This car was specially designed for the Yosemite Valley Lumber Co. to
operate on an incline 8,000 feet long, with a maximum grade of 78%, the
rise in feet from the foot of the incline to the top being 3,100 feet,
the incline being in a vertical plane, but following the general slope
of the mountain side and changing from one slope to another. The cars
are let down the incline by means of 1½ in. wire rope, attached to a
donkey engine.
This car was designed to meet these conditions, and is provided with a
steel backbone, reinforced at the ends forward of bolsters to provide
for the extreme angle of cable pull from a horizontal line and at the
down hill end to support the bulkhead, which is provided to keep the
logs from shifting. The vertical bulkhead posts are riveted to the
steel backbone. At the cable end a special combination buffer and cable
casting of cast steel is secured to the backbone by means of gusset
plates, and is also riveted to end sill.
The backbone is built up of steel plates and angles in the form of
a box girder, of the fish belly type. Cross bearers are located
intermediate of the bolsters, and are sufficiently strong to carry
the loads from the side sills to the center construction. Experience
has proved that for logging cars, steel is unsuited for use in side
sills, as continual shocks, resulting from discharging the load, cause
their failure. For this reason red fir side sills were introduced in
this car, making the underframe a composite construction of steel
and timber. The side sills being supported at four points, viz.: at
bolsters and cross bearers, no trouble has been experienced from
failure of these sills. In case of failure, they are readily replaced,
and the work can readily be done at any camp.
The bulkhead is constructed with a steel frame, with planking for the
bulkhead proper, so that in case blocking is necessary to fill out
between the log and the Bulkhead, this blocking can be nailed to the
bulkhead to secure it in place, the object being to provide against the
possibility of the log starting to shift.
The cable casting is made with a machine-fit pin to engage the shackle
on the cable and place the pin in positive shear.
The cars were equipped with four Hercules Bunks, to provide for short
or long logs.
The trucks are of the Diamond Arch Bar type, with cast steel bolsters.
The bolsters are of special design, with hemispherical center bearing,
to take care of the rock of the trucks in passing over the sharp,
vertical curves.
Axles with 4¼×8 in. journals, and 33 in. chilled cast iron wheels are
used.
Cars are equipped with Westinghouse automatic air brakes and inside
hung metal brake beams.
The draft rig is of the twin spring type, with automatic couplers.
[Illustration: General View of our Yosemite Grade Destroyer]