PCC Acceleration & Speed

[Jim Holland]

Greetings!

	Have already archived the other posts, but Dr. Fred corrected himself
on PCC acceleration downgrading from 4.75 mphps to 4.25 mphps.  I
mentioned that I had always seen the former figure.

	The chart on pages 56-57 of *PCC The Car That Fought Back* show
statistics for a wide variety of cars for comparison.  It shows the
original PCCs to be 4.75 mphps and Pgh 1600 to be 4.0 mphps; balancing
speed is 42mph and 40 mph respectively.

	Before these books, my main source of information was an article
entitled *The American P.C.C. Car* published in the British *Passenger
Transport Journal* of 1945.12.14.  On page 348 it lists the acceleration
as 4.75 mphps and it shows a graph of the acceleration which you had
mentioned.  In 60 seconds the car was at 37-38 mph but had gone only
2,700 feet, not a whole lot more than half a mile!

	It is in this same article where I got the speed figure for climbing
grades.  On page 349 in the second column under the heading *Start*(?),
I shall quote the whole paragraph:
	"Fig. 2 shows the typical speed-time, distance-time curves for a car
weighing 38,000 lbs. on the level.  The rate of acceleration grows
gradually at the start but is required on test to achieve 4.75
m.p.h.p.s. in from 1 to 1 1/4 seconds.  The rate of change of
acceleration must not exceed 5.5 m.p.h.p.s. in any quarter second
interval.  The maximum speed is 42 m.p.h.; balancing speed is 28.5
m.p.h. up a 6 per cent gradient."

	Didn't know they could measure so closely then!

	I wasn't and am not challenging your figures; it seems that both
figures are correct.  It certainly makes sense that as the car got
heavier, performance would drop.

	Sound has much to do with our perception of speed as we have already
mentioned!  Rail joints were 30-40 feet apart on average and are not
conveniently located like model snap track - they are often staggered
and there are also shorter pieces of rail.  Heading outbound thru the
Mt. Wash tunnel in the good ol' PRCo days with rail joints at 28.5 mph
sounded more like the car was doing well over 50 - but obviously it
wasn't.  Doing 30 mph on the surface would seem like an extremely fast
ride!

	I stood at the north end of the McKinley Park trestle (1959-1960) and
filmed two different outbound cars.  The second car sounded so much
faster that it took my breath away and made my heart stop!  Yet one
cannot perceive the difference in speed by watching the movie - without
sound!  It was then that I realized the futility of silent movies and
hoped for a way of simultaneously recording sound.  About five years
later I got a portable Akai tape recorder while on duty with Uncle Sam's
Canoe Club in the South Pacific (and that was a real clunky thing in
those days) hoping to use it in conjunction with making movies of the
Pgh. streetcars, but never did!

James B. Holland
------- -- ---------
        Pittsburgh Railways Company (PRCo), June of 1949 -- June of 1953
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