Sticking with a hub motor ...

[rocketman58]

I once again I researched replacing one of my hub motors for a mid drive motor. And once again I chose to stay with a hub motor. I had hoped in the two years since I started down the e-bike path with my trike that things might have changed enough. But it seems not. It all comes down to compromises, including those that end up being deal breakers. For me that was excessive Q factor and surprisingly, non round chainrings.

I could not find an after market mid drive that did not poses a Q that was well over 200mm by the time it was set up for me. This set up included: 1) Equal spindle lengths on each side (most motors have their cranks offset further out to the right). 2) Required the use of straight cranks that had no offset or ankle clearance to achieve a Q of 200. (I pedal slightly toes out and require some offset for my ankles.) I set my trike up with pedal extenders to simulate the best possible Q factor I could expect. By the end of a week my hips and inner thighs were killing me. These areas are sensitive due to both surgery and radiation treatments related to cancer. I do not think it will be possible for an aftermarket mid drive to ever meet my special needs because of this.

 

[maiz]

I once again I researched replacing one of my hub motors for a mid drive motor. And once again I chose to stay with a hub motor. I had hoped in the two years since I started down the e-bike path with my trike that things might have changed enough. But it seems not. It all comes down to compromises, including those that end up being deal breakers. For me that was excessive Q factor and surprisingly, non round chainrings.

I could not find an after market mid drive that did not poses a Q that was well over 200mm by the time it was set up for me. This set up included: 1) Equal spindle lengths on each side (most motors have their cranks offset further out to the right). 2) Required the use of straight cranks that had no offset or ankle clearance to achieve a Q of 200. (I pedal slightly toes out and require some offset for my ankles.) I set my trike up with pedal extenders to simulate the best possible Q factor I could expect. By the end of a week my hips and inner thighs were killing me. These areas are sensitive due to both surgery and radiation treatments related to cancer. I do not think it will be possible for an aftermarket mid drive to ever meet my special needs because of this.

After my hips healed a bit I returned the Q back to my normal 170mm, and swapped out my non round rings for standard round rings of the same size. Long before I started tinkering with e-assist, I had found that old school Biopace rings helped smooth out my pedal stroke and lessened knee pain while riding a recumbent bike or trike. I needed to find out if this was still the case with e-assist. Turned out yes it was, at least when using a hub drive. Perhaps with a mid drive' higher power less pressure would be needed on the pedals, but since I cannot use a mid drive that is a moot point.

So for now I will continue to motor about with my hub drives, looking forward to a possible day when a better solution presents itself. One that fits my needs without any deal braking compromises required.

Did you look at the revel propulsion?

 

[rocketman58]

Did you look at the revel propulsion?

I took a look, but data is limited. I could find no information on Q factor, it only takes a 36w battery, there is no throttle option.

 

[maiz]

I took a look, but data is limited. I could find no information on Q factor, it only takes a 36w battery, there is no throttle option.

From PaulD, revel developer and member on endless "Q-factor is about 180mm for a 73mm BB. Q-factor for a 68mm BB is about 175mm. Offset is 3mm towards the driveside. If you use an extra pedal washer or two on the non-drive side that would be pretty close to symmetrical. More info is here: Mid drive kit — Revel Propulsion Ebike Mid Drive Conversion Kits"

Also the lightest motor from bikee has good q from my understanding. And the bikeOn allows you to keep your own cranks.

Each has its own limitations but q-factor is starting to be addressed in newer offerings

 

[rocketman58]

All look to have a lower Q. But it looks like Propulsion is sold out, Lightest has a max chinrings of 43 (I need a 48T minimum), and BikeOn will not work on a trike like mine. thank you for trying to help though.

 

[rocketman58]

OK, now that I had my rant and got this out of my system, I still have to figure out what to do.

After todays group ride I realize that my hub motor (and even more so myself), are no longer sufficient for keeping up with the rest of my trike group. I need more power than the 45Nm the motor puts out and I need a better connection between my effort and the hub motor's output. Of course something like a torque sensing mid drive motor would probably do the job. I guess the search continues...