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E-Bike Hub Motor Wheel Building

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E-Bike Hub Motor Wheel Building

Old 10-06-20, 12:44 AM
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aaronmichael
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E-Bike Hub Motor Wheel Building

Hello fellow bicycle enthusiasts,

As usual, I'm back with a wheel building question. I've found answers here and there on the web but it has been difficult to find answers to some wheel building questions. Particularly about e-bike wheels. I have recently had multiple e-bike hub motor wheels presented to me, in terms of lacing the (Bafang) hub motor to a regular wheel. This has left me with some questions.
  1. Can a regular double wall wheel (of any quality) withstand the forces of a hub drive motor? Or will the rim give way because of spoke tension or over stress?
  2. Can a hub drive motor be laced to a rim using 14G spokes with brass washers underneath the head? Is that enough to reduce the play in between the oversized hub drive motor holes and a standard 14G spoke?
  3. Will a 14G spoke withstand the forces of the hub drive motor? Or will spokes break prematurely? I suppose a spoke hardly ever (if at all) breaks in the middle due to stress. This maybe ties directly in with question #2 .
  4. If it is possible to build with 14G, is this safe?
  5. Does the weight of the hub affect required spoke tension? If the answer is yes, then this should play a huge roll in hub motor wheels.
  6. For a regular sized 26" or 29" hub drive motor wheel, would a 2x pattern be sufficient for a build?
I think I'm forgetting something else that popped through my head, but I'm sure it'll come up later. If anyone is bored and has some input on these questions, it would be greatly appreciated. Thank you!
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Old 10-06-20, 11:23 AM
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Originally Posted by aaronmichael View Post
Hello fellow bicycle enthusiasts,

As usual, I'm back with a wheel building question. I've found answers here and there on the web but it has been difficult to find answers to some wheel building questions. Particularly about e-bike wheels. I have recently had multiple e-bike hub motor wheels presented to me, in terms of lacing the (Bafang) hub motor to a regular wheel. This has left me with some questions.
  1. Can a regular double wall wheel (of any quality) withstand the forces of a hub drive motor? Or will the rim give way because of spoke tension or over stress?
  2. Can a hub drive motor be laced to a rim using 14G spokes with brass washers underneath the head? Is that enough to reduce the play in between the oversized hub drive motor holes and a standard 14G spoke?
  3. Will a 14G spoke withstand the forces of the hub drive motor? Or will spokes break prematurely? I suppose a spoke hardly ever (if at all) breaks in the middle due to stress. This maybe ties directly in with question #2 .
  4. If it is possible to build with 14G, is this safe?
  5. Does the weight of the hub affect required spoke tension? If the answer is yes, then this should play a huge roll in hub motor wheels.
  6. For a regular sized 26" or 29" hub drive motor wheel, would a 2x pattern be sufficient for a build?
I think I'm forgetting something else that popped through my head, but I'm sure it'll come up later. If anyone is bored and has some input on these questions, it would be greatly appreciated. Thank you!

1. No super lights or light weights . . . middle weights on up. You want inner wall thicknesses of 2.2mm or higher.
2. Washers are NOT hole fillers - they are head / elbow spacers.
3. The bigger the hub and the smaller the rim, the more likely the spoke breakage. Overall, spokes on hub motors will not last as long as non hub motor wheels. Hub motors apply instant full torque. This is why you see a trend toward crank / bottom bracket centric motor setups.

I recommend 2.34 / 2.00 single butted or 2.34 / 1.8 / 2.0 triple butted at a minimum - just to put a teeny bit of beef where it matters while still building a traditional pre-stressed wire-spoked wheel.

4. What does a single 14g broken spoke do? Poke you in the eye? Scream "Geronimo", and force you over a cliff? Wrap itself around your fork or stay for dear life and send you flying into the back of an opportunistickly placed ambulance?

5. Weight = Load = Stress

6. https://www.mrrabbit.net/wheelsbyfleming/php Spoke length calculation spreadsheet has a t-chart tab. If it's a small cute motor at 36 holes in a 26" - 29" rim...both 3x and 2x will do.

=8-|
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Old 10-07-20, 09:00 AM
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Thank you for your input!
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