Thread: Tensiometer
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Old 01-23-12, 10:52 AM
  #43  
mrrabbit 
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Bikes: 2001 Tommasini Sintesi w/ Campagnolo Daytona 10 Speed

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Originally Posted by reddog3
I don't build anywhere near as many wheels as some folks here. I also don't know near as much about building wheels as some of the folks here. I built quite a few wheels before buying a tensiometer. I bought a TM-1. It wasn't the cheap side of me coming out, but I just couldn't see the benefit in spending more. It's only to check what my fingers and ears are telling me. After I realized that the "same tone" in every wheel/spoke combination didn't necessarily produce the same tension- I needed some measuring device to test the work and get closer to the target number (whatever that is.) The TM-1 will tell me what I need to know as well as any other instrument currently available.

What is disturbing are the reports on the need to "recalibrate." I lost my Park instruction sheet but I recall somewhere in there about the cost of sending it back for re-calibration. What? I'm not gonna fiddle with the initial factory settings, and I can't see the spring relaxing enough to throw deflection readings off. To check this occasionally I've built a little fixture with spokes having a known deflection using the TM-1 when it was new. It's simple to test that the tool continues showing the same deflection as originally witnessed.


So... Every tensiometer I see out there uses a spring to "deflect" the spoke. That spring isn't under huge tension at any time, and it doesn't cycle with the frequency that will cause a "weakening" of the spring, so what gives? It should never need recalibration if designed properly. Maybe someone needs to re-think how spoke tensiometers are built.

ALL measurement tools need calibration. They fall generally into three categories:

A. Those that are static in nature - calibration ONCE up front at production. Rulers, dials, etc...

B. Those that are dynamic in nature and require calibration throughout their lifetime. Spring loaded, displacement sensitive, balance beam sensitive. Tensionmeters, scales, etc...

C. Those that are dynamic in nature and require a specified stable input to determine specified output. Oscilliscopes, Time Domain Reflectrometers, etc...

Re-calibration is a normal and expected part of B and C.

You are raising alarm and disturbance where there is none. It is expected...

It just so happens though that spring-loaded measuring tools typically require the most re-calibration...like flexing spokes...the spring goes through changes due to fatigue from use.

=8-)

I have two TM-1s and a calibration wheel. I used the first TM-1 to set up the calibration wheel. I then continued to use the first TM-1 as my regular tensionmeter. I used the second TM-1 to verify the calibration wheel and the first TM-1 concurrently. The second TM-1 is locked away in its box never to be touched again UNLESS I have a reason to suspect that someone has messed around with my calibration wheel.

=8-)
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