Hmm, this is perplexing, someone posted the answer we were looking for early on, but it is gone now. So we will take the last answer, Coleman. While Coleman was the builder of this truck, we also have to give a partial credit to the Ford answers, as some Ford components were used. At least nine of these yard donkeys were built for PIE. Sergey "Trucker" had the right answer. Thanks to John Frances for these photos, and also for providing this info from "Distribution Age" magazine in 1951.
PACIFIC Intermountain Express Co. is using a new single-seat tractor, called a "yard donkey," to spot and tow semitrailers at freight docks and maintenance facilities.
The "donkey" is equipped with a hydraulic fifth wheel controlled by the driver. This permits the yard hostler to back under a semi-trailer and, after the king pin is locked, lift it without cranking up the "landing gear." The landing gear under the semi-trailer is lowered when the road tractor is unhitched to hold the former in a level position. By use of the hydraulic fifth wheel on the "donkey," it is not necessary to raise and lower the landing gear in the yard, as the hydraulic fifth wheel raises the semi trailer high enough for the wheels on the gear to clear the ground as the trailer is moved.
From his seat, the hostler can also reach back and connect or disconnect the air lines carrying air to the semi-trailer brakes. A special stand holds the lines at a convenient level to the rear of the seat. The hostler is thus able to back a semi-trailer into the dock or pull it into position for over-the-road service without lost motion. By making the air connection, brakes on the semi-trailers can be tested before hooking on to line-haul power equipment.
The short coupling permits mobility that could not be obtained by a standard tractor. This feature is particularly important in the movement of semi-trailers in maintenance and overhaul shops. A 35-ft. semi-trailer can be turned around in its own length or switched easily from one service line to another while undergoing inspection maintenance.
The unit measures 13 ft. 2 in. It is fabricated under company specifications by Coleman Motors, Littleton, Colo. Bartlett Trailer Co., Chicago, furnished the hydraulic fifth wheel. Power unit and component parts were supplied by Ford. The company has nine of the units in operation.