Calibrating Park Tool TM-1 spoke tension meter

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531colin
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Re: Calibrating Park Tool TM-1 spoke tension meter

Postby 531colin » 3 Oct 2017, 6:26pm

Brucey wrote:chart in a post above. '28' is allegedly 173kgf,................


I can't read that on my phone.

Its 10 years since I retired from Spa, but I think they now check (all) their Park gauges against something much more expensive.
In my time there we sent back a whole batch of Park gauges which read way too high, and it looks like there are one or two more mentioned on this thread.

I don't think 173kgf is actually achievable.

On the whole, theres much more nonsense than enough talked about wheelbuilding.
Getting them round, true, tight and even is just the start.
Unless something is badly awry, NDS spokes will never be the first ones to fail for the simple reason that their tension is the lowest of them all.
Properly stress-relieved spokes will see off more than just one set of rims where the brake blocks have worn the rim away.

Samuel D
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Re: Calibrating Park Tool TM-1 spoke tension meter

Postby Samuel D » 3 Oct 2017, 10:35pm

mercalia wrote:Even if the guage is not accurate it still does allow you to get the tensions reasonably even without trying to assess that from the tone on playing the spokes?


When I built my first wheel this summer (with nothing but a spoke key) I noticed that plucking the spokes near the nipples showed amazingly small variations in tension. I haven’t used a Park Tool TM-1, but looking at its design, I can’t see how it would reveal variations in tension as well as listening to the tones of the plucked spokes.

Plucking the spokes doesn’t tell you much about absolute tension, but this thread suggests the TM-1 doesn’t either!

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andrew_s
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Re: Calibrating Park Tool TM-1 spoke tension meter

Postby andrew_s » 4 Oct 2017, 12:46am

Samuel D wrote:
mercalia wrote:I can’t see how it would reveal variations in tension as well as listening to the tones of the plucked spokes.

If you are tone deaf, plucking the spokes tells you virtually nothing, so the Park gauge is much better

Brucey
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Re: Calibrating Park Tool TM-1 spoke tension meter

Postby Brucey » 4 Oct 2017, 1:24am

some folk have tested the calibration of their TM-1 and have produced graphs like these.

Image

Image

(which I found via a thread on weightweenies). I have no idea if the data is correct or representative BTW, but the curves do (I think) suggest that the tension meter in question tends to overestimate the tension.

If the spring force gets less with this tension meter, the measured deflection gets less (higher number reading) and the tension in the spoke appears to be higher than it really is.

This is the kind of error that you would expect if they have cheaped out buying the spring (wrong temper), the spring is overstressed in any way, or if the points at which the spring bears settle or wear at all.

BTW tone deafness afflicts about 1/20th of the population, or something like that, I think.

cheers
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mercalia
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Re: Calibrating Park Tool TM-1 spoke tension meter

Postby mercalia » 4 Oct 2017, 8:52am

not sure what tone deafness is

i can tell if 2 tones are the same or wildly different or similar but keeping it all in memory as you work around a wheel another matter a may be close to b, b to c, c to d but a to d not :!:

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531colin
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Re: Calibrating Park Tool TM-1 spoke tension meter

Postby 531colin » 4 Oct 2017, 2:29pm

What is the point of looking at tensions of 30 or 150kgf when the range you are going to use is probably only 80 to 120....?

It looks to me that (provided the thing is correctly calibrated at the start) that gauge is perfectly OK for real world tensions and real world accuracy.

pete75
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Re: Calibrating Park Tool TM-1 spoke tension meter

Postby pete75 » 4 Oct 2017, 2:57pm

531colin wrote:What is the point of looking at tensions of 30 or 150kgf when the range you are going to use is probably only 80 to 120....?

It looks to me that (provided the thing is correctly calibrated at the start) that gauge is perfectly OK for real world tensions and real world accuracy.


Yep and anyone who thinks differently could always dig deep and get one of these - a snip at £359.99


Image


https://www.sjscycles.co.uk/tools/dt-sw ... ion-meter/

alexnharvey
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Re: Calibrating Park Tool TM-1 spoke tension meter

Postby alexnharvey » 4 Oct 2017, 6:44pm

Use two and take the average surely.

Brucey
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Re: Calibrating Park Tool TM-1 spoke tension meter

Postby Brucey » 4 Oct 2017, 6:53pm

alexnharvey wrote:Use two and take the average surely.


we'll be on "n+1" for tension meters before too long.... :wink:

cheers
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SimonCelsa
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Re: Calibrating Park Tool TM-1 spoke tension meter

Postby SimonCelsa » 4 Oct 2017, 8:35pm

Unless something is badly awry, NDS spokes will never be the first ones to fail for the simple reason that their tension is the lowest of them all.
.
That was my initial simplistic reaction but on further investigations I came across many comments on the same vein as below;

if you think about it, the NDS spokes are more likely to break from fatigue than the DS...they have less tension and flex/move around more. i see this w/ some regularity on wheels w/ low-ish tension.


Which makes some sense! Whether it is correct I don't know, that's for the material scientists.

Anyhow, I bought a 3mm wire rope thimble, some 3mm wire rope grips (couldn't get 2mm), a small sus M5 'u' bolt & I have one of them old baby bouncer things you clamp to a doorframe. I will soon have fabricated the mk1 calibration device!!

All the best Simon

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531colin
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Re: Calibrating Park Tool TM-1 spoke tension meter

Postby 531colin » 5 Oct 2017, 8:49am


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Mick F
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Re: Calibrating Park Tool TM-1 spoke tension meter

Postby Mick F » 5 Oct 2017, 11:08am

Brucey wrote:
alexnharvey wrote:Use two and take the average surely.


we'll be on "n+1" for tension meters before too long.... :wink:
We were weighing Mrs Mick F's suitcases the other day using a luggage weighing device bought from Lidl's. She was near the allowed weight limit, so we "confirmed" the figure by weighing me holding the suitcase, then weighing me without it. The difference was the suitcase weight of course, and it was within a gnat's whisker of the Lidl weight.

We were happy with that, but the acid test is what the scales say at the airport check-in ................................ and who's to say they are correct?
They have a vested interest in them weighing low perhaps? :wink:

So long as you get two devices that seem to agree, that's all you can do. Tension meters included.

Me?
I use my hands to feel, and my ears to hear the ping of the spokes.
Mick F. Cornwall

JonMcD
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Re: Calibrating Park Tool TM-1 spoke tension meter

Postby JonMcD » 5 Oct 2017, 12:31pm

531colin wrote:Lots of similar discussion here...https://forum.cyclinguk.org/viewtopic.php?f=5&t=117674&start=15


....and still more here.

Brucey
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Re: Calibrating Park Tool TM-1 spoke tension meter

Postby Brucey » 5 Oct 2017, 12:57pm

Mick F wrote:
So long as you get two devices that seem to agree, that's all you can do. Tension meters included.


well yes I suppose so. On that very topic I have some proper weights that I use for checking the calibration of electronic scales, to avoid troubles with luggage on aircraft etc.

BTW I intend to build a device that allows one to check the calibration of tension meters. Once I have it up and running, maybe I could offer a calibration checking service to others?

As Colin pointed out, some meters might give good results over a small range but not be super-accurate outside of this. If needs be I could check/set the calibration to give the best accuracy in a particular range of tensions for a particular type of spoke, according to the user's particular needs....?

cheers
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Des49
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Re: Calibrating Park Tool TM-1 spoke tension meter

Postby Des49 » 5 Oct 2017, 11:00pm

This thread got me interested in checking my TM-1, I am just completing building a new pair of wheels so timely.

Trying to keep things basic and work with what I have to hand I have come up with the set up below.

A set of scales that go up to 100kg, hooked this to a bolt that goes through the wall, a couple of 1/4" galvanised shackles where I drilled a 2.5mm hole through the pins.

Then I could hang a spoke through the shackles, held in place by the J bend and a spoke nipple.

Next step is to hang weights and check the reading from the meter. Early indications on a 2.0/1.8/2.0mm spoke seem to point that my meter is reading too high, i.e. instead of 70kgf it was indicating over 80kgf.

I may drill a ring bolt into the floor and then use a ratchet tie down strap or rope to achieve higher tensions.

Unfortunately I can only check up to 100kg, but I feel if I can get readings at say 80 and 100kgf then that will be pretty relevant.
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