iameter for the wheels we have to use in freight service.

When we take up passenger service we come to a much more difficult and
interesting part of the subject, for here we must consider it in all
its bearings, and meet the complications that varying conditions of
place and service impose. In consequence, I do not believe we can
recommend one diameter for all passenger car wheels although such a
state of simplicity would be most desirable. For instance, in a sandy
country where competition is active, and consequently speed is high
and maintained for a length of time without interruption, I would
scarcely hesitate to recommend the use of cast iron for car wheels,
because steel will wear out so rapidly in such a place that its use
will be unsatisfactory. If then cast iron is used, we will find that
we cannot make with it as large a wheel as we may determine is
desirable when steel is used. And just to follow this line out to its
close I will state here that we find that 36 in. seems to be the
maximum satisfactory diameter for cast iron wheels, because this size
does not give greater mileage than 33 in., costs more per 1,000 miles
run, and seems to be nearer the limit for good foundry results. On the
other hand, a 36 in. wheel rides well and gives immunity from hot
boxes--a most fruitful source of annoyance in sandy districts. It is
also easily applicable where all modern appliances under the car are
found, including good brake rigging. In all passenger service, then, I
would recommend 36 in. as the best diameter for cast iron wheels.

Next taking up steel wheels, a great deal might be said about the
different makes and patterns, but as the diameter of wheels of this
kind is not limited practically to any extent by the methods of
manufacture, except as to the fastening of the wheel and tire
together, we will note this point only. Tires might be so deeply cut
into for the introduction of a retaining ring that a small wheel would
be unduly weakened after a few turnings.

On the other hand, when centers and tires are held together by
springing the former into the latter under pressure, it is possible
that a tire of larger diameter might be overstrained. But allowing
that the method of manufacture does not limit the diameter of a steel
wheel as it does a cast iron one, the claim that the larger diameter
is the best is open to debate at least, and, I believe, is proved to
the contrary on several accounts. It is argued that