On 8/6/68 a trough machine was approved to fire 9-pr. Hale's rockets,and on 10/7/68 a similar trough of larger dimensions was approved for 24-pr.
The following general description applies to both:-
Each size consists of a sheet-iron V trough ; the side made at a angle of 80% with each other,supported at rear by three legs made of wrought-iron tubing, two short ones oppening right and left ,and one long one to the front beneath the trough ,each terminating in a prong .
On the front one runs a gun -metal ring connected by two bars with a V near the front of the trough, the bars pivot on V and ring;the elevation is given by slipping the ring up and down the front leg,and champing it with the arrow on the rear edge of the ring at the required line of graduation up to 15° of elevation for 9-pr., and 25° for 24- pr.machine,with reference to the plane on which the machine stands.
At the back end of the trough is a iron stop preventing the rocket sliding back;it is slotted to form a crutch for copper friction tubes.
In firing the rocket with friction tube ,in order to prevent the machine being disturbed ,the lanyard must be pulled smartly or else the foot pressed against the leg of the machine, or again the lanyard may be under the foot.