Step 10: Wheel building- Spoke calculation.
I am starting with the front wheel as they are symetrical and therefore easier; rear wheels have an offset which means that the spokes are longer on one side than the other.
Ok, All of my information is coming from Sheldon Brown's site.
He begins by linking to a selection of Spoke calculation sites.
I found this one to be the most straightforward.
As the photos show it has a very simple layout with a help section.
My photos are too low resolution to be much help so please go to the site.
I've used callipers and ruler to get measurements; it's a bit tricky.
For the rim measurement :
Take two spokes cut down to 200mm. Glue on a nipple so that the top of the spoke is flush with the bottom of the slot in the nipple.
Place in opposite holes in the rim and hold taut. Measure between the ends and add 400mm. Average several diameters.
3x is the usual spoke pattern found in wheels; it simply means that each leading spoke crosses 3 training spokes on that side of the hub This sounds complicated but easy to understand once you have read the method on the wheelbuliding link.