Page:Popular Science Monthly Volume 88.djvu/918

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��Popular Science Monthly

���Four four-mule teams are more efficient when pulling together than when separate where

extensive transportation is necessary. The maximum traction effort required is less than

four times the maximum for a single team

��Expensive Transportation

IN many engineering projects, the cost of transporting equipment and ma- terials assumes a very high relative value.

In illustration, may be cited the case of the hydro-electric development of Big Creek in California. The site of the works was to be located fifty-six miles from the nearest railroad. It was estimated that to do this work with teams, the transportation cost would have been about twenty dollars per ton. So, the contractors built a stand- ard size railway.

But they could not con- struct a railway in order to supply materials for transmission line, which is two hun- dred and forty-one miles long. Teams had to be employed.

A little con- sideration will make clear why it is better to unite four four- mule teams in- to one than to use them sep- arately. A

���The test-car is used for detecting faulty railway scales

��loaded wagon must ordinarily be hauled by a team able to overcome the maxi- mum difhculties. A string of four wagons would hardly all of them have their individual maximum difficulties at the same moment. In other words the maximum traction effort required for the string is probably less than four times the maximum effort required for a single wagon.

��A Traveling Laboratory for Testing Railway Scales

ONE of the interesting phases of the United States Bureau of Standards* work is the testing of railway-track scales by means of traveling test-cars which make their way over the great railway systems of the country.

Two test-cars are now engaged in this work. Each test - car carries ninety thousand pounds of standard weights, eight of ten thousand pounds each

and four of two thousand, five hundred pounds each. The car carries also a small truck driven by an electric mo- tor on which the weights can be placed so as to be rolled on to the trucks of the scale to be tested.

At the for- ward end of the car there is a crane which can be ex tend - ed through the end doors, and which carries an electric hoist for raising the truck and placing it on the track. The work of the first test-car demonstrated that seventy per cent of the number of freight scales tested showed an error of at least two hundred pounds in weighing a freight car of one hundred thousand pounds. This proves that the test-car was needed.

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