[PRCo] Re: Trolley speed

[Boris Cefer]

Don't I see our favorite topic again? I made a demonstrative diagram and
shared it with Jim several weeks ago, thought it could be useful one day.
Just now!
Of course, on steep DOWNGRADE you can run any vehicle at 55 mph or more, but
something shall damage itself. In case of PCC car supposedly traction motor
armatures. Maximum safety speed for these is 50 mph, with some reserve of
cca 12 mph. We can expect that motor armatures might destroy themselves at
speed about 60 - 65 mph, which is in average, and also the age and technical
condition of each motor playes important role, however.
On UPGRADE is the maximum (balancing) speed always lower than on tangent
level track. And again, the balancing speed of PCC - 42 mph - mentioned in
books, has relevance only on TANGENT LEVEL TRACK.
My draft shows just that case of tangent level track:
Three curves of car tractive force in dependance on speed:
for (1) full motor field exciting (car with removed field shunting)
for (2) weakened motor field
for (3) strongly weakened motor field (interurban 1700s)

One curve is of car running resistance (mechanical, i.e. rail & wheel
contact, air stream, gears) for tang. lev. track.

As a result you can see three different maximum (balancing) speeds for each
type of car control.
For downgrade you need to move the car resistance curve downward in relation
with track slope. The same upward for upgrade track. In any case, the point
of intersection of traction force curve with car resistance curve shows the
balancing speed under appropriate conditions.

Boris

----- Original Message -----
From: "Bob Rathke" <bobrathke at comcast.net>
Subject: [PRCo] Trolley speed


> Yes!  I once heard that PCC's could reach 45 mph....or maybe it was 55
> mph....
>


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