Join Date: Apr 2010
Location: Sunnyvale, CA USA
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Originally Posted by jyl
Just a quick wheelbuilding question, please.
I am toying with the idea of lacing in a generator hub. To keep the cost down I went looking for such a hub with dimensions similar to the Normandy. I came up with the Sanyo H27 which also happens to be among the least expensive genhubs.
According to the spoke calculators I checked, rebuilding this wheel with the Sanyo hub requires 294.1 mm spokes.
It may or may not work.
Aiming for the nipple tops I'd expect to run out of thread, and for the slots it wouldn't surprise me on at least one or two spokes.
DT spokes (9.5mm of thread) bottom in 12mm DT nipples (8mm of thread to the top) 2.5mm above the slot bottom and 1.5mm past the top. which gets you right to the limit aiming for the slot.
Other brands are similar.
You're starting with 2mm of error, could get close to 0.5mm of stretch from butted spokes, and may be even farther off due to how some one else measured the rims.
Measure ERD before you start - put spokes in opposite holes, thread nipples on to your target depth, measure across the elbows with calipers, and add twice the spoke length. Repeat in a few spots and average because rims can be slightly egg-shaped.
If you're close to working or not use nipple washers which increase ERD by 1.5 - 2mm.
Last edited by Drew Eckhardt; 04-04-14 at 11:18 AM.