Building a DMU
Part Five: Adding the Floor, General Workshop Views and Elecrical Components
Images thirty-eight to forty-six in the booklet.
"Floor Panels Being Welded"
Negative 5C76
Taken 15/12/55. Inside a DMBS vehicle, the corrugated floor sheets are being welded together. Also a vertical plate has been added to the bottom of the inner bodyside, creating a box section for added structural strength. More details on the body construction can be found in this article.
"Body Construction"
Negative 5C133
Taken 12/06/56. A general workshop view with an intermediate DMBS, still without a roof.
"Body Construction"
Negative 5C132
Also taken on 12/06/56, two leading DMBS vehicles with a Mark One coach on the left. The DMU vehicles are progressing well, with doors fitted, interior bulkhead walls appearing and even some electrics fitted judging by the wire hanging out the route indicator box of the right vehicle.
"Body Construction"
Negative 5C131
The third image from 12/06/56 shows the same two vehicles as image 5C132, with another Mark One at the far end. The rainstrips have also now been fitted, the closest vehicle is still to receive the small end piece.
"Leading End"
Negative 5C84
This image of a leading DMBS on 20/01/56 is interesting as it is on stands without bogies, the only image in the collection of this to happen.
"EP Control Relay Box"
Negative 5C85
The next four images are of components. The first three are electrical components taken on 6/2/56. The first is an E.P. (electro-pnuematic) relay box. The White Circle control system on the 79xxx vehicles was somewhere inbetween the yellow diamond and the blue square systems, using components from each. Relays were added for through train control, meaning each vehicle would now use its own power to operate E.P. valves rather than rely on a feed from the driving car.
"EP Valve Relay Box"
Negative 5C86
The wiring diagram on the lid shows the three relays as being local stop, start isolation and start. The relay panels were manufactured by J.Stone & Co. (Deptford) but supplied by B.U.T. (British United Traction). The lid cover carried the B.U.T. branding on the outside.
"E.P. Valve Box"
Negative 5C87
Five electro-pnuematic valves. Each power car would have two of these boxes, this one has three valves (both on and off types) for the throttle and one each for forward / reverse. The other box would have four to control the gears. The main body of a valve is an elecrical coil, the two screws are to attach the electrical feed. Inside the coil is a needle which is pushed up when the coil is energized. The valves are bolted at the top to an air manifold, for each valve there is an air feed and an outlet, the outlet connected by an air line going to the throttle, gear or final drive as appropriate. The needle in the E.P. valve opens or closes the feed between the inlet / outlet, depending on the type of valve. At the bottom of each valve is a button for manual operation for testing.
"C.A.V. Fuel Injector Nozzle and Fuel Holder"
Negative 5C135
A sectioned fuel injector, dated 21/6/56. The large fuel connector on top is the main fuel supply, fuel is delivered to each injector in a defined sequence from the fuel pump under pressure. When the pressure is sufficient to counteract the spring on the right it pushes the valve up (to the right in this image) and the diesel is sprayed into the piston chamber through the nozzle on the left. The small fuel connector to the right at an angle is the return pipe for any excess fuel.