I dunno if any of you frequent the forums at endless-sphere.com, but I've been an active link in the cross-country trek of one Justin Lemire-Elmore.
For those who aren't aware of the thread (and it's worth going over there to read), Justin departed Vancouver BC on an e-bike on August 2nd, and is currently only a few days away from completing his journey in Halifax, NS.
Justin has forgotten more than most of us will ever know about the theory and construction of BLDC hub motors, and has made his entire journey with a controller of his own design. When he was doing his test runs (on Vancouver Island) of his rig, he had chosen the Golden Motor BLDC as his first pick for the job of getting him across the country.
Why?
Because it actually has the best efficiency and least cogging torque of any of the motors he has tested. Unfortunately, it's poor at dissipating heat - he managed to kill a GM motor on a steady incline (over 1km) pulling his rig (which, with him on it, weighs nearly 300lbs). He went for a Crystalyte 5304 for the real deal, but still likes the GM motors... WITH caution...
Justin runs
www.ebikes.ca, and has had his mitts on many motors. While he was stopped over here (in Ontario!) we spoke about the fact that he's dropped GM products from his site... His reasons had less to do with the fact that the were a bad product (after all, he himself was going to use one to cross the country) as much as he'd come to the conclusion that they were NOT made in one factory.
That's the thing that made me sit up and take notice, and which is relevant to this thread.
He's selling Crystalyte - whose motors have as many idiocynrasies as GM, and which are almost entirely hand-made. However, they're CONSISTENT. He was telling me that he's opened enough Golden Motor product to be absolutely convinced that the innards come from different factories/suppliers. The differences he's seen are radical, and is why he dropped them.
The motors I have are brilliant, and I maintain they are a great value. Unfortunately, all of the recommendations I have made to others to buy GM are now tainted with the knowledge that their mileage may certainly vary.
I'm still happy with what I got for the dollars paid, and that's what counts. I'm considering ordering further units, as well.
Yup - communications with China suck. But you eventually DO get the product.