Help needed from wheelbuilders for 24 spokes on 36 hole hub.

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cryoplasm
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by cryoplasm

The 12/12 looks better. Effectively radial/x-radial NDS and crossed DS. You moved some of the intersections from the DS to the NDS. Those radial and crossed spokes aren't going to have the same tension on the NDS just to be clear. All the DS spokes ought to have the same tension and same length.

bricky21
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by bricky21

cryoplasm wrote:The 12/12 looks better. Effectively radial/x-radial NDS and crossed DS. You moved some of the intersections from the DS to the NDS. Those radial and crossed spokes aren't going to have the same tension on the NDS just to be clear. All the DS spokes ought to have the same tension and same length.


I would imagine the crossed spokes and the radial spokes will have a different deflection rate with a tensiometer, but does that necessarily mean they will have a different amount of tension?

What I mean is that if you take two different spokes one being 100mm and the other being 300mm and apply 100kg's of force to each I'm assuming the rate of deflection would be greater with the longer one even though the same force is being applied.

by Weenie


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cryoplasm
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by cryoplasm

bricky21 wrote:I would imagine the crossed spokes and the radial spokes will have a different deflection rate with a tensiometer, but does that necessarily mean they will have a different amount of tension?

What I mean is that if you take two different spokes one being 100mm and the other being 300mm and apply 100kg's of force to each I'm assuming the rate of deflection would be greater with the longer one even though the same force is being applied.


The longer/crossed spoke will deflect more. But then some of the deflection will be offset by the intersections. The spoke tensions aren't going to be the same to keep the rim true. You will see this in the meter which will give a relative difference between two measurements.

rruff
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by rruff

cryoplasm wrote:I further suggested a cross pattern on the DS. The wheel would have a symmetric spoke ratio (3:1 throughout) with further load offset by the cross pattern which is also in a regular pattern.


You are welcome to try that out and let us know how it works. It will take a very stiff rim just to avoid excessive warping.

rruff
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by rruff

cryoplasm wrote:Those radial and crossed spokes aren't going to have the same tension on the NDS just to be clear.


The difference will be too small to notice.

rruff
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by rruff

bricky21 wrote:What I mean is that if you take two different spokes one being 100mm and the other being 300mm and apply 100kg's of force to each I'm assuming the rate of deflection would be greater with the longer one even though the same force is being applied.


If you mean stretch, then yes... the long one will stretch 3 times as far... but you don't need to worry about that. As far as the wheel is concerned, the spoke is a force vector acting on the rim and the hub. So if all the parts are perfectly uniform, then the crossed spokes would have slightly higher tension. Compared to radial spoke with the same lateral offset, a tangentially crossed spoke on that hub would deviate ~280/(280mm^2-22.5mm^2)^.5 = 1.0032... the crossed spoke would have 0.3% higher tension. That is totally in the noise. Crossed spokes will vary more than that depending on which side they are on, and variations in the rim are at least 10 times greater (typically).

bricky21
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by bricky21

rruff wrote:If you mean stretch, then yes... the long one will stretch 3 times as far


Thats not what I was talking about, but it does bring me to my next question regarding this build which is how should I factor in spoke stretch when I calculate the spoke lengths. I know how to solve the spoke length equation, but this will actually be the first wheel build that I don't have a spoke calc to rely on and the one's I've used have factored in spoke stretch.

What I was talking about with the spoke deflection comment was that if you had the two different length spokes(100mmvs.300mm) and hung a 100kg weight on each one and then checked the tension with a tensiometer such as a Park TM-1 you would get more deflection in the longer spoke even though they both have the same amount of force on them. This is just the conclusion I've come to after noticing that the deflection of a spoke is higher when placing a tensiometer at the center of the spoke than when taking the reading at the end of the same spoke.

lechat
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by lechat

Don't know if it' been covered, but I had the same idea for my xr-1 rims. Was gonna use the 20 up front and add 8 spokes to the 16 for the rear. Problem was, the valve hole was right where a spoke should have gone.

rruff
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by rruff

bricky21 wrote:Thats not what I was talking about, but it does bring me to my next question regarding this build which is how should I factor in spoke stretch when I calculate the spoke lengths. I know how to solve the spoke length equation, but this will actually be the first wheel build that I don't have a spoke calc to rely on and the one's I've used have factored in spoke stretch.


DS spokes will stretch ~1mm and NDS ~0.5mm. (EDIT: CX-Rays at 110kg DS).

What I was talking about with the spoke deflection comment was that if you had the two different length spokes(100mmvs.300mm) and hung a 100kg weight on each one and then checked the tension with a tensiometer such as a Park TM-1 you would get more deflection in the longer spoke even though they both have the same amount of force on them. This is just the conclusion I've come to after noticing that the deflection of a spoke is higher when placing a tensiometer at the center of the spoke than when taking the reading at the end of the same spoke.


The tensiometers have a test section of a certain length, so the length of the spoke is unimportant. I'm not sure why you saw a difference with position, unless it was butted. Maybe if the spoke was bent...

bricky21
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by bricky21

rruff wrote:DS spokes will stretch ~1mm and NDS ~0.5mm. (EDIT: CX-Rays at 110kg DS).

Ok, thanks I'll factor that in after I've calculated the spoke lengths.
rruff wrote:The tensiometers have a test section of a certain length, so the length of the spoke is unimportant.

Good point...It's something I cant explain :noidea: but I'll post a picture when I start measuring tension on these wheels.

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cryoplasm
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by cryoplasm

I've done the calculations for the new rear wheel for you. Once you supply rim and hub data you'll get explicit numbers by plugging them in the formulae.

Image

Image

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cryoplasm
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by cryoplasm

rruff wrote:If you mean stretch, then yes... the long one will stretch 3 times as far


?

rruff wrote:If you mean stretch, then yes... the long one will stretch 3 times as far... but you don't need to worry about that. As far as the wheel is concerned, the spoke is a force vector acting on the rim and the hub. So if all the parts are perfectly uniform, then the crossed spokes would have slightly higher tension. Compared to radial spoke with the same lateral offset, a tangentially crossed spoke on that hub would deviate ~280/(280mm^2-22.5mm^2)^.5 = 1.0032... the crossed spoke would have 0.3% higher tension. That is totally in the noise. Crossed spokes will vary more than that depending on which side they are on, and variations in the rim are at least 10 times greater (typically).


WTF? Can't see where you pull those figures from.
The crossed spoke would have to be under higher tension relative to a radial one in the same "grouping". Due to its angular position in the wheel.

bricky21 wrote:Thats not what I was talking about, but it does bring me to my next question regarding this build which is how should I factor in spoke stretch when I calculate the spoke lengths. I know how to solve the spoke length equation, but this will actually be the first wheel build that I don't have a spoke calc to rely on and the one's I've used have factored in spoke stretch.


Only consult the spoke manufacturer.

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cryoplasm
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by cryoplasm

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rruff
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by rruff

cryoplasm wrote:WTF? Can't see where you pull those figures from.


Do the calculation and you will see.

The crossed spoke would have to be under higher tension relative to a radial one in the same "grouping". Due to its angular position in the wheel.


Yes... ~0.3% higher.

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cryoplasm
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by cryoplasm

rruff wrote:Do the calculation and you will see.

Yes... ~0.3% higher.

Explain where you got those numbers from. You can calculate anything but with numbers pulled from thin air??

by Weenie


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