Motors: 4 AM RedlineA (2 per side)
Gearing: 2 DeCIMates running 3.75:1 coupled into 2 ToughBox Nanos with 12.75:1 gear sets. For an overall reduction of 47.83:1 (1 DeCIMate + Nano per side)
Roller Chain: 1:1 stage connecting the Toughboxes to the drive roller
Drive Roller: 6" Laminated Plywood
Powertrain New Output
Driving Torque: 49.74 ft-lbs @ axle
Max Torque (stall): 99.49 ft-lbs @ axle
Motors: 2 CIM (1 per side)
Gearing: 2 ToughBox Nanos running 12.75:1 gear sets. (1 per side)
Roller Chain: 1:1 stage connecting the Toughboxes to the drive roller
Drive Roller: 6" Laminated Plywood
Powertrain Original Output
Driving Torque: 22.44 ft-lbs @ axle
Max Torque (stall): 44.88 ft-lbs @ axle
Design Process:
The bright green line is the original powertrain configuration. This is the only option I included with the CIM motor. Red, blue, purple were all configured with AM Redline As. Orange line is the brushless NEO motor. One criteria during my evaluation of the configurations was that I didn't want to go much slower, it would be preferable to gain a little speed.
The red configuration is a little faster than the original setup in the tank. Blue was my first choice based on the analysis; however, other factors came into play and changed my plans. Beyond the speed/acceleration the current draw was a major concern, hence the graph below.
An important point about this graph, the calculated current comes from the current draw if the drive train were driving up a vertical incline. While this isn't the true current drawn to move the robot; it does provide a metric to compare the current draws. The blue line was my original pick during the redesign; however, the gearboxes for the red line were on sale. Current draw is a little lower than blue, and only about half of the current of the current configuration. The NEO setup still draws a huge amount of current, and would have required purchasing new motor controllers. Purple is a variation of the DeCIMate + Nano combo, using 10.71 gears in the Nano instead of the 12.75 set that is used in the red configuration. The red configuration ultimately won out, and this final graph sealed the deal for me. Who doesn't love more power in their tank?
In summary, the red configuration had slightly better speed than the original, much lower current draw, and twice as much pushing power. There were two factors that led to blue falling out of favor, it would have been slightly more expensive, and the form factor was not lending itself to being a drop in replacement for the current CIMs. NEOs would have required purchasing motors and motor controllers which made them prohibitively expensive while not significantly lowering the current draw, and only for a gain of roughly 2 feet per second. The purple option is still on the table, as it would be an inexpensive/free change if I find I still need a touch more speed. However, it will require some significant deconstruction to make the gear swap so I am reluctant to do that.
