Paxman Ventura

The Paxman Ventura is an internal combustion diesel engine for railway locomotives, built by Davey, Paxman & Co.

Paxman Ventura
Overview
ManufacturerDavey, Paxman & Co
DesignerGeoffrey Bone[1]
Also calledYJ
Production1960 (1960)–1992 (1992)[2]
Layout
Configuration60° vee: V6, V8, V12 or V16[3]
DisplacementV6: 39.42 litres (2,410 cu in)
V8: 52.56 litres (3,210 cu in)
V12: 78.84 litres (4,810 cu in)
V16: 105.12 litres (6,410 cu in)
Cylinder bore7.75 inches (197 mm)[1][2]
Piston stroke8.50 inches (216 mm)[1][2]
Cylinder block materialcast iron
Cylinder head materialaluminium alloy
ValvetrainOHV, 4 per cylinder[1]
Compression ratio13:1
Combustion
Operating principlefour-stroke turbo-charged high-speed diesel[3]
Fuel system2x CAV monobloc fuel injection pump (4x on V16), 11,500 psi (790 bar) (total) direct injection[1]
Fuel typediesel
Output
Power outputV12: 1,200–1,500 brake horsepower (890–1,120 kW; 1,200–1,500 PS) at 1,500 rpm
V16: 1,600–1,870 brake horsepower (1,190–1,390 kW; 1,620–1,900 PS) at 1,500 rpm
Chronology
PredecessorPaxman YH, direct injection medium-speed diesel
SuccessorPaxman Valenta

The type YJ or Ventura was developed in the mid-1950s as Davey, Paxman's first high-speed diesel engine.[4] With a view to the forthcoming modernisation and dieselisation of British Railways (BR), it was intended as a successor to Paxman's existing medium-speed engine, the direct injection YH.[5] High-speed engines offered higher power-to-weight ratios, which in turn allowed locomotives to have a lower axle loading and greater route availability. The YJ was to have a weight of less than four tons for a 1,200 horsepower (890 kilowatts; 1,200 metric horsepower) V12, with versions of V6, V8, V12, and V16 configurations.[1][4] Their construction and reliable use though required more sophisticated manufacture than previously, with better metallurgy and balancing of the moving parts for faster running and a stiffer crankcase to avoid vibration.

A total of 1098 engines were built by Paxman in Colchester, England (147 V6, 190 V8, 426 V12, and 335 V16); a further 37 were built under licence in Italy by Motori Breda of Milan for the D.343 Class locomotives of the Italian State Railways.[2]

Description

Like its medium-speed predecessor the Paxman YH, the Ventura is a 60° V engine with 6, 8, 12 or 16 cylinders.[2] The engines are similar in many details, and broadly similar in capacity and power; their main differences are in their operating speed, the improvements necessary to achieve this, and the Ventura's resulting lighter weight.

The crankcase / cylinder block for MOD vessels were fabricated from steel by welding a mixture of steel castings and plate-work. This gives a more rigid structure than the YH's cast light alloy cylinder block. The aluminium alloy bed-frame of the YH and ZH engines had previously given trouble with cracking, and had to be replaced in the Class 17 with a cast iron frame, at Paxman's expense.[6] Both engines have individual aluminium alloy cylinder heads for each cylinder. All other applications had cast iron crankcase / cylinder block.[5] Centrifugally cast iron wet cylinder liners are used with aluminium alloy pistons in both.[3] These pistons have three compression rings and two oil-control rings. The top ring is carried in a cast iron insert. The combustion chamber of this direct injection engine is a toroidal recess in the piston crown.[3]

The YJ engines were primarily developed for diesel electric locomotives (however Paxmans main design philosophy was maximum power for a given size and weight) and so their crankshafts have the unusual feature of an additional main bearing at the drive end, to help support the weight of the generator armature, where a single-bearing generator can be otherwise unsupported at one end.[3] Fork and blade connecting rods are used, with the inner rod running on the outside of a shared bearing sleeve.[3] There are four valves per cylinder, driven by pushrods and rockers from a single camshaft between the cylinder banks. The fuel injector is centrally mounted between the valves, and is supplied by a pair of inline CAV monobloc fuel injection pumps, one per bank (four injector pumps on V16).[3] The single turbocharger is carried above the engine, with its axis longitudinal.[1][3]

Smaller, single bank six- and eight-cylinder engines, the 6YJ and 8YJ, were derived from the V engine.[2]

More than twenty V16 engines (16YJC) were supplied to the Air Ministry, used to power 11 kilovolt (kV) generating sets for the Linesman early warning radar system used by the Royal Air Force. The first batch were installed at locations including RAF Neatishead, RAF Staxton Wold, and RAF Boot Hill. A second batch was installed at RAF West Drayton; this controlled not only the entire RAF radar system, but also controlled the civilian radar as used by Heathrow Airport air traffic control.[2]

Paxman licensed the Ventura design to ALCO, with a reciprocal agreement also permitting Paxman to build the popular ALCO 251.[4] As an indication of the high power / weight ratio of the Ventura, this was around three times that of the 251.[4]

Use

V6 engine – 6YJ
V8 engine – 8YJ
  • Royal Navy, 38 engines for Royal Navy frigates.[2]
  • Ceylon Government Railways, four engines.[2]
V12 engine – 12YJ
V16 engine – 16YJ

References

  1. Carr, Richard (28 September 2022). "Ventura (also known as the YJ)". PaxmanHistory.org.uk. Richard Carr's Paxman history pages. Retrieved 15 August 2023.
  2. Carr, Richard (29 October 2008). "Paxman Ventura (YJ) diesel engines". PaxmanHistory.org.uk. Richard Carr's Paxman history pages. Retrieved 15 August 2023.
  3. Bolton, William F. (1963). The Railwayman's Diesel Manual (4th ed.). pp. 79–80.
  4. Evans, R.K. (May 1964). "The Ventura – Paxman's high-speed engine". Modern Railways. pp. 328–329.
  5. Diesel Manual (1963), pp. 49–53.
  6. Carr, Richard (28 September 2022). "Paxman ZH". PaxmanHistory.org.uk. Richard Carr's Paxman history pages. Retrieved 15 August 2023.
  7. "New BR 650hp Type 1 Diesel-Hydraulic Locomotive". Modern Railways. August 1964. pp. 106–107.
  8. Marriott, Leo (1986). Type 22. London, England: Ian Allan. ISBN 0-7110-1593-7. OCLC 16806469.
  9. Carr, Richard. "Paxman Rail Traction Diesel Engines". PaxmanHistory.org.uk. Richard Carr's Paxman history pages.
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