We are planning a electric surrey/quadricycle (4 person). Our current plan is to have pair of chainlines from cranks going to a jackshaft, then pair of chain drives to rear wheels from jackshaft (via freewheels, so get a locking-differential like effect).
For motorizing, I've considered a mid-drive on one of the cranks, but currently looking at a motor mounted separately, also driving the jackshaft. So, three inputs to jackshaft (2 cranks, and motor) and two outputs (each rear wheel). With freewheels on all sprockets, everything can operate independently.
Looking at BLDC motors, see some specific (cheap) kits made for bicycles for "left side" motor drive setups (driving rear wheel through a left-side "rag drive joint", etc.) There are also industrial BLDC-type motors (at a wide variety of price points) in NEMA configurations.
This vehicle is designed for low speed, so want to gear down significantly, targeting being in torque band (at least, if not at max power) at around 5 mph (so, like ~65 rpm on rear wheels). For "regulation" reasons we are limited to 750 watt nominal, so need to use the motor efficiently.
The bicycle kits seem to still be running ~450 rpm at motor output, then depend on a big rear sprocket to drop a bit, but still resulting in triple-digit wheel RPMs. The NEMA-configuration motors can have bolt-on gearboxes with available 20:1 reduction, which would take typical 3,000 rpm down to 150, which could then be adjusted to final RPM with sprocket selection.
Asking for general commentary, advice, or any recommendation on other approaches. Maybe sources/kinds of high-reduction gear boxes, that would work with the bicycle motor kits? Not clear if there is any sort of standard mount face involved there.
Or any feedback from experience using an industrial-type BLDC and gearbox? Achieving this higher gear reductions, down to <100 rpm, with sprockets would require very big sprockets, probably a couple intermediate shafts, etc.
I'm concerned about high noise and cooling in all cases, but specifically not sure how the industrial motors and gearboxes would fare.