Of all the motors I've personally had, seen inside of or seen pics of inside, QSmotors are the best looking, in manufacturing quality and cleanliness and design.
Whether they are engineered the best *as motors* I don't know; I suspect they could be made to run more efficiently, but they do actually list that sort of thing in specs on their site for at least some of their motors (perhaps all, I haven't looked at everything).
They give a LOT more info on their motors than any other manufacturer of this type of motor, and actually have dyno plots for some of them (if you don't see one for a motor you want, ask, and they might have it).
From everything I've seen so far, they don't overrate their motors--if they say 2kw, they mean that it will take that all day long. Some companies are known for overrating their stuff, though more often that is on the vendors, not the manufacturers (most stuff you can't even tell who made it--QSmotors is pretty obviously proud to cast their logo into their covers and put their seal on them, etc. ).
As a negative example, MXUS's "3kw" motor is supposedly only good for that in a 20" wheel--say a 26" or a fatbike 29er, etc., would put more load on it than it could deal with at 3kw continous. And they're poorly made, based on the two I have here. I wouldn't buy an MXUS on purpose again.
Communication...from what I've seen in their sale thread and in some other threads, QSmotors do at least answer questions, where most don't, but it can sometimes require patience and repetition. No personal experience.
My one niggle with them (and everyone else) is they still do what "everyone else" does: they still pass the wires thru a hollowed axle, which weakens it, and complicates getting the wires out and around things like brake rotors, etc., and they're still using axle flats to transmit all the torque. There are better solutions that wouldn't cost much, if any, more (see Grin's GMAC for one example).
You *can* still break their motors (though probably not the axles if they didn't use the flats for torque transmission), like by taking a 3kW QS205-50h motor and using it at 22kW. :lol: (when the original owner did this to one I have here, the axles were sheared off at the shoulders, but that was more down to the flatted axles and the insufficient clamping they had in the frame they were mounted in--if they'd been using integrated torque arms transmitting via the larger-diameter shoulder or even outside that, it probably would have survived even the 7+ times it's rating power applications). Pics of that motor, inside and out, are in my SB Cruiser thread, if interested.
If I were ever to buy brand new motors for anything...it'd probably be QSmotors.
