Thanks Wesley -- good point that not everyone wants the 'budget' alternative as you do give up something. I hadn't previously done exacting measurements.
What have your measurements indicated for typical stock motors? They spec out at 1300kV (15700/12), not 1400 -- but that's assuming the Johnson 683LG-001 is really the model being used here. The 8514 Banebots motor is 19500 RPM @ 18V, which is 1080 kV. So the Nichibo would seem to split the difference. I don't know how often the manufacturer specs end up being "close" and how often they're effectively made up. These seemed to be reasonable/close, but "eyeballing" the vehicle speed is difficult, and at this point none of them are stock enough to really compare directly very easily.
I'm curious whether you got the flat-nose 775-7013F (with large vents) or the cone-nosed ones (with smaller vents). I got one shipment of the flat-nose ones first; my second shipment was cone-nosed ones, and the third order was all flat-nosed. The cone-nosed ones have a lower no-load current draw (1.65A vs. ~2.2A for the flat-nose). I don't have a measurement methodology that will directly measure winding resistance accurately enough to tell the difference, and didn't have one that isn't installed somewhere at the moment, or I could have added it to my experiment.
Speaking of... I decided I'd try to measure a few. I don't have any 'official' motor tester, so I came up with something else that should be quite accurate (+/- 2%) . I used a brand new 15-16-17T gearbox and a few different motors. I used a clear indicator on the output gear and took 30fps video (25-30s of runtime), extracted exactly 20s (600 frames) of it, and counted how many revolutions the indicator made. I can do this frame-by-frame and get within ~1/5 of a revolution without a lot of extra focus. I also measured voltage at the motor and current from the supply (I was using an XBOX 360 12A 12V supply).
Those measurements do indicate the 7013F is slower -- the two new ones I tested are about 5% slower than spec -- making them 6-7% slower than stock. I did get 1250kV, rather than 1200. Sample-to-sample consistency is about what I'd expect, though I expect even more variation if I did 10 of the 7013F motors.
The stock FP ones (from brand-new gearboxes) were basically within expected tolerances (1300 +/- a few %), and the used one -- from a Craigslist F150 that had gone through at least one set of tires -- was also spot-on. The (used) Mabuchi 8514 was noticeably faster than spec.
I was glad to see the KC3SFN-8021F Jameco special ($2.50 each) landed right on spec at 23000 RPM, which backs up my original measurements (done in a similar fashion, but in-car using marks on the wheels with it off the ground), which were also taken with the Corvette motor at that time and I'd estimated a 15-20% speed increase (15% measured here) between the two.
Generally the no-load current I saw with the motor standalone (eg. not attached to the gearbox) is about 10% lower. The drag from the gearbox really isn't too bad, and that also indicates that the motor is spinning [u]very [/u]close to its "free" RPM (current draw will linearly ramp to the stall value as RPM goes to 0). Put another way, the 7013F I measured at 2.2A free, and 2.4A here, with the gearbox attached. The 200mA increase can be used to infer the RPM difference between gearbox attached (extra friction/load) vs free. Using the 66A stall specification, we calculate it's going to at about 99.7% of the free RPM (1 - 0.2A / 66A stall). That's about 50RPM (which I can't measure
F-150 - 24-36V with homebrew 100A variable-speed motor controller, 4x 775 motors (no, it's NOT all-wheel-drive--look HERE
for more details!)
Pink Rocket Princess Mustang - 15mph, 36V, 4x 775 motors, homebrew PWM controller rev 2....
Hurricane - 24V w/50A step-down controller, 775 motors