20hp

Rolls-Royce 20hp

This first small Rolls-Royce car became an instant success and is easily distinguished by the horizontal radiator shutters on all but last few produced. It had a 6 cylinder 3 litre engine with a monobloc cast iron cylinder block and crankcase, and detachable cylinder head. It was better suited to lighter coachwork than the Silver Ghost and later Phantoms.

Production numbers
2940
Year
1922 - 1929
Engine
6 cylinder monobloc with detachable cast iron head. Capacity 3127cc. Overhead pushrod operated valves. 2-part aluminium crankcase. 7-bearing crankshaft with vibration damper. Pressure fed lubrication with relief valve feeding rocker shaft and timing gears. Oil capacity 10 pints.
Ignition
Coil with standby magneto standard from 1924. Semi-automatic timing advance.
Cooling system
Engine driven pump and fan. Horizontal thermostatic radiator shutters.
Carburation
2-jet type with starting carburettor and automatic air valve.
Fuel system
Rear mounted 14 gallon tank with Autovac. Direct-acting gauge on tank. 2 gallons reserve from 1928.
Transmission
Gearbox in unit with engine. 3-speed with centre gearchange. 4-speed with right hand gearchange from 1925. Singe dry plate clutch. Open drive propeller shaft.
Suspension
Semi-elliptic leaf springs front and rear. Friction shock dampers, hydraulic from 1926 front, 1928 rear.
Brakes
Initially rear wheel only, internal expanding drum, separate independent shoes for foot and hand brakes. Front wheel brakes from 1925 with mechanical servo motor driven from the gearbox.
Steering
Worm and nut.
Chassis lubrication
Oil gun. Part centralised lubrication system from 1929.

The 20hp chassis series A – E are not clearly defined in the Technical Data published by Rolls-Royce. If you need to find out the chassis series of an early 20hp chassis please let us know.