56. Where are the handspikes applied in traversing the carriage?
To the pivot-bolts of the traverse-wheels, which project to the rear; or under the traverse-wheels.
57. Why does the chassis slope towards the front?
In order to diminish the recoil, and aid in running the piece into battery.
58. Describe the columbiad gun-carriage.
It is a triangular frame-work, consisting on each side of an upright, a horizontal rail or tie, and a brace, firmly mortised and bolted together, forming the cheeks, which are joined by a transom at each end. These project below the lower surfaces of the ties, and fit in between the rails of the chassis, serving, like the flanges on the rollers in the other barbette-carriages, to prevent the gun-carriage from slipping sideways off the chassis.
Through the front transom, and near the front ends of the ties, an iron axle-tree is passed, working in iron boxes fitting in the ties. On the projecting ends of this axle-tree the rollers or manœuvring wheels are fixed (the axes of which are eccentric with the axis of the axle-tree) the extreme ends of the axle, being octagonal in shape, to fit the wrench of the iron handspike.
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These eccentrics are so arranged that when the centres of the wheels are at their lowest points, the surfaces of the wheels bear on the rails of the chassis and raise the gun-carriage tie from it; and when the centres are at the highest points, the surfaces of the wheels do not touch the rails, and the ties are in contact with them.[2] A similar arrangement is made for the rear part of the carriage, except that the axle does not extend all the way through, but the wheel on each side has a projecting piece of axle which works into a box placed near the end of the tie.
The wheel is thrown into or out of gear, that is, made to bear on the rail of the chassis or relieved from it, by turning the axle with a wrench placed on the octagonal end. In the direction of the radii of the wheels, but inclined outwards, mortises are placed for the reception of the end of the iron handspikes, by acting on which while inserted the wheels are turned, and the carriage moved back and forth on the chassis. Ordinarily, when the wheels are thrown into gear, the carriage being back, it will run into battery of itself.