Wednesday 9 January 2019

Spoke tensiometer calibration jig - production version!

First post in 2019 with great update: finally the spoke tensiometer calibration tool has been released and first batch of devices manufactured!
Beginning of the New Year could not be better for Blackcat wheels!

But, first things first. What's this tool about? For those who didn't read the previous entry, look here.

I won't repeat everything what I wrote previously but in the nutshell this device allows you to calibrate your tensiometer and to create brand new tension charts for new type of spokes which were not considered by the manufacturer of your tensiometer.
Examples? Berd spokes, Pillar Wing spokes and many more to come. Those spokes are newly introduced in 2017/2018 so all tensiometers do not consider those.

Every good wheelbuilder is aware of the need to properly tension the spokes. Today in the era of modern and very light rims, the precise tension is a key. Going above allowed tension will result in rim's spoke eyelets cracks sooner or later (rather sooner these days). If you combine that with an expensive build of high-end carbon rims, the overall risk is significant for your reputation and your wallet.

There are few similar tools in the market already available but we wanted to have something smarter. The idea was to build a modular and universal base to which you could attach any type of measuring device and any type of spoke.

Did we achieve that? Let me walk you through how this tool works.

As shown above, there are two sections in the tool:
  • Section 1 is dedicated for the measuring device. Thanks to moving carriage there is a plenty of adjustable width so you can mount basically any measuring unit. Digital weight scale as in my case or load cell.

  • Section 2 is for the spoke. Here, also adjustable length of the spoke holder so any spoke length from 150mm to 320+mm will work. That means that you don't need to cut a specific spoke length for measurements. You can use a spoke from the planned build, run a quick check if your tensiometer shows correct values and continue with the wheel build.
Once all is mounted you start "pulling" the spoke by rotating the wheel with the screw. Spoke is being pulled and tension is applied. You rotate the wheel until you reach a desired tension on the digital scale/cell, for example 120kg. Next you use your tensiometer and measure the tension on the spoke directly. In that way you obtain the real and accurate reading of your tensiometer. Having that you can use those values straight away for the build or for calibration chart of your tensiometer.
All traditional tensiometers needs re-calibration on frequent basis, depending on how often do you use them. The reason being is that the spring is getting weaker over the time and slowly but surely the readings are less and less true. 
Also as mentioned before, the new type of spokes with unique shape design like Pillar Wing series gives completely different readings so all existing charts are not even close to reality. Having said that I truly recommend such tool for sake of proper and long lasting wheel builds.
Now, few close-ups to show you some fine details of this device. Big kudos to for doing all that magnificent job! 

Wheel with the screw to apply the tension. Be careful as the whole construction is very powerful. One full turn and you have 100kg!
Small but useful patent - a lock ring to lock the tension. Can be useful to run several measurements in a row with different tensiometers when you calibrate a whole series
 Solid mounts for scale or cell
Spoke mount from nipple side. 
We ensured enough space also for big fingers so you can mount a spoke and screw the nipple without any problem.
 View on the spoke holder from the other side. All holders are modular which means that in the future we can deliver a new types or special demand holders if needed.

Spoke holder from head side. This was demanding part but thanks to unique design the holder accepts almost all type of spokes. J-bend, straight pull, aero, wide and thick aero any many more...
As shown on the picture, the position of the holder can be changed for super short or super long spokes. Mid section will work for 90% of the spokes without any need of re-adjustment
 At the same time, holder accepts J-bend and Straight pull. Two in one module!

A moving carriage on high quality sliders is essential part of this tool. It makes it completely different from all other, fixed-frame based tools.
All the main parts are from steel, cut on laser.  Handmade assembly and welding. High quality black powder coat finish. Massive amount of work!

In order to meet your expectations we offer the tool with or without the measuring device to optimize your investment. If you have already a scale or cell you can just purchase the base and mount your own device.
The prices are very fair and start from 550 CHF for base and 650 CHF for base with digital scale. We will also introduce a set with load cell and display.
All options and detail pricing available in the shop

Units are available in Europe but we ship world wide. Tools are well secured in the wooden boxes, shipment is insured with tracking number available. 

If you have any questions don't hesitate to drop me an email on [email protected]



  1. A stirling job BlackCat! We're working on a DIY unit for ourselves right now but yours is looking stunningly good: I hope to pick one up in the future!

    1. Thank you! It's very encouraging to hear that. I hope other wheel-builders and shops will recognize a need to control spoke tension. I'd love to see my tool on other workbenches around the world.
      Share it further. Based on the success of this project I have in plans to start the second one, even more interesting! Stay tuned ;-)