SimonCelsa wrote:The only let down with the suspended mass calibration is that the Park Tool TM1 instructions state that the meter should be used in the horizontal plane. Whether this makes much of a difference I'd have to check.
This doesn't seem to make much difference, as Brucey alludes to as well. When I have a wheel in the jig and hold the TM-1 vertically or horizontally there doesn't seem to be any noticeable difference on a well tensioned spoke. Maybe there is more likely to be a difference in looser spokes. My set of scales are pretty heavy themselves and need to be hung vertically, they used to be used for mainly weighing out hundredweight sacks of spuds by my grandfather.
SimonCelsa wrote:I got stuck in the baby bouncer last night and it took a while to extricate my thighs from the bouncing arrangement,
That would be an interesting one for the fire brigade to be called out to!
I did a few measurements this morning:-
With an 80kg load on a 1.8mm spoke the TM-1 indicated 21, which is 105kgf on their chart. With 96kg load the gauge indicated 22.5 which seems to be 124kgf.
With a 2.0mm spoke and a 96kg load the TM-1 showed 25 which is 120kgf.
So my gauge is over-reading a substantial amount.
I have just completed a nice DT Swiss RR440 asymmetric rim, Ultegra 6800 hub 32h, 2.0mm PG spokes on drive side, tensioned to 27 on my gauge (which should be close to the max recommended for this rim of 120kgf), NDS DB2.0/1.8mm spokes comes out at about 21, which should be about 80kgf on my gauge. It feels a very nicely balanced build on an 11 sp hub thanks to the asymmetric rim.
As a further reference I have a Spa built front dynamo hub on a family member's bike, this is very tight and actually shows 25 on my gauge for a 1.8mm spoke. So even allowing for my gauge to be about 25kg over the top this wheel is still very tight and it feels it too.
Also I measured a Zipp 202 set of wheels, these use bladed spokes of 2.2x1.0mm and Zipp say that they use tensions of 100kgf front and RDS, 65 rear NDS. On my gauge the DS comes out at 15 which equates to 126kgf on the chart, again an over reading of about 26kg. The NDS measures 7.5 on the gauge which equals 65kgf on the chart, which looks about right. So maybe the gauge is accurate at lower tensions and over reads about 25kg on the higher tensions seen with normal wheels and normal round spokes.
I haven't tried to adjust the gauge to correct it yet, the adjustment can only be done in half turns so I wonder how tunable it actually is.
I have been building my own wheels for over 30 years with no issues and only got the gauge a couple of years ago. It is useful to check the relative tensions of spokes but obviously the actual values given need to be used carefully.