120 mm geared rear hub motor?

[Joe EE]

Good morning all. Is anyone aware of such a motor. I saw a toylike model online yesterday but I am curious if anyone knows of something like this that is 500 Watts minimum. Thanks.

 

[harryS]

Do you mean the width of the axle (drop outs) or the diameter of the hub (between spoke holes)?

 

[Joe EE]

I mean a motor that will fit on a bike that has 120 mm drop outs in the back. Thanks.

 

[Nova Haibike]

I do not know, but assuming the frame is steel, cold-setting it to a more modern wider spacing is a common practice.

 

[harryS]

If you're willing to drop down to a single one gear sprocket or able to find a freewheel with only 3 or 4 gears, some motors have spacers on that end that are removeable.

For example, this is a Q128H. Here, I loosened the nut to show how they use spacers under the freewheel to hold the 135mm dropout width. People run this motor at 500W, but the seller rates it at 350W.

 

[tomjasz]

Good morning all. Is anyone aware of such a motor. I saw a toylike model online yesterday but I am curious if anyone knows of something like this that is 500 Watts minimum. Thanks.

Which frame is 120mm? typically rear are 135mm and front 110. A folder?

 

[tomjasz]

Bafang has some 120mm

 

[Nova Haibike]

Which frame is 120mm?

120mm was the standard way back in the day, when "10 speed bikes" were all the rage.

 

[Joe EE]

I recently did a DIY front hub on my Nirve Switchblade and I am very happy with it as it is but I am a “push the envelope” type of guy and now I am toying with the idea of an AWD bike.

 

[JRA]

"now I am toying with the idea of an AWD bike."

Isn't that what you already have?

 

[Joe EE]

Yes, my friend. I guess I should’ve said a dual motor set up.

 

[harryS]

I think your Nirve is steel and if you feel lucky, maybe you could spread the rear ....15mm is like 5/8" for a rear hub motor. The rears have a nice curve on your frame. It might go well w/o stressing the welds, but what do I know. My steel Trek 800 was 130mm, so I only had to spread it 5mm. Used a scissors jack and didn't even think there were any implications.

You probably want a mondo uber motor though, and you would also lose any remaining braking power that you bike has.

Consider a mid drive. Maybe it can be mounted inside the frame, rather than in front. Except you have to get one that works with coaster brakes. They make a version of the TDS-Z2 for that.

Or you could have tabs welded on for disk brakes.

 

[Joe EE]

How did it go with your Trek? I’m thinking this might be next years upgrade but why not think ahead. I am going to inquire around with LBS and see if there is any interest. I am also thinking about putting the same motor in the rear to uncomplicate matters and have everything run off the same throttle and pedelec. She will be a Direct Drive monster at roughly 2500 Watts. Also dual regen should be plenty of stopping power except below 5 MPH... where I will have nothing LOL . I still have not worked that part out yet, but I’m not close to actually doing it. I will probably have some mounts welded on for at least some caliper brakes to stop below 5 mph. All still in the early planning stages. I am going to ride the hell out of this bike as it is all this summer and get used to her. Still very busy continuing to customize what I have already done. Thanks for the helpful reply.