Hub motor with left hand freewheel?

[Lia Raven Gerty]

Aloha,

I've been wanting create a hybrid electric moped out of my Tomos for almost four years now. To do this with my bike, I need a hub motor that can accept a left-hand drive freewheel. I have been searching and searching but have not found anyone who makes one, just one youtube video of someone in some unknown country with one.

I know I'm going to have to get creative about chain tension, disk caliper mounting and whatnot, but I can braze so I'm not too worried. Currently, dropouts are 140mm, axle is 12mm, and it has a 16" x 3" rim (20" x 3" in bicycle sizing). I have a 58V battery I'd like to use as well as some old Grin Tech displays and whatnot. I need it not be be a drag at 45 MPH, but don't particularly care which end of the range it provides torque - the gas motor will be doing most of the work.

Reason I'm looking to to a rear wheel is because the silly engine doesn't ever disengage above 10mph. It would kill two birds with one stone if I could get an electric motor back there with a freewheel! That, and the front fork has a 12mm through axle with a very nice disk brake, I'd rather not spend $300 on a new fork on top of the motor.

Also, I am the OP of viewtopic.php?f=3&t=32982 just lost my login.

Mahalo!
Lia

 

[mistercrash]

If the controller you will use is programmable, can you simply flip the motor around and reverse the rotation in the programming. Or am I missing something?

 

[amberwolf]

The threads on the hub will be the wrong direction if you do that, and unless you add a grub screw or slotted key or other mechanical antirotation device, the freewheel would just come unscrewed as torque is applied to it.

But you can do that (it's been done). If the controller doesn't have a built-in way to reverse rotation, you can simply change the order of hall and phase wires to do that (see the forum thread or ES Wiki article for How To Determine the Wiring for a Brushless Motor)

The freewheel used in this case must be threaded all the way thru, so that it coudl be installed "backwards" onto the hub.


You can also setup the chain so it is not wrapped around the freewheel, but is driven by it like Rassy's trike, "under" the freewheel. His drives the right side still but this should work on the left side too, I think.


Or you can use a motor with a disc brake mount, and get an adapter from that to a left-handed freewheel thread, and get a left-handed freewheel.

 

[mistercrash]

The threads on the hub will be the wrong direction if you do that, and unless you add a grub screw or slotted key or other mechanical antirotation device, the freewheel would just come unscrewed as torque is applied to it.

Now that is what I was missing.

 

[gogo]

…I need it not be be a drag at 45 MPH…

Its possible to have the electric motor always engaged and then adjust the throttle to provide zero torque at any speed. This would prevent drag from the electric motor at 45 mph. You can also 'trim' the throttle to provide a charging current from the motor at any speed, but that would be at the expense of some motor drag.

 

[Lia Raven Gerty]

…I need it not be be a drag at 45 MPH…

Its possible to have the electric motor always engaged and then adjust the throttle to provide zero torque at any speed. This would prevent drag from the electric motor at 45 mph. You can also 'trim' the throttle to provide a charging current from the motor at any speed, but that would be at the expense of some motor drag.

Oh, nothing that fancy, I just mean whether I've got the throttle on or not. My old e-bike's motor would get up to 45 at 48 volts, but if I was headed down a hill faster than that it became a drag. I just mean the windings, I'm running 58 volts, so I wouldn't want a motor designed to need 72 volts to spin 45 MPH.

I suppose I may have to find a motor with enough material in the right place and have threads turned at a machine shop.