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PostPosted: Fri Sep 19, 2014 7:33 am 
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Hi, I am hoping someone can help me figure out how to calculate the spoke length for lacing a 32h Alfine 11spd hub into a 24h 16" rim (ERD = 330) for a folding commuter!

Typically I see something like triplet lacing rear wheel = 3 X DS / 1 X NDS. However, it is my understanding that IGH have less dish. Would this affect the calculation or lacing pattern?Also, the hub weights about 1700gr, but the spokes are short, so presumably stiffer, no?

In short, can someone please give me some pointers on the best way to lace a 32h IGH on a 24h rim??

I think these guys did something similar:
http://www.englishcycles.com/custombikes/superlight-alfine/


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PostPosted: Fri Sep 19, 2014 10:19 pm 
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it won't work. 3x on a alfine hub with a 16" rim. 1x is all you will be able to do both side. Why try and make life complicated the alfine hub is not meant for triplet lacing it has the wrong geometry.

Buy a 32H rim.

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Posted: Fri Sep 19, 2014 10:19 pm 


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PostPosted: Sat Sep 20, 2014 12:12 am 
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bm0p700f wrote:
it won't work. 3x on a alfine hub with a 16" rim. 1x is all you will be able to do both side. Why try and make life complicated the alfine hub is not meant for triplet lacing it has the wrong geometry.

Buy a 32H rim.


What would be the right geometry?? How can I determine that?


Last edited by Estuche on Sat Sep 20, 2014 12:17 am, edited 1 time in total.

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PostPosted: Sat Sep 20, 2014 12:15 am 
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Can I lace the Alfine 32h on a 24h rim then by just skipping holes in the hub??


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PostPosted: Sat Sep 20, 2014 9:39 pm 
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A triplet lacing hub has the NDS flange placed far from the hub centre an standard hub is not made that way, there is no off the self hub for triplet lacing that works well they are normally standard hubs with less holes on the NDS pointless in other words. Yould try and skip holes and have a comprimised build (and hard work working out the spoke lengths) or just buy a 32H rim.

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PostPosted: Thu Nov 13, 2014 8:48 am 
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bm0p700f wrote:
A triplet lacing hub has the NDS flange placed far from the hub centre an standard hub is not made that way, there is no off the self hub for triplet lacing that works well they are normally standard hubs with less holes on the NDS pointless in other words.

Average spoke tension of a wheel with ERD 350 and a Tune Mag 150 ( a "normal" hub)
Code:
                                         Tension 
Hub              Crossing             Left - Right
Tune Mag 150   16:0x/16:1x            491N - 1000N (*)
Tune Mag 150    8:0x/16:1x            982N - 1000N (half the spoke count doubles the tension)
bm0p700f hub    8:0x/16:1x           1000N - 1000N (dogma)

(*)Calculated with Spokomat - most parts of the software are translated into Englisch: "Setup-Sprache-English"

With a hub specifically made for triplet lacing - with the NDS flange placed more far from the center - one would increase NDS avg. spoke tension about 16N. I can't see, why this makes the one design usefull and the other one pointless. :noidea:

Nevertheless. The Alfine, being a gear hub, surely has much more even flange-to-center distances then the Mag150 hub wich is a 11-speed cassette hub. Most likely the differences between flange-to-center distances are so small, that with triplet lacing the NDS spokes will need significantly more tension then the DS spokes. I don't have its data at hand, otherwise I would have made the above calculations for the Alfine too.


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PostPosted: Thu Nov 13, 2014 7:21 pm 
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Since you are halving the number of spokes on the NDS you are also losing lateral stiffness. A triplet specific hub brings the NDS flange further from center to regain lateral stiffness and still have an acceptable amount of tension in the spokes.

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PostPosted: Fri Nov 14, 2014 10:08 am 
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Ok, i see. My misapprehension was to assume that bm0p700f propagates 1:1 tension. On the contrary, the concept seems to be to tension NDS spokes significantly lower then DS spokes, but higher then with a non-triplet solution.


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PostPosted: Sun Nov 16, 2014 8:21 pm 
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I also doubt you could lace a alfine hub 3x on the drive side with a 16" rim.

Lower tesnion on the NDS is fine as the lateral stiffness increases. My own 700c 2:1 laced wheels have a tension balance of 70% but are the stiffest wheels I have ever built. Shame I needed a custom royce hub which was not cheap I can assure you.

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PostPosted: Mon Nov 17, 2014 9:21 am 
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bm0p700f wrote:
Lower tesnion on the NDS is fine as the lateral stiffness increases.


Could you explain why the lateral stiffness increases if the NDS flange is set further to the left side?


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PostPosted: Mon Nov 17, 2014 9:55 am 
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Its down the the bracing angles. If you increase the bracing angle by moving the flange further out lateral stiffness increases. Do some maths and it all becomes apparant. Maths is the only thing that really explains it.

Wheel stiffness is proportional to the square of the cosine of the bracing angle see this paper http://people.duke.edu/~hpgavin/papers/ ... -Paper.pdf

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PostPosted: Mon Nov 17, 2014 1:53 pm 
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Sorry I have no time to condense this, but if I do some math, the following happens.

1. One can divide the tension of a spoke into a lateral component and a radial component. Depending on the bracing angle the proportion between lateral and radial components varies. (If you increase the spoke angle and keep the overall spoke tension, the lateral component will increase and the radial component will decrease).

2. The higher the value of the lateral components of the spoke tension, the higher is the lateral stiffness of the wheel.

3. The position of the rim above the hub is determined by the proprotion of the lateral forces coming from the DS and from the NDS. If you increase the lateral force in direction of the NDS, the rim will move to the left. If you decrease the lateral force in direction of the NDS, the rim will move to the right.

4. If you move only the NDS flange further from the center and want to keep the rim centered, the situation at the DS does not change. DS flange to rim angle stays the same and therefore the proportion of the lateral and radial components stays the same. That means, if you keep the tension on the DS, the lateral forces coming from the DS spokes keep the same, regardless the position of the NDS flange.

5. If the DS spokes generate the same lateral forces, then the lateral forces coming from the NDS spokes have to be unchanged too, even if the NDS angle changed. Otherwise the rim would move sidewards.

If all the above were correct, the conclusion would be that their is no change in lateral stiffness by moving the NDS only, because the lateral forces coming from the tension of both sides spokes stay the same.

What am i missing?


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PostPosted: Tue Nov 18, 2014 9:17 pm 
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higher tension does not equal higher stiffness. The stiffness of the wheel is determined only by the stiff of the rim, the bracing angles, stiffness of the spokes and number of spokes.

See equation 5 in this paper http://people.duke.edu/~hpgavin/papers/ ... -Paper.pdf

This is the problem when you try to analyse a problem without understanding the physics. That is not a crisitism by the way.

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PostPosted: Tue Nov 18, 2014 10:43 pm 
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Only point 1) is correct. 2) is just plain wrong. 3) is right 4) miss one key point. The horizontal component of tension is Th= Tsin(bracing angle). As the bracing angle goes up the sin of it goes up too. So as the NDS flange moves out the rim can remain centred if the DS tension remains the same.
5) is correct until you equate tension with stiffness again. This is what you are missing.

This is thing that is missed when folk talk about tension balance. The horizontal compoennt of tension on the DS and NDS spokes is the same and equal for a given DS tension no matter the bracing angles. So when people warm against using hub with poor tension balance they forgot the horizontal component of tension is dicated by the DS flange spacing. So you might as well move the NDS flange out as far as you resonably can to maximise wheel stiffness.

I hope that explains it.

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Posted: Tue Nov 18, 2014 10:43 pm 


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PostPosted: Tue Nov 18, 2014 11:33 pm 
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- If my 2) is wrong. How would you explain, that the lateral stiffness changes with the bracing angle?


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