home made tensiometer (advanced)
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  1. #1
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    home made tensiometer (advanced)

    after some experimenting i came up with the final design of this tool...SAM_9383.jpgSAM_9443.jpgSAM_8757.jpgthk trans.jpgSAM_9434.jpgSAM_8735.jpgSAM_8817.jpgSAM_9442.jpgtensio hst1.jpgSAM_9362.jpg
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  2. #2
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    Looks production-ready...Good job.
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  3. #3
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    As Campy 11 chains don't follow the 12 1/16" rule, it's wise to change them at 132.60 mm max.
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  4. #4
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    Quote Originally Posted by mikerp View Post
    the difference is that this one has cross roller linear bearing THK VRT made in Japan (usually these are used in laboratories to carry measuring instruments and regular retail price just for this component is mind blowing...) so instead of using frictional slider where two materials rub against each other and eventually wearing out increasing the possibility of incorrect reading here we have virtually frictionless and play free linear bearing which is by the way totally rebuildable...thk trans.jpg

  5. #5
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    Looks like a cool tool. Are you selling these? Is this just a troll, free advertising thread?
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  6. #6
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    Quote Originally Posted by PBL450 View Post
    Looks like a cool tool. Are you selling these? Is this just a troll, free advertising thread?
    no, i don't actually mass produce this, just occasionally when i think of some improvement i make a new tool and when i want to sell some of these i put them on ebay, sometimes even on auction with starting price 1$...

  7. #7
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    Quote Originally Posted by govedo View Post
    the difference is that this one has cross roller linear bearing THK VRT made in Japan (usually these are used in laboratories to carry measuring instruments and regular retail price just for this component is mind blowing...) so instead of using frictional slider where two materials rub against each other and eventually wearing out increasing the possibility of incorrect reading here we have virtually frictionless and play free linear bearing which is by the way totally rebuildable...thk trans.jpg
    I use these in gage and fixture designs (am a quality engineer in manufacturing) and they are robust for sure. I don't believe that you will ever need to rebuild one in your application, knowing what we put them through I am certain you will never need a rebuild. Have you considered non-bearing guides and carriages? It would be a significant cost savings but depending on how much play you can tolerate may or may not make them practical. I use Misumi for a source frequently McMaster has some non-bearing types as well. There are many others.

    Very nice unit you've made none the less. As a side note I'm a Mitutoyo fan too.
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  8. #8
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    What are the details of the spring?
    ... 'cuz that's how I roll.

  9. #9
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    Quote Originally Posted by looigi View Post
    What are the details of the spring?
    it is Japanese Yokomo R12-18RSS (after experimenting with few dozen of custom ordered and also stock available springs i found that this particular model is perfect for the job, now do you ask also for dimensions or spring rate in grams/mm or the setting which i use to get the pressure force on the spoke at the starting point of measurement?


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  10. #10
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    Quote Originally Posted by govedo View Post
    no, i don't actually mass produce this, just occasionally when i think of some improvement i make a new tool and when i want to sell some of these i put them on ebay, sometimes even on auction with starting price 1$...
    Very cool!
    To date, philosophers have merely interpreted the world in various ways. The point however is to change it.

  11. #11
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    Great looking tool.

    I'm in the planning stages to build one of my own and your info on the spring is a definite help. Do you know the spring rate? What about length and diameter?

    Also, I have a question about the Jobst Brandt tensiometer design. All of the examples I've seen use ball bearings for the spoke supports, while none of the others (DT, Hozan, Icetoolz, chinese dt clone) do. What is gained from using the ball bearings?

    Any input would be helpful.

  12. #12
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    Quote Originally Posted by b_profane View Post
    Great looking tool.

    I'm in the planning stages to build one of my own and your info on the spring is a definite help. Do you know the spring rate? What about length and diameter?

    Also, I have a question about the Jobst Brandt tensiometer design. All of the examples I've seen use ball bearings for the spoke supports, while none of the others (DT, Hozan, Icetoolz, chinese dt clone) do. What is gained from using the ball bearings?

    Any input would be helpful.
    the spring choice has whole science behind it, there are many parameters that you should watch out for, length and diameter and thickness of the wire should be chosen in a way so the spring has as low as possible spring rate while allowing enough travel after the point of engaging in order to make room for putting the spoke in place comfortably while on the other hand providing around 1.8 kg pressure at the point of measuring (of course you can use slightly higher or slightly lower force but you must calibrate the tool accordingly) and of course the diameter and length should be determined in a way so the spring don't buckle (there are many online calculators that can help you make right choice in order to fit your particular design but the problem is the minimum quantity that should be ordrered) another way to go are the Japanese RC toys manufacturers who offer wide variety of springs that are standardized and are of very high quality so you can order few different types (they are not very expensive) and then make the decision according to your design specification, the bottom line is that you can use virtually any spring you like as long as you make proper calibration for each type of spoke...and the use of ball bearings as contact points eliminates the errors that would be caused by the friction while taking measurement compared to non-rotating contact points

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