Flex... and flexibility

Isbern acknowledges that a good option for a tri-mode Class 319 would have been London Overground, but with the Gospel Oak-Barking route now being electrified that particular customer has been eliminated. 

Most of Porterbrook’s work to date has focused on the Class 319 Flex, but the concept could be deployed on other fleets. Isbern says the Marshlink route from Ashford, deep in third-rail territory, is an option - it only needs DC plus diesel power. 

“The Flex concept could be deployed on fleets such as Electrostar and displace DMUs for use in other parts of the country,” he says. 

Simpson says there is no Flex ready yet, but work has begun. And timescales for the project are impressive. 

She explains: “When production is up and running, each ‘319’ will take four to six weeks to convert. The rafts will be built in advance and simply be bolted on to the train during conversion at works, thus minimising downtime.

“The design of the control system is largely developed and an Ethernet backbone will be used to monitor output and balance loading between the two engine rafts. The physical modifications needed are relatively straightforward and are largely limited to the driving vehicles - fitting the new engine/alternator raft, some new control technology and some minor relocation of existing equipment. It is a modular concept and it is cost-effective as a result.”

She admits that while the first train will take longer, as per all usual rebuilds and refurbishments, the timescales will improve dramatically when the production is up and running. Initially eight Class 319s will be converted, and form part of the Northern fleet of 32. 

“The first four could enter traffic in December 2017,” Isbern tells RAIL. 

The ‘319s’ to be converted have been identified by painted number already. Initially they will all be ‘319/4s’, but any of the four sub-classes could be used. Isbern says it makes sense to use the ‘319/4s’ first as they are the most readily available. All of Northern’s Class 319s in traffic currently are ‘319/3s’, but ‘319/4’ Flex units will be able to couple and work in multiple with any ‘319’ sub-fleet.

Northern will be responsible for maintenance. Depending on their diesel utilisation, Isbern is not convinced that the new engine rafts will need overhauling during the lifetime of the Northern franchise (which began in April 2016 and will run for nine years, plus a one-year option). This means that trains introduced in December 2017 could run for nine years without the need to visit works for major engine attention. 

Isbern adds: “We don’t know yet which exact routes Northern will use the Flex units on. We know they outperform a ‘150’ on a number of different routes and diagrams, and will certainly outperform a Pacer. We are working closely with Northern on approvals for their selected routes.” 

Certainly routes in the North West where new OLE is being erected, or where journeys are mostly under the wires, are likely future candidates. 

Simpson adds: “The costs benefit model is interesting. Under the wires the pantograph can go up and the engine is switched off. In diesel mode, the engine is running at maximum efficiency through the existing traction equipment and is as fuel-efficient as a new DMU. Overall, you end up with a much more efficient train compared with running diesels under the wires.

“Track access is marginally more than an existing ‘319’, but comparable to a mid-life DMU. It is roughly the same weight as two ‘150s’ and should give a comparable track access charge. The fuel savings of only running diesel engines when you need them, and running them at a maximum efficiency, give a significant total energy cost saving when compared with a pure DMU option.”

Simpson explains that when running as an EMU the top speed for Flex is 100mph. She adds that, being conservative, when running on diesel it’s likely to be around 91mph-92mph. “Really detailed point-to-point analysis shows what it does well, and which routes and journeys will deliver the biggest benefits to operators,” she tells RAIL.

So how far has Porterbrook got? 

“We have done all the concept design work, gauging work, and weight analysis, structural modelling, braking, journey time and performance calculations have all been completed,” says Isbern.

“Detailed design is now well under way. We know the suppliers we’ll use, and it is about getting into the details. The materials are ordered - we are really cracking on with it.” 

Porterbrook and Northern have yet to decide on an interior, but discussions are in progress.

One unit has moved to Loughborough (319427), but this is not one of the eight destined for Northern. Instead, it will be deployed for dimensional analysis. Only so much can be planned on paper and computers, and this will enable the various teams to evaluate the train and ensure everything fits. 

Isbern reveals that when the first production unit is released from Loughborough, it will move to Allerton depot, where Northern maintains its other ‘319s’. Refuelling will be no problem, given that this is also a DMU depot.

The predicted reliability of the units is measured in miles per technical incident (MTIN) and is not too different from a ‘319’ with a target level of 20,000 miles per incident, says Isbern.

He is keen that Flex is marketed to other areas beyond Northern. The ‘319’ fleet is in good condition and all of the units selected for Flex are also already PRM-TSI (Persons of Reduced Mobility - Technical Specifications for Interoperability) compliant, which means they can be used beyond January 1 2020. “We can see Flex units operating beyond 2025,” says Isbern. 

This is a project that seems the right option for right now. The nationwide shortage of DMUs has even been debated in the Commons by Rail Minister Paul Maynard in recent weeks. This low-cost alternative to brand new trains offers train operating companies the opportunity to introduce refurbished bi-mode trains using an asset that has plenty of life in it. It’s surely a win-win for all those involved?