- Mon Aug 28, 2017 11:04 am
Several things will kill gearboxes. One problem I had was that that heat from the 550 motor at 18V+ would end up transferring into the 1st gear and gearbox, soften the plastic, and allow the pinion shaft to spin or strip teeth off the edge.
Running a 775-motor keeps the temperatures down. But you're right, it's going to push more torque. Even if you get a relatively tame 775 motor (such as the Nichibo 775-7013F), it's still 33% more torque. Most people run 'hotter' 775 motors; if you get something like the Banebots motor and you're running w/o an ESC or other current limiter, it'll be 2.5x the stock torque and will break things for sure. An ESC or other current limiter will help reduce strain on the gearbox by limiting the peak current (which in turn limits the peak torque), and should be considered a hard requirement if you're going to put in a motor like that.
You can reduce the overall torque applied to the gearbox by getting a gearbox (and pinion gear) with a higher tooth count, eg. go from a 17T (I think the Escalade stock) to a 22T. The higher tooth count means less force at the interface between the two gears. But you have to buy a new gearbox case (can be empty -- the gears just swap over) for that.
For instance, iIf you go with the 'more-like-stock 775-7013F motor, with a 22T gearbox & gear, that setup would help get rid of some of the heat and you'd get a 30% speed boost (vs. 17T stock) and the same torque as the stock motor -- if running at 12V. When you push it to 18V it's obviously going to be 50% more of both (torque & speed) again. Total cost is going to be $20-25 (two empty gearboxes), $16 (4 motors), $16 (two pinions), and some effort -- so $60-70 for that changeover.
Is it going to be reliable? At 12V, everything would probably last a very long time. At 18V, the motor will probably run forever. I'm not as certain on the gearbox at that voltage, as I've broken a few various gears even with fairly 'wimpy' current limiting -- when you're running 8-9mph and the kids are spinning the wheels on uneven surfaces, things sometimes break.
BTW, kudos on the doing the brake mod -- that's a huge help on reliability.
F-150 - 24-36V with homebrew 100A variable-speed motor controller, 4x 775 motors (NOT all-wheel-drive), and fading color
Hurricane - 24V w/50A step-down controller, Mabuchi 8514 motors
Princess Mustang - 12V w/23000 RPM 550 motor and 23T gears