th. by J.F. Gedney, Washn.]

[Illustration: SPACES REQUIRED for working DIFFERENT CLASSES OF GUNS
ON TRUCK CARRIAGES. (_with muzzle 18in inside of centre of Port_) C.K.
Stellwagen, del. Lith. by J.F. Gedney, Washn.]

CHAPTER III.

GUN-CARRIAGES, GEAR, IMPLEMENTS AND EQUIPMENTS.

GUN-CARRIAGES.

207. All gun-carriages shall be constructed in exact conformity to the
drawings furnished by the Bureau, and no alterations whatever will be
permitted without its express sanction.

The Inspector of Ordnance will keep approved copies of all plans, and,
in order to insure uniformity, will report to the Bureau any
deviations from the standard drawings which he may observe in
carriages received from other Yards.

The spaces required for efficient working of all guns are represented
in diagrams X, Y, Z, and these, as well as the distances between
pivot-centres, sizes and positions of bolts, are to be strictly
adhered to.

The distance between pivot-centres of all XI-in., X-in., IX-in., and
100-pdr. carriages shall be either 142 or 117-3/4 inches, depending on
the breadth of beam, position of hatches and other obstructions, and
shall not be deviated from except by explicit directions of the
Bureau, on a report of the particular circumstances in each case.

For the 60-pdr. Parrott, 130 inches between centres; and for the
30-pdr., 120 inches.

The sizes of sockets and pivot-bolts are established as follows:

FOR XI-IN., X-IN., FOR 60, 30,
IX.-IN., AND 100-PDR. AND 20-PDR.
Inches. Inches.

Length of bolt under the head 18. 14.
Diameter of bolt 4. 3.
Do. hole in socket 4.1 3.1
Do. boss 10.5 8.
Height of boss 1.5 1.1

Slot in the pivot-plate, 1/16 larger than the boss.

For XI-in., X-in., IX-in., and 100-pdr. carriages, the fighting and
shifting sockets are bossed, the housing-socket plain.

For 60-pdr., 30-pdr., and 20-pdr. carriages, the shifting-socket alone
is bossed.

For broadside-guns, the following positions for bolts are established:

20 AND 24 IN. 16 AND 18 IN.
PORT-SILLS.