The cars kept the same 'Derby' front end as the Class 114, but changed to the high density layout for their suburban use. This entailed carrying large numbers of people over short distances, so no gangways or toilets were fitted when built.

The body and roof framing were of conventional BR design, in 'top hat' section, with the cab roof made of moulded polyester glass laminate. Insulation was with asbestos (though to be in just the first two of the three batches).

The underframe was of a mild steel welded construction. The standard Derby DMU bogies had Timken roller bearings. The Gresham & Craven quick release vacuum brake system was fitted. The picture shows the almost completed bottom end of a vehicle. Even the cab desk as almost complete, before the jig built sides and ends are added.

Large round Oleo buffers were carried from new although during the '70s and early '80s, a number of sets ran with the oval type, before reverting back to the large round type. A few units (mainly from the last batch) were fitted with the oval type in the early '60s.

The standard BUT power train and control equipment was used, and the power/weight ratio was 6.3 : 1. The exhausts originally joined above the gangways, emitting through a single box as visible on Derby Lightweight single cars 79900/1.

The Birmingham sets were fitted with ATC from new.

An example of a Class 116 interior, the vehicle being preserved DMBS 51131, taken during the Railcar50 event in October 2004. Mathew Hawley

Coupling Codes
The Class was the standard Blue Square, although for a short spell one set was Blue Square with diagonal stripe, due to the final drive having a different gear ratio.

Marker Lights
The first batch of vehicles had the four lamp arrangement (and just one windscreen wiper). The later ones received a two-character headcode box below the centre cab window, with just two lamps, one either side. Just the last batch received two windscreen wipers from new, but the earlier sets had a second added later.

Seating
To give maximum seating capacity, the high density design was used. With doors at each seating bay there was no need for gangways or a through corridor. The DMS had solid partitions, and although the DMBS did have a doors in the partitions, this was purely so the guard could get to the driver, and as it was considered that the limited gap between the seats were not designed for public passage, the staff were instructed to keep these doors locked.

Gangways
In a period from about 1968 to the early '70s gangways were fitted to the WR sets (as well as doors through the internal partitions where required). It is almost certain that the vehicles were painted into blue at the same time. 

Refurbishment
The 116 units were one of the classes selected for refurbishment and this began in the mid 1970s with the South Wales sets. This involved a complete renovation of the internal fittings with tungsten lighting being replaced by fluorescent tubes, reupholstered seating and a modified heating system.

The two character train describer boxes which by this time were out of use were removed and a steel plate was flush welded in it’s place, (on unrefurbished cars the plate, where fitted, just covered the redundant box). The earlier four lamp fronted cars had the lower central lamp removed and the top roof dome mounted lamp was disconnected or was fitted with a blanking plate. The exhaust pipes  were each fitted with exhaust silencers as they rose either side of the gangways to supplement the original underframe mounted silencers, this dramatically reduced but thankfully didn’t completely eliminate the typical DMU rasping engine note, which was most noticeable when pulling away from station stops etc, the trade mark of all unrefurbished units.

It’s interesting to note that refurbishment did not include the fitting of gangway connections, this work being undertaken separately. Those allocated to the LMR, SCR, and ER, were treated later, though some refurbished and gangwayed sets were transferred to Tyseley from Cardiff, in the late 70's.

Not all of the class 116 vehicles were refurbished, and a small number remained rail blue well into the 1980s, though by this date most cars whether refurbished or not were at least repainted blue and grey

Although toilets were never fitted to the trailers, in the '80s displacement of similar trailers of Classes such as 127 which had toilets saw them replace the 116 trailers.

Gangways
The Tyseley based sets were generally not gangwayed until the withdrawal of the older asbestos contaminated TC vehicles in 1982/3 when these 127 (and 101) trailers were substituted.

In August 1983 a modification programme began on twenty pairs of Tyseley’s 116s, to add the gangways. This was due to a requirement for more through gangwayed sets for the increasing number of paytrain services. The work was being done at Carlisle Currock C&W repair shops, and involved cutting a gangway aperture in the car ends, after removing the interior against it, moving a piece of ‘H’ section framing to above the hole, fitting newly made gangway hanger brackets, and gangway connections and doors recovered from withdrawn Class 120 trailers.

The DMBS already had access through the interior partitions but the DMS had to have doors made in their two bulkheads. Although intended to work with Class 127 trailers displaced from Bedpan services, the first four pairs were back in traffic in late Nov. ‘83 with redundant ER 101 trailers.

These were:
TS 602 51133 59533 51146
TS 604 51129 59570 51142
TS 605 53851 59527 53904
TS 607 53862 59107 53872
The next sets were being converted at the end of 11/83, being TS 520 (53827 & 53880), and 51131 & 51134, as well as the first 127 trailers.