Ryan_M

I can't find any real documentation on these, and what I do find is fairly unsuable since alot of it is unitless. I made a copy(ish) of them but working out the final details. I'm pretty sure my spring tension is way too low. I made a test jig for some spokes I'm working with and at 140kgf I was only getting 0.13mm deflection. At an absolute best accuracy of +/- one digit thats an inherent grey area of ~7.6% before you add in any other inaccuracies. I'd like to know what you measure so I can fine tune things. I have a more stout spring that I'm going to try, printing the parts now. I would still like to compare. Thanks!

FBinNY 

Try replacing the spring with elastomer so you'll have more options. Once you find the right constant, you can stay with it or search for a comparable metal spring.

Or approach it analytically. You have a pair of data points. Decide how much deflection you want for your scale to be relevant, then use simple ratios to work back to find the spring constant.

Dan Burkhart 

My Wheel Fanatyc meter usually registers in the.29 to .35 mm range across a range of spoke types and thicknesses at my target tension which is a far smaller deflection range than my other meters register.
Note that a meter that shows the value of the actual deflection registers a lower number at higher tension as opposed to the more intuitive scale of the Park meter and it's clones that shows a higher number at higher tension.
The spring in the Park type meter is much stronger than the Wheel Fanatyc. I can quantify this in my calibration jig.
Typically, the reading on the scale will increase by about 6% when taking a reading with the Park meter but only about 2% with the Wheel Fanatyc.
This really doesn't matter but it explains why the WF has a narrower deflection range.
AS long as your meter delivers consistent and repeatable readings, all you really need is a reliable means of calibrating it.

Ryan_M

Thanks! Very useful info. I tried the new spring and it's maybe a touch on the strong side but I think I'll roll with it. It's a little stiff to compress by hand, it's fine for me but might be too much for someone with smaller hands - if anyone else even ever uses it. I did make a calibration jig and the spokes I'm working with now (Pillar 1420) gave me a deflection of ~1mm at 90kgf, mind you the spokes are bladed and I was measuring across the 0.95mm cross section. I'm actually surprised by the repeatability. I tested from 40-140kgf in 5kgf increments, and at each tension I put the tensionometer on and took it off 4 or 5 times. In about 80% of the times I got the exact same number, the other times were only out by one digit. Dont think I can ask for better than that! Cheers!

Dan Burkhart 

Did you compare how much the reading on the scale increased with the new spring as compared to the original one?
Not that it matters if you are properly calibrated but it would be interesting to see the relationship between that and the readings you got previously.

Ryan_M

I did have a look at that, but wasn't much concerned with it beyond a curiosity. What I was seeing a bit less than 1% which can't be realistic. I suspect the test jig diluted the additional tension I would see if the spoke were installed in a wheel. The jig has an L-bracket to hold an eye bolt to which the digital scale is mounted which hooks into a U-bolt that has a span of steel with a hole drilled in it to mount the spoke, yada, yada. Lots of different bits to flex and swamp out the ever so slight shortening of the spoke when the tensionometer deflects it ~1mm.

TBH I don't think this particular error matters much. Ok sure I may think I'm tensioning to 118kgf but really only tensioning to 113kgf, can't say I care. What I do think is valuable is the consitency and repeatability in the readings so I can acurately compare tension in one spoke to the next. Caveat, I'm a very novice wheel builder so could very likely be a case of I don't know what I don't know, only expressing my opinion of what makes sense to me... at my current level of ignorance lol!

Dan Burkhart 

The increase in the scale reading with the meter applied wouldn't produce an error because it returns to normal.
I was just interested to see how it compares to the increase I observe on my calibration jig with a meter that registers about a third of the deflection you are measuring.
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mpetry912 

The spoke tension is determined by measuring the deflection in the spoke when a known force (the spring tension) is applied.

note that spokes of different guages will measure differently, or put another way, will have different tension under the same deflection

It sounds like you have a calibration jig of some sort so you can measure the deflection of spoke with a known load.

There is a process for "zeroing" the WF tensiometer at the start of each measurement run.

/markp

Dan Burkhart 

I realized I mis spoke when I talked about increased tension with the meter applied.
I meant to say the scale reading increased. I corrected my post in hopes it makes more sense.

Road Fan

Seems to me the manufacturing tolerance of spoke diameter is also a factor. The 7.6% seems like a "noise margin," within which you may get a reading, but can't really count on it as a measurement.

My Park tensiometer came with a reference card to let me see how my build might compare to a standard I may have found, but it is very difficult and finnicky for me to match two spokes in a given wheel, due in part to sticktion in the spoke nipple threads, spoke windup, and friction in the nipple to rim interface. I haven't tried building with a lubricant yet.

Ryan_M

Fully agree with you, a 7.6% built in possible error in the tensionometer is not trustworthy. Mine was too touchy, and was picking up the not quite straight spoke if I measured to close to the cross. This is why I was looking to use a stiffer spring, to swamp that out. I think I got there. The spring I'm using now gives me ~1% error. There is the argument that the measurement itself affects the tension measured. I'm not so concerned with that as long as it's consistent and repeatable - which it is - now.

This style of tensionometer (for the most part) negates the spoke diameter deviation as the two reference surfaces (the bearings) and the measurement are done on the same side. Regardless, for assured accuracy I calibrated with the spokes I have in hand.

I'm using bladed spokes for this build and I'm really liking them and will probably continue to use them in the future. If there is any wind up it's very apparent, but I use a tool I printed to hold the spoke straight so pretty much a nonissue. I use silver antisieze that I add some drops of generic oil to, to get a nice consistency. I use it on the threads, as well as on the nipple where it seats on the rim and I'm happy with it. There's sooo many opinions out there on what to use, and I'd bet all of them are perfectly valid. I'll keep using what I'm using because I like it and it hasn't spontaneously combusted.... so far. LOL