INTERLOCKING TOWERS...

[Anonymous]

Exactly what was the purpose of these structures and why are they no longer built (or are they?). Either way, it is pretty charming to see the ones that are still standing, these little houses by the railroad tracks. Next time I rent an apartment I'm going to make sure that it's here on the southside (chicago), near some railroad tracks. BUt seriously, what was the purpose of these towers and what does the term "interlocking" refer to? And why aren't they b uilt anymore. .. trainwatching at the BRC today. Take it easy...

[jimrice4449]

The purpose was to house the machinery and it's operator at RR junctions or points of intricate trackwork They're called interlocking towers because the machinery was based on a series of bars built at a 90 degree angle to one another. One set, (lets call it horizontal) would activate rods or electrical contacts to operate switches and signals. The other set of bars would have slots and/or blocks to permit or stop movements of the first set, providing interlocking safety to prevent the accidental setting up of conflicting movements.
Let's take the simplest arrangement for an example. At a crossing at grade of two single track lines you would have the crossing protected by 4 signals. The normal position for all four signals would be "stop". On the approach of a train the opr clears the signal governing it;'s route. When he moved the bar controlling that signal a cam on the bar causes a horizontal bar to slide and place blocks in the path of the other three signals' bars, preventing their being moved to clear the signals governing the other three routes. After the train clears the plant,the signal is restored to "stop" which moves the blocking bar clear of the other signal bars and the plant is ready for the next train.
Many multi-track RRs had sets of crossovers every few miles w/ towers(frequently called cabins in the East) to allow the dispatcher to move trains from one track to another to let fatser trains pass slower ones etc. As technology improved the manual switch controls (moved by rods along the ground) were replaced by power switch mechanisms which permitted the control function to be moved to the dispatchers, office and as a consequence most on-site towers have been taken out of service although the building might remain.

[CSXrules4eva]

jimrice4449, thanks for the well written and in depth exlpaination of what actually occurs at many interlockings. I personally didn't understand what the dispatcher did to control points at an interlocking but, you cleared that up!

Green Machine, your right interlocking towers are a thing of the past. At least around here in southeastern PA they are. The only one that I know of that is actually still in operation is on Septa's R5 route in Lansdale, PA. The dispatcher here contols I belive about six interlockings and gets a birds eye view of the five track grade crossing, which is pretty neat.

[rvos1979]

Interlocking towers may not be built too much anymore, but there are still a few that are operating in the Chicago area. I know Towers A2 and A5 are still in operation, I also think that B17 on the west side of Bensenville yard is also still operating. These areas have heavy traffic and somewhat complex track arrangements.

Randy (Spent many a night waiting at A5 for a signal)

[edblysard]

An interlocker is any series of tracks and switches that are designed and connected mechanically in such a fashion that only one route at a time may be lined for a through movement, and no conflicting movement may lined.

Once a particular through route is lined, all other routes are "locked out"

The towers housed the control mechanism or "Armstrong" machine, and were often two stories or more tall, to allow the operator to actually see the entire interlocking plant and the trains he was lining up.

More often than not, today’s interlocking plants are remotely controlled from a dispatching center miles away, often in another state.

It really creepy to be standing by an interlocker at night, and suddenly have all these switches start to move, clicking into place, for no apparent reason, till you can see where the dispatcher is lining up a move through the plant.

There are also manual interlockers, with signals to direct traffic, which requires the conductor to hand line a series of switches, or, depending on the location and the railroad, simply push a "time out" button on a interlocking control box, and wait for the signal system to time through and then line it up the requested move.

Actual operating towers are rare today, and those that still exist are often empty of both personnel and machines.

The lucky ones get purchased or donated to preservation societies or museums, the unlucky ones get bulldozed and replaced with control boxes and remote switches.

Ed

[videomaker]

I couldnt have explained it better myself,You guys are on top of it..Good Job! Videomaker

[dehusman]

Just for the record a "manual" interlocking is one where a person (control operator) has to line the route. The control operator can be located at the interlocking or a thousand miles away in a dispatch office. It can be an "armstrong" or all powered switches, doesn't matter. Its still a manual interlocking.

An automatic interlocking is where an electrical or electronic system determines the route and a person does not line the route under normal circumstances.

Dave H.

[Anonymous]

Hey Randy, where's tower A5? Yeah, b-17 is still going. I see 'em there whenever I pass through the area. There's some pretty good rasberry bushes around that area, as well. Good stuff when they're ripe.

[robscaboose]

[8D][8D]Take a trip to Terre Haute IN. We have 2 interlocking towers at our museum. Haley has pistal grip switches that electrically switch the track. & Springhill which had "armstrong levers" that one had to pull to cause the switch to move. They called them armstrong as you had to manually pull a lever that caused the switch to move & the switch may be 100's+ yards away from your location.

Rob

[BR60103]

There is still a tower at the west end of Toronto Union Station. It had its roof removed when they built a walkway over it, but there is a video of the operation. I think there is a tower at the east end as well, but I'm not sure.
I have a working interlocking panel that a friend built for his model railway. No irea how it was actually hooked up to the model railway.

[jimrice4449]

There are 3 types of plants (that I'm aware of). The "armstrong", or manal, or mechanic so named because the actual moving of the switch points was by brute force (imagine two sets of switch points on a crossover w/ as much as 100 yards of steel pipe). Electro-pnuematic used electricity to activate air cylinders that did the moving of the points and, most recently, mini-CTC boards that did the interlocking by electronic means and moved the points electrically. About 4 days after I bid off of the third trick towerman's job at Burbank Jct on the SP, an inbound Coast train derailed and tore up all the track but missed the 2 story wooden tower (that's why RR structures tend to be built on the outside of curves...all the wreckage piled up 2 and 3 cars deep on the inside of the curve). When they rebuilt the track (in the pre-wreck configuration) they replaced the mechanical plant and tower w/ a tin shed and CTC board.

[dehusman]

"Automatic" and "manual" interlockings, as defined by the rules, have nothing to do with the method that is used to throw the switches or signals, just the logic behind them.

At an automatic interlocking the route is determined by a machine. At a manual interlocking the route is determined by a person.

Dave H.

[JoeKoh]

marion tower in marion ohio and tower "A" in cincinnati show what life was like in a tower.
stay safe
Joe

[spbed]

Last I was at Dolton there is still a operating one their. [:o)][:p]

Originally posted by Green Machine

Living nearby to MP 186 of the UPRR  Austin TX Sub

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