SAFETY FIRST IN TURNTABLE FIRE ESCAPES.
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Details of the New Leyland-Metz Fire Fighting And Rescue Appliance.
MANY EFFORTS have been made to increase the efficiency of the turntable fire escape and hose tower, and at the same time to reduce the considerable element of risk which has often attended the employment of these valuable aids to brigade work, and in the latest Leyland-Metz product of this type these desiderata appear to have been attained in no small measure.
So far as the chasis is concerned, this is practically a standard Leyland production from the well-known works at Chorley, specially vtrengthened by combined pressure and tie rods for the side members, but one unusual feature is the provision of a device, operated by hand from the rear of the vehicle, which locks both the front and rear axles in-position, so that there can be no movement of the upper portion of the, vehicle on its springs. This is a most essential fitting as, at the best of times, there is a certain amount of sway with a ladder stretching to heights of perhaps BO ft. or more, and this would only be emphasized if the spring action were also permitted. Apart from this the locking of the axles practically transfers the base width from the spring centres to the tyre centres, thus making for stability.
The moss important feature of the actual ladder gear is the automatic plumbing device, which operates in such a manner that, whether the ground upon which the vehicle stands he even or uneven, the ladder always remains plumb. There is also a _positive safety device which automatically cuts out the elevating mechanism if the load exceeds a set maximum or a set minimum.
It is easy to understand -what the maximum load implies, but to explain the meaning of minimum load is rather more 'difficult. We will take a specific instance. Supposing the ladder is being raised through a cloud of smoke and it is unintentionally forced against the wall of a building, in this case the pressure, instead of being imposed on the upper portion of the.ladder by the weight, acts on the underside and creates what may be called negative pressure, and directly this exceeds the limit of safety further raising of the ladder is automatically arrested.
. The various details of mechanism may appear to be somewhat complicated; but they are, what may be termed, mechanical jobs; in other words, the whole can be dismantled • and re-erected by a qualified mechanic without any special difficulty.
All the motions are effected by positive gearing driven from a power takeoff situated at the front end of the main gearbox of the chassis, and the motions are brought into action by oil-operated plate clutches. It is this oil control which enables the automatic devices to be brought into action in such a facile manner. For instance, the pendulum controls the plumbing through a type of servo-motor, and is very sensitive in operation.
The moving ladders are fitted with sheet-steel gusset plates, which entirely prevent/ loosening of the rungs and the consequent jarring of the ladder sides; which often occurs in ladders not so stiffened, the ladders rising in a series of jerks at each side alternately. If, in some emergency, it is decided that it would be justifiable to take additional 1-isks, the various safety devices can be cut-out 'by the use of a special lever. Apart from this, all the motions can be effected by hand as well as by mechanism.
The turntable ladder which was demonstrated last week by the Leyland Motor Co., Ltd., before the Professional Fire Brigade Association—including representatives from all over the kingsicim, and delegates from various corporations —was a type giving a maximum ladder height of 85 ft., but other sizes can be built to Special order.
Everyone who saw the demonstration was very impressed with the practicability and safety of the new machine, and we were also informed that the fire brigade authorities have added favourable comments.
There are three control handles most conveniently situated together on the near side of the machine. These are for elevating, extending and turning, and dials show the extension in feet and the inclination, or transverse extension, also in feet.
In addition to automatic cutting-out of the elevating motion, a special pointer indicates how near the extremes have been approached, and by this it is easy to tell if it be safe to send a second or third man up the ladder at any particular angle of inclination.
Windage must also be considered, as this is a most important factor, which alone may give negative pressure-or increase positive pressure to an undesirable extent.
The whole machine has really been designed on " safety first" lines, and it is almost human in the way it responds to changes of circumstances without any exterior control.
During the test with the new escape, we were interested to note the extremely easy and smooth manner in which the raising, lowering, extending and turning of the ladder could be effected In spite of the drive to the various motions being, as we stated before, positive, the contulle appeared to give ample elasticity,
there being no apparent harshness in any of the movements.
The weather at the time the ladders were raised was very windy, and consequently the test offered conclusive evidence of the stability of the whole machine.
Certain members of the Leyland staff took the opportunity of testing the capebilitiee of the machine, although we ourselves preferred to remain on terra-firma, not that we had any doubts about the safety of the machine. Few companies who manufacture firefighting eq,uipment has e. had such a wide experience as have Leyland Motors, Ltd., and there is no doubt that this new form of turntable ladder will do much to enhance an already sound reputation. During the demonstration other appliances than that described were tested