hub motor axle extensions - instantly longer axles

[mlt34]

Anyone ever seen something like this before? I hadn't, and stumbled upon it in my local ebike shop. They were custom machined. Seems like a brilliant idea - you can lengthen your axles easily like this. Two scenarios that I can immediately think of that are good for this are 1) using a front motor in a rear application, or 2) using a hubmotor in a fatbike (no more rears in the front!)

I bored one of the out to allow for the axle wire to exit. On a motor with a side exit axle that wouldn't have been necessary. In the course of boring it out, I discovered that either my bits are sharper than I remembered or this is seriously soft steel. I'll remember that when it comes time to crank down the axle nuts.

Also I'll need to add on some flats for wrenching and a torque arm. Still a neat idea though, if not quite a finished idea.

 

[Ykick]

Had similar idea 2-weeks ago while fat bike dreaming and wondered if something like that was out there... 12 or 14mm? How much do they sell for?

 

[mlt34]

They are 12mm. I'm using one to put a BPM motor in the front fork of a fatbike. I've just got to dish the wheel to re-center the rim and account for a long axle on one side.

The guy wanted $25 for one. If it was good quality steel and finished, I'd say thats a fine price for something useful and rare like this. Considering these examples are crap metal and I have to put my own flats on it and bore it out, it seems steep. But considering I've never seen something like this before, I took them and I just have to pass the cost along to the customer.

I'm thinking of having some of these machined for me and perhaps make them available to ES folks if they turn out nice. These have stupid long shoulders (each adds 30mm, hence why I'm only using one) which seems excessive. I'd want to have a couple sizes of longer and shorter shoulders to fit different projects.

 

[docnjoj]

Someone in the group had a similar idea to this for restoring stripped axles on motors. They mentioned a site to get 20mm ones and it seemed like a great idea. I just can't remember who or when. They were stock items so no drilling.
otherDoc

Here we go! The original thread by tkollen on stripped axle repair.

http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=43287&start=25#p651193

 

[Hillhater]

how do you "lock" them to the original axle so the torque arms work ?
Or will you put your torque arms onto the original axle still ?

 

[Ykick]

This be interesting - http://www.mcmaster.com/#93020a783/=wbpkj3


Easy enough to find hardened 12mm threaded rod/bolt, maybe use a jam nut?

Not much concern about regen on 12mm axle motors. In all the years I've messed around with these components 'yet to see anything but gear/clutch hub motors using 12mm axles.

14mm or larger DD motors different story, if you bother with regen. I don't, not worth the trouble for my situation(s).

 

[John in CR]

Keep in mind that with thread on extensions if the torque arms aren't attached to the axle itself, only the right side will bear motor torque and the left side regen torque.

 

[mlt34]

Keep in mind that with thread on extensions if the torque arms aren't attached to the axle itself, only the right side will bear motor torque and the left side regen torque.

This is true, but I'm using a geared motor which means I won't have to worry about regen. And the extender is going on the right side, so it should be self tightening.

Today I filed some nice flats on the threaded portion and was real proud of my work, only to realize afterwards that I should have waited until I got the motor back from the wheel builder for that step. I have no idea where the axle extender will bottom out on one side, so who knows if the flats will line up with the flats on the axle on the other side.

oops