Spoke Calculation Help

[Gooseman]

I've received hub and measured erd of my rim to be 544mm but want to double check i have calculated the spoke length required correctly. What would be the best cross pattern to use?

1 cross pattern = 220mm & 221mm
2 cross pattern = 231mm & 232mm
3 cross pattern = 247mm & 248mm

 

[vfr400]

According to the motor drawing, the centre of the motor and the spoke flanges are only off-set about 2.5mm from the centre, which is negligible. You have 10mm in the box. Also, the flange spacing is 42mm not 18mm. My calculator says approximately (rounded up) 222mm and 233mm for 1 and 2 cross.

 

[Gooseman]

According to the motor drawing, the centre of the motor and the spoke flanges are only off-set about 2.5mm from the centre, which is negligible. You have 10mm in the box. Also, the flange spacing is 42mm not 18mm. My calculator says approximately (rounded up) 222mm and 233mm for 1 and 2 cross.

Thanks for that. I can see where i went wrong on the flange spacing i was measuring the holes next to each other. Where are you measuring the off-set? my measurement comes from the 100mm width, one side to centre is 54.7mm so the other side would be 45.3mm giving approx 10mm offset? (I trust you are correct i just want to understand).

 

[vfr400]

Yes, sorry, 5mm offset. I wasn't thinking straight.

A 5mm off-set makes a theoretical difference of 1mm in the spoke lengths, but it's not worth getting different length spokes for the sake of 1mm. just get the longer ones, which would still be 222mm or 233mm.

The only time spoke length is critical is when you use a single-walled rim because they poke through into the tube if too long. On a double-walled rim they can be 5mm longer and it normally won't make any difference, except a bit easier to build.

That's useful when you're buying from a stockist and they don't have your exact lengths, say when you buy them from the motor supplier, like these, where the best fit would be 235mm and I'd have to do 1-cross. 220mm for 2-cross would work, but a little on the short side, so a bit harder to build. The longer the spokes, the easier they are to assemble, but you can't have them so long that you run out of thread on the nipple.

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[Gooseman]

Yes, sorry, 5mm offset. I wasn't thinking straight.

A 5mm off-set makes a theoretical difference of 1mm in the spoke lengths, but it's not worth getting different length spokes for the sake of 1mm. just get the longer ones, which would still be 222mm or 223mm.

The only time spoke length is critical is when you use a single-walled rim because they poke through into the tube if too long. On a double-walled rim they can be 5mm longer and it normally won't make any difference, except a bit easier to build.

That's useful when you're buying from a stockist and they don't have your exact lengths, say when you buy them from the motor supplier, like these, where the best fit would be 235mm and I'd have to do 1-cross. 220mm for 2-cross would work, but a little on the short side, so a bit harder to build. The longer the spokes, the easier they are to assemble, but you can't have them so long that you run out of thread on the nipple.

Brilliant thanks for your help i'm understanding it now.

 

[Gooseman]

thanks vfr400 for your help Laced wheel today and all went smoothly only a couple of hours was expecting alot longer.

 

[vfr400]

Very satisfying, isn't it? After you've done a few, you get the feel for how hard to turn the key so that you can get all the spokes the same tension, which keeps the rim true.