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How to calculate spoke length?


mrpj6
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I think the difference is a cut thread removes material, a rolled thread squeezes it to form the thread,

ie no material lost. The nipples are obviously designed to accommodate. If you use a nipple on a cut thread there is little contact / strength.

I had a go at cutting a longer thread on a spoke tonight. The one i tried it on turned out to be M4 i ran the die down the thread like a nut. at the end of the thread it dropped off on the the shaft of the spoke! there is nothing there for it to cut in to. Like you said the thread must be rolled or pressed on to the spoke as one piece. So there is definitely no chance that you can cut the thread on a spoke any longer than it is when its made. It makes finding the right spoke for the job first time all more important.

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Thanks for the two posts above. I am in the UK So i checked out Central wheels. Fabulous parts! But sadly out of my financial range on this build.

I looked up spoke rolling out of interest, and from what i could tell its a little roller box with three rollers with the desired thread on them. You line up your spoke to be cut and hand crank a handle and the rollers squidge the end in to the thread form.... Nice little bit of kit... The roller heads are about 25 quid a set. I think i could work out a way to turn the spoke in it, so that may be a way to go... I could probably use the spokes i have from the donor wheel then. That way it stays cheap and i get to do the rolling bit, and that will interesting! And at the end of it all. If i can work out all the jargon on the spoke calculator, i can check the length i end up with against the calculated length. Should be an interesting few days for me.

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found this

formula.gif

http://spokeanwheel.110mb.com/

SL = Spoke Length

RRSP = Rim Radius plus Spoke Penetration

HSR = Hub Spoke Radius

SAA = Spoke Anchor Angle

HFO = Hub Flange Offset

Just wanted to say an extra thanks to Motovintage.. This formula really works! I did a full sized drawing and measured the spoke length then checked it against the formula... It came out to within a mill or two.. Looks like i need 175mm spokes!.
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