Celebrating the products of AEC Southall Ltd, most famous as builder of London's buses.

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PostPosted: Tue Apr 08, 2014 3:24 pm 

Joined: Tue Jan 24, 2012 4:44 pm
Posts: 171
Leyland O:900 Albion EN901

Facts from Milligan and Adams Albion of Scotstoun ©Albion Vehicle Preservation Trust 1999, conjecture, mainly about British Rail policy, from me.

Leyland had intially planned this engine to be wet-liner, but Scotstoun were tasked with production engineering for it from 1953 with dry liners; basic dimensions were settled at Leyland but Albion developed the block, liners and head gaskets. It was produced at Scotstoun.

A similarly-sized Büssing engine was purchased from West Germany in 1954 as part of the development process and used in a works mule HD23 (an MoD spec 6x4 lorry) in order to test various transmissions at the higher torque and power-outputs the new engine would produce. The EN901 was launched in 1956.

Albion only used the engine in one home-grown model, the 1958 HD175 Royal Scot dirt-road 6x4 bus for South African Railways. Like the Büssing this was a horizontally oriented (EN901H) engine. (Büssing built all its engines to this layout.) Leyland Motors used vertical versions of it in the Super Buffalo and Super Hippo, whist Scammell made it availble in the Super Constructor, although it seems most customers for this chose the Rolls-Royce C-series alternative. The major application for the EN901 on the home market was in the EN901H6 and developments used in BUT/British Railways “cross-country” DMUs at ratings of 200-230bhp. I am aware of problems later in life with these engines, notably in the Trans-Pennine sets, which had the higher rating and used one motor(check?) per carriage in a six-car set, but these were said to be caused by problems with the cooling group, notably (Atlantean maintenance staff will note) failures of radiator mounting brackets. It was also used in a marinised version marketed by Ajax Marine engines of Cheshire.

The early withdrawal by British Rail of the Albion-engined DMUs compared to those with Leyland 680 and AEC 11.3 engines was based on a lot of the cross-country work being moved to loco-haulage using surplus Type 2, 3 and 4 Locomotives hauling mark one and two carriages also surplus; notably also the use of driving van trailers with locomotives from Glasgow Queen Street to Edinburgh Waverley. The Albion–powered types had by the natue of their diagrams covered more miles, and were a small class, notably Leyland 600 and AEC 9.6 powered DMUs had been withdrawn earlier.
The continuation of Rolls-Royce engines and Twin-Disc transmission on Bedford-St Pancras was a horses for courses change of decision: based on their accelerative properties and union resistance to the driver-only EMUs due to replace them: orignally all R-R powered DMUs were to have been withdrawn at the same time as the Albions.

The Sprinter and Super-Sprinter types used to replace the 1950s and 1960s DMUs in British Rail service used either the Cummins 14 Litre or similarly sized Perkins units of Rolls-Royce origin, in both cases coupled to Voith Hydrualic transmission, these or their post-privatisation counterparts returned secondary long-distance routes to DMU operation.

The EN250 and the rest of that family of truncated Leyland Engines had acknowledged weaknesses and Albion designers were unhappy with four studs to secure the cylinder head gaskets; Albion had previously used six; development of this series of engines from concept drawings to production was in less than two years whilst the series of four-cylinder engines that culminated in the EN335 had ten years in development (although that did include World War Two when devlopment work on non-military engineering was curtailed).

It was early failures with the horizontal Claymore and Nimbus engines that sealed the fate of the model range, although some operators got good service from the Nimbus, particularly in the type of low–demand rural bus service for which it was designed. The Nimbus’ most vocal detractor, Geoffrey Hillditch encountered his first batch used on Great Yarmouth driver-only work interworking with 65 seat crew-operated double deckers, and although Great Yarmouth’s territory was flat, these Nimbii often carried standing loads; at Halifax the terrain was also against their Nimbus fleet, and although meant to be confined to light-duty routes traffic requirements often led them onto heavier services; one went to Harvey of Mousehole, Cornwall, where it remained operational on a rural route requiring a narrow manouvreable and short bus into the 1980s.
Bristol Commercial Vehicles ‘chinese copy’ of the Nimbus, the SU, differed only in minor mechanical aspects and coupled to an ECW body served very well on this type of route, many working in the West Country with the type’s sponsor Western (and Southern) National for much longer than such a lightweight could be expected to; some also having an after life in Guernsey well into the 1980s. Use of the type on Royal Blue express duplication (some got as far as Mansfield) was not such a good idea however.

Mandatory power to weight ratios in 1970s C&U regulations got rid of such ultra-lightweight vehicles and I feel sure drivers and passengers are better served, but it’s interesting to note that the next generation of diesel-mechanical and diesel-hydrualic double deckers will use four-cylinder engines of about five litres capacity, the distinction as Wrights, for one, envisage using an automated constant mesh transmission rather than a torque-converter based transmission unit, about 250 bhp is considered a low–rating from these Euro 6 engines, they need apparently to work at high states of tune to burn off the particulates and sufficently oxidise the nitrogen…

Automated constant mesh is common in haulage these days but it scares Bus and Coach operators in the UK because of the dire reliability of early examples from Avon Maxwell, Scania and Volvo in the 1980s and 1990s, the poor availability and lack of economy of Northumbria’s two Volvo Expressliners so fitted compared to manual and full-auto Bova Futuras on the Newcastle-London run was used in evidence to the competition authorities in the UK when National Express tried to enforce the EGS Volvo/ Plaxton Expressliner as its only coach type. No official decision was ever taken by the august competition police but Northumbria got more Bovas with Natioanl Express blessing and the two Expressliner Volvos moved to Go-Ahead Northern when less than a year old. I recal that by then National Express no longer ‘required’ but instead ‘strongly recommended’ the Volvo-Plaxton combination. When Volvo moved to the side-radiator version of the B10M, the EGS automated gearbox was also dropped for bus and coach applications in the UK, ZF manual and increasingly automatic transmission, taking over.

Incidentally the last original-shape Bova Futuras were delivered to a British operator in February this year; as the type was announced in 1983, that’s a 30 year run for a coach which is unchanged in outline; coaches previously considered a fashion item destined to last a handful of seasons.

Best Wishes

Stephen Allcroft


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