Quiz Answer

[Edward H. Lybarger]

In lesson #7, we learn the inspection intervals for "regular" (low floor)
and PCC cars, among other things.  After listing the intervals for varying
degrees of inspections for both types, the text tells us:

"In the case of the regular cars, the intervals between inspections are
usually referred to as so many miles, but they are really determined by
kilowatt hours.  Each car has a watthour meter which measures the amount of
electrical energy used by the four motors.  The heaters, lights and air
compressor are not connected to the meter.  Hence the kilowatt hours
recorded by the meter show the amount of work done by the motors in
propelling the car.  This is believed to be as satisfactory for measuring
wear and tear on the equipment as to use actual mileage.

"These meters have special dials which are designed for inspection purposes.
The "A" dial has 10 divisions each of which corresponds to 1000 kilowatt
hours.  Thus the "A" inspection which is performed at a reading of 4 on this
dial is in reality done at 4000 kilowatt hours.  An ordinary car uses this
amount of energy every week or ten days.  The "B" inspection is performed at
a reading of 8 on this same dial.

"The "B" dial also has 10 divisions but each division is equal to 4000
kilowatt hours which is four times that of the "A" dial.  The "C" inspection
period which is 16 divisions of the "B" dial is determined by a reading of 6
on the "B" dial on its second revolution.

"A "C" dial is also provided on the meter.  This was originally intended for
use in car overhaul, but is not being used for any inspection purposes at
the present time.

"These inspection dials are very easily read and any person may tell at a
glance whether a certain car is due for inspection or not.  When inspections
are completed the foreman in charge may insert a key and set the proper
inspection hand back to zero.  Thus no one can tamper with these dials nor
can they be moved accidentally.

"It is possible to convert kilowatt hour readings at any car house to fairly
accurate mileage values by using average conversion factors based on the
actual performance at that location.  These values vary considerably for
various car houses depending on the type of service.  However, a general
average for the entire system is very near to four KWH per car mile.  This
figure is used in approximate conversions when speaking of the inspection
period in terms of miles.

"The PCC cars are equipped with a mileage meter which is mounted on one of
the wheels.  These meters are called hub odometers.  They are operated by a
weight which is suspended on a pin and which turns the mechanism as the
wheel revolves.

"This device gives a reading in miles travelled similar to a speedometer on
an automobile.  There are no inspection dials, hence the inspections are
made when the mileage reading has increased by the proper amount, for
example, 6000 miles for the "C" inspection."

So while Jim's logic was good, PRCo's was too...this was the cheapest way to
get the desired information!

I'll have another question later in the day.

Ed