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PostPosted: Wed Apr 16, 2014 4:02 am 
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The SS is 13% lighter than the cx-ray. It stands to reason that you could build a wheel of the same strength and mass using 13% more super spokes - 18 SS vs 16 cxrays for instance.

Why am I wrong?

Edit - the cx-super is 17% lighter.

I am miffed that Sapim would make this elementary mistake. The stiffness of a spoke is determined by the material modulus of elasticity, not the tension on it.

"The recommended spoke-tension to build a stiff wheel-set with the Super Spoke is:

Front wheel: at least 950N
Rear wheel: at least 750N (opposite of the sprocket wheel)

As you probably already know, a high tension is always better. The higher the tension the stiffer the wheel."

http://www.sapim.be/spokes/butted/super-spokes


Last edited by F45 on Thu Apr 17, 2014 9:06 pm, edited 1 time in total.

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Posted: Wed Apr 16, 2014 4:02 am 


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PostPosted: Wed Apr 16, 2014 5:26 am 
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My understanding is that <spoke's cross section(or unit weight) x spoke number> is not proportional to lateral stiffness.

There are more factors that affect a wheel's stiffness, such as rim stiffness and hub dimensions.

Thus, reducing the spoke number by half and using spokes twice as heavy doesn't make a wheel with the same stiffness.


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PostPosted: Wed Apr 16, 2014 11:00 pm 
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F45 wrote:
The SS is 13% lighter than the cx-ray. It stands to reason that you could build a wheel of the same strength and mass using 13% more super spokes - 18 SS vs 16 cxrays for instance.

Why am I wrong?

Even if that were true you'd only be saving about 10 g at most and it would cost you $100 extra, I don't see the advantage.


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PostPosted: Thu Apr 17, 2014 11:55 am 
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If you're considering the Super spoke, I recommend going for the CX-Super (when attainable). This is the bladed version of the Sapim Super spoke with the same advantages over the Super Spoke as the CX-Ray over its round counterpart, the Laser.

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PostPosted: Thu Apr 17, 2014 1:47 pm 
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Hi,

Quote:
I recommend going for the CX-Super (when attainable).


The j-bend version seems to be available. (At long last)

Ciao, ;)

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PostPosted: Thu Apr 17, 2014 8:59 pm 
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pam wrote:
Even if that were true you'd only be saving about 10 g at most and it would cost you $100 extra, I don't see the advantage.


What I'm saying is, say you wanted to build up a 16 spoke front wheel. You could build it with 18 SS and spread the load out more evenly for the same overall weight.

Point taken on the CX-Super.


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PostPosted: Thu Apr 17, 2014 9:27 pm 
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Hi,

You want to build a 16 spoke wheel using 18 spokes? :lol:

If you want to build a x gram wheel and use 18 Super spokes then it would be stiffer than the same build using 16 cx-rays. That's what you mean, correct?

Ciao, ;)

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PostPosted: Thu Apr 17, 2014 11:10 pm 
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Not stiffer, stronger, because the load is distributed on the rim more uniformly.


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PostPosted: Thu Apr 17, 2014 11:29 pm 
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Hi,

O.K. but you will have killed two birds with one stone though: it will end up stiffer and stronger.

Ciao, ;)

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PostPosted: Fri Apr 18, 2014 3:01 am 
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F45 wrote:
I am miffed that Sapim would make this elementary mistake. The stiffness of a spoke is determined by the material modulus of elasticity, not the tension on it.


Actually modulus x cross section / length.

Pretty sad, but hey... they just make spokes, they don't need to know anything about wheels.

They have some practicality for front wheels if your hub has a high bracing angle, and also for the NDS rear if your NDS offset is high relative to the DS. The 1.8mm threads are annoying however.

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PostPosted: Fri Apr 18, 2014 3:58 am 
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Hi,

Quote:
I am miffed that Sapim would make this elementary mistake.


As far as I can tell from the link you provide that's not what they're claiming:

Quote:
As you probably already know, a high tension is always better. The higher the tension the stiffer the wheel. Please make sure that you respect also the requirements provided by your rim-manufacturer and do not forget that the tension of each wheel-side should be equal.


When I read this I have the idea they actually mean stiffer in the horizontal plane referring to the wheel.

That said, a translation is rarely perfect. and of course the build the spokes, not the wheels...

Ciao, ;)

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PostPosted: Fri Apr 18, 2014 9:03 pm 
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The super spoke is 1.8mm dimeter at the elbow and is therefore less fatigue resistanced than a CX-ray also spoke holes that are 2.6mm dimeter will result in more movement of the spoke and faster fatigue. With the super spoke a flange with very small maybe 2.0mm spoke holes would be needed but since these are not made then a holes no more 2.3mm diameter should be used.

In short the super spoke is one of those pointless spoke with more downsides than upsides.

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PostPosted: Fri Apr 18, 2014 9:11 pm 
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also spoke tension has no effect of wheel stiffness so long as the spokes have tension. Load the wheel so one side looses tension and stiff drops that is a different thing though. Spoke stiffness mathematically depends on on the following
1) length
2) Youngs modulus of the steel
3) area of moment of inertia

That fact that this myth continues to be out there staggers me as simple high physics can demonstrate otherwise.

I know Sapim state this myth on there website but they are wrong.

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PostPosted: Fri Apr 18, 2014 9:23 pm 
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Could not agree more with http://www.thecycleclinic.co.uk. Along with those observations (which were bang on). Here are a couple more. The super spoke has no means to resist twisting i.e. there are flats to hold. Therefore getting the wheel to a higher tension is a real challenge. Yes you can use a Twist Resist or something of that nature but that does not guarantee no rotation will occur and this type of tool can mar the spoke generating a stress riser which will lead to premature failure. The Super Spoke is hardened (like most upper end spokes) and if the spoke winds up beyond its yield strength it will have lost loads of its strength and begin to act more like Taffy.
The other thought is, since the girth of the spoke is so minimal it lacks the ability to resist lateral and torsional loads. This means that since the spoke will be hard if not impossible to get to a 120 to 130 kgf tension then the wheel will be prone to unnecessary movement leading to premature spoke failure due to work hardening (also a result of the added movement of the 1.8mm spoke in the 2.6mm flange hole).

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Posted: Fri Apr 18, 2014 9:23 pm 


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PostPosted: Fri Apr 18, 2014 9:43 pm 
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bm0p700f wrote:
The super spoke is 1.8mm dimeter at the elbow and is therefore less fatigue resistant than a CX-ray also spoke holes that are 2.6mm dimeter will result in more movement of the spoke and faster fatigue. With the super spoke a flange with very small maybe 2.0mm spoke holes would be needed but since these are not made then a holes no more 2.3mm diameter should be used.

In short the super spoke is one of those pointless spoke with more downsides than upsides.


That's a good point. I'd have to order a hub custom drilled, or order it un-drilled and have a local machine shop take care of it.


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