r wheels are of steel and have double helical teeth; the shafts
are also of steel, and the principal bearings are adjustable and
bushed with hard gun metal. This crane has a separate pair of engines
for each motion, which are supplied with steam by the multitubular
boiler placed in the cage as shown. The hoisting motions consist of
double purchase gearing, with grooved drum, treble best iron chain
with block and hook, driven by one pair of 8 in. by 12 in. engines.
The transverse traveling motion consists of gearing, chain, and
carriage on four tram wheels, with grooved chain pulleys, driven by
the second pair of 6 in. by 10 in. engines, and the longitudinal
traveling motion driven by the other pair of 8 in. by 12 in. engines.
The transverse beams are wrought iron riveted box girders, firmly
secured to the end carriages, which are mounted on four double flanged
steel-tired wheels, set to suit a 38 foot span.

[Illustration: IMPROVED OVERHEAD TRAVELING CRANE]

[Illustration: FIG. 2 SIDE ELEVATION]

[Illustration: FIG. 3 PLAN]

* * * * *

BEST DIAMETER CAR WHEELS.[1]

[Footnote 1: By Samuel Porcher, assistant engineer motive power
department, Pennsylvania Railroad. Read at a regular meeting of the
New York Railroad Club, Feb. 19, 1891.]

It goes almost without saying that for any given service we want the
best car wheel, and in general it is evident that this is the one best
adapted to the efficient, safe and prompt movement of trains, to the
necessary limitations improved by details of construction, and also
the one most economical in maintenance and manufacture.

It is our aim this afternoon to look into this question in so far as
the diameter of the wheel affects it, and in doing it we must consider
what liability there is to breakage or derangement of the parts of the
wheel, hot journals, bent axles, the effect of the weight of the wheel
itself, and the effect upon the track and riding of the car, handling
at wrecks and in the shop, the first cost of repairs, the mileage,
methods of manufacture, the service for which the wheel is intended
and the material of which it is made.

Confining ourselves to freight and passenger service, and to cast iron
and steel wheels in the general acceptation of the term as being the
most interesting, we know that cast iron is not as strong as wrought
iron or steel, that the tendency of a rotating wheel to burst is
directly proportional to