London Transport's New Advanced Coach
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AS the result of two years collaboration between London Transport and the Leyland Company, a new experimental Green Line coach is about to be placed in test service. In several .respects this vehicle embodies ideas which have been suggested in The Commercial Motor, for it has an underbody engine and a driver's seat some 18 ins. above the ordinary height, whilst the floor is level throughout, permitting all the seats to face to the front.
Use has been made of practically standard units. The engine, for instance, is a Leyland oiler turned over on to its side and merely modified, mainly, in respect of the cylinder heads, to allow for the new arrangements for exhaust, etc. The cylinder heads come close to the off side, and both they and the fuel pump are rendered readily accessible by lifting a panel. Air is drawn in through a grille at the front, the fan helping both the air flow and the ventilation of the body.
Hydraulic Clutch.
The design incorporates an hydraulic clutch and a Wilson gearbox. Other leading features are air-pressure brakes of Clayton design and an electro-pneumatic system for changing gear. The gear-control lever is situated immediately below the steering wheel and can be operated by a little finger, being of the preselective type. Operation of the pedals is rendered extremely easy, ,the pressure required being 40-50 lb., although this can be reduced if required as the triver becomes more accustomed to the slighter push necessary.
One of the most important characteristics, however, is the remarkable D54 range of vision afforded the driver. He may be termed as being situated half in and half out of the main part of the body, and can see the road to 'within 6 ins, of both front wheels, so that a child or animal can be observed at once.
There are two seats to the front of the near-side sliding door; these give exceptionally good view, whilst the total accommodation is also increased, by two. an air-pressure reaction valve coupled to the gear-engaging pedal. This valve normally admits a prearranged air pressure to the cylinder, thus holding the selected gear in engagement. When the pedal is depressed 4t closes the reaction valve, releases the air and allows the busbar to fall and permits a gear change in the usual manner.
Solenoids carried on the side cover of the gearbox replace the usual camshaft, and these are wired to the gear lever, the circuit including' an electropneumatic switch connected to the pedal. When the pedal is up and the air pressure on, the switch breaks the circuit, and no solenoid is energized.
Gears Preselected.
When the gear lever is moved to a gear position, the required circuit is preselected, and as the pedal is depressed air pressure is released and -the electro-pneumatic switch closes the circuit. The particular solenoid then becomes energized and pushes in the strut required. Immediately the pedal is released, the circuit is broken and the solenoid is de-energized, the strut is retained by the busbar and the gear becomes engaged in the usual Wilson manner.
Neutral is obtained by partial engagement of first and reverse speeds, and the solenoids for these are perrnamently spring loaded. When a gear is obtained these solenoids are energized and withdrawn while the change is made. The others are not Ioaded and merely push their struts as required. For reverse the first speed solenoid is withdrawn, the remainder not being energized. In the case of first gear the reverse solenoid is withdrawn.