Spoke math

[udallcustombikes]

Ok, I need someone to help me with some spoke math. I have a matching wheel set and I am putting a different hub in the front and rebuilding the rear with the same coaster hub.

I need to find the correct spoke length for the front
Here's where I am at- the rear has 270mm spokes and I am thinking if I find the straight spoke diameter (270+distance across opposing holes on the hub+270) it should be the same as the rear (right?). So if I subtract the hole distance on the front hub from the total and divide what's left I should have my new spoke length (right?)

Gaaahhhh! Math is hurting my brain tonight.

 

[jon]

hey i didnt know you knew how to speak japanese !!

 

[StephenH]

I'm thinking there's some online spoke calculators out there, see what you can google up.

I think the proper way to do it would be to calculate X, Y, and Z coordinates for both the spoke hole in the rim and the spoke hole on the hub, and then take the square root of the sum of the differences squared.

 

[user 135]

Better calc it.
http://www.bikeschool.com/spokes/
http://lenni.info/edd/

 

[Walker]

Here is another one
http://www.bikeforest.com/CAD/

 

[Ratfink1962]

I dont mess with all that math stuff
But I did find the equation for calculating spoke length...

:lol: :lol: :lol:
I take the easy way out and just take it down to Alan at Tom Sawyer's.

 

[stretch]

well you got the area of a circle, long division, sum of an infinite series, sum of a finite arithmetic series, geometric substitution, that square root mess at the bottom, and some quadratic division right there. :lol: (i studied all of that this year, im in algebra II)

 

[Ratfink1962]

Wut? :|

 

[stretch]

haha. math mumbo jumbo i gotta learn to graduate.

 

[udallcustombikes]

Well I decided to give it a shot today and with the help of algebra and it worked.

The original hub was 72mm wide across the hub flanges along the axle and the spoke holes were 40 mm across the axle. The new hub was 70mm wide and 50mm across.

The original spokes were 270mm so as I started figuring in my head: 270+40+270= 580mm streached length
I decided to go with my theory and subtracted the new hub width from the total: 580-50=530 divided by two gives me a new spoke length of 265mm. Just happened to have a wheel to steal the 265mm spokes from. Laced up the new hub to my old rim and it laced up beautifully.

It worked for me this time, can't say it will work for you but it might.

 

[diceman]

AWWW MAN . Ratfink , ya just gave away my grandmas recipe for neutronium based corn bread muffins .
she gonna be maaaaaaad at you .

 

[Ratfink1962]

yeah but I didnt say a word about the 1.21 jigawatts


Oops

 

[udallcustombikes]

AWWW MAN . Ratfink , ya just gave away my grandmas recipe for neutronium based corn bread muffins .
she gonna be maaaaaaad at you .

They were delicious, but they did seem to burn a hole through the side of my oven.

Oh there's where I went wrong- f(x)=x/3+5. I had x/5+3.

 

[sojudave]

I figure that you would measure the inner diameter of the rim (M) then measure the diameter of the spoke flange (F) and subtract to get the length you need. M-F=spoke length.

 

[udallcustombikes]

I figure that you would measure the inner diameter of the rim (M) then measure the diameter of the spoke flange (F) and subtract to get the length you need. M-F=spoke length.

That would work if the spokes were running in a straight radius pattern, but you have to take into account the twist to the hub to get the right tension on the spokes