Nick Payne writes:
>>>> How would you verify the tension of a wheel built with bladed spokes such as Sapim CX-Rays?
>>>> Would the tensiometer readings still be valid?
>>> It is for the new DT tensionometer...
>> No, for the standard Wheelsmith one. Just not sure if the deflection measurement is accurate and
>> reliable if I were to use
>> it.
> On mine there is no conversion table for that size of spoke. Even when the spokes are bar tight
> the deflection readings are still very small (10-15). I just used the table column for 0.9x3.1
> spokes and a fudge factor to account for the spokes only being 0.9x2.3 cross section.
These instruments all measure across the spoke thickness so the thickness enters into the reading.
For this reason I built my own instrument that was in small production for a year or so, first under
Avocet, and then under DT. In all about 120 reached the market. Unfortunately, all such instruments
are designed by people unclear on the problem.
The bending stiffness of the spoke also enters into the measurement that is based on the theory that
the spoke is a flexible strand although it is not entirely so. For that reason a small test load
that causes little bending must be used, but this in turn requires a precise measuring instrument.
For that purpose I used a 0.0001 resolution dial gauge.
In addition, small irregularities in spokes are large enough to distort readings and for this
purpose my instrument had a "tare" zero adjustment that was set in situ. Currently the tensiometer
problem is not served as well as it could be.
Jobst Brandt
[email protected] Palo Alto CA
