Narrow drop-out rear hub motors

[pdf]

Anyone know of a rear hub motor for a narrow drop-out rear? I have a cruiser with a drop-out spacing of around 124 mm. Want to convert to a single-speed rear hub. I think ebikes.ca used to sell a rear hub motor with a narrow dropout spacing, but I don't think they do anymore.

 

[spinningmagnets]

One option may be to use a conventional rear BMX hub with a disc-brake flange as a jackshaft. Put a narrow front E-hub with a disk-brake flange on it. Both left-side disc-brake flanges have a fixed sprocket bolted on and a live chain connecting them.

The right-side freewheel on the jackshaft has a chain from that freewheel to the conventional BB-chainring.

http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=7192&start=30#p401162

 

[dogman dan]

Easy as pie to bend a steel frame 1 centimeter. An alloy frame is likely to have enough flex to fit as well, without actually kinking anything. Just the flex in the stays should give you 5 mm per side.

If you will be running a single speed gear, then you will actually have a ton of space on the gear side. Enough to shave 10 mm off the axle shoulder, or shorten a spacer if that is the case. Then dish the wheel back 5 cm to center the rim.

It's not much of a problem at all really.

 

[cell_man]

I have some custom 110mm rear Mac 500W shafts available. You could use that with spacers to build it out to whatever width is required. Basically, the shaft is the same on the disc side of the motor, but the freewheel side has the M14 threaded section extended by 25mm. Could get an existing stock motor swapped over to 1 of these shafts. The thread for the freewheel is the standard type for 7 speed freewheels, so as long as the single speed uses the same, it should work just fine.

As Dogman said, it's easy enough to spread a steel dropout by 10mm.

If you want to have a chat, best to email me rather than PM, address is listed on my site, www.emissions-free.com

 

[pdf]

Hmmm. Further in, it looks like brakes will be a bigger issue. I think spreading the frame is probably easy enough, or using a custom axle and shimming it out as Cell_man suggested.

This is a cruiser style bike with drum or roller brakes (not sure which) but will have none if I replace the rear wheel. Looks like fitting the disk brake parts to the frame is not trivial. Can't find exactly what I am looking for so far. Any threads were someone did this (added rear disk brake to a cruiser)?

 

[itselectric]

Anyone know of a rear hub motor for a narrow drop-out rear? I have a cruiser with a drop-out spacing of around 124 mm. Want to convert to a single-speed rear hub. I think ebikes.ca used to sell a rear hub motor with a narrow dropout spacing, but I don't think they do anymore.

I was just look through some of our archive photos, here are few cruiser bikes that we did few years ago. It is exactly what you have described:
- 110 - 120mm dropout, not 100, not 135, but in between in a single speed
- it had a drum brake on the rear wheel, and no front brake
- it is Nirve cruiser bike

Here what I have done to bike:
- taken a Crystalyte 408 front motor (100mm dropout), change the cover plate replace with threaded cover plate
- added single speed freewheel
- change out the regular axle and replaced with extended axle (you can see it in the picture)
- relace the front wheel with sturmey archer drum hub with dyno (i know the wire is handing out, we rushed to take photo before it was finish)

And the end result look like this:
View attachment 4View attachment 2

Here is another one that we did almost the same thing with Nirve Street King:
View attachment 1

 

[Brentis]

There are ways to add disc brakes.

Adapter style
http://www.choppersus.com/store/product/307/Disc-Brake-Bracket-Billet/

Weld on style
http://www.chainganglowrider.com/ProductDetails.asp?ProductCode=CHP01213

The bigger issue, which will likely preclude rear disc brakes, is the chain stay spacing.

On bikes designed to run roller, coaster, or v-brakes, there tends not to be enough room to run a disc.
Even a small 140mm disc will rub against the stays. Even as you spread for the hub motor.

Hate to be the bearer of bad news.
I ran into the same problem with my "Ghetto" build.(see sig.)
Best solution I came up with is,
Powerful front brake and regen. on the rear.
I run 40kmh with only a front but I'm sick in the head.

Otherwise keep searching for a mountain bike with rear discs.
Good luck.

 

[johnrobholmes]

I just converted a Felt Slant cruiser for my wife. I took a regular rear motor and ground the shaft slotting back to frame width and fit a single speed freewheel. 203mm brake rotor clears the frame fine, but the caliper is hitting the puma motor.

 

[pdf]

Some good advice here. If it will work, I think I am going to first try the adapter suggested by Brentis. Can't tell if it is designed for horizontal or vertical dropouts. Mine are horizontal. The picture looks like it is on a horizontal (edited to change from "vertical") dropout.

The chainstays probably have a lot of spacing compared to some bikes due to their design. I don't know if you can tell in the picture (mine is the 2010 Felt cruiser the bottom of the page: http://cruizerbikes.com/New_Belgium_Cruisers.php)
but the chainstays are shaped like a giant "U", they don't taper like some, which are 135 at the dropouts but quickly taper to just over the width of the tire. So you get the full clearance the entire diameter of the tire. That might help. Won't know until I try.

John, I'm sure you know this but someone on here has a link to a site that sells brake calipers that are thin on the motor side. Couldn't find it right away but if anyone remembers it, please reply because I will probably need it. There was a thread a few days ago by a guy whose caliper was scratching his motor and I think someone had the link there. Also, when you say "ground" I assume you did this with a shop machine and not a hand grinder? In my case, I probably can spread the frame a bit. I'd rather not but might have to.

Would really like to use a 9C 2810. I have one on a mountain bike that climbs like a goat for a short distance if you keep the speed above, say, 10 mph or so on 18s LiPo. I love that bike, although officially it is my son's. I ride it more than he does though. Looks funny with an adult on the small frame, but when you don't have to mash the pedals, you can get away with it. I ride it as my commuter when I don't need the cargo space of the Xtracycle

 

[johnrobholmes]

I used a dremel with a burr and took about ten minutes. The caliper I have is a Hayes Stroker, and there was enough material to remove and make it fit.