn't go in on the drive side, but it was still useful for the radial left side.
I enjoyed the trial, and I've - and am still - enjoying this thread.
The front wheel - radial both sides - the tool worked admirably.
The rear, only 50% as it wouldn't go in on the drive side, but it was still useful for the radial left side.
I enjoyed the trial, and I've - and am still - enjoying this thread.
Mick F. Cornwall
Re: Spoke Tensionometer
But spoke length and tension are not independent variables.jb wrote: ↑31 Oct 2022, 2:40pm ...........Like wise, a non dished wheel could have a lateral swash or side to side movement and still have equally tensioned spokes. For a wheel to be true it needs equal tensioning 'and' spokes of exactly equal lengths (& a perfect rim), which is the tricky bit for a hand built wheel as even when starting off with all the nipples screwed to the point were the thread disappears errors will creep in which have to be corrected.
............
The effective length of the spoke is the length from the elbow bend where it fits the hub to the underside of the nipple where it fits the rim.
As you say, you can have an area of lateral run-out with identical tensions both sides; slacken one side a quarter turn, tighten the other side a quarter turn and you may achieve a true wheel with identical tensions.....all you have done is alter the effective spoke length by a quarter of the thread pitch.
If you are going to buy a tension gauge, the sensible time to use it is as soon as you start getting some tension on the spokes, and throughout the rest of the build. If you "finish" the wheel and then use the gauge to "check" the tensions, you either have to ignore the tension readings you have just got, or set about balancing the tensions.
My "final repeating cycle" is......stress the wheel, true the wheel, balance the tensions......repeat, repeat,.....until I get a stable wheel with a proper balance between trueness and evenness of tension. (a stable wheel is a wheel which doesn't go out of true when I lean on the rim with the axle end supported...this is not stress-relieving the spokes, which is done once as soon as the spokes are at full tension, and the wheel reasonably true)
Bike fitting D.I.Y. .....http://wheel-easy.org.uk/wp-content/uploads/bike-set-up-2017a.pdf
Tracks in the Dales etc...http://www.flickr.com/photos/52358536@N06/collections/
Tracks in the Dales etc...http://www.flickr.com/photos/52358536@N06/collections/
Re: Spoke Tensionometer
I absolutely agree. (not that I'm in the habit of disagreeing with professional builders )531colin wrote: ↑2 Nov 2022, 7:04amBut spoke length and tension are not independent variables.jb wrote: ↑31 Oct 2022, 2:40pm ...........Like wise, a non dished wheel could have a lateral swash or side to side movement and still have equally tensioned spokes. For a wheel to be true it needs equal tensioning 'and' spokes of exactly equal lengths (& a perfect rim), which is the tricky bit for a hand built wheel as even when starting off with all the nipples screwed to the point were the thread disappears errors will creep in which have to be corrected.
............
The effective length of the spoke is the length from the elbow bend where it fits the hub to the underside of the nipple where it fits the rim.
As you say, you can have an area of lateral run-out with identical tensions both sides; slacken one side a quarter turn, tighten the other side a quarter turn and you may achieve a true wheel with identical tensions.....all you have done is alter the effective spoke length by a quarter of the thread pitch.
If you are going to buy a tension gauge, the sensible time to use it is as soon as you start getting some tension on the spokes, and throughout the rest of the build. If you "finish" the wheel and then use the gauge to "check" the tensions, you either have to ignore the tension readings you have just got, or set about balancing the tensions.
My "final repeating cycle" is......stress the wheel, true the wheel, balance the tensions......repeat, repeat,.....until I get a stable wheel with a proper balance between trueness and evenness of tension. (a stable wheel is a wheel which doesn't go out of true when I lean on the rim with the axle end supported...this is not stress-relieving the spokes, which is done once as soon as the spokes are at full tension, and the wheel reasonably true)
I think Micks 'experiment' was if you concentrated on equal & exact spoke tension then a true wheel would automatically be the result but that would only be true if the nipples were all precisely set at the same length to start with and then adjusted by exactly the same amount on each and of course the rim was perfectly drilled (and assuming most decent hubs are accurate these days), and that's ignoring the de stressing process.
This process might work on the 'London Eye' but is probably impractical in a back shed workshop.
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J Bro
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Re: Spoke Tensionometer
Longer spokes at the same tension as shorter ones would vibrate at a lower frequency.
"It takes a genius to spot the obvious" - my old physics master.
I don't peddle bikes.
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Re: Spoke Tensionometer
Hi,
As you said - even spoke tension and true is ideal.
Brucey quoted that even tension is more important than getting the rim perfect.
Of course a rim braked wheel does need realative trueness to be useable, a disc not so.
Like wise you could have even tension spokes but a run out.pete75 wrote: ↑30 Oct 2022, 3:18pmI've always thought you need to get spoke tensions as even as possible consistent with the wheel being true.NATURAL ANKLING wrote: ↑29 Oct 2022, 9:44pm Hi,
Its possible to get even tension in spokes but the wheel could be wavy.
Thats to say that the rim could be parralel to aflat plane, but be out of true and still have even tension spokes.
It won't (tool) build a wheel, you need to do that and true wheel yourself.
Its a comparitor.
It's possible to build a "true" wheel with widely differing tensions. It won't last long though.
As you said - even spoke tension and true is ideal.
Brucey quoted that even tension is more important than getting the rim perfect.
Of course a rim braked wheel does need realative trueness to be useable, a disc not so.
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Re: Spoke Tensionometer
So you are looking for same note (frequency) only on the same side rear dished wheel.
Front non disc is all the same note. assuming all other things equal.
Unibalance (which shimano pioneered, and I used on my devon and cornwal coast ride with 32 spokes, with lugage) uses a very low dish ratio (spokes are Off the top of my head barely 1 MM diffence side to side, well you use 2 MM diff but their effective assemble length is 1 MM)
NA Thinks Just End 2 End Return + Bivvy - Some day Soon I hope
You'll Still Find Me At The Top Of A Hill
Please forgive the poor Grammar I blame it on my mobile and phat thinkers.
You'll Still Find Me At The Top Of A Hill
Please forgive the poor Grammar I blame it on my mobile and phat thinkers.