Shrewsbury ‘Syphons’ – The Railway Hub | So Good News


Coleham depot is home to Network Rail’s small fleet of ERTMS-equipped Class 37s, now designated as Class 97/3s. Graeme Pickering finds out how these survivors of British Railways’ modernization era continue to perform impressively in a unique role.

A general view of the one-way shed at Coleham with No. 97302 Ffestiniog & Welsh Highland Railways/Rheilføyd Ffestiniog ac Eryri outside. The shed is south of Shrewsbury station on the west side of the line just before the Cambrian lines begin at Sutton Bridge Junction. All photos taken on 14th April by GRAEME PICKERING

More than six decades since the first examples entered service, English Electric Type 3s are still a relatively familiar sight on Britain’s rail network.

While they still earn their keep, the increasing availability of more modern traction has seen the role of what became known as the Class 37 become more peripheral, but for the three examples the redesigned Class 97/3 – based at Coleham depot, near Sutton Bridge Junction, south of Shrewsbury station – work continues to be intensive and varied.

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Their renaissance as Class 97s was linked to the scheme to introduce the European Rail Traffic Management System (ERTMS) with ETCS (European Train Control System) level 2 on the Cambrian lines, 135 miles of rail, from Sutton Bridge Junction via Welshpool and Machynlleth to Dovey Junction, branches south to Aberystwyth and north to Pwllheli. As the frequencies used for the former Radio Electronic Token Block (RETB) signaling were due to be handed back to the government within a few years, and the routes were seen as a relatively independent part of the network, it was decided to use them for an ERTMS pilot scheme of 95 million pounds. It became operational throughout March 2011.

As ETCS Level 2 uses an in-cab display to communicate signal instructions to the driver rather than relying on physical lineside equipment, 24 Machynlleth-based Class 158 diesel multiple units, which are used on passenger services on Cambrian lines, were fitted with the system. Four Class 37/0s were also modified, becoming Class 97/3s. Three of them, Nos. 97302 (ex-37170), 97303 (37178) and 97304 (37217) make up the fully equipped ERTMS fleet and act as pilot locomotives for the routes. The fourth – or numerically first – of the locomotives, No. 97301, was used to evaluate Hitachi ETCS equipment and is currently stored in siding at Loram UK in Derby, retained with a view to potentially returning it to service at some point .

“You have an engine, a generator, traction motors,” says Simon Metcalf, business delivery manager for Colas Railfreight, which operates and maintains Class 97/3s for Network Rail. “If you compare them to a Colas Class 70, it’s like the Starship Enterprise compared to Noah’s Ark, but they’re reliable, they’re robust and there’s nothing else. You can’t just go to the shelf and say ‘I want a new RA5 moves”. That’s all there is.”

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​The degree of RA, or route availability, (higher numbers mean greater restrictions) is necessary for the more weight-restricted sections of the Cambrian lines, but is not a feature of more modern locomotive types that can perform a similar range of tasks. All of these have higher axle loads (and therefore higher RA) and class 66 is, for example, RA7.

Keeping yellow locomotives clean is never easy! No. 97302 is part of the process in this picture.

On board ERTMS

Inside the locomotives, in the area formerly occupied by the steam boiler, sit the racks of cabinet-mounted electronics that are the heart of the ERTMS system on board, known as the EVC (European Vital Computer).

The EVC manages functions and diagnostics of the on-board system and receives instructions from balises (transponders) placed in the ‘quadripod’ between the rails as well as GSM-R (the railway’s mobile voice and data communication platform). It also supports Automatic Train Protection (ATP) as well as legacy systems in place on the wider rail network, such as TPWS and AWS.

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To accommodate the cab display (known more technically as a driver machine interface or DMI), the traditional Class 37 instrument panel has been reconfigured.

On the underside of the locomotive is the balise antenna and, in place of one of the two fuel tanks, doppler radar equipment to measure instantaneous train speed.

As with many diesel engines of their era, the English Electric Type 3s are known to produce clouds of smoke when starting from cold, but the Class 97/3s have been fitted with a programmable preheater to overcome this.

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Inside the shed at Coleham, where the team have succeeded in maintaining excellent availability of the three Class 97/3 locomotives. The one-way shed is equipped to handle much of the maintenance, although work involving lifting locomotives or removing roof sections is carried out at larger depots.


The tasks for this trio of locomotives are different. They were used for route testing after the February storms, and since their “home” lines had fully reopened after repairs, Nos. 97304 and 97303 even took responsibility for the first timber seen on Cambrian Metals for years (see Freight page 78).

“You can do a tinker on Wednesday, bring it back on Wednesday night and the locomotive is straight out on a train for rail treatment,” explains Simon. “Each of the departments within Colas and Network Rail have to work quite closely together to work out what we actually do with the resources. You may find that if a locomotive is needed in Derby for an infrastructure monitoring service, one of the guys from here will take it over, or one of the guys from Derby can retrieve it or vice versa.”

For aging machines that lead busy lives, maintaining reliability is critical. Network Rail locomotive fleet engineer Nathaniel Lotarew adds that as they approached a decade in service as Class 97/3s, the decision was made to undertake another major overhaul and further improvements: “They went through an extensive G-examination process, which is equivalent to a 10 year overhaul and at that time we took the opportunity to do various reliability modifications, they got all new wheelsets too, to a new monobloc design which removes some of the fault points we have with wheelsets with tyres.

“They’re doing pretty high mileage compared to what they used to do, at the moment about 24,000 miles per year,” he says, observing that an E exam in 2023/4 will be the next big task. “At that point we will look to do some additional life extension work on the vehicles to ensure we can still deliver them to our customers.”

The No. 2 driver controls on No. 97303 Dave Berry. The original Type 3 English electric instrument panel layout has been modified to accommodate the Driver Machine Interface (DMI), the screen showing instructions instead of traditional line-side signaling for ETCS Level 2.


That investment, combined with the care and attention of staff at Coleham, has paid off in terms of performance.

“The 97s, for the 2021/22 financial year, delivered pretty much 100% for track renewals,” notes Nathaniel, explaining that the last two years have seen an “upward curve”.

They may be dealing with much heavier, slower machines than their motorsport counterparts, but Simon Metcalf says the timing of maintenance is “like Formula 1”, especially with the autumn rail trains.

“It is so intensive that they come out of RHTT and go on to something else, and the exams go in between,” he elaborates. “An A exam might take three or four hours maybe, so you only have that window between the set coming in and coming back out to actually do it.”

The small single track shed, which is part of a larger Network Rail site on the opposite side of the railway where Coleham steam depot stood, handles much of the maintenance of the three locomotives.

“Anything that requires major work, like a roof off or a vehicle from the bogies, we have to send to a level 5 depot, so that would be like Derby RTC or Barrow Hill as a place that can handle class 37 and 97, but we is very well equipped here to do most of the routine maintenance, says Nathaniel.

External equipment for the ECTS signaling system includes antennae to relay messages from balises (transponders) set within ‘four feet’ between the rails and a doppler radar to calculate the speed of the locomotive or train. This takes up space previously used for a second fuel tank.


Due to obsolescence, some parts have to be ‘reversed’, but Nathaniel says the most difficult issue at the moment is wheelset lead times: “You’re looking at over 8-12 months for most of the main components for Class 37 wheelset assembly. Suspension tube bearings, wheel pans, the wheels themselves, the axles. They all have great lead times now, not helped by current global issues.”

At this stage, even the team themselves admit that it is difficult to know how long they will need to operate the ’97/3s’.

“If all the rolling stock that needs to use that line is equipped with ECTS, you don’t need a pilot service anyway,” says Gwyn Rees, Network Rail’s interim head of maintenance delivery on the Wales Route. “It will basically be a choice for the industry because at the moment the only fleet fitted is Class 158s, all of which are based on Machynlleth.”

As new trains are delivered, embedded ECTS offerings are becoming more common, and the Class 197s which will replace Cambrian ‘158s’ are one of the latest examples. But decisions to adapt the technology on a more widespread basis to other locomotives and tracked machines are those that will have a direct influence on the continued use of Class 97/3 in the area.

Although he adds that there is “a lot of discussion” about what to do and how to approach it, it seems likely that the Cambrian lines will be a stronghold for the Shrewsbury ‘Syphons’ for quite some time to come.

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