All,
Bob Simon has provided us with images of the West Eola board in
the files section. While I did say that I would comment on the board
I'm pretty sure that a lot of what I might have to say would leave a
lot of people in the dark. Gonna start with the basics and get into
the board in part 2 or 3.
If you are having a problem with "line wrap" maximize the window.
I'll try to keep the lines short.
Interlockings:
The Railroads realized pretty early that where it was necessary to cross
another Railroad at grade or where a number of tracks converged they
needed a better system than a Switchtender on the ground with a flag.
Things just moved too slow and there was a lot of room for human error.
Interlockings were developed that could position switches and signals
from a central location and were designed to rule out any conflict
between movements. As they developed there were different kinds
designed but in many ways an interlocked junction that was installed in
1920 is just as safe and efficient as a CTC installation that was done
last year. The different types:
Manual Interlocking:
This is a current rule book term and can mean many things. Best to just
leave it alone.
Automatic Interlocking:
Another current rule book term that describes interlockings that operate
on a "First come, First served" basis. Will not discuss these either.
Lever Interlocking:
Often called "Armstrong Interlockings" but that term doesn't sit well with
me. Can't really classify it as a Railroad term and it implies something
about the Operator that would put him/her in a class with body builders.
Will stick with the concept of "Lever Interlocking". West Eola was in
this group.
This design moved switches, signals, and derails by means of steel pipes,
(about inch and a half diameter), that were supported off the ground on
sets of rollers. The pipes were moved by levers. Each lever was a little
over waist high and had a metal latch about 2/3 of the way up from the
floor that would only latch if the lever was all the way in or out. At the
end of the lever the distance of travel was about three feet. At floor level
it was about 18". Normally the row of levers was on the second floor of
the tower since the longer the travel of the lower end of the lever the more
force would be applied to the pipeline. The pivot point was just below the
2nd floor and at the bottom end of the levers there were bell cranks that
transferred the movement of the levers at right angles to the tracks to
pipes that ran along the tracks. At the other end of the pipes there had
to be another set of bell cranks to change the longitudinal movement of
the pipes to horizontal movement of the controlled device. The pipes did
have to go under tracks and other obstacles to reach the controlled device.
In the case of semaphore type signals the bell crank system just converted
the motion to vertical and the pipes went right up the signal bridges.
What does "Interlocked" mean? The levers were usually towards the back
side of the tower with an aisle between them and the back wall for the
Operator to walk back and forth and operate the levers. Between the levers
and the front wall was a system of sliding steel slats called the "Bed". The
steel slats were attached to each lever and they had notches milled into
them. Very similar to those little hardwood puzzles that can only be put
together if the slots lined up. There were both crossways and lengthwise
slats. If the route the Operator was trying to set up was incomplete or in
conflict with another route one of the slats would come up against another
slat where there was no slot and it would not move. All the notches had to
line up in order to move any lever. At West Eola with about 80 levers the
bed was maybe 20 feet long, 7 feet deep, and about 2 feet high. It extended
almost up to the front wall of the tower. Between the bed and the front wall
there were vertical pipes that supported the board, which was about head
high. These pipes also routed the wiring down to or through the floor to
relays that lit the lights on the board so the Operator knew what was going
on. The bed at West Eola was covered with tar paper to keep dirt out and
there was really no problem in walking on it. These things were built to last.
The steel was blackened and looked like the same kind they used for rifle
barrels or handgun mechanisms.
The semaphore signal apparatus was the most difficult to maintain so it
was modified fairly early. 30's or 40's usually. A double head semaphore
had to have two levers and two sets of pipes. With electrically lit signals
one of the levers would be taken out and a single lever would control the
signals for that track at that location. Relays could look at the route and
decide which signals to light and which aspect to display. Since that
complicated bed had all those metal slats it had to be modified also. Since
the levers for the two semaphore heads were normally right next to each
other the normal fix was to weld a cross bar connecting the slats for both
levers together. When you moved the signal lever a relay told the signal
bridge to change aspects but as far as the Interlocking logic was concerned
you were really using two devices. A simple and elegant solution.
Time Releases:
Every lineup is not always used. Plans change, trains are delayed, might
not even be the right lineup. I think simple logic would dictate that if you
take a cleared signal down you should not be able to immediately start
throwing switches and so forth. If there is a train there the train may not
be physically able to stop. The solution is time releases. A combination
of a wind up clock with contacts and relays. This is in a round metal case
about 6 inches across with a glass dome. A knob comes out of the center
of the glass dome. These would generally be mounted on the front wall or
a piece of plywood under or to the left or right of the board. Had to walk
on the bed to get to them. Didn't need that many because the same release
would be used for different routes. The time factor was based on the maximum
authorized speed of a train approaching that signal. The Operator went to the
correct release for the device and turned the knob all the way to the right.
A mechanical clock would start up and move it back to the left until certain
contacts closed and then the other devices would work. Common error was
in not turning the knob ALL the way to the right. You would stand there and
wait, say five minutes, and nothing would happen at all. Only thing you could
do then is go back and do it over. DOH!
Lock Levers:
As another form of redundancy each switch, crossover, or derail had a lock
lever. What paint that was left on the lock levers was light blue. All the other
levers were red.
How Did You Use It?
If all switches were in their normal position and all signals were at "Stop"
then
all the red levers would be "in", towards the mainline, and all lock levers
would
be "out", towards the back of the tower. Got a hot move to make, a train
needs to go West from track #1 to track #2. Lets say that crossover is
switches #26 & #27. Lock lever should be #28. You walk over and release
the latch on #28 and push it forwards. Since all it moves is slats in the bed
a good push should send it right up to the point where it latches. A step to
the side and you tilt forward and grab the latch on #27. As it releases you
transfer your body weight back to you heels and pull it all the way out
until it latches. Once all that pipe gets moving it will usually keep moving
until it runs out of room. The "secret" is a smooth, long, pull using your
body weight. #27 is all the way out and latches. Same drill on #26. After
you have both switches reversed it's back to #28. Lean forward and
release the latch, pull all the way out. No strength required here, just
moving slats. The Westbound signal for track #1 is say, #12. Walk over
and unlatch #12 and pull it all the way out. Semaphores are long gone
so it is just moving slats and making the contacts that control a relay.
A quick look at the board shows the Westbound signal light on track #1
to be "green". That would be the only lamp lit. You "know" the switch
positions by looking at the switch levers. That's all there is to it. Time
to go back to the Teletype and work on that 95 car train list for a while.
Electric Interlockings: Next Time.
End of part #1.
The VLBG
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