BULKHEADS and
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PARTITIONS
their bearing upon passenger-body design
Securing Rigidity in the Constructional Units of a Coach or Bus Body. Placing Doors to the Best Advantage
THE upright members of the front bulkhead of a rearentrance bus consist of two corner pillars and the intermediate pillars which reinforce the structure and divide one window from another. The corner pillars • are ef larger section, because they receive the ends of the horizontal framework members both of the front and side of the body. Weight is saved by hollowing out the pillar on the inside, and as the outside corner is rounded the pillar in section ip practically quadrant-shaped.
When there is a forward cabin a central pillar is required, to which is framed one side of the cab. The upper part of each half of the bulkhead may then be divided into two windows. If, however, the centre pillar be made strong enough, or two members be set out close together, the intermediate pillars may be omitted, with the advantage that on the near side there is a large window affording good observational facilities.
The top cross-rail of the bulkhead is shaped to the camber of the roof and is, as a rule, straight on the under side, so that it is of deepest section in the middle, where the greatest strength is required.
The two sides of the bulkhead are also held together by the rails at the waist, seat line and bottom. At the waist there may be one rail, 5 ins. or 6 ins. deep, or two lighter rails may be used. The height of the waist may be decided by that of the side waist rails, although it is sometimes raised above them so as to conceal as far as possible the back of the driving seat. As the front bulkhead is flat and it is not pierced by a doorway, crossbracing may he resorted to below the bottom of the windows.
The bulkhead of a front-entrance bus with the conventional type of steering has an arrangement of pillars which is controlled by the position of the steering-column centre and the width of doorway required. Unless the steering column be mounted outside the chassis the inner end of the driving seat is usually within an inch or two of the longitudinal axis of the vehicle. Consequently, the bulkhead entrance is on the off side and not directly in line with the central gangway of the saloon. This arrangement leaves only a small space for a window and panelling on the near side of the bulkhead entrance. .
It is considered that all 'passenger chassis in which the steering column is behind the engine should have the column placed so that this doorway may be set out centrally in the same way that it is done with a rear ' bulkhead.
This would not only improve the entrance, but it would also be possible to increase its headroom an inch or so, because the centre line of the entrance would coincide with the highest part of the roof: Furthermore, there would be more comfort for the passengers sitting on the front near-side seat, because they would not obstruct the entrance to the same extent.
When there is a half-cabin in front of the bulkhead the design of the near-side half may be varied by rounding the corner to a radius of 8 ins. or 9 ins. This style of front corner is adopted for coaches, because it is considered that it gives the vehicle a more elegant appearance.
If the inside of the framework at the corner be made straight a flat glass may be inserted so as to save expense. Nevertheless, the bent gIass is, from the point of view of appearance, better, even if it be apt to distort the view. When curved glasses are adopted for any part of a coach it is a good plan to standardize them In order that only a small stock of spare ones is necessary.
Shaped windows are usually avoided buses, because, apart from their expense, delay is entailed if they have to be specially ordered.
A partition which does not form part of the main framework of the body is usually made up as a „separate unit, because it simplifies assembly. That is to say, the partition has its own upright members which are in line with the body pillars.
These are set out so that, when viewed from the outside, the ends of the partition are concealed. It follows:, therefore, that a partition will often control the setting out of the window spaces.
The position of the bulkhead is chiefly decided by the seating plan. Therefore, a partition which divides the saloon into smoking and nonsmoking compartments, or is used to enclose a luggage compartment or lavatory, may be the cause of uneven window spacing.
This may be considered a disadvantage, but, on the other hand, a partition helps to stiffen the general structure and may often' be inserted where additional strength is particularly required, such as in the centre of the saloon, or. behind the rear axle.
There is seldom, any need for a heavily framed partition, because, although it may add rigidity to the body, this function is only incidental, Its framework need be thick enough to form only a firm foundation for the panelling or any glazing adopted, or for the hanging of a door.
The door to a lavatory should open inwards, whilst the door communicating with a luggage compartment or buffet should open outwards, so that all available &Or space may be fully utilized. , Sliding doors have the advantage that they take up a minimum of room for their operation, but they ate not .so frequently adopted as their advantages would lead one to expect. The hinged door is, no doubt, less expensive, but equipment for the sliding door is available which, when properly fitted, ensures smooth operation and absence of rattle, The sliding door is particularly suitable for incorporation in the passenger vehicle that is used on urban work, entailing journeys of, say, 30 or 40 miles, with numerous stops to pick up and set down passengers. The sliding door is generally considered to be more speedy in operation than 18 the orthodox coach type.
If a partition door does not require any glazing the merits of the roller shutter should not be overlooked. A shutter fitted to the doorway of a luggage compartment would facilitate loading and unloading, and any decrease in headroom, owing to the presence of the rolled-up shutter, would be less of a disadvantage than would a swinging door. It is doubtful whether the roller Shutter has yet been used in this country in connection with coaches and motorbuses.