Darlington Railway Centre &
Museum
A standard gauge railway museum located in Darlington, County Durham.
Darlington Works
Main works for the former North Eastern Railway.
Dart (1)
A handle used to secure the smokebox door of a steam locomotive.
Dart (2)
A long straight fire iron.
Dead-man's handle
A control device on electric or diesel trains which the driver must keep depressed in
order to prevent the brakes from being automatically applied.
Dean Forest Railway
A standard gauge preserved railway in Gloucestershire.
Dean, William
Locomotive, Carriage and Wagon Superintendent from 1877 to 1902 for the
Great Western Railway.
Decapod
A locomotive which according to the Whyte classification is of the 0-10-0
wheel arrangement. The term is sometimes used also for 2-10-0 locomotives.
Deeley, R.M
Chief Mechanical Engineer from 1903 to 1909 for the Midland Railway.
Deflector plate
An inward-protruding plate inside the firebox of a steam locomotive, secured
just above the firehole door. The plate is used to deflect incoming cold air
away from the tube plate. Also known as the flame scoop.
Derby Works
Main works for the former Midland Railway.
Detonator
A small explosive charge set off by the wheel of a train passing over it.
Detonators consist of a small metal cap attached to two soft metal strips
which would be used to clip it on top of a rail. Used in emergencies to
provide a clear audible warning to drivers. Carried on all trains for use by
the guard in emergencies.
Diamond crossing
The crossing of one train track with another on the same level.
Didcot, Newbury and Southampton Railway
Incorporated in August 1873, the section from Didcot to Newbury opened in 1882
and the Newbury to Winchester section in 1885. The final section from
Winchester to a junction with the London and South Western Railway was
authorized in 1888. Its 44 mile length was worked by the Great
Western Railway and became part of the Great Western Railway at the 1923
grouping.
Didcot Railway Centre
A standard gauge railway preservation site at Didcot in Oxfordshire.
Die block
A component in the Walschaerts valve-gear which is able to slide within the
radius link; or a similar sliding device in other forms of valve gear.
Diesel Electric
Diesel Electric locomotives are effectively electric locomotives which carry
their own generating plant. The diesel engine and generator typically being
directly coupled together, and the motors being mounted on the bogie frames.
Diesel Hydraulic
Diesel Hydraulics are largely mechanical in principle and rely on the
properties of liquids, namely that they are practically incompressible, as
such they can be used to transmit force that can be guided into well defined
channels. A hydraulic torque converter is basically a pump
and a hydraulic turbine in a common casing. Since there is no direct
mechanical connection between input and output, an infinitely variable range
of speeds is possible between fixed limits. Power is transmitted to the
wheels via mechanical driveshafts from the torque converter/gearbox.
Diesel Mechanical
Diesel locomotives with mechanical transmission rely upon gear boxes in a
similar way to most cars and drivers therefore have to change gears regularly
as the speed varies. Usually only used for low power shunting locomotives.
Direct admission valve
A valve fitted to a brake cylinder of a vacuum-braked train. The valve is designed so
as to open and allow atmospheric air into the brake-operating system when only a
small reduction of vacuum has occurred in the train pipe. This has the effect, in a
long train, of bringing the brake fully on, quicker than would have been the case if
the vacuum had simply leaked away through the brake-actuating valve.
Disc signal
A semaphore signal where the indication is given by a rotatable disc.
Displacement lubricator
A device often seen secured to the side of a steam-locomotive smokebox. The
device is used to bleed oil into a steam pipe for lubricating the cylinders.
It usually has the appearance of a small vertical cylinder, with an adjusting screw
on the top and a drain cock on the bottom.
Disposal
The disposing of the remains of the fire at the end of a days working for a
steam locomotive. This consists of three main tasks, removing the
remnants of the fire from the grate, emptying the ashpan and emptying the
ash out of the smokebox.
Distant signal
A caution signal which when in the on position, indicates that the next
stop signal is at danger, or at least one of the stop signals within the
approaching station limits is at danger.
DMU
Common acronym for Diesel Multiple Unit.
Dolly
Slang term for a ground signal.
Dolphin
A LNER long (62-64ft) open wagon with drop sides used for ballast, rail and
sleepers. BR later adapted this design for their Sturgeon wagons.
Dome
A dome-shaped protrusion on the top of a steam-locomotive boiler.
Typically this conceals the steam collection pipe for the regulator, which
needs to be at the highest point of the boiler to minimize the chances of
priming.
Domes may also be used for other purposes.
Doncaster Works
Main works for the former Great Northern Railway.
Double chimney
An elongated chimney of normal width, but about double normal length, into which two
blast pipes exhaust steam.
Double frames
A railway-vehicle frame which has side plates located both between the wheels and
outside the wheels.
Double header
Double heading
A train which is hauled by two locomotives coupled together.
Double slip
The combination of a diamond crossing of small crossing angle interlaced with
four sets of points so as to provide a route between any two opposite tracks.
When four of the point blades are located totally within the central diamond, it is
called an "inside slip", and when all point blades are outside the diamond, it is
called an "outside slip".
Double track
A railway route in which one track is provided for each
direction of travel.
Down line
That line on a multi-track main line where the direction of travel is
away from the major city.
Drag box
A cast or fabricated member at the extreme rear end of a locomotive main-frame, and
on which the draw-gear is mounted.
Drain cock
Used to drain the contents of a cylinder or other container. See also
cylinder drain-cocks.
Draw-ahead signal
A subsidiary signal, usually mounted on the same post as a starting
signal. When the draw ahead signal is off, the train may draw ahead
cautiously against the starting-signal's indication, but only as far ahead as the
line is clear, or as far as an advanced starting signal (see also
calling-on signal, shunt ahead signal and warning signal).
Draw gear (or Drawbar)
A mechanism having spring-controlled movement, which is connected to the main frame
of a railway vehicle, and on to which a coupling is attached.
Drawbar pull
The force exerted by a locomotive on the leading coupling of the vehicles
which it is hauling. (see also equivalent drawbar-pull).
Drewry Car Co
A locomotive building company in Preston.
Driving Wheel
The wheels which actually drive the vehicle along. In the case of a steam
engine these will be the large wheels in the middle of the locomotive connected
together by coupling rods. They may sometimes have smaller wheels either in
front of behind them - see wheel arrangements for more details.
Drop coach
Another term for a slip coach.
Drop Head Buckeye coupling
A buckeye coupling that can be lowered to reveal a standard hook for a screw
or three link type coupling.
Drop-light
The opening window in a carriage door, or other similar window which opens
by dropping down into the coach body.
Dropper wire
Wires hanging from a catenary on to which the contact wire for railway
electrification is attached.
Drummond, Dugald
Chief Mechanical Engineer from 1882 to 1890 for the Caledonian Railway and
for the London & South Western Railway from 1895 to 1912.
Drummond, Peter
Chief Mechanical Engineer from 1896 to 1911 for the Highland Railway.
Dual-fitted stock
Rolling stock which is fitted with both vacuum brake and air brake
systems.
Dual gauge
A mixed-gauge railway line designed for two different track-gauges.
Dubs & Co.
Locomotive builders based at Queens Park Works in Glasgow.
Manufacturing began in 1863 and the company was merged with others to form the
North British Locomotive Company in 1903.
Ducket
Lookout for the guard which projects from the side of a brake coach or
guards van.
Dumb buffers Long-ago-obsolete type buffers used on rolling stock. Instead of the usual metal construction and spring control, these buffers consisted of a leather protrusion stuffed with horse hair or similar material. The earliest goods wagons often had just a simple wooden block.
Duplicate signal arm
The lower arm of a co-acting signal.
Dynamometer car
A railway vehicle which incorporates apparatus for measuring drawbar pull,
speed, and work done by the locomotive to which the vehicle is coupled.