Discussion on “notes on the use of alternating current in unloading coal” (Ryerson and Crane), Pittsburgh, Pa., April 27, 1912. (see proceedings for March, 1912)

Wilfred Sykes: Having been more or less responsible for the first of the man trolley equipments installed at Duluth using alternating-current, I would like to draw attention to a few points in the paper. The maximum rate of operation of the man trolley bridge has been given as 500 tons of coal per hour. I have some tests showing that in the case of one test, extending over a period of five hours, in which twelve minutes delay was incurred, due to waiting for the boat, leaving a net period of 4 hr. 48 min., the bridge made 389 trips; about 40 per cent of these trips were to the first hopper for loading direct into the cars, and about sixty per cent of the trips went back 150 feet on the pile. That gave an average rate of operation of 74 trips per hour. The capacity of the bucket averaged a little more than five tons, so that the total amount of the coal handled was about 2050 tons. The maximum rate of operation over one hour was found to be 83 trips; the number was about evenly divided between trips to the hopper and trips to the pile.