20mm axle through motor

[cwah]

Hello all,

I've just found this motor on leafbike site:

http://www.leafbike.com/products/diy-bike-conversion-kit/24-inch-electric-hub-motor-kit/single-shaft-24-inch-48v-1000w-hub-motor-bike-conversion-kit-1002.html

Doesn't that open us a new world of possibility to fit motor on latest front forks? Dual drive would be more common with this maybe?

 

[Chalo]

That's not a 20mm through axle (which is a 20 year old fad standard anyway, still with us on DH bikes). It's a single sided stub axle hub, like what you'd use on a recumbent trike or velomobile. It could hypothetically be used on a single sided fork, but you'd have to make the fork to match.

Thanks for the link; it's good to know that such a thing is still available. Grin used to carry them, but it's been quite a while.

20mm through axle forks are out of fashion except for heavy, long travel DH equipment. 15mm through axle is the new hotness for overpriced crash bikes. Neither standard offers any obvious way to anchor motor torque, other than clamping a round shaft with the fork tip. That might do the job, or not. At least it won't waste the fork tip if the axle spins; only the hub wiring would be damaged.

For a smooth axle hub motor to be compatible with a through axle fork, the fork tips must be able to open all the way and admit the axle. Most don't do that.

 

[Mundo]

Justin still carries the single sided DD Motor.

http://www.ebikes.ca/shop/ebike-parts/motors/m3540ss.html

 

[Hillhater]

Unless I am mistaken....A through axle fork ( or hub) requires that the axle is completely separate from the hub/motor.
That's a tricky engineering problem for a hub motor unless it has some separate form of torque restraint. :?

 

[Leebolectric]

wouldn't it be easy...to design a motor hub, with a 20mm outer axle which can handle the wiring, and extends the width of the dropouts with internal sections stepped down to 10mm.
...then have a 10mm through-axle that passes through the center, leaving room for the wiring to pass between the two and exit before the dropout?

even better...have the 10mm through axle, with nuts that are 20mm diameter operated by allen key....
...so you can use the fork's pinch bolts on the axle nuts, making it VERY solid.

...or something like that?

that 20mm outer axle could have slots in it to accept torque arms.
the 10mm inner diameter would mate to rear drop outs too..with a wider spacer.

 

[Chalo]

Justin still carries the single sided DD Motor.

http://www.ebikes.ca/shop/ebike-parts/motors/m3540ss.html

Good to know. Last time I saw them, they were Crystalyte 400 series with 20mm axle stubs. As I said, a while back.

 

[Chalo]

Unless I am mistaken....A through axle fork ( or hub) requires that the axle is completely separate from the hub/motor.
That's a tricky engineering problem for a hub motor unless it has some separate form of torque restraint. :?

In the past, I used a Hanebrink through axle fork (with 6-bolt pillow block fork ends) to hold a BMX hub I had machined 20mm dummy axle ends for. Those particular 6-bolt fork ends would probably be adequate for holding motor torque, but most I've seen are not suitable. Most wouldn't even allow installation of a fixed axle.

 

[amberwolf]

wouldn't it be easy...to design a motor hub, with a 20mm outer axle which can handle the wiring, and extends the width of the dropouts with internal sections stepped down to 10mm.
...then have a 10mm through-axle that passes through the center, leaving room for the wiring to pass between the two and exit before the dropout?

even better...have the 10mm through axle, with nuts that are 20mm diameter operated by allen key....
...so you can use the fork's pinch bolts on the axle nuts, making it VERY solid.

Um, in this setup, what exactly do the nuts do?

Normally they are only needed to hold the axle to the dropouts, so they have no purpose if you use clamping dropouts, and would be a problem if you only used the nuts to clamp the dropouts to--the axle will rotate inside the nuts, on it's threads.


FWIW, it's easy to *design* a lot of different possible axles and motors, that are MUCH better than what is typically actually manufactured. Many such have been posted here on ES. Heinzmann actually makes one.

But so far none of the typical hubmotors are made with any of those designs, only the common and flawed flatted-axle design, with a few variations (passing wires thru a hollow axle to the nut end, or passing them only partway thru to the inside of the dropout, are the two most common).

If you can get these hubmotor companies to start making them *generally* with the better designs (not just in a small special batch just for you--cuz they'll make *anything* that way, for the right price), I'm sure a lot of people would thank you.

 

[teklektik]

Justin's motor 'sneak preview' back in 2013 (20mm through axle).


Release was postponed to resolve some magnet placement issues and for heating/cooling wind tunnel research reported in ES thread:
Definitive Tests on the Heating and Cooling of Hub Motors.

 

[Hillhater]

Well remembered teklektik ,
There is also a thread on thro' axle motors somewhere.!