Is it possible to fit a Bafang rear hub motor to a Felt DD70

[tokyjoe]

Hi

I want to convert my Felt DD70 to electric, I would like to use the Bafang 750w rear motor for it, but the problem I have with is with the axle. I would prefer to use this drive over the mid drive as I was to try to keep it looking like an e-bike as best I can. Unlike most bikes the DD70 do not have rear lugs which you slide the wheel onto. Instead it has a large 12mm skewer that fits straight through the hub and screws into a threaded hole on the derailleur side. I have had a look around but cannot find an exploded view of the drive, can the axle be replaced, or is it pretty much a fixed item? If it cannot then I am pretty confident that I can pull the rear forks wide enough to place the wheel in, but them I have a 8mm axel going into a 12mm hole so would using a sleeve be possible, the total length of the current skewer is approx 220mm. I have included a couple of pictures to explain it a bit better.

If it comes to it I will fit a mid drive, but as I sad previously i prefer the stealth look of the rear hub, especially as the bike will have a rack and panniers fitted.

View attachment 1

 

[amberwolf]

The torque reaction is transferred from the motor to the frame via the flats on the axle. If it's a geared hubmotor then it also uses the axle to mount the sun gear, which transfers the torque from motor to wheel via the planetary gearset.

So while you could re-engineer the motor to use a removable thru-axle, you'll have to account for all those things in it's design.

There is a thread around here about doing exactly that, which has been posted to in the last couple months, but I dont' remember what it was called.

 

[spinningmagnets]

That frame is not designed to accept a conventional axle (as you stated), so...I would say that "IF" you used two torque arms, you could cut slots into where the dropouts normally go. I "think" it would work.

That being said, I have occasionally experimented with a frame...went "A bridge too far", and then had to throw it away. It's risky, but who knows?

 

[tokyjoe]

I am starting to think converting my frame to the correct size then hopefully be able to pull it apart enough to get the wheel in. Without even trying I have an easy 20-40mm of flex at the back.

I have found these QR adaptors which even though are not designed for my application, look like they could work as sleeves. My only thought is that QR 9mm and the Bafang axle 8mm, or would that be the correct size?

http://www.tredz.co.uk/.Halo-Spin-Doctor-Pro-Axle-Conversion_24828.htm?sku=107273&utm_source=google&utm_medium=cpc&utm_campaign=google_shopping&gclid=CK6j2q2rgM0CFRATGwodVHkAyg

https://www.evanscycles.com/mavic-crossmax-12mm-rear-axle-adaptor-EV198593?esvt=1502-GOUKE323972&esvq=&esvadt=999999-0-35282-1&esvcrea=61235635856&esvplace=&esvd=c&esvo=EV198593-NA-NA&esvaid=50080&gclid=CKHRlZKngM0CFUWNGwodjDkF3A

http://www.aliexpress.com/store/product/freeshipping-fatbike-wheels-hub-adapter-hub-transverter-15mm-change-to-9mm-thru-axle-15mm-to-9mm/223018_32306507820.html

 

[amberwolf]

Without even trying I have an easy 20-40mm of flex at the back.

If it's not a steel frame, you may cause stress fractures that will later cause the frame to shear apart without any warning whatsoever, while under load during a ride.

That would really really suck.

I have found these QR adaptors which even though are not designed for my application, look like they could work as sleeves.

Without flats for the motor axle to transfer the torque, those won't do the job.

They might let you get the axle into the existing holes and not rattle around, but you will still have to custom-make torque plates to mount to the frame to do the rest of the job.

 

[tokyjoe]

I suppose it would be possible to engineer the torque plates as well, but then it would start becoming a too big a job compared to installing a mid drive, trust me to own a bike that is made by a company that decides not to build it the normal way lol......

 

[amberwolf]

I forgot about this motor, but it's not released yet. You might check with Grin Tech:
https://endless-sphere.com/forums/viewtopic.php?f=30&t=62327&p=931938&hilit=20mm+axle+grin#p931840