North British 0-4-0DH: Coronation
|Weight||33tons (in working order)|
|Power Unit||Paxman 6 cylinder in line, 6RPH Mk1 (turbocharged by Brown Boveri)|
|Rating||302bhp at 1250rpm|
The North British Locomotive Company were a prolific loco builder that were sadly rather less successful with many of their diesel locos, even though an early post-war entrant. Signing a licence-build agreement with both Voith (transmissions) and MAN (engines), they aimed to build almost all the locomotive “in house”, but the generally held view seems to be that they attempted to manufacture with the machinery (and thus the accuracy) applicable to steam locomotion rather than the standards required for internal combustion.
Their first product, using a German-built Voith and a UK Paxman 6RPH engine, was 'Coronation'; built for Shelton steelworks. Preserved initially at Foxfield in 1986, it passed through other hands before being bought by Andrew from the East Kent Railway and taken initially to Peak Rail (where photographed- above in 2006 and right in 2013). British Railways trialled two batches of NB 0-4-0DHs under the modernisation plan, and the first batch, like 'Coronation' are known as "piano backs" due to the bulge of the rear cab sheet. BR did not find the locos satisfactory, although many NB 0-4-0DHs and 0-6-0DHs were bought by coal and steel industries in the UK, and NB exported up to 0-8-0DH versions.
As a sign of its age (it is the oldest s.g. diesel hydraulic in the country) the first problem encountered after its initial acquisition in 2004 was that the fabricated header tank on the radiator had rusted through from the inside. Since the radiator is in fact 3 seperate coolers (the outward facing matrices are for engine coolant, whereas the internal matrices are split between transmission and engine oils) designing and manufacturing a replacement, using laser cut components, was not a simple job and had to be completely fluid tight, to prevent any cross-contamination. Another quirk in the design was that the fuel tank (located in front of the cab and up to the cab roof) featured a depressed area in which the filler cap was located, so as not to infringe the load gauge. However, being depressed it collected rainwater, which was prone to seeping into the tank through the filler seals. The 6 cylinder Paxman engine is an oddity in itself - Paxman developed the V12 RPH series as a submarine prime mover in the '40s. After the war, the quickest way to produce a lower horsepower version at minimum (development) cost was by converting the V12 into a straight inclined 6, i.e. blanking off one bank. Thus opening casing doors on the left hand side reveals nothing but a set of cylinder heads, whilst the right hand side has sufficient space for 2 or 3 people to climb inside. A Brown Boveri turbocharger is mounted to the front bulkhead.
After rectifying the cooler group, initial test running indicated that the transmission was only operating in one range, but this subsequently changed to no range! The controlling valve assembly (known to be affected by condensation when left for long periods) needed to be lifted out and overhauled, but other projects had precedence. For various reasons, Andrew transferred the loco to Elsecar with the expectation, that, nearer to home, he would be able to give it more attention.
Unfortunately, owing to the unexpected decision of the Elsecar Heritage Railway company board in August 2010, Andrew was requested to remove the locomotive and regretfully saw no option other than to put it up for sale. It left Elsecar on the 13th September 2010, having returned to its first owner in preservation and its old home on the Foxfield Railway. Nevertheless, Andrew remained in close contact with the owner and when it was found that the engine was in far worse condition than first thought (possibly the result of engine works carried out before Andrew bought it) and other circumstances, he was in a position to re-aquire the loco as a long term restoration project. At the same time, the East Anglian Transport Museum near Lowestoft were looking to get rid of their large generator set (used for powering trolley-buses before a suitable mains supply was provided) and this happened to have the quite rare Paxman 6RPH Mk1 as its prime mover. After being removed the from its building, the generator set came north to Rowsley during February 2013.
Coronation returned to the collection on the 17th May 2013, being transferred from Foxfield to Rowsley, where in due course the replacement 6RPH will be installed. In view of its historic significance, it is not expected to be a regular performer.