pic: 3CIM Ball Shifter

[apalrd]

We didn't want a 4 speed, we wanted a 3 speed. We wanted a fast and very fast gear, like our current design goals for high and low, but we had less power, so we needed a low low for pushing (remember this is back before bumpers) and couldn't get away with the fast-low we like now.

But, with the resources we had, it was easier to build a 4 speed than a 3 speed (since we end up with 2 2-speeds in series). The shift patterns are then low/low,low/high,high/low,high/high, with a different ratio spread of each of the 2-speeds in series. But the 2-3 shift (going from low/high to high/low) requires a double-swap shift which is just plain nasty to execute synchronously between two shifters while under power. A possible solution is to run it like a 3-speed with two options for 2nd gear, and essentially jump-shift past the 2-3 shift. This would add complexity to the shift scheduler, although more than 2 speeds already adds complexity to our shift scheduler.

A ball shifter design can do any number of speeds just by adding more gear pairs to the shafts, so it's possible to do a 3-speed instead of a 4-speed, but it's much harder to manufacture than the dual 2-speed with andymark parts or dual 2-speed mesh shifter design (or even the dual 2-speed ball shifter).

So 4 speeds was easier to build, but the 2-3 shift is bad.