spoke sizes

[Wildcat]

Travel between towns has been severley restricted, so I have tons of free time. I will learn how to lace a wheel. The vids on youtube look easy enough. My wheels will be 36 hole 3 cross pattern with no dishing. I unlaced a set of 24" wheels off my old bike and will use those for learning. So I have 2 identical rims and 72 spokes with two hubs.
Here's my question: How are all the spokes the same length when the hubs are different diameter? The front is much smaller than the Sram 2 speed from the rear, but the spokes are all the same length and they were laced up in a 3 cross pattern.

 

[Couch tater]

Off topic from the original question but relevant, when you are truing and tensioning, you can use a cheap guitar tuner to get them spot on. I checked the pitch from a built wheel to one I was building and this method works great & much cheaper than buying a for real tension gauge. http://www.bikexprt.com/bicycle/tension.htm

 

[Wildcat]

The front was probably a 2 cross and the larger rear flange a 3 cross. In that regard same length spokes could be used properly. The other explanation is that spokes were sized to fit the smaller hub. Flange pitch can vary quite a bit. Say your rear flange pitch is 60mm and the front is 37mm. If both are 3 cross the difference for 'ideal' spoke length would be 4.5mm. With a 2 and 3 cross the diff would only be 0.7mm. I believe is was a 2 / 3 cross set of wheels.

I'll look up flange pitch to see what that is.
Can you tell the spoke patterns from this pic?

 

[hamqqea]

It's hard to tell from your reference but it appears both are 3 cross. That would mean the spokes would either be short for one wheel, or thread past the nipple.

 

[Wildcat]

It's hard to tell from your reference but it appears both are 3 cross. That would mean the spokes would either be short for one wheel, or thread past the nipple.

I'll find out tomorrow as I try to do the front wheel. Thanks!

 

[clamdigger]

I found that there are the basic wheel build " How Too " , and the more technically informative " Tutorial " . This one by John Allen has info I don't usually see about Spoke Torsion, then Stress - Relieving. https://www.sheldonbrown.com/wheelbuild.html

 

[Wildcat]

I was able to lace it up, 3 cross. But the truing will have to be done at the shop. I would do the rear wheel but I want a coaster hub instead of the freewheel. I may get a ss hub and try it again.

 

[Wildcat]

I laced a SA coaster 3 speed hub 3 cross, and the spokes were way too long. But it was easier than the front hub. It is nearly the same diameter as the Sram that was on there, so the rear wheel must have been 4 cross to begin with. If I'm thinking right, the smaller hub should take a longer spoke and vice versa.

 

[Wildcat]

Mystery solved! The front was 3 cross, the rear was 4 cross. Now I'm going to work on truing.

 

[stik70]

Well Done!

 

[Wildcat]

Thanks. I just used the spoke calculator webpage to see if I was entering in the right info and it came out exact. For these 24" wheels, 257mm spokes were calculated and that's what they are. So, for my next wheel set, 26", I'll need 267mm spokes.