Hi Guys. Say, can a front hub motor wheel be put on back?

[MikeFairbanks]

Is it possible for me to take a front wheel hub motor (already mounted to a rim) and put the whole assembly (rim and all) on the back instead of the front? I realize it can be done if I take out all sprockets, but would it be possible to easily move it to the back and keep one small sprocket in the back? I'm thinking of converting a single-speed bike, but want to use the existing rim, etc.

Just an idea.

I'm getting the itch to play again.

Also this week I'll be taking apart the seat assembly on our Worksman tricycle (front hub motor) and will build a truck bed in the back with my students. I'll post pics at the end of the week.

Happy New Year, everyone.

Mike

 

[StudEbiker]

The dropout widths are different. Also, how do you plan to mount the "one small sprocket" to the front hub?

 

[Drunkskunk]

A front wheel is 100mm between the dropouts.
A normal rear for a 7 speed is 135mm.
But some single speeds are 110 to 120mm.

you might be able to make that work.

You could add a single speed freewheel to a front motor if that front motor had a thread on disk brake adaptor, and was a direct drive hub. you simply mount it backwards and set it to run backwards. Otherwise, you'll have to get creative on mounting gears.

 

[neptronix]

With a surly pugsley solid chromoly fork, a 135mm rear motor will fit on the front. Otherwise your dropouts better be the same size on both sides.

 

[amberwolf]

As long as your bike's rear dropouts are the same width as the front hub's designed spec for dropouts (usually 100mm) then you may be able to make it work. If not, you would have to bend the rear stays inward (evenly!) to be able to make it work.

After that, it depends on your motor. Some of the older Fusin geared hubs like the first one i got from Dogman were left with a little bit of threaded area on them, even when they were machined down to be front hubs (apparently all casings built as rears and then just shaved down to become fronts if needed). The newer ones avaialble now I don't know what they're like.

With the older 9C motors, you could probably take a rear threaded cover and install it on a front and it would just work, otehr than the axle maybe not being long enough to fully thread the outer nuts on especially if you needed torque arms.

Alternately with some motors you could cut the freewheel-threaded end off of a regular rear hub starting from just left of the spoke flange, drill out some of the spoke holes larger, remove the bearing cup, then mount that on the right side of a hubmotro, bolting it to the case. Might not be enough axle length for that, though. (this is the method I ahve considered most often myself, to do the same thing you're talking about).


Another way that's similar to the above would make a fixie single-speed of it: Bolt a chainring directly to the side of the hub, thru the cover, with spacers just enough to keep the chain from rubbing the cover. If you have to you can use freewheeling cranks instead, so the pedals won't be forced to turn by the motor or just by coasting.

 

[John in CR]

With metal working capability, then anything is possible. eg Front hubs typically have too short axles, but an interior threaded axle extension is pretty easy to make, and the one on the right side where the most extension is needed will screw on tight against the axle hip with motor drive torque. In that manner a much better axle for spreading the torque load can be fabricated, even with built in torque arm using a bit of ingenuity. Regen braking will throw a bit of a monkey wrench into the plan and require machining flats for the left side extension after the right side is fit, because the regen torque is want will screw that extension firmly to the axle hip.

Not all DD motors work identically forward vs reverse, what motor are you talking about? There are also typically some relatively minor fabrication issues for getting a rear wheel sprocket, single or multi-speed, mounted to the cover.

Also, steel bikes are quite easily adapted, since they can be bent or put under tension to fit, while aluminum bikes can only give a little with both bending and putting them under tension being problematic and high risk.

John

 

[dogman dan]

The sprocket would be the main impediment. At the very least, you'd need a rear humbotor cover for the sprocket side, so you can screw on a freewheel. Chances are, you could bend in the steel bike some, but you might still have the issue of whether the axle would be long enough for the sprocket and still be able to get a nut on it.

One viable option, could be to buy an unlaced motor only, in the rear type. Then take the stator out, and replace with the rear motor stator and covers.

But even laced in a rim, just the motor is generally fairly cheap.

I know money is super tight for you Mike, but have you see this? Motor only could be really cheap for you if he still has some of these 2810's in rear. http://endless-sphere.com/forums/viewtopic.php?f=31&t=31146&hilit=wife+kit

There's also watching the for sale used section. Good deals on 9c's or similar clones come along from time to time.