BULKHEADS
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and
PARTITIONS
their bearing on seating layout
THE term " bulkhead " is used to describe any unit of the transverse construction of a coach or bus body dividing one part of the vehicle from another. The main saloon is separated from the forward-control cab by the front bulkhead.
At each end of this partition there is a corner pillar which is stouter than those of the sides of the body, because it has to be large enough for the joints of both the side and cross framework. Moreover, when there is a front entrance the near-, side corner pillar has no support from the side waist rail.
Occasionally the front corner is made up of two pillars screwed together so that the necessary strength is obtained without cutting into thick and expensive ash planks.
Between the waist and the roof the maximum amount of natural lighting is required. A body 7 ft. 5 ins, wide overall measures about 7 ft. between the corner pillars.
33213 Although this span is considerable, only one central support is required if both the support and the top crossrail be of substantial proportions.
The central support, whether it consists of one member or a pair of closely spaced pillars, is a convenient arrangement, because each front window has its own blind, which can be lowered after dark in order to prevent reflections on the windscreen. The setting-out of the front bulkhead framework below the waist depends chiefly on the presence or absence of a rear dash plate. If this be supplied with the chassis, a good foundation is available, which gives scope for a lighter and simpler form of construction. Before the introduction of the dash plate the front bulkhead was often reinforced with a sheet-iron panel.
Another type of partition is that which is frequently to be found on each side of a rear or central entrance. It is necessary when the bottom of the door is at the floor level and the step is between the door and the side of the bus, because there must be door pillars.
Furthermore, the body must be enclosed on each side of the entrance. A similar partition is required for an entrance at the front or rear, in order that an enclosure be formed with the front bulkhead or with the back of the body. These partitions are one of the factors that determine the seating arrangement. There should be a cross gangway, between the partition and the front of the seat which faces it, at least 1 ft. wide, otherwise there is insufficient legroom., With the modern bus this cross gangway is usually of good width between the front bulkhead and the first row of crosswise seats. This gangway is notably wide in the upper saloon of many doubledeckers, particularly when this compartment is of maximum length and the front seats are not arranged forward of the line as represented by the front bulkhead of the lower saloon.
The bulkhead separating the front and rear saloons of an observation coach has a central opening about 1 ft. 10 ins. wide. The seats which have their backs against this bulkhead, project into the central opening and only some 1 ft. 3 ins. re mains at the cushion level. If a larger opening be required it is offset and there is only a single seat on one side.
The flight of two treads that leads to the higher floor at the rear is entirely behind the bulkhead, so that sufficient headroom is afforded when ascending the stairs.
The general design of the observation coach is improved if it has a sunk central gangway in the front saloon, such as is possible when the cardan shaft is offset.
The greater the difference in height of the two compartments the larger may be the front lights of the rear saloon, the outlook from which tends to be obstructed by the frontsaloon roof.
The partition in a small vehicle, such as a seven-seater, is usually confined to panelling and glazing only behind the driver's seat, or it is continued across the full width of the coach, there being a door on each side of the partition.
In order to make the best use of the space available between the back of the partition and the next row of seats, the panelling is sloped so as to provide more room at the floor level.
The partition windows may slide horizontally or drop. There is a drop pattern which, although it runs in vertical channels above the waist, slopes forward as it falls below this level. In this way full advantage Is taken of the slope of the back of the front seat, which determines the angle of the partition panelling.
When there is an emergency door at the back of the vehicle a step well may be designed similar to that provided with a side entrance. This wall is then at the end of the central gangway and is protected by means of a floor flap.