Class 315 Withdrawals

London Overground only have units 801 - 817, the rest (818-861) are all TfL Rail sets. Another factor that should help clarify the difference at this stage is the lack of LO replacement units to enable their 315s to be withdrawn - only the TfL Rail/Crossrail units have been delivered for passenger use so far

Anybody know why these modern, sliding door units haven't been reserved by Vivarail as likely candidates for re-engineering?

I quite like 315s too, but don't forget Vivarail hasn't found many homes for D78 stock yet, so why buy another old fleet? And even if there was a good case in a year or two there are lots of BREL York EMU trains coming up for withdrawal soon, so there's quite a choice if one was needed.

Trains have had sliding doors for more than a century - indeed the old LNER-design class 306s, which were replaced by the 315s, had them. British Rail was unusual in sticking with slammers until the late 1970s - a legacy of the Southern Railway's conservative design policies. (Like Trigger's Broom or the Ship of Theseus (depending on your preferred cultural references), many 1960s-era SR units had originated as Edwardian-era steam-hauled stock, of which the underframes and bodies had been replaced at different times over the years - sometimes more than once - but still conformed to more or less the original layout.) The SR slam-door designs, rather than the more modern LMS and LNER designs, were the basis of most BR multiple unit designs until the late 1970s. (Even then, the PEP types could be seen as special cases - the 313s, 314s and 507s were destined for lines with long underground sections and, along with the 315s, were to replace or run alongside existing sliding door trains.

Were the 312s the last EMU design to be built with slam doors?

Yes, they were built in two batches; The 1975 batch was for 19 x 312/1 for Liverpool Street - Clacton/Southend Vic services and 4 x 312/2 for London Midland to compliment their 310s out of Bletchley Depot. 
The later batch was 26 x 312/0 for the Kings Cross outer suburban lines which were still being delivered in 1978. They were the last of the Mk 2 derived EMUs and also the last of what are now referred to as "1st Generation" EMUs.

The production of 315s followed on from the 312s at BREL, York with the first few units arriving at Ilford late 79/early 80, though their design preceded them with the PEP experimental units then the Class 313 from 1975/6. 

So the 315 is essentially a later build of an early 70's design. Modern it certainly is not and there will be much newer rolling stock heading for scrap soon. 

Ah yes, Hugh's book is invaluable as are Ashley Butlin's guides.

I think the planned roll-out of 312/0s was delayed by the GN electrification if memory serves me well. Great Eastern clearly thought little of the numbering imposed by Euston House and didn't wait long to start renumbering theirs in the 781-799 series. Some even having printed numbers in their cab windows for a time.

I can remember taking a ride from Ilford to Chelmsford in 1977 in one of the brand new 312s and thinking even then that they weren't a very advanced design, especially as I'd got into a smoking compartment by mistake. They seemed to me to be less modern than the 305/1s I was more used to.

The video on this thread explains why D78s were suitable for Vivarail's project.

The big advantage is the all aluminium construction. The reduced weight makes battery operation possible.

The bogies were also replaced.

true - but that means as an asset it holds it's value for longer and the potential for scrap value will always be there - so keep sweating it until it really does need to go!

I hope this shows up...

Sorry Richard,

It only arrived in my twitter feed today!

These things take time to do the rounds.

Simon