Again, I just want to thank you profusely for giving me(us) the opportunity to take a closer look at this all before it arrives and for offering your opinion of same.
I've only seen differentials and gearboxes on cars, and the one trike I looked at was pedal powered from the 70's or 80's.
There's also IGH, pinion gear drive trains and belt drives to think about.
An IGH is basically a gearbox that could be adapted to the Quad somehow?
The advantage of a mid-drive motor is that uses the gearing of the e-bike (cassette, free-wheel, IGH, pinion) to keep the motors rpm in the sweet spot.
On a regular hub drive, if you're going up a hill that's too steep, you will slow to a crawl or maybe even stall.
If your hub drive slows to a crawl, you still have 750 Watts going into the motor, but almost all of it gets turned into heat in the motor.
A hub motor has a speed limit too, and stops putting out power/torque after it gets to a certain speed/rpm.
A mid-drive let's you pick a lower gear to keep the motor spun up faster where it's more efficient, or you pick a higher gear to slow down the motor so it can keep helping.
That quad is half way there with it's mid-drive setup, but it only has one gear.
There's got to be something that can be done using available parts to add gearing to what you've got.
That 750 Watt motor should be plenty of power and torque if you can run it through some sort of gearing.
This is all just speculation on my part and I have no idea what is available or what would fit on your Quad.
Your Quad looks like it's half way towards being a true mid drive motor.
It just needs some gears between the motor and wheel.
A Grin motor alone won't change anything whether you mount it in the middle, or in one or both wheels.
It is still a single speed hub motor.
I think gearing is your answer.
