Before purchasing the expensive components, I made cardboard models for a fit check. This is the beloved technique called cardboard-aided design. A 3-D computer model would be more accurate, but it would have taken a long time to create, and I don’t think it would have given me any more confidence than placing physical models inside the actual frame.
The motor model revealed that the ME1003 would fit inside the frame, with the front sprocket nearly in the original location. Tolerances were tight all around, leaving no room for error in the motor mount.
The battery models confirmed that two stacks of modules (a stack of five and a stack of six) would fit inside the frame if the frame plates were designed properly.
This also allowed me to see how the stacks could best be oriented. The final design was very much like the fit check, except the smaller battery stack was placed below the larger stack.
Additionally, I made models of the SMP72400 controller and the AXE7245.
This revealed that the SPM would not fit either under the seat or inside the tank shell, but the AXE would. You can imagine how happy I was to discover this before ordering the wrong controller.
Next: Draw the Schematic