How To HANG A COACH DOOR
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This Week Our Bodybuilding Expert Deals with the Various Methods of Hinging Doors, Making Useful Suggestions
THE ash framework of a coach door consists of two pillars—a door top and bottom. At the middle there is an outer waist rail and an inner garnish rail, between which there is space for a window to drop in the grooves formed in the pillars.
The design of the lower part of the door depends on the type of window mechanism used. Sometimes a bar is required to support this mechanism, but as a rule the metal-framed window rests, when down, on a pair of ribber buffers. Battens may be added to support the outside curved panels, whilst the inside surface of the door is usually boarded, or is covered with a plywood panel.
The lower half of the door is, therefore, a casing which conceals the window when down. Even if the window be designed to prevent the ingress of water, variations of temperature of the air confined within the door casing tend to set up condensation. Consequently, the door casing should be made so that any accumulated moisture may readily escape. For this reason holes are drilled in the door bottom, aS well as in any rail between it and the bottom• of the glass runs.
Above the waist line the groove in the pillar is made by rebating it and screwing a fillet DLL the inner side. A similar fillet may form one side of the groove in the door top. Being detachable, these fillets are a ready means for inserting or removing the frame of the glass.
The garnish rail may be decotated with a polished wood facia, whilst the top edges of this rail and facia are usually concealed by another filiisher.
544 As a rule, the door is hung on three butt hinges. As the vertical axes of the hinge-pins must be in line, the greater the vertical curve of the door, the more must the pin of the bottom hinge project beyond the panel. A pronounced turnunder is therefore undesirable.
The hinges having been aligned, the correct hanging of the door can be maintained only if the hinges have sufficient strength and if there be plenty of substance in the pillars in which to insert the screws of the hinge flaps.
It is also essential that the framework into which the door shuts shall be rigid and shall not alter in shape, although slight irregularities in the registration of the door are adjusted by means Of dovetails and buffers on the shutting side.
The opinion is sometimes expressed that the usual butt hinge is not the best means for hanging a wide and heavy door. It is an improvement if the hinge be self-aligning, and this may be effected by providing a steel ball for the main bearing.
The ball is drilled to receive a pin, which is slotted at the top and takes a nut at the bottom. The ball is not only self-aligning and prevents any undue strain on the screws in the pillars, but it has a larger bearing surface than has the ordinary pin. Moreover, the halves of the hinges are easily separated, so that it is a simple matter to remove the door.
A ball joint could also be made by forming it in the solid with one of the hinge flaps. The other flap would then be made with an upper and a lower socket bearing, the lastnamed being assembled by screwing on.
Another method of hanging the door is by means of top and bottom pivots rather than by hinges. The corresponding parts of the top pivot are screwed under the cant-rail and the upper surface of the door top, respectively. In the case of the lower pivot, one half is screwed to the top of the step and the other to the insid;., of the bottom of the door.
Or pivot being on top of the door and the other behind it brings the vertical axes of the pivots on a line inside that of the turnunder of the door. Mechanically, this is a better arrangement than having the pivot • line outside the door, as it is with the conventional method of hanging. The pivoting may be varied by using an outrigger style of hinge, which projects inwards, at the top, and the bottom pivot which is placed under the door. This style of hanging is suitable only for a wide .door, because when the •door is open that -portion between the pivot and the
nearest pillar projects inwards and reduces to a small extent the effective width of the entrance.
When the mechanically operated folding door was Adopted a design was introduced which extended below the floor level, thus forming a step well. With the extension of the panels below the top of the chassis a step well became necessary for the coach with the ordinary hinged door.
This step well is often covered by a flap hinged to the door. This should be unnecessary if the edge of the well nearest the main saloon be protected by a small partition. Occasionally the floor space, as represented by the flap, is required for the feet of the passengers occupying the adjacent near-side seat, but it is considered that a seat thus placed is too far forward.
The use of the flap is also defended on the plea that it excludes draught, but this may be overcome by fitting a rubber strip at the bottom of the door.
Some development has taken place in the use of cast doors made of light alloys. Most of these have been of the sliding pattern, but this method of construction might also be applied to the hinged door.
In view of the fact that little has been achieved so far as the standardization of bodywork is concerned, it might be regarded as impossible to make up a standard cast door which would be suitable for practically any design of vehicle.
It is, however, suggested that the casting could be designed with an extra flange around it which could be cut off as necessary in order to provide three different widths and heights of door, according• to whether one or both outer rims were removed, as shown in one of the accompanying illustrations.