Construction
The Mark 3 looks similar to Mark 2D, 2E and 2F coaches, but is a completely different design. A difference aiding quick recognition is the ridged roof of the Mark 3 compared with a smooth roof on the Mark 2.
The bodyshell is 75 feet (23 m) long, almost 10 feet (3.0 m) longer than the Mark 2, of full monocoque construction with an all welded, mild steel, stressed skin, and has gained a reputation within the railway industry for its exceptional strength and crashworthiness. Another important advance over its predecessor was the adoption of secondary air suspension between the body and the bogies giving the passengers an exceptionally smooth ride. The bogies, classified BT10, were designed specifically for the Mark 3 and have coil spring primary suspension with hydraulic dampers enabling a maximum speed of 125 mph (200 km/h) — the Mark 2 is limited to 100 mph (160 km/h). Disc brakes in place of the Mark 2 design of clasp brakes completed the engineering package - enabling efficient deceleration from 125 mph and almost silent brake operation.
Ancillaries such as electrical and air conditioning systems were grouped together in discrete modules housed behind an aerodynamic skirting between the bogies; on the Mark 2 these were mounted above and below the passenger seating area. The lighting and air conditioning fittings were for the first time integrated into the ceiling panels. Other new features (first seen on the Mark 2F) were the pneumatically operated automatic gangway doors which were triggered by pressure pads under the floor, and a speed operated central door locking system for the manually operated slam-doors.
The main difference between the HST vehicles and the loco-hauled Mark 3A relate to electrical supply arrangements. HST MK3 coaches take an industrial voltage/frequency 3-phase supply directly from an auxiliary alternator in the power car to supply on board equipment such as air conditioning. The loco hauled vehicles take a standard single phase 1000 V AC or DC train heat supply from the locomotive and convert it through motor generator units located under the floor. These convert the train supply to 3-phase 415/240 V 50 Hz AC to power air conditioning and other ancillaries. This difference makes the two types non-interconnectable in service conditions. The other main difference is the lack of buffers on HST coaches.
The later Mark 3B build provided additional 1st Class loco hauled vehicles for the West Coast Main Line. These are virtually the same as earlier Mark 3As, but have an improved motor alternator unit with compound wound motor and seating derived from the Advanced Passenger Train (APT)
Read more about this topic: British Rail Mark 3
Famous quotes containing the word construction:
“There is, I think, no point in the philosophy of progressive education which is sounder than its emphasis upon the importance of the participation of the learner in the formation of the purposes which direct his activities in the learning process, just as there is no defect in traditional education greater than its failure to secure the active cooperation of the pupil in construction of the purposes involved in his studying.”
—John Dewey (1859–1952)
“When the leaders choose to make themselves bidders at an auction of popularity, their talents, in the construction of the state, will be of no service. They will become flatterers instead of legislators; the instruments, not the guides, of the people.”
—Edmund Burke (1729–1797)
“There’s no art
To find the mind’s construction in the face:
He was a gentleman on whom I built
An absolute trust.”
—William Shakespeare (1564–1616)