Calibrating Park Tool TM-1 spoke tension meter

[broadway]

Have you checked the tension on any other wheels to see what figure they give?

[531colin]

If you send it to me I'll happily calibrate it against my own gauge and also the "new" gauge we keep at the shop for this very purpose. I'll PM you an address.

[georgew]

Simon.....do not lose hope as you're not alone.

http://www.bikeforums.net/archive/index ... 43983.html

[jb]

Theres a lot of high expectations for this cheap and cheerfull tool. Try it against a known quantity, note the difference and allow for this with future builds.

Park tool 60 squids profesional tool 300 squids, theres the difference.

[SimonCelsa]

Thanks for the comments, I will send her on her way to Colin shortly for some expert analysis.

I sent you a PM Colin but not sure if I followed the correct routings. Anyhow, hopefully you'll receive it shortly & would be grateful for a quick check, will cover postage etc & will buy you a beer if our paths ever cross, small World at times,

All the best, Simon

[Mick F]

Just building my wheels, and stopped for a cuppa ..........

Question re spoke tension meters:

I understand they work by deflecting the spoke and you read off how much deflection on a scale, then transfer this reading to a chart where there are different thickness of spoke. Obviously, a thin spoke will deflect more than a thick spoke for any given tension.

So, how do these things work with respect to different toughness? Surely a harder/tougher/stronger spoke will deflect less?

[531colin]

Mick
You are spot on with how the (Park) tension gauge works.
As for the other question, the gauge deflects the spokes in their "elastic zone"...they will spring straight back.
Forming the elbow angles, you have to take the wire past "yield point" so it deforms plastically ie, it takes a set and doesn't spring back.
Maybe a metallurgist or the right sort of engineer could tell us the relationship between those different types of bending?

[Nettled Shin]

So, how do these things work with respect to different toughness? Surely a harder/tougher/stronger spoke will deflect less?

The Park Tool website has a chart / spreadsheet for interpreting the tensiometer reading. It contains (some) info on aluminium, steel, plastic, titanium, round and aero profile spokes. You are right that the elastic modulus of the material will have a bearing on the reading, so the chart is a bit broad-brush.

It would be an easy task for the OP to calibrate the tool against the actual spoke he is using. Suspend children of known weight from the spoke, and apply the meter.

[bicyclejourneys]

Hi,

Firstly, thank you to SimonCelsa for starting the thread. Handy to find.

My original wheels were built up by Spa Cycles some 7 years ago. These were Rigida Sputniks 26" alloy 36H. Using Sapim Race front and NDS. Sapim Strong on the rear DS. They have served me well on self-supported laden tour/s around the south island of New Zealand, round Cornwall, up through Wales and more recently up through Morocco, Spain and France.

This time I've built my own using the same components. Except Rigida now Ryde!

The first Sputniks were indeed as Mr Musson has in his book: Type 1 offset. The pair I have now (Ryde Sputniks) are a Type 2 offset!

The build was very enjoyable and satisfying to ride ones own wheels. But I wanted to be sure that the tensions were near about equal, as I'm off to Oz on some hard trails later in the year. So I got a Park Tool TM1 tension meter. Except for a few spokes under they weren't too bad.

Using the TM1, Park Tools app and following Colin's advice on tension:

All within a 15% variance.

Front 21 - 105 kgf Sapim Race
NonDS 19 - 85 kgf Sapim Race
DS 25 - 120 kgf Sapim Strong

Now I've checked my old Rigida rims (built by Spa) and they are showing (identical spokes as new build.):

Front 23
NonDS 24
DS 29-30

Now either my NEW TM1 needs calibrating or Spa's need calibrating!?

I can feel a greater tension in the older wheels compared to mine with these TM1 readings.

Any further advice please, but in the interest of science I may build a tension calibrating rig.

Nigel

[Brucey]

So, how do these things work with respect to different toughness? Surely a harder/tougher/stronger spoke will deflect less?

The Park Tool website has a chart / spreadsheet for interpreting the tensiometer reading. It contains (some) info on aluminium, steel, plastic, titanium, round and aero profile spokes. You are right that the elastic modulus of the material will have a bearing on the reading, so the chart is a bit broad-brush. It would be an easy task for the OP to calibrate the tool against the actual spoke he is using. Suspend children of known weight from the spoke, and apply the meter.

park tool calibration chart for TM-1



BTW in theory you don't need to worry about variations in steel properties affecting the reading; the deformations in the spoke are elastic, and the steel modulus does not vary appreciably with likely variations in spoke composition/ strength. The main determinants of calibration are spoke material and spoke diameter.

cheers

[andrew_s]

It would be an easy task for the OP to calibrate the tool against the actual spoke he is using. Suspend children of known weight from the spoke, and apply the meter.

It's probably easier to use a lever. If the spoke is attached 1/5 of the way along, and you weight the end, it's 200 ml water for 1 kgf, and a decent sized bucket should do it. Don't forget to allow for the weight of the beam & bucket.

[531colin]

Hi,

Firstly, thank you to SimonCelsa for starting the thread. Handy to find.

My original wheels were built up by Spa Cycles some 7 years ago. These were Rigida Sputniks 26" alloy 36H. Using Sapim Race front and NDS. Sapim Strong on the rear DS. They have served me well on self-supported laden tour/s around the south island of New Zealand, round Cornwall, up through Wales and more recently up through Morocco, Spain and France.

This time I've built my own using the same components. Except Rigida now Ryde!

The first Sputniks were indeed as Mr Musson has in his book: Type 1 offset. The pair I have now (Ryde Sputniks) are a Type 2 offset!

The build was very enjoyable and satisfying to ride ones own wheels. But I wanted to be sure that the tensions were near about equal, as I'm off to Oz on some hard trails later in the year. So I got a Park Tool TM1 tension meter. Except for a few spokes under they weren't too bad.

Using the TM1, Park Tools app and following Colin's advice on tension:

All within a 15% variance.

Front 21 - 105 kgf Sapim Race
NonDS 19 - 85 kgf Sapim Race
DS 25 - 120 kgf Sapim Strong

Now I've checked my old Rigida rims (built by Spa) and they are showing (identical spokes as new build.):

Front 23
NonDS 24
DS 29-30

Now either my NEW TM1 needs calibrating or Spa's need calibrating!?

I can feel a greater tension in the older wheels compared to mine with these TM1 readings.

Any further advice please, but in the interest of science I may build a tension calibrating rig.

Nigel

I have no access to my Park chart just now....what does 29 to 30 come out at in kgf? My recollection is that I couldn't crank it up above about 130 kgf without power tools. I suspect your gauge is reading way too high.

[SimonCelsa]

Since the original post I've built a further 10 wheels (not a lot admittedly) and fitted them to various bikes; single speed, tourer/commuter, tandem. These bikes have travelled a combined mileage of circa 20,000 and touch wood, as yet none have given me any problems from a wheel perspective. The only problem I've encountered in that period was 2 NDS spokes breaking on a SPA built rear wheel!!

Since the initial 'problems' with the Park Tool TM-1 instrument I haven't really used it for wheelbuilding. I think if you are just putting together general usage wheels with no fancy hubs / lacing patterns / superlightweight rims then it is a purely mechanical exercise & if you follow the guidance in Roger Mussons 'Professional Guide' then you really can't go wrong. It is definitely not an 'art', as I must be one of the least artistic people around. Lace the wheel, use the nipple driver to take up the initial slack and then basically go around each spoke giving each the same amount of tweak.....a little bit more or less as necessary to true out any deviations. With the small triangular spoke wrench I use it hurts your fingers before you get to the stage where you are that tight where the nipples start to round off.

Admittedly I've been building with mainly robust components i.e Sputniks, but I've also built a couple of 'Mavic Open Sports' on track hubs & they haven't yet collapsed. My latest build I have just finished, a SP-PV8 dynohub into an Exal XR2 rim (both ex SPA) with DT Swiss Comp spokes ex Rose Bikes. Out of interest I did go round the wheel with the tension meter & obtained reasonably consistent readings of 24 on the gauge. For 1.8mm spokes this equates to a tension of 148 kgf which is rather high....do I trust the gauge - basically no, but after recently watching a you-tube clip on how to calibrate one then I may cobble something together soon to finally perform an accurate check.

Good Luck, Simon

[mercalia]

I had similar high readings from my own Spa wheels some time ago with the Park guage ( I did tell the builder to build them strong so maybe he did just that, he did at the time phone me up telling me the really good rims were the ones in black that the new stock silver ones werent ) but gave low readings on my original factory wheels. Any way I aimed for some thing in between and my wheels have been fine carrying 17 stone over 1800 miles. 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?

[Brucey]

I have no access to my Park chart just now....what does 29 to 30 come out at in kgf? My recollection is that I couldn't crank it up above about 130 kgf without power tools. I suspect your gauge is reading way too high.

chart in a post above. '28' is allegedly 173kgf, '29' is not indicated.

cheers