Routemaster - pre-select
 

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

The driver operates the gearchange by the selection of the gear required on a quadrant similar to an auto box selector but marked...... R (reverse) N (neutral) 1 2 3 4

The basic idea is FIRST you move the gear lever to the next desired gear, and THEN when you wish to change you operate the pedal.

To start off from stationary first (second in some cases) is selected and the change gear pedal depressed. As soon as the change gear pedal has been released the next gear can be selected.

With the engine speed increased -

The centrifugal clutch bites by means of bob weights which fly out and cause pressure plates to close on twin clutch plates..

A fluid flywheel acheives this by the transfer of fluid to the outside or periphery of the flywheel.

http://en.wikipedia.org/wiki/Presele...x#Use_in_buses

I wonder what happened to:- http://en.wikipedia.org/wiki/Self-Changing_Gears ?
I believe that Lucas/CAV had a system too (maybe they manufactured the hand-control lever and actuators?).

Looks interesting:- http://books.google.co.uk/books?id=ZLJvEcZweroC

I once asked a local driver about this and he said "You can select any gear you want, anyone you want, but it won't go into it untill you depress the clutch". He selected all the gears in no particular order to demonstrate this to me on a journey of about a mile or so. Nothing happened cos he didn't depress the clutch.

Info on the Routemaster -

http://www.routemaster.org.uk/faq_fandf.html

Thank you sir, that is exactly the kind of explanation I needed. I now fully understand what the driver has to do as well as the mechanical processes involved.

Correction
 

The Routemaster never had a pre-selector gearbox and certainly no clutch or operating pedal. The RM had a fully automatic gearbox which operated in auto when the selector lever on the steering column was in 4th gear. It was possible to override the auto by using the gear selector to select a lower gear and reverse. On some buses notably the Green Line Rms the auto was de-activated and gear selection weas necessary, this was called semi-automatic mode. Pre-selection geraboxes were fitted on the RT family and required the operation of a pedal on the left to operate into the selected gear. The gear selector could then be moved to the anticipated next gear position without changing the gear.

I was employed by London Transport (The Board) driving Routemasters on the No.9 route from Mortlake Garage to Liverpool Street. High Bay Man explains it very well that the Routemaster didn’t have a pre select gearbox; that belonged to the RT. The RMs automatic gearbox was a dream. You could move off in first gear by selecting first gear or second by selecting second gear but third gear would not operate under 15 mph and fourth gear was the automatic position which automatically moved off in second gear. Happy days.