Originally Posted by
212man
I'm being a bit thick. Can you elaborate? I know what the quill drive is, but don't get how the load required to recharge the battery would be so high - the high load occurs during the engine start
Yes, but when starting the first engine it's generator isn't immediately online - the first high load is taken by the battery. As soon as the first engine's generator comes on line it will try to replenish the battery. If the second engine is then set to crank, the first generator may get overloaded because it's replenishing the battery
and supplying a load to crank the engine.
The earlier Squirrels reputedly had a delicate quill drive to their starter/gennies. The generator switch wasn't selected on until after engine start was complete because in starter mode the quill drive is driving the engine. In generator mode the quill drive has a reverse load, i.e. the engine is driving the generator. The critical part was the sudden reverse load/torsion, caused by driving to being driven.