SPEEDING-UP ROAD CONSTRUCTION.
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How a Contracting Company Intensified Its Lorry Loading and Unloading by DevelopTng a System of Centralization.
G'ERAL contractors, as well as those specializing in highway construction,. will -be interested in the centralized lorry-loading plant used by the Bical Contracting Co., of Kansas City, Missouri. This company recently obtained a contract to construct six miles of brick road, on a concrete base, in Wichita, Kansas, and found that by installing such a plant an appreciable saving, both in labour and material, could be realized. The quantity of material required for this work was considerable, as will be gathered from the fact that the concrete base was to be 7 ins, thick in the centre of the road and 5 ins, thick at the sides, quite apart from the huge quantity of paving bricks.
The metal, sand and cement used for building this road were received by rail,
• unloaded into storage piles and diecharged into automatic measuring chambers. The bins, used for the metal and sand were each equipped with five measuring hoppers, the metal comport-merits holding 10 Cu. ft. each, and the sand compartments 6 cu. ft. each.
When it was desired to charge the five metal-measuring hoppers, the metal-bin Operator pulled a lever which released five spouts. When the measuring hoppers were filled the lever shut off the metal supply, and the hoppers were ready to discharge into lorries, the bodies, of which were also divided into five compartments. The movement of the sand from the bin to the measuring hoppers was controlled by five levers, separately operated, but the dumping of the sand from the tipping hoppers into the compartmented lorries was accomplished by the pulling of one lever.
One of the illustrations shows the metal hoppers being discharged into the respective compartments of the lorry. The flow of metal was uniform, and the charge delivered in less than a minute. .
Alter receiving the metal, the lorry was backed under the sand hoppers and the sand loaded in About 15 secs. The lorry was then moved forward 500 ft. to the cement' storage building, the cement being loaded in a similar fashion to that which took place at the metal hopper. In this way cement sacks were kept at the central plant, and the loss of both cement and sacks was reduced to a minimum. Metal and sand wastage was also kept at the lowest figure, whilst there was little opportunity of foreign materials getting into the mixture. '
The transport of these loads involved a
maximum one-way haul from the loading bin to the concrete mixer of three miles, or six miles fur the round trip. Six 3i-ton Republic lorries, equipped with specially designed steel tipping bodies partitioned into five independent compartments, were used for this work. Each of the five compartments held sufficient metal, sand and cement to charge the concrete mixer.
The lorries were scheduled to start • from the loading plant at intervals of seven minutes, travelling towards the mixer at a speed not exceeding 12 m.p.h. The mixer was approached by means of a specially laid track, for the sub-grade, which was of a sandy character, necessitated the Use of such a tiack.
The lorries were able to turn and back
down this track by means of a specially . designed turntable,. which permitted i he
truck to be reversed in less than one minute. After being turned, the lorry
was backed over 300 ft. towards the concrete mixer, and during this section of the tfip the body was lifted to an angle of 45 degrees by a Wood hydraulic hoist. Consequently, the lorry was in a position to dump the contents of the rear. most section oa its arrival at the mixer.
After the first batch had been tiPpel into the mixer apron, the lorry moved forward two or three feet, while the apron was hoisted and the material tipped into the mixer. The apron was then lowered, and the lorry again backed • up to tip the material from the second compartment. The contents of each succeeding compartment were dealt with in a similar manner.
When the lorry was empty it proceeded to a point halfway between the mixer and the tuntable. There it left the track. This enabled the following lorry to save time by using the turntable and backing down as close as possible to the mixer plant, and immediately the previous lorry had passed off the track the waiting vehicle backed down to the. mixer to dispose of its load. . On the maximum haul of six miles the lorries made the round trip in 42 sums., travelling 60 miles each day with a petrol consumption of 3.75 miles per gallon. This comparatively high rate of consumption was due to the fact that the engine was kept running during the time of loading, turning and discharge. The scientific operation of thisfleet entailed considerable shill on the part of the drivers in maintaining their schedules, and each driver received a wage of $5 a day. In order, that a minimum of breakdown and delay should be experienced in maintaining the schedule, a completely equipped repair shop, in the charge of a competent mechanic, was located at the loading plant. All the lorries received a thorough inspection and oiling each morning before commencing the day's work. Work of this nature demands an adequale and reliable supply of water. The supply in this case was obtained through a duplicate set of pumps and engines, which took water from the Arkansas River, delivering it through a 2-in. pipe line to the mixer, roller, sub-grade and finished road. Each pump was capable of supplying 40 gallons per minute against 60 lb. pressure, and one pump was always held in reserve. The pumping apparatus was moved and reset once in each mile, and thus the maximum pumping radius was never more than half a mile, so that no overloading of the pomp could occur.