[JamesPB]

Hello all, this is one of my first threads here, so apolgies if I'm on the wrong forum.

One of my younger brothers used to drive London AEC Routemasters a few years ago, specifically Nos 23 and 7 out of Westbourne Park.

Now one thing he has never been any good at is explaining mechanical engineering or technical things.
So he could never explain properly to me about the pre-select gearbox on the Routemaster.

So my question is this, what are the mechanical and physical driver processes that occur when using a pre-select gearbox?


Sorry for the basic newcomer question, but it's been bugging me for years

Thanks
James