When Rover was selected for production of Whittle’s designs in 1941 they set up their main jet factory at Barnoldswick, staffed primarily by various Power Jets personnel. Rover felt their own engineers were better at everything, and also set up a parallel effort at Waterloo Mill, Clitheroe. Here Adrian Lombard developed the W.2 into a production quality design, angering Whittle who was left out of the team. Lombard went on to become the Chief Engineer of the Aero Engine Division of Rolls-Royce for years to come.

After a short period Lombard decided to dispense with Whittle’s “reverse flow” design, and instead lay out the engine in a “straight-through” flow with the hot gas exiting directly onto the turbine instead of being piped forward as in Whittle’s version. This layout made the engine somewhat longer and required a redesign of the nacelles on the Meteor, but also made the gas flow simpler and thereby improved reliability. While work at Barnoldswick continued on what was now known as the W.2B/23, Lombard’s new design became the W.2B/26 centrifugal compressor turbojet engine.

By 1941 it was obvious to all that the arrangement was not working; Whittle was constantly frustrated by what he was seeing as Rover’s inability to deliver production-quality parts for a test engine, and became increasingly vocal about his complaints. Likewise Rover was losing interest in the project after the delays and constant harassment from Power Jets in the critical testing process stage, where testing new designs and materials to breaking point is vital. Earlier, in 1940, Stanley Hooker of Rolls-Royce had met with Whittle, and later introduced him to Rolls’ CEO, Ernest Hives. Rolls had a fully developed supercharger division, directed by Hooker, which was naturally suited to jet engine work. Hives agreed to supply key parts to help the project along. Eventually Spencer Wilks of Rover met with Hives and Hooker, and decided to trade the jet factory at Barnoldswick for Rolls’ Meteor tank engine factory in Nottingham. A handshake sealed the deal, turning Rolls-Royce into the powerhouse it remains to this day. Subsequent Rolls-Royce jet engines would be designated in an “RB” series, standing for Rolls Barnoldswick, the /26 Derwent becoming the RB.26.

Problems were soon ironed out, and the original /23 design was ready for flight by late 1943. This gave the team some breathing room, so they redesigned the /26’s inlets for increased air flow, and thus thrust. Adding improved fuel and oil systems, the newly named Derwent Mk.I entered production, the second Rolls-Royce jet engine to enter production, with 2,000 lbf (8.9 kN) of thrust. Mk.II, III and IV’s followed, peaking at 2,400 lbf (10.7 kN) of thrust. The Derwent was the primary engine of all the early Meteors with the exception of the small number of Welland-equipped models which were quickly removed from service. The Mk.II was also modified with an extra turbine stage driving a gearbox and, eventually, a five-bladed propeller, forming the first production turboprop engine, the Rolls-Royce RB.50 Trent.

The project was to be of the same maximum diameter, in order that it might be installed in standard Meteor nacelles, but it was to develop 2,000 lb thrust. Drawings were started in April 1943 and by July the new unit was ready for test. In November of that year it passed its 100-hr type-test at the full 2,000 lb rating and in April the following year it went through its first flight tests in a Meteor, with a Service rating of 1,800 lb and a weight of 920 lb.

The Derwent II gave a thrust of 2,200 lb, and the III was a special unit to provide suction for boundary-layer removal; the Derwent IV was rated at 2,400 lb thrust. The Derwent 5 was an entirely new engine-still of 43in diameter, but developing twice the thrust of the original Derwent I. It was, in effect, a scaled-down version of the Nene, and its development was motivated by the promise shown by the Nene and the knowledge that the Meteor could utilize thrust greatly in excess of the original estimates.

The basic Derwent design was also used to produce a larger 5,000 lbf (22.2 kN) thrust engine known as the Rolls-Royce Nene. Development of the Nene continued in a scaled-down version specifically for use on the Meteor, and to avoid the stigma of the earlier design, this was named the Derwent Mk.V. Several Derwents and Nenes were sold to the Soviet Union by the then Labour government, causing a major political row, as it was the most powerful production-turbojet in the world at the time. The Soviets promptly reverse engineered the Derwent V and produced their own unlicensed version, the Klimov RD-500. The Nene was reverse-engineered to form the populsion unit for the famous MiG-15 jet fighter. The Derwent Mk.V was also used on the Canadian Avro Jetliner, but this was never put into production.

On 7 November 1945, a Meteor powered by the Derwent V set a world air speed record of 606 mph (975 km/h) TAS.

An unusual application of the Derwent V was to propel the former paddle steamer Lucy Ashton. The 1888 ship had her steam machinery removed and replaced by four Derwents in 1950–1951. The purpose of this was to conduct research on the friction and drag produced by a ship hull in real life conditions. Jets were preferable to marine propellers or paddles as these would have created a disturbance in the water, and the force exerted by them was harder to measure. The four engines could propel the Lucy Ashton at a speed in excess of 15 knots (28 km/h; 17 mph).

The Derwent 5 was superseded by the Derwent 8 and 9. The 8 incorporated two outlets to feed compressor-air through piping to heater muffs on the exhaust unit; tappings were taken from these muffs to heat the cabin and the guns and/or camera. The 9 used the same method of heating, but had in addition larger combustion chamber-inter-connectors and high-energy ignition to give more consistent relighting in flight as well as to increase the altitude at which relighting was possible.

Experimental Derwents included the RD.9, which had a 15 per cent increase in mass flow, and the RD.10-a scaled-up version utilizing the rotating parts of the Nene. The RD.11 was another scaled-up development.

The body of a typical Derwent is built up on the compressor rear casing which, though immensely strong, is very light and is considered by Rolls-Royce to be a fine example of their foundry technique. On the front face are the diffuser ring, the front casing and front air intake, and the wheelcase. To the rear the main structure comprises the rear air intake, the cooling-air casing and the centre and’rear bearing-housings, which successively lead to the nozzle-box assembly. This last takes the gas flow from the combustion chambers and distributes it to the annulus of stationary nozzle-guide vanes; it also carries the auxiliary coolingair ducts leading from the region of the turbine disc and rear bearing housing.

Centrally runs the main rotating assembly, and disposed round the engine, between the compressor casing outlet elbows and the nozzle-box, are the nine combustion chambers. So carefully balanced is the rotating assembly that as much as a minute and a half elapses before it comes to rest after the engine is shut down, At maximum static thrust the characteristic double-sided impeller deals with 62 lb of air per second, with an efficiency of 80 per cent and a compression ratio of 4 : 1. For this task it needs about 8,000 h.p., which is transmitted from the turbine through the coupling. The impeller is 24in in diameter and has 29 vanes on each side. Guide vanes convert axial to radial flow.

Variants:
Derwent I – first production version. Straight-thru development of the trombone style W.2 configuration, with compressor and turbine upflowed by 25% to give 2000lbf (8.9 kN) static thrust
Derwent II – thrust increased to 2,200 lbf (9.8 kN)
Derwent III – experimental variant providing vacuum for wing boundary layer control
Derwent IV – thrust increased to 2,400 lbf (10.7 kN)
Derwent 5 – scaled-down version of the Rolls-Royce Nene developing 3,500 lbf (15.6 kN) of thrust
Derwent 8 – developed version giving 3,600 lbf (16.0 kN) of thrust

Applications:
Avro 707
Avro Canada C102 Jetliner
Fairey Delta 1
Fokker S.14 Machtrainer
Gloster Meteor
Nord 1601
FMA I.Ae. 27 Pulqui I

Specifications:

Derwent I
Type: Centrifugal compressor turbojet
Length: 84 in (2,133.6 mm),
Diameter: 43 in (1,092.2 mm)
Dry weight: 975 lb (442.3 kg),
Compressor: 1-stage double-sided centrifugal compressor
Combustors: 10 x can combustion chambers
Turbine: Single-stage axial
Fuel type: Kerosene (R.D.E.F./F/KER)
Oil system: pressure feed, dry sump with scavenge, cooling and filtration, oil grade 150 S.U. secs (32 cs) (Intavia 7106) at 38 °C (100 °F)
Maximum thrust: 2,000 lbf (8.90 kN) at 16,000 rpm at sea level
Overall pressure ratio: 3.9:1
Turbine inlet temperature: 1,560 °F (849 °C)
Specific fuel consumption: 1.17 lb/lbf/hr (119.25 kg/kN/hr)
Thrust-to-weight ratio: 2.04 lbf/lb (0.0199 kN/kg)
Military, static: 2,000 lbf (8.90 kN) at 16,600 rpm at sea level
Cruising, static: 1,550 lbf (6.89 kN) at 15,400 rpm at sea level
Idling, static: 120 lbf (0.53 kN) at 5,500 rpm at sea level

Derwent V
Type: Centrifugal compressor turbojet
Length: 88.5 in (2,247.9 mm)
Diameter: 43 in (1,092.2 mm)
Dry weight: 1,250 lb (567.0 kg)
Compressor: 1-stage double-sided centrifugal compressor
Combustors: 10 x can combustion chambers
Turbine: Single-stage axial
Fuel type: Kerosene (R.D.E.F./F/KER)
Oil system: pressure feed, dry sump with scavenge, cooling and filtration, oil grade 150 S.U. secs (32 cs) (Intavia 7106) at 38 °C (100 °F)
Maximum thrust: 4,000 lbf (17.79 kN) at 15,000 rpm at sea level
Overall pressure ratio: 3.9:1
Turbine inlet temperature: 1,560 °F (849 °C)
Specific fuel consumption: 1.02 1.28 lb/lbf/hr (103.97 kg/kN/hr)
Thrust-to-weight ratio: 3.226 1.724 lbf/lb (0.0316 kN/kg)
Military, static: 3,500 lbf (15.57 kN) at 14,600 rpm at sea level
Cruising, static: 3,000 lbf (13.34 kN) at 14,000 rpm at sea level
Idling, static: 120 lbf (0.53 kN) at 5,500 rpm at sea level

Derwent 8
Maximum thrust: 3,600 lb at 14,700 r.p.m
Specific fuel consumption: 1.01 lb/hr/Ib.