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Date: 19 Jun 2007 07:41:16
From: Tosspot
Subject: Hookes Law
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Since I have acquired home bodged spoke tensiometer and a "conversion
chart", I was wondering if the conversion chart is accurate. So, I
reason, it should be easy enough so suspend a given volume of water from
a spoke and measure the deflection.
My question is this, can I get away with say 5,10,15 and 20 kgs (about a
bucket in 5 litre increments), or do I need to get closer to the 70-90kg
that a spoke experiences.
In short, is it linear?
For those that are interested, the principle of the bodge job is the
same as the DT Tensio
http://www.dtswiss.com/index.asp?fuseaction=proline.bikedetail&id=8
but a bit (ok a lot) more Heath-Robinson
http://en.wikipedia.org/wiki/Heath_Robinson
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Date: 20 Jun 2007 13:33:10
From: datakoll
Subject: Re: Hookes Law
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On Jun 20, 9:19 am, datakoll <datak...@yahoo.com > wrote:
> I haven't tried this exercise but its widespread fersure as several
> rube Goldberg devices ahhhh spring to mind. Yet I haven't read of
> one ??? is there a website devoted to gearloose tensiometers? but off
> course-at least 15 as of 9AM EDST
>
> http://www.google.com/patents?spell=1&q=wire+tensiometer&btnG=Search+...http://www.google.com/patents?id=W8AwAAAAEBAJ&dq=spoke+tensiometer
>
> an unbendable "beam" holding a given spoke length and a fish scale
> coordinated to the beama acquisition....
AHHHH. do it backwards with a pull then release into the digital
readout!
the problem could be-designing to avoid grade 9 hardware
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Date: 20 Jun 2007 13:19:00
From: datakoll
Subject: Re: Hookes Law
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I haven't tried this exercise but its widespread fersure as several
rube Goldberg devices ahhhh spring to mind. Yet I haven't read of
one ??? is there a website devoted to gearloose tensiometers? but off
course-at least 15 as of 9AM EDST
http://www.google.com/patents?spell=1&q=wire+tensiometer&btnG=Search+Patents
http://www.google.com/patents?id=W8AwAAAAEBAJ&dq=spoke+tensiometer
an unbendable "beam" holding a given spoke length and a fish scale
coordinated to the beama acquisition....
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Date: 19 Jun 2007 20:46:43
From: jim beam
Subject: Re: Hookes Law
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Tosspot wrote:
>
> Since I have acquired home bodged spoke tensiometer and a "conversion
> chart", I was wondering if the conversion chart is accurate. So, I
> reason, it should be easy enough so suspend a given volume of water from
> a spoke and measure the deflection.
>
> My question is this, can I get away with say 5,10,15 and 20 kgs (about a
> bucket in 5 litre increments), or do I need to get closer to the 70-90kg
> that a spoke experiences.
>
> In short, is it linear?
no it's most definitely not. your tensiometer is testing a material in
3-point loading, with both tension and bending being factors. you
therefore need to be in the loading zone found in practice to have
accuracy - extrapolation for lower tensions is highly unreliable.
>
> For those that are interested, the principle of the bodge job is the
> same as the DT Tensio
>
> http://www.dtswiss.com/index.asp?fuseaction=proline.bikedetail&id=8
>
> but a bit (ok a lot) more Heath-Robinson
>
> http://en.wikipedia.org/wiki/Heath_Robinson
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Date: 20 Jun 2007 07:36:43
From: Tosspot
Subject: Re: Hookes Law
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jim beam wrote:
> Tosspot wrote:
>
>>
>> Since I have acquired home bodged spoke tensiometer and a "conversion
>> chart", I was wondering if the conversion chart is accurate. So, I
>> reason, it should be easy enough so suspend a given volume of water
>> from a spoke and measure the deflection.
>>
>> My question is this, can I get away with say 5,10,15 and 20 kgs (about
>> a bucket in 5 litre increments), or do I need to get closer to the
>> 70-90kg that a spoke experiences.
>>
>> In short, is it linear?
>
>
> no it's most definitely not. your tensiometer is testing a material in
> 3-point loading, with both tension and bending being factors. you
> therefore need to be in the loading zone found in practice to have
> accuracy - extrapolation for lower tensions is highly unreliable.
Thanks for that, I shall find a bigger bucket then!
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Date: 20 Jun 2007 05:47:53
From: jim beam
Subject: Re: Hookes Law
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Tosspot wrote:
> jim beam wrote:
>> Tosspot wrote:
>>
>>>
>>> Since I have acquired home bodged spoke tensiometer and a "conversion
>>> chart", I was wondering if the conversion chart is accurate. So, I
>>> reason, it should be easy enough so suspend a given volume of water
>>> from a spoke and measure the deflection.
>>>
>>> My question is this, can I get away with say 5,10,15 and 20 kgs
>>> (about a bucket in 5 litre increments), or do I need to get closer to
>>> the 70-90kg that a spoke experiences.
>>>
>>> In short, is it linear?
>>
>>
>> no it's most definitely not. your tensiometer is testing a material
>> in 3-point loading, with both tension and bending being factors. you
>> therefore need to be in the loading zone found in practice to have
>> accuracy - extrapolation for lower tensions is highly unreliable.
>
> Thanks for that, I shall find a bigger bucket then!
what are you putting in the bucket? 100kg of water is quite a volume.
100kg of lead is not.
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Date: 20 Jun 2007 18:37:29
From: Tosspot
Subject: Re: Hookes Law
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jim beam wrote:
> Tosspot wrote:
>
>> jim beam wrote:
>>
>>> Tosspot wrote:
>>>
>>>>
>>>> Since I have acquired home bodged spoke tensiometer and a
>>>> "conversion chart", I was wondering if the conversion chart is
>>>> accurate. So, I reason, it should be easy enough so suspend a given
>>>> volume of water from a spoke and measure the deflection.
>>>>
>>>> My question is this, can I get away with say 5,10,15 and 20 kgs
>>>> (about a bucket in 5 litre increments), or do I need to get closer
>>>> to the 70-90kg that a spoke experiences.
>>>>
>>>> In short, is it linear?
>>>
>>>
>>>
>>> no it's most definitely not. your tensiometer is testing a material
>>> in 3-point loading, with both tension and bending being factors. you
>>> therefore need to be in the loading zone found in practice to have
>>> accuracy - extrapolation for lower tensions is highly unreliable.
>>
>>
>> Thanks for that, I shall find a bigger bucket then!
>
>
> what are you putting in the bucket? 100kg of water is quite a volume.
> 100kg of lead is not.
Well, I was thinking of water because it's easy to transport in a
hodepipe and easy to dispose of later. The current thinking is one of
those "IKEA Bags", which look waterproof and will certainly hold the weight.
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Date: 20 Jun 2007 09:12:37
From: Paul Myron Hobson
Subject: Re: Hookes Law
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> Tosspot wrote:
>>
>> Thanks for that, I shall find a bigger bucket then!
jim beam wrote:
> what are you putting in the bucket? 100kg of water is quite a volume.
> 100kg of lead is not.
Hell, sand would be a huge improvement over water. (wet sand even better)
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Date: 19 Jun 2007 21:50:20
From: datakoll
Subject: Re: Hookes Law
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On Jun 19, 9:50 am, datakoll <datak...@yahoo.com > wrote:
> can we see a digital representation of this device?
the problem is? the tool samples a predetermined length of the spoke's
shaft and relates that specific length bit by the tool to the tool's
gauge
whereas hanging weight from a spoke twists the spoke's complete length
and twists the hub end.
what that does to the measurement ? is trial and error on your end
right?
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Date: 19 Jun 2007 13:50:47
From: datakoll
Subject: Re: Hookes Law
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can we see a digital representation of this device?
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