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Spoke Tensiometer Calibration Rig (Ideas / Projects)

calibration spoke tensimeter wheel_building

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In order not to "clutter" the existing thread on Tensiometers, this topic is now open to discuss how to calibrate the growing numbers of tensimeters that are appearing on Thingiverse. Hopefully we can discuss parts lists, design ideas and the like, in an effort to come up with cost effective and easy to build / print calibration devices.

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Updated image, now with M8 rods and all parts installed. A different scale might allow calibration. I can't find the instructions or method to recalibrate this scale. I have to hope it is correctly calibrated at the Chinese factory.

In use, you have to hold the end wing nut to keep the whole rod from turning and causing spoke wind up. so the outer wingnut must have some medium to high strength thread locking compound on it. I also think that on version 2, those extrusion insert (the yellow items within the rails) will be full length at least on several sides, just for looks.

First version is working. It is still missing a part (Thrust Bearing) and there are a couple of things I would change but here it is

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In the picture above the spoke is being pulled with 102.7 kg so the spoke tension is 1000 newtons. I double checked my Park Tool TM-1 chart together with my rarely used TM-1 and it was close. The TM-1 was one marking too low with a 1.8 mm spoke. So here is the parts list.

  • 2 - 20 mm x 200 mm T-Slot
  • 2 - 20 mm x 500 mm T-Slot
  • 4 - 2020 Corners
  • 8 - M5 x 10 mm Button Head Screws
  • 8 - M5 T-Slot Nuts
  • 1 - M8 x 35 mm Button Head Screw
  • 1 - M8 Washer
  • 1 - M8 Flat Thumbscrew
  • 1 - M8 x 200 mm Threaded Rod
  • 1 - M8 Hex Bolt
  • 2 - M8 Acorn Nuts
  • 1 - 8 mm Roller Thrust Bearing
  • 2 - M8 Clevis Rod Ends
  • Small Crane Scale (150 kg or more capacity)
  • 1 - Brass Spoke Nipple
  • Some 3D Printed Parts

This list will build the model with the items I would do differently. The difference is that the pictured version uses an M6 Threaded Rod and that should change to an M8 or M10. It is not a strength issue, it is a space issue. Besides this you need a few drill bits and a way to drill straight holes. Some Allen Head Hex Wrenches and some time to print the 3D parts and putting it all together.

After using this for an afternoon, I already have some ideas on how to improve this model. Here is what I think will make it better:

  • Replace the allthread threaded rods with an acme lead screw, the adjustment will be finer and easier to get more exact.
  • Make it bigger than 6 mm, again, it is a space thing, not a strength thing.
  • Add plates to the back side to make the frame a bit more rigid. This is just to guarantee that the frame stays square.
  • Add some sort of feet to the back side so this can be placed on a benchtop. Of course, as is, it can be placed in a vise or some other appropriate holding mechanism during use.

It is currently a bit tedious to use if you are creating an entire conversion chart. It works better as a one off measurement for each tension requirement for the current wheel build. I don't know if my improvement ideas will change that any.

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So far the only section that is complete. This is the J-hook end of the spoke attachment. Still waiting on the slow boat from China for a few parts to complete the other end.

Even though the crane scale has WH-C100 in the model number it is actually rated for 150 kg or 1471 newtons.

In order to make the M8 clevis joints fit inside the opening on the crane scale I had to break out the Dremel and sanding drums. First the opening in the plastic housing needed to be widened. After the sanding a few wipes with an Acetone soaked paper towel and it looks almost like it was never sanded. Then the actual clevis fixtures needed the top edge and top corners knocked off so that it fit freely within the slot. The spoke attachment is a blade thumb screw with a 5 mm and 3 mm hole drilled in the center (close to the center, it was hand drilled). The spoke just hooks onto the thumbscrew. I should soon have a complete parts list (W.I.P.), including which parts can be 3D printed.

Hey looks greatfull! So you spend your christmas holiday by building this up. - I appreciate this so thumbs up for that! Thank you for sharing your ideas.very impressive work I hope we will see more until next year or at least during the following year.

Actually I might have this one done before the weekend. I also started figuring out just how much this might cost to build if you had to buy every part. So far I am looking at about $80 USD using US based online retailers. The second version is only a frame at the moment and won't be complete until the end of January.

Two frames are built, just waiting on a few more parts. The frame made from 2020 series extrusion appears to be strong enough to stand on. The 3030 series may be over designed. I am still missing the threaded rods and clevis joints to the one that uses a Crane scale. As soon as those arrive I will finish up the drilling and tapping and assembly. Hopefully before the end of January. A few items are coming from McMaster-Carr, a bit expensive but available in the US.

Sounds realy good! My wooden one stands in the corner because I don't have time for this project ... .
Do you have a solvement for the attachment of the spoke?
I will look forward with special interests on the frame that uses the cranescale :)

I have two solutions for spoke attachment., Personally I think both are rather innovative and only require a drill and two drill bits and a tap (one option). But I am biased.

For the threaded end I have two solutions, one requires a spoke nipple and the second doesn't. The easier to build version requires a 4 mm hole to be drilled through an M8 bolt in the center. With this version you slide the threaded end of the spoke through the hole and attach a standard brass nipple to the end. It requires that you remove the fitment and reinsert it for every spoke you measure. The harder one to make requires a #2-56 tap and a #51 drill bit. You drill the M8 bolt with the #51 bit through the center, then tap the hole with the #2-56 tap. This eliminated the need for the nipple. No removal of the fitment is needed when changing spokes with the second version. When you see the attachment you will know why drilling and tapping the hole is my preferred method of attachment.

For spokes threaded on both ends you will need two of the fixtures. For straight spokes with a flared end you could make one that has a 2.5 mm hole.

For J-Hook spokes you will need three items, a blade type thumbscrew and two drill bits. The way I envision it is that you drill a 2.5 mm hole just above the centerline of the blade section of the thumbscrew, followed by a 5 mm hole just under the centerline. File out the rest to make a pear shaped hole. This will allow the J-Hook end to be pushed through without having the thread the spoke like you need to in a hub. It makes removal easier. Again you will need to see it all together to better visualize the attachment method.

The plan is to make this a very clean looking calibration rig. Even though it is of bespoke design, I want it to look and work like a polished product.

The crane scale version requires clevis rod ends to attach the scale to both the frame and the spoke fitment.

Parts are slowly trickling in. So far I have one crane scale, with a second one arriving within days. The 300Kg load cell should also be here by the beginning of next week. A digital weight indicator (to attach to the load cell), should be here in a couple of weeks. As well as the 30 Series aluminum extrusion and connectors/corners. I already have the drill bits for the spoke holders. My idea there is to take a steel bolt, drill a hole through the center using a #51 bit then tapping the hole with a 2-56 UNC tap. That will match all currently available DT Swiss, Sapim, Wheelsmith, etc. spokes on the market for bicycle use. Still deciding how to attach the J-hook end, I do have a couple of ideas. I have most of the plastic parts printed. When it all arrives I will dig out my drill press and get to work. If I can pat myself on the back, I think the spoke attachment method I plan on using rivals any commercially sold unit out there and only requires two tools to make and no machining. Actually so far as I can tell the only exotic tools needed would be the drill press and the thread-forming tap. The entire project should be able to be built with readily available parts.

If you must build something like this on a budget, parts will have to be sourced from China. There is no way around that. Some may object to using Chinese sources, but the reality is that most inexpensive options locally sourced have some roots or are entirely made in China. That is the only way to keep the costs down.

I certainly hope that if anyone else has designs in mind that they will also share them here.

New Model to help in building a rig, https://www.thingiverse.com/thing:3259309
150Kg Crane Scale, small and portable.

150Kg Crane Scale

I am currently working on two designs for a spoke tensiometer calibration rig. It is to help calibrate and create conversion charts for the various spoke tension meters here and available commercially. I think I have most of the fixtures worked out but will accept any suggestions to help reduce the cost and/or make assembly much easier. I am trying to design these so that they can be built with some 3D printed parts and hand tools. My current idea for the spoke attachment device does require a drill press and or thread forming tap.

There are two versions which will eventually be released on Thingiverse as well as other repositories. When comparing these two designs with what is commercially available it is considerably cheaper to build. Many calibration rigs for sale worldwide range in price from $500 - $700 USD (€440 - €620) (£390 - £550). There are also many bespoke calibration rigs that have been built by various wheel builders over the years. Not a single one of them has a parts list or instructions on how to build one yourself. Many of them also "look" and "feel"
homemade. Not that that is a bad thing. A search through Google will find a bunch of those images if you are brave enough to guess at the hardware and want something really cheap. Quite a few require welding, I am hoping a design can be made that just bolts together. I am a considerable way into the design and have parts that should be here before the end of the year to build up a prototype or two,

Since starting this project I have looked at several commercial calibration devices as well as home made units, I have a pretty good idea of what I actually want to build. I am now currently working on two designs. One can be built pretty cheaply, requires no machining, a few 3D printed parts, and can bolted together. I am pretty sure that if someone located in the US can likely build this cheaply. If you scour eBay and Aliexpress, don't mind waiting a month for parts to arrive I think you can build this for under $75 USD, all in. That model is version 1.0 and is not quite done yet. The Crane Scale shown in that model won't actually work and is just there for illustration purposes. I still need some ideas on how to finish the spoke attachment fixtures. Maybe someone here can give me some ideas. The source files can be downloaded from: https://a360.co/2qXYbrr
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Version 2.0 is completely rethought and it a sturdier version of the calibration tool. It is stiffer and should be able to withstand use by an active, maybe even commercial, wheel builder. It uses an electronic load cell and digital readout. It is built with larger extrusions and hardware. Only a few parts are 3D printed. It is still in the preliminary stage of development. My estimate for building your own version, again sourcing parts from China, should be under $150 USD. In it's current form it is about 100 - 150 mm too long, shortened it should be able to handle any length spoke up to 310 mm. The files can be viewed and downloaded from this link: https://a360.co/2RbAOWN
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Please feel free to critique either or both designs. Offer suggestions on how to lower the cost. Make improvements that allow for more 3D printed parts. Add your own thoughts on how to build it better.

I am hoping that others will contribute to the designs here. I have started to work on my version and so far I have a model of the frame done. If you want to download a 3D model file use this link, https://a360.co/2qXYbrr. It will always be the most current version of my design. The idea is to fully model it before actually building it to make sure it is something that can be built.

Hi, thanks for sharing your model here. I'm also interested in building a spoke tensiometer. However, I had the more "traditional" scissor design in mind, similar to a Park tool. I'm curious how your design posted would interface with the spoke to measure tension. Can you please explain that?

@gogodoit I think you really want to be in this thread, https://www.thingiverse.com/groups/bike/forums/general/topic:28979

The linked topic thread is about tensiometers, this topic thread is about a calibration device that can be used to create datasets to convert the deflection read from the tensiometer into actual spoke tension.

Amazing! Thank you for sharing your 3d model of your calibration device. That will make the invention easyer. What kind of aluminium rods do you use (I mean the diameter) ? Are you sure that it will withstand the foce? And how do you attach the crane scale to it?

I think my previous message is under moderation because of too many edits.

This is only the start. I will probably build it first then finalize the design "as built". I haven't figured out how I want to attach the Crane Scale yet, that is why it isn't included in the 3D model. I also thought about building a more expensive version with a load cell, but that will wait until next year.

It is standard OpenBuilds V-Slot 20x20 extrusion. Sold all over the world and there are a lot of models here on Thingiverse for parts. You can 3D print T-nuts, Corners, Plates, Handles, GoPro attachments, whatever you want using that extrusion.

https://openbuildspartstore.com/v-slot-20x20-linear-rail/
https://openbuildspartstore.com/components/?mode=6

I know those aluminium extrusion rods they are well suited for special builds like this. But I don't think that 20 mm x 20 mm right strong enough to handle the force of tension ... !?

I ordered some 3030 profile and corners, If the 2020 doesn't work I can al least build a second one with 3030. I also updated my Fusion 360 file with more parts, still not complete, but closer. Have to think of a way to attach a spoke J-Head.

It is what I have, there are sizes up to 40 x 40 in square profiles. I am going to try it and see if it works, If not I will repurpose the aluminum parts for some other projects. My feeling is as long as the cross member is rather short and is supported properly at both ends that is where all the stress is really located. It is not like we are trying to achieve tensions over 200 Kgf. I can also double up the ends to make them 40 x 20 mm or print a 100% infill insert that sits in the internal channels. But I won't know what works until someone actually tries it.

Comments deleted.

This is all preliminary, I am using 20 Series Aluminum extrusion. It is basically the same extrusion used in all the square box 3D printers found on here, readily available all over the world.
https://www.thingiverse.com/search?q=2020+extrusion

I haven't decided how the Crane Scale will attach. More than likely, I will get to the point of assembling the jig, then doing the 3D design in what I would call "as built" rather than a blueprint to follow.

Good idea to start a new thread for this. I've comment in the "tensiometer development thread" but my comment was flagt for moderation ... .
So here is what I have made last weekend. I decided to keep it as low cost as I can and use stuff what I had.
The complicaded thing ist to create a device that the spoke is attached to. And I want to use a crank/winder to set up the tension.
By that it is maybe possible to use a hexagonal screw and design/print a crank to use with.

My thought is to keep the cost down also. I don't want to spend more than $100 USD on a setup. I am building mine from scratch and only have screws in various toolboxes, so everything has to be bought.

My idea is to use 2020 Aluminum Extrusion, I just bought 2 one meter long pieces for $34 USD. I also got a 200Kg Crane Scale for $19 USD. That is basically all the expensive parts.

My second criteria is to make it easy to build, some or none of the parts could be 3D printed. but I wanted people (including myself) to be able to build it with just a few hand tools.

Third, It must be easy to use with repeatability. No calibration jig is worth anything if it doesn't allow for repeatable results.

Hopefully when I am done with my current ideas and project, I should be able to supply a complete parts list as well as instructions for use.

The idea to build it with metall or aluminium rods is good (I have had the same ;D ). I think that you also have in mind to create 3d printed corner parts to fix them together!? That might be nice and usefull to build it without welding or something.
So when we can print our Tensionmeters then it should possible to do that to a calibration device :D
For the moment I will work with a wooden device. But I will looking forward to see what kind of calibration tool you will create.
To reconstruct it in the future.

pretty sure its not possible universally due to different lengthts and density of spokes

Spoke length is irrelevant. It is all about tension. It is just physics. A DT Swiss Competition spoke under the same tension load has the exact same deflection in a 244 mm or even a 302 mm.

So you can build a "universal" calibration jig pretty easily. But if you want to make a calibration device that can support different length spokes, that is possible with a bit of forethought.

Of course the cross section of different spokes will require multiple charts or even a spreadsheet so that each type of spoke is accounted for. If you are trying to compare a Competition to say something like a Sapim CX-Ray the deflection will not be the same at the same spoke tension. That is why you need charts. A calibration rig will allow you to create those charts.