Originally Posted by
mrrabbit
Whole point of re-calibration is to bring the tool back into sync with the chart so to speak. Once again, it's a rough process - but quite okay as we don't need the precision or resolution necessary that one might need when doing machinist work such as turning a piece on a lathe in the thousandths of inches.
Of course, ideally, one would want to calibrate guage by guage - and redo the chart for each.
If you have the original Wheelsmith chart, you'll notice that they are referencing their own Wheelsmith brand of spokes quage by guage - not others.
Like many brands with different level of spokes - CN has the standard and Mac spoke. The standard is slightly lighter for 14g than the Mac - and behaves a tad different deflection wise. An ideal chart would accommodate that - same for Pillar (Richman), Shun Lih (SL), etc.
But once again, our wheels are are tensioned to rough numbers - 110 kgf for example - not 110.00.
As to the Park Tool TM-1 - the reading for 14g will start to over read by about 5-7 kgf after anywhere from a dozen to a hundred wheels. So I end up having to tighten up the spring. For my first of two, I'm about ready to email Park and ask, "Do I request a new spring, or would you guys like to have the whole tool for testimonial purposes?"
The constant re-calibration doesn't bother me - the tool works just fine.
=8-)
Yeh,
And, my limited experience suggests that spokes vary sufficiently from one brand to the next or between lots to render the interpretation chart more or less inaccurate. I don't have my micrometers in the garage, but, when I can get one home I'll mic a few spokes and see what we get.
I've also found that the chart supplied with my TM-1 does not yield the same result as entering the meter value into parks TCC tension calculating spreadsheet. Which I could reconcile with a calibration check.
Which still leaves the question of "just how important is absolute tension?" somewhat unanswered.
Basically, I'm learning that if I build wheels that are well tension balanced they hold up exceptionally well (so far). Becasue of my weight I have been hedging toward the top of the manufactures tension range for my rims. Or, even a little over, +10kgf. And given the possibility that my meter may not have matched the conversion chart to begin with, may have altered since then and that the chart doesn't match the calculator I may be off by 5-7kgf. (probably under)
rabbit, do you find that your tool stabilizes at the +5-7kgf, or, does it continue to drift if left uncorrected?
And, when you say it 'works just fine', do you find that you need to take several readings on each spoke to ensure that any spurious readings are discarded?
I've found that even with frequently application of nose grease to the indicator slide slot I get the occassion 'off' reading. It seems as though I sometimes need to read the same spoke several times to get a accurate indication of what the tension is. On your everyday 1.8mm spoke a variation of 1/2 a gradation on the deflection scale is equivilent to 7kgf. And, I would say that I'm not unaccustomed to seeing my readings on a given spoke vary by +/- 1/4-1/2.