The same way as ayn e-bike with a working chain (only far more reliable!), you get home on muscle power....no chain no fuss? what happens if your battery is flat?
Correctly cut straight gears, waste very little power, which is why they are used often in car gearboxes for racing and rallying, the only negatives being (with high reving cars), that they are "LOUD".... But I doubt if that will be much of a problem with muscle power assisted by a motor!So the bike is shaft drive rather than chain. Back in the eighties I had a Moto Guzzi shaft drive motorbike. Very nice and no cain to lube or adjust during service. But chains transfer power more efficiently than gears. So energy will be lost by the gears needed to transfer th drive through 90° to the shaft and then through another 90° to the wheel. Also the gear assemblies are likely to cost and weigh more.
I wonder if you could make a chisel out of that stuffBulk Metallic Glass