RLH Bus Information Centre

Technical Specification

Body

Provincial style Weymann design, built at Addlestone.

Passenger Capacity/ classification: L27/26R (= Low bridge, 27 upstairs seated, 26 downstairs seated, rear entrance). Total 53 seated, max 5 standing (downstairs only).

Electrical system: 24V double insulated. All functions from two main 12V batteries, dynamo charged only when engine revolutions above idling.

All interior (saloon) lights were by unshielded pearl tungsten 24 Volt bulbs down each side of the ceilings. These were rated at 12 Watts (although 20W can be used), and the bulbs were smaller upstairs (38mm diameter) compared to downstairs (50mm diameter) to cater for the reduced headroom and general circulating space of the former. The cap fittings were 2 pin bayonet OBC / BA22D. As of 2008, the 38mm diameter bulbs are still readily available in the UK.

Refer to the mechanical Diagrams for dimensional information

Differences between first and second batch

Modifications since new

September 1958 onwards - Direction indicator flashing lights ('trafficators') were retro-fitted. RLHs previously had no built-in way of indicating, not even semaphore arms, although the small sliding window in the cab door was referred to as the signalling window, for the driver's arm to indicate a right turn.

1950s- Rear offside corner lower panel on first batch made a separate unit, for easier replacement

October 1961 onwards - Country area buses only - one heater fitted in each saloon, on the front offside, controlled by switches under stairs. Fan blowing air past a small hot water radiator.

January 1964 onwards - Central area buses had saloon heaters fitted, as above.

1960s- Central area buses repainted with flake grey cant rail band instead of original cream


Mechanical

Generally similar to the mass produced RT (Regent III) design. Built by AEC at Southall, Middlesex

Majority of threads, style: British Standard Whitworth (BSW)

Engine Capacity: AEC Type A217 9.6 litres. Max torque 430 lb ft at 1000 rpm. Compression ratio 16:1. (Note 11.3 litre and other versions can be adapted). 115 b.h.p. at 1800 r.p.m.

Oil Capacity: 8 Imperial Gallons or 8+3/4 Imperial Gallons

Maximum governed speed: under load 1800 rpm, no load 2000 rpm

Dynamo (generator): Mounted on side of engine, creating a bulge in the bonnet side

Engine air filter: Oil bath, mounted on top of engine (this meant a high bonnet line was required).

Cylinders: 6 cylinder diesel. 120mm bore x 142mm stroke. Firing order 1, 5, 3, 6, 2, 4 (numbers from fan end)

Water capacity: 6.5 Imperial gallons

Fuel injection pump: Simms SPE6B80E (note CAV types can be used)

Fuel lift pump: CAV DFP1

Transmission: Fluid flywheel

Gearbox: Pre-selective, epicyclic (Wilson) 4 speed + reverse. Ratios: 1st gear 4.50:1, 2nd gear 2.53:1, 3rd gear 1.64:1, 4th gear 1:1, Reverse 6.90:1. Air operated.

Drive line: Worm differential at rear, ratio 5.17:1

Fuel tank capacity: 35/45 Imperial gallons

Ground clearance: 7 in (under rear axle worm casing)

Wheelbase: 16ft 4in

Chassis frame side members ran all the way to the back of the bus, underneath the platform entrance. This is different to the RT design where the members finished at the rear riser behind the rear wheels.

AEC's patent anti-roll stabilizer fitted

Front Wheel: x2 Tyres 9.00-20 Rim diameter 20in Rim width 6.00in Wheel offset 4.375in?
Rear Wheel: x4 Tyres 9.00-20 Rim diameter 20in Rim width 6.00in Wheel offset 5.375in

Brakes: Drum brakes on all wheels. Service brakes are air pressure operated. Hand brake is manual, on rear wheels only. No automatic adjuster is fitted for the shoes. The foundation brake has an S cam arrangement with a 15.5 inch diameter drum, which gave considerably more clearance between it and the wheel compared to the London RT's 16.75 inch diameter. This gave 2 advantages: thicker brake liners could be used (3/4 inch instead of 5/8 inch), and liner life was longer due to reduced temperature. In fact, six RTs were converted to the RLH arrangement as an experiment in the early 1950s, leading to a similar design used in the new Routemaster bus being developed.

front drawing

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