Views - this wheel trueing stand?

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NetworkMan
Posts: 644
Joined: 25 Aug 2014, 11:13am
Location: South Devon

Re: Views - this wheel trueing stand?

Postby NetworkMan » 9 Sep 2019, 11:15am

Mike Sales wrote:I seem to remember that when I was a beginner in wheelbuilding, I read that a correctly tensioned spoke should sound a particular note when plucked. Middle C, I think. My wheel was gratifyingly close.
Has anyone else heard (!) this?
Of course various factors, not least drive and non-drive side, modify this.
Comparative tension can be assessed by plucking spokes too.

Surely a slim DB spoke will ring at a different pitch from a plain gauge one won't it?

Mike Sales
Posts: 3228
Joined: 7 Mar 2009, 3:31pm

Re: Views - this wheel trueing stand?

Postby Mike Sales » 9 Sep 2019, 11:20am

NetworkMan wrote:
Mike Sales wrote:I seem to remember that when I was a beginner in wheelbuilding, I read that a correctly tensioned spoke should sound a particular note when plucked. Middle C, I think. My wheel was gratifyingly close.
Has anyone else heard (!) this?
Of course various factors, not least drive and non-drive side, modify this.
Comparative tension can be assessed by plucking spokes too.

Surely a slim DB spoke will ring at a different pitch from a plain gauge one won't it?


Wouldn't know. Perhaps somebody can tell us?
Unless you mix spokes pitch will still give comparative tension.
I never used a piano after that first experiment. I wind spokes up to tension by judgement, and sometimes pluck for comparison.

NetworkMan
Posts: 644
Joined: 25 Aug 2014, 11:13am
Location: South Devon

Re: Views - this wheel trueing stand?

Postby NetworkMan » 9 Sep 2019, 11:58am

Mike Sales wrote:
NetworkMan wrote:
Mike Sales wrote:I seem to remember that when I was a beginner in wheelbuilding, I read that a correctly tensioned spoke should sound a particular note when plucked. Middle C, I think. My wheel was gratifyingly close.
Has anyone else heard (!) this?
Of course various factors, not least drive and non-drive side, modify this.
Comparative tension can be assessed by plucking spokes too.

Surely a slim DB spoke will ring at a different pitch from a plain gauge one won't it?


Wouldn't know. Perhaps somebody can tell us?
Unless you mix spokes pitch will still give comparative tension.
I never used a piano after that first experiment. I wind spokes up to tension by judgement, and sometimes pluck for comparison.

Yes it will - the answer is here:-
https://proportionaltech.myshopify.com/ ... calculator
(saved me digging out my physics books!)
At a tension of 100 kg (Is that reasonable?)
A 27 cm length (I just measured roughly)
of steel wire (about 8 gm/cm**3)
2 mm diameter (common plane gauge)
will ring at about 366 Hz

Middle C is about 256 Hz.
Plug in 50 kg and you get 259 Hz - spot on!

Mike Sales
Posts: 3228
Joined: 7 Mar 2009, 3:31pm

Re: Views - this wheel trueing stand?

Postby Mike Sales » 9 Sep 2019, 12:05pm

NetworkMan wrote:
Yes it will - the answer is here:-
https://proportionaltech.myshopify.com/ ... calculator
(saved me digging out my physics books!)
At a tension of 100 kg (Is that reasonable?)
A 27 cm length (I just measured roughly)
of steel wire (about 8 gm/cm**3)
2 mm diameter (common plane gauge)
will ring at about 366 Hz

Middle C is about 256 Hz.
Plug in 50 kg and you get 259 Hz - spot on!


It is many years since I plucked a spoke next to a piano. I can't remember if spoke diameter was specified in the place I got the idea from. Wouldn't a DB spoke, of varying diameter, give a different pitch?

NetworkMan
Posts: 644
Joined: 25 Aug 2014, 11:13am
Location: South Devon

Re: Views - this wheel trueing stand?

Postby NetworkMan » 9 Sep 2019, 12:31pm

Mike Sales wrote:
NetworkMan wrote:
Yes it will - the answer is here:-
https://proportionaltech.myshopify.com/ ... calculator
(saved me digging out my physics books!)
At a tension of 100 kg (Is that reasonable?)
A 27 cm length (I just measured roughly)
of steel wire (about 8 gm/cm**3)
2 mm diameter (common plane gauge)
will ring at about 366 Hz

Middle C is about 256 Hz.
Plug in 50 kg and you get 259 Hz - spot on!


It is many years since I plucked a spoke next to a piano. I can't remember if spoke diameter was specified in the place I got the idea from. Wouldn't a DB spoke, of varying diameter, give a different pitch?

Oh, yes:
If I plug in 1.8 mm (thin part of a race spoke) it goes up from 259 to 287 Hz which I think may be about D or D# above middle C so not much difference. It's butted so the difference will be less I expect.
Anyway, if the rim doesn't affect things (and I think it might), and you have perfect pitch or can use a smartphone app say, then this might be a way of getting the right tension.

Mike Sales
Posts: 3228
Joined: 7 Mar 2009, 3:31pm

Re: Views - this wheel trueing stand?

Postby Mike Sales » 9 Sep 2019, 12:36pm

NetworkMan wrote:
Mike Sales wrote:
NetworkMan wrote:
Yes it will - the answer is here:-
https://proportionaltech.myshopify.com/ ... calculator
(saved me digging out my physics books!)
At a tension of 100 kg (Is that reasonable?)
A 27 cm length (I just measured roughly)
of steel wire (about 8 gm/cm**3)
2 mm diameter (common plane gauge)
will ring at about 366 Hz

Middle C is about 256 Hz.
Plug in 50 kg and you get 259 Hz - spot on!


It is many years since I plucked a spoke next to a piano. I can't remember if spoke diameter was specified in the place I got the idea from. Wouldn't a DB spoke, of varying diameter, give a different pitch?

Oh, yes:
If I plug in 1.8 mm (thin part of a race spoke) it goes up from 259 to 287 Hz which I think may be about D or D# above middle C so not much difference. It's butted so the difference will be less I expect.
Anyway, if the rim doesn't affect things (and I think it might), and you have perfect pitch or can use a smartphone app say, then this might be a way of getting the right tension.



Thanks for your work. I think I will stick to my method though, using only a spoke key (and jig).

Brucey
Posts: 35201
Joined: 4 Jan 2012, 6:25pm

Re: Views - this wheel trueing stand?

Postby Brucey » 9 Sep 2019, 5:06pm

the pitch also varies with length as well as diameter; using the calculator at fixed 100kg load

1.6mm (16G) , 30cm span = 416Hz
1.8mm (15G), 30cm span = 370Hz
2.0mm (14G) , 30cm span = 333 Hz

1.6mm, 25cm span = 500Hz
1.8mm, 25cm span = 444Hz
2.0mm, 25cm span = 400Hz

[ also;
2.0mm, 25cm span, 120kg load = 438Hz
2.0mm, 23cm span, 120kg load = 435Hz]

So you can see that a 'one size fits all' pitch = tension measurement is unlikely to provide accurate results; you need to allow for spoke diameter and span measurements. A ~2cm variation in span changes the pitch by an amount that is equivalent to a 20kg change in tension.

Note that in practice, the note you hear is liable to be 'coloured' by overtones of various kinds, specifically because of the spoke crossings. Thus on a wheel built with radial spokes the pitch can correlate easily/well with tension, but on a crossed spoking pattern, a comparison to another (similar) wheel/spoke is easy, but an absolute measurement is somewhat less reliable from pitch alone.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Mike Sales
Posts: 3228
Joined: 7 Mar 2009, 3:31pm

Re: Views - this wheel trueing stand?

Postby Mike Sales » 9 Sep 2019, 5:10pm

Brucey wrote:the pitch also varies with length as well as diameter; using the calculator at fixed 100kg load

1.6mm (16G) , 30cm span = 416Hz
1.8mm (15G), 30cm span = 370Hz
2.0mm (14G) , 30cm span = 333 Hz

1.6mm, 25cm span = 500Hz
1.8mm, 25cm span = 444Hz
2.0mm, 25cm span = 400Hz

[ also;
2.0mm, 25cm span, 120kg load = 438Hz
2.0mm, 23cm span, 120kg load = 435Hz]

So you can see that a 'one size fits all' pitch = tension measurement is unlikely to provide accurate results; you need to allow for spoke diameter and span measurements. A ~2cm variation in span changes the pitch by an amount that is equivalent to a 20kg change in tension.

Note that in practice, the note you hear is liable to be 'coloured' by overtones of various kinds, specifically because of the spoke crossings. Thus on a wheel built with radial spokes the pitch can correlate easily/well with tension, but on a crossed spoking pattern, a comparison to another (similar) wheel/spoke is easy, but an absolute measurement is somewhat less reliable from pitch alone.

cheers


Do you find such precision is necessary?

Brucey
Posts: 35201
Joined: 4 Jan 2012, 6:25pm

Re: Views - this wheel trueing stand?

Postby Brucey » 9 Sep 2019, 5:28pm

if you want certain wheels to be reliable, a fairly accurate tension measurement is very useful.

If the spokes are too slack, the nipples back out. If the spokes are too tight, lots of rims will crack around the spoke holes. In dished rear wheels you basically don't have much choice over spoke tensions; there is a vary narrow range in which the NDS spokes are not too slack and the DS spoke tensions are not too tight.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Mike Sales
Posts: 3228
Joined: 7 Mar 2009, 3:31pm

Re: Views - this wheel trueing stand?

Postby Mike Sales » 9 Sep 2019, 5:33pm

Brucey wrote:if you want certain wheels to be reliable, a fairly accurate tension measurement is very useful.

If the spokes are too slack, the nipples back out. If the spokes are too tight, lots of rims will crack around the spoke holes. In dished rear wheels you basically don't have much choice over spoke tensions; there is a vary narrow range in which the NDS spokes are not too slack and the DS spoke tensions are not too tight.

cheers


I have found my wheels are reliable. I think that I must be getting tensions in the right range.
I understand the problems with too tight or too loose spokes.
I quite agree that with modern rear hubs there are difficulties with the relative tensions, DS and NDS.

Brucey
Posts: 35201
Joined: 4 Jan 2012, 6:25pm

Re: Views - this wheel trueing stand?

Postby Brucey » 9 Sep 2019, 5:41pm

FWIW whether spokes/nipples are slack enough to back out or not also depends on the rim, build, and the riding style. Heavier/stronger/more aggressive riders using lighter/less stiff rims with fewer spokes can make nipples back out where more moderate use is tolerated.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Mike Sales
Posts: 3228
Joined: 7 Mar 2009, 3:31pm

Re: Views - this wheel trueing stand?

Postby Mike Sales » 9 Sep 2019, 5:43pm

Brucey wrote:FWIW whether spokes/nipples are slack enough to back out or not also depends on the rim, build, and the riding style. Heavier/stronger/more aggressive riders using lighter/less stiff rims with fewer spokes can make nipples back out where more moderate use is tolerated.

cheers


Indeed, so I have found.

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Sweep
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Joined: 20 Oct 2011, 4:57pm
Location: London

Re: Views - this wheel trueing stand?

Postby Sweep » 14 Sep 2019, 7:27am

Morning merry bodgers.
Well I didn't do any trueing or building as such but I did yesterday do some experimenting using a bike frame.
I have an old ally compact frame with no bars fitted which promised to be ideal.
Put a broom handle through the stem and all nice and stable.
Slight issue sighting zip ties on rim as lower down than would be on a stand which I could put on a small table.
Real problem at the back where the ziptie rim interface was just too far back, so after spotting an issue, I would have to put a finger in the rim to mark the offending spot, then rotate the wheel towards me to manipulate the relevant spoke, then back again to check. Etc etc. Would drive me nuts trying to build like that I think. The mounts on a stand are of course angled to bring the rim towards you.
So a Unior it will be I think before undertaking serious work.
Sweep

Brucey
Posts: 35201
Joined: 4 Jan 2012, 6:25pm

Re: Views - this wheel trueing stand?

Postby Brucey » 14 Sep 2019, 8:08am

hence the value in having a pointer that makes a sound when it touches the rim; you don't need to be squinting at it in order to true the wheel.

If you are sitting in a chair then a frameset can be stood on the fork/head tube, leaning against something, and the rear wheel can be trued with pointers on the seatstays.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~