SECURING SAFETY IN TOWER WAGON DESIGN.
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How Stability is Obtained in a Three-stage Karrier Vehicle.
lUrOST of the prominent municipal _LV_Lauthorities in this country which operate overhead tramways find that the motor-propelled tower wagon is an invaluable type of vehicle for the maintenance and repair of wiring systems. The same remark applies, of course, where trolley-buses have been substituted for tramcars. The class of vehicle largely used for this work is shown in the accompanying illustrations, which depict a Karrier wagon recently supplied to the tramway authorities in Halifax. The chassis serving as the basis of this machine is the company's CI 2-tanner, which incorporates in its design a 25-36 h.p. engine, a four-speed gearbox and a worm-driven rear axle.
The tower superstructure is of the three-stage type, and, when extended, its full height is 22 ft, whereas when the sections are lowered its height is 13 ft. Instability of the superstructure has, hitherto, been a disadvantage associated with -three-stage wagons, but this drawback has been eliminated in the ease of the Karrier wagon by the use of a patent wedging device which ensures that the tower remains perfectly rigid throughout its life. Tests which have been conducted have shown that the angle to which the vehicle can safely be tilted from the vertical is 30 degrees when the tower is extended, and 37 degrees when it is lowered.
The tower is built of well-seasoned oak which is soundly braced and baited together. All sliding surfaces are steelplated and the elevating gear is of the screw-and-wire-cable type. The main lift is effected by screw gearing, the middle section raising the top by wire cable at the same time, and the whole series of operations is quickly performed by one man.
The tower can be locked at any height, and a ladder which extends with it during the process of raising enables access to be gained to the rotating platform which is fitted with a folding
guard rail 2 ft. 9 ins. deep. Between the tower and the driver's cab is a capacious toolbox, whilst at the rear is a work bench. The driver's cab provides accommodation for three people. The machine, which is finished in e. shade of red, smartly lined, is fitted with a 12-volt lighting set.