The carriage above described is one suspended only on C springs. Sometimes elliptic springs are used in conjunction with C springs, and the former are then termed under-springs. In the latter case, of the double combination of springs, the constructional timbers may be of a less size or scantling, owing to some of the strain and concussion being removed. In this case the axles are clipped to the under-springs; but the general mode of construction is the same.
In first-class work a wrought-iron perch is used instead of the before described wooden one. This generally follows the contour of the underside of the body, and is called a swan neck. It enables the perch to be constructed of a much lighter appearance, and being really light, and to a certain extent elastic, all the beds and iron stays may be proportionately reduced in weight. The wheels and axles also, having less to carry, may also be made lighter. The system was introduced by Messrs. Hooper about 1846, and at first was only applied to broughams and sociables, but it has gradually been applied to the largest carriages, especially barouches and landaus. These perches are supported on horizontal under-springs, and are not now made so light as at first, for it is found that unless the hind wheels follow steadily, not only is the carriage heavier behind the horse, but the perch itself is frequently bent against very small obstructions; a stronger and stiffer perch is therefore now used, and it is found easier both to the horse and to the passengers.
When the body is suspended from C springs by leather braces, great care should be used in the selection of the material for these latter, and for this purpose the best and strongest leather is required.
The use of brake retarders to the hind wheels has now for some years superseded the old-fashioned drag shoes. It is evident that the action on two wheels must be better than on one only. The brake can be applied or removed without stopping the carriage, which is necessary if a drag shoe be used. This is rather an important consideration in undulating country, for it would be a great inconvenience to have to get down and put on the drag shoe when descending a hill, and when at the bottom to stop and get down again to remove it, in order to proceed along level ground or up the next hill, and so keep on like this all day. The lever brake was the original form, as still seen on drags, &c., but in many parts it is superseded by the foot or treadle brake, more especially in Scotland. This kind of brake is also the one used by the London Omnibus Company. The blocks which press upon the wheels have been made of various substances—cast iron, wrought iron, brass, wood, india-rubber, and leather. The wood is the best for the hold on the iron tyre and absence of noise and smell, but it wears out fast. India-rubber, especially for light carriages, seems to be the most satisfactory.
We have given, generally, the operation of framing together the under or carriage parts of the vehicle. But as some very important considerations regulate the shape, construction, and formation of most of these parts, they must be discussed separately. For this purpose they will be considered under the following headings:—
Wheels.
Axles.
Springs.
Wheel-plates and fore-carriages.
Ironwork generally.