Fast Work with Latest Straddle Carrier
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THE British Straddle Carrier Co., recently taken over by Short Bros. and Harland, htd. (The Commercial Motor, June 20), last week demonstrated their latest model, the Mark H. They did so in the timber yard of Burt, Boulton and Haywood, Ltd., at Belvedere, and at Short Bros. and Harland's airfield at Rochester. The object was to show the diverse loads that this novel vehicle could carry.
Working with timber, the carrier showed how it could be used when discharging cargo from a ship. Three-ton loads of timber. which would have been placed on the quayside by the ship's derricks or dockyard cranes, were picked up and speedily conveyed to the storage .point to be stacked by mobile cranes or fork-lift trucks. The manceuvrability of the carrier and its suitability for working in narrow alleyways, because the load was carried longitudinally, were apparent.
The Straddle Carrier then travelled some 12 miles to Rochester takingonly slightly longer for the journey than an A.E.C.coach, an excellent indication of its road performance made possible by a maximum speed in forward or reverse of 30 m.p.h. with a payload of 14,000 lb.
At Rochester a number of special loads had been prepared, ranging from oil drums to bricks. A load of girders and concrete blocks was easily transported, even though this represented a 10 per cent. overload for the model shown. Special pallets enabled 24 oil drums of 40-gal. capacity to be carried. Ten beer barrels were also conveyed.
Seven tons of bricks, which it was stated would have taken two men at least an hour to load on to a lorry and a further hour to unload, were picked up on a pallet and carried for 200 yd. in less than a minute. The manufacturers believe that the Straddle Carrier could well be used both on and off the road as a delivery vehicle for builders' supplies.
Other loads carried were telegraph poles, heavy lead dies, filled sacks, largebore pipes and assorted crates.
In 70 seconds a 4-ton load was carried 220 yd. and set down, the carrier returning to the starting point in reverse. High speed in reverse is aided by good rearward vision for the driver.
The power unit is a Perkins L.4 oil engine producing 62 b.h.p.-at 2,000 r.p.m., coupled, through a 14-in.-diameter clutch. to a David Brown gearbox giving three forward and three reverse ratios.
An Eaton 16,500 two-speed differential is mounted at the rear of the upper chassis framework, drive being taken from this unit through universally jointed half-shafts to chain-toothed sprockets. Semi-enclosed chains drive similar sprockets on each rear stub axle. With this transmission combination, providing six similar ratios in forward or reverse motion, the vehicle is equally suitable for speed on the road or heavy-duty work on rough ground.
All four wheels are shod with 11.0020-in. tyres and are steerable. Light steering is assured by a Marles integral power-assisted unit, hydraulic pressure being provided by a separate enginedriven pump. The rear wheels are locked for use on the road. Lockheed brakes are fitted on all wheels, with vacuum assistance by a Hydrovac.
Suspension is of the sliding-pillar type, employing an undamped coil spring in each unit, permitting an overall deflection of 6 in.
Apart from the provision of four-wheel steering, the other major change in design occurs in the clamping and lifting hooks. Formerly rigidly mounted in a vertical position, they are now modified to swing outwards before picking up the load. Thus, accurate positioning of the vehicle over the load is-not so important. The hooks clamp under the bolster or pallet, alignment being achieved by gravity.
Power for the lifting rams is provided by a hydraulic pump driven from the front of the engine crankshaft and in continuous operation while the engine is running. A balance valve requiring reversed pressure to release it, automatically holds the load in the raised position.
The machine costs about £4,500.