All interlockings and/or Control Points are designed and built to support a desired from of operations at the specific point it was installed - no matter the physical manner in which it is manipulated - that manipulation can be by armstrong levers and pipelines, electro-pneumatic operation, non-dual control electric or dual- control electric.
As a operator, when stationed at a Armstrong pipeline plant, the Signal Maintainer would take a few minutes in the qualification routine to run through the procedures required to ‘bar over & spike’ switches and/or crossovers before authorizing trains to pass stop signals in accordance with the appropriate rules.
I never worked a electro-pneumatic plant. On my territory(s) as a Dispatcher, there were several electro-pneumatic control points. If there were issues with the operation of the switches - a Signal Maintainer was the ONLY recourse to move trains past the control point, as there is no means for the Dispatcher to insure switch position without the plant in fully functioning order.
Plants that are equipped with non-dual control electric switches, when the switches cannot be operated, require the Operator or Signal Maintainer to unlock a cover on the switch machine and use a small crank to move the switch points from normal to reverse of vice versa - once the switch points have been moved by the crank method they must be spiked into position for the movement to be authorized past the stop signal in accordance with the rules.
Dual Control electric switches have the switch machine in the field equipped with a two position lever - Power on one side, Hand on the other side. If the switch(s) cannot be operated with normal electrical power, personnel (Signal Maintainer or Train Crew) can be authorized by the Train Dispatcher to move that lever
I’m interested in visiting an interlocking tower that operates an actual interlocking, even if it’s just a small part of one, using the armstrong levers, the pipes, the affected mechanical switches.
I am wondering if any museum or tourist road has that, where one can actually see/feel it all work, even if they are “routes to nowhere.”
The BNSF Rochelle crossing is completely automatic. It doesn’t appear on the UP dispatcher’s CAD screen. The BNSF crossing in Fremont NE is a manual interlocking and does appear on the UP dispatcher’s screeen. The UP dispatcher controls the interlocking. BNSF trains used to always switch over to the UP radio channel as they approached and called the dispatcher for a signal. The dispatcher would either say keep coming or wait 10 to 30 minutes. (The best one was when the UP had taken the diamonds, which they maintain, out of service for said maintenance. The BNSF train evidently hadn’t got the memo. They called and said they’ld be down in 10 minutes if the UP could take them. The dispatcher said it would be about 6 hours.) Lately, I haven’t heard them call. Possibly they’ve given the UP dispatcher access to the BNSF radio channel or some other protocol is in place.
We have some of those hyrid manual/automatic interlockings in my area. A couple places the UP switch, junction or siding, is in the plant where a foreign railroad crosses. The crossing part is automatic, but the dispatcher has to clear our trains over the switch, too. Instructions usually are if the signal is red, first contact the dispatcher and if s/he isn’t holding the signal to then operate the release box for the automatic portion.
The last two interlocking control machines that were in use in Iowa are both preserved. One, out of the tower in Des Moines at Short Line Jct, is now at the Boone & Scenic Valley Railroad. It currently is not on display and is an old pistol grip type machine.
The other, also an older pistol grip (the grips are much smaller than the Short Line Jct machine) is still in the tower at Iowa Falls, called Mills Tower on employee time tables. It controlled at one time, the RI north/south main crossings of the IC and a RI branch. The branch crossed both the
there was no mechanical frame anywhere that was still connected to pushrods and cranks to move switchgear and derails at the time of writing. Miller and perhaps some others preserve the mechanical locking bed, and the experience of moving the levers with strictly mechanical route interlocking, but not the full-tilt experience Balt and some others describe of having to move the whole plant ‘by hand’.
I know of no restoration that intends to put back a purely-mechanical armstrong tower and plant; that’s not to say that someone isn’t contemplating it somewhere – or has completed one somewhere that hasn’t been documented yet.
My father and I in about 1976 and 1977, visited the CNW tower at Tama, IA. It controlled the Milwaukee Road crossing there. It was a lever/mechanical interlocking, and I was permitted to line up a couple of CNW trains. We only saw one MILW train, and this was from the tower. The operator went down to the ground to inspect the CNW trains, but he said he didn’t always do that for the MILW trains.
About 6 to 8 months later, a MILW train derailed and knocked the tower down. At first they couldn’t find the operator, thinking he was in the wreckage of the tower and train. Fortunately, he later showed up unhurt. He had been down doing a roll-by when the train derailed. He decided since there was nothing more he could do and it being his bulletined meal period, he went uptown to a restaurant for lunch. The old heads in talking about him, said he was a character. Yes, I guess maybe he was.
The other active tower I’ve been in was the RI’s at Short Line Jct. It was in June of 1979 and a friend and I stopped in. The operator explained the operation of the interlocking, how if it’s not set right you can’t move the pistol grip and the switch or signal it operated. He told me to pull on this one grip, that it wouldn’t come out. I pulled on it and it came out. Then he was, “Now how did that happen?” He obviously didn’t have the plant set up like he though he did.
" SONO Switch Tower Museum" in South Norwalk; please view their web site.A circa 1880 “armstrong lever” technology.The tower is the subject of a recent book with the word “Classic” in the title.Also on view isl the control-board that “supervised” the 11,000 volt circuit-breakers at the adjacent “anchor bridge”. Recently a man from Westchester Pa. who is expert on mechanical devoted a considerable amount of time to compile a “dog chart”. (???) The Tower is located where the Danbury Branch veers of the main line , so after visiting the Musuem you can continue by train to the Danbury Rail Musuem, this presuming there’s an end to the covid 19 virus.
Mills didn’t have the armstrong levers. It was a pistol-grip type interlocking machine.
Until recently, one of the people involved with the Iowa Falls Historical Society would open up the tower grounds at various times. Since he was a railfan, he would open it when there were railfan/model railroad shows in the area or just to have a place for the local railfan fraternity to have a day out.&n
Very little is visible on their site: the history is being ‘rewritten’ and their picture gallery requires Flash Player, which crApple doesn’t support, but the video says the frame ‘is not hooked up’ to any mechanical linkage.
They do note that the plant was interlocked in the safety sense, but not ganged so multiple levers were thrown together… you pulled the individual levers in order until the ‘iron was lined’.
I suspect the ‘dog chart’ was the schematic of the internal bars in the actual interlocking mechanism… something I am still a bit in awe of for a plant like SONO with 68 levers, let alone a large one with well over 100 as in some terminals…
At the interlocking track 2 has turnouts A to track 1 then turnouts B from track 1 to track 2. track 2 is out of serice between A and B but not interferring with A or B. Can a train appproaching A be routed to track 1 then back to track 2 on B ? I can imagine the possibilities on the NEC 4 tracks with a train on track 4 going to track1 then back to tracks 2,3, or 4 . Would this be possible at all interlockings or just some ?
Now what would the signal aspects and displays for such moves. Can imagine might different for different RR divisions and whether speed signaling or route signaling is used? Cannot imagine how the signaling on the old B&O CPLs. Balt is this movement possible at AF and once it becomes 4 MT ?
Jeff wrote earlier in this thread: “An ‘automatic’ interlocking lines up a route automatically when a train hits the approach circuit. First train gets the light.”
How does the automation know which route the train is supposed to take?
TL;DR: additional intelligence and executive action is involved for anything but a plain crossing at grade.
In ‘traditional’ CTC the route is selected by the dispatcher, and lined for each step “before the train gets there”.
Jeff’s version is a little more like an automatic version of the north end of the ‘Races to the North’ in late Victorian England where the two competitors had to ‘share’ a single track at the end, with the ‘first to get there’ getting the occupancy. That still involves someone determining routes in either direction through the plant, and then lining things physically according to the “choice” for the train first getting to the limits (and knocking down or choosing an alternate route or hold on the later one). If you are clever you can have a computer do this with speed and efficiency, but if you are wise you will always have a human in attendance on it.
Note the extension of Jeff’s idea to a world in which there is proper CBTC and cab signaling with no non-emergency waysides. Each cab display is nearly continually updated (e.g. once every 6 seconds) with advisory display of all other traffic; if there is going to be a ‘close call’ it can be avoided by predictive logic well ahead of the point that the first train reaches the ‘decision point’. The line might be chosen to expedite the ‘first’ train, or it might give precedence to the modern equivalent of a ‘superior’ train or class – for example loaded Z trains over manifests, or trains with crews starting to run foul of hours of service. Incremental adaptation of whatever LEADERlike speed/grade profile is being used then follows to adjust train speed with minimum opportunity cost in order to get everything through the interlocking expeditiously. (Repeat this continuously f
In my proposed answer to the very fdifficult deverging-route problem at Shell Interlocking, which I did as an unpaid Klepper-Marshall-King project for my goםd friend Noah Caplin, planner at Metro North, while I was a Metro-North reverse-commuter, entrance-and-exit control, with a computer-system or very complex solid-state relay actual control of switches and signals, will be necessary to minimize delays with the maximum number of same-time parallel movements:
Amtrak had pushed for a simpler and more straight-forward solution: Going west from New Rochell, the four tracks through the station would become six, and each track between the local and express track in each direction would rise and fly-over for the Pwenn. Sta. direction. But this would have required considerable widening of the RoW at the choke point, meaning removal of many homes and business, and streets. East of the station, MN has plenty of land, where there once were a coach yard, rounhouse, and turntable.
Track 5 is the old Harlem River Shuttle siding, not use often now, but still there.
I just stumbled across this discussion, sorry to be late to the party.
I have always been a “tower fan” - back in the 70s there were several towers/cabins which I would spend the day, with permission from the operator. Those days are long gone. The last tower I visited (with permission) was in Springfield, Il - Ridgely Tower…was invited upstairs by the operator…back in 2007 I was in transit to a customer in Western Il, and stopped by. The tower featured Armstrong levers and the associated hardware.
Friendly operator and I could have stayed all shift, but a 1030am appointment got me on the road. The operator indicated (at the time) Ridgely was in no danger of closing as the investment would be over $9 million. He indicated only five towers existed on UP at that time - Lennox Tower in Mitchell, Lake St and Clybourn in Chicago and Avondale Tower in Louisiana and Ridgely.
On April 7, 2010 I again stopped at Ridgely and the operator indicated “30 more days”…new hardware was in place. That was my last visit to Ridgely.
Not sure how many towers are still operating. Here in NW Indiana, I can think of two - Hick on the NS and the bridge at Michigan City on Amtrak Michigan line. Both control bridges.
I am happy these days to find towers still in existance. I know the Marion, Oh tower is operating as a museum. There are a few in Chicago still in operation (correct me if wrong), but there is no way one will be invited into those.
There is a very nice tower at Berea, Oh still standing…in fact I monitor the Berea webcam (and scanner) and the tower is on my other computer screen as we speak.
The most knowledgeable expert on towers is Jon Roma. Google him and you will find a wealth of information on his web site.
Towers were great places to visit, as long as one was invited and stayed out of the way. During my travels in the 1990s, I would come across a
Most “automatic” interlockings are protecting diamond crossings - there are no complicated routes, just preventing both railways from occupying it at the same time.
There is an “approach” circuit with a timer, when a train occupies the approach block it triggers the interlocking and clears the signal. A train approaching on the other railroad will NOT get a clear signal because the first railroad hit it first.
Specific indications depend on the RR, since RRs have different styles of signals and sets of indications/signal rules.
However, there is a general logic to how things work that can help determine what the answer is.
Basically there are two general types of signal systems: Route signalling, and Speed signalling.
Route signalling basically gives simple “clear” or “diverging” aspects, and the crew must figure out their speed based on TT speed restrictions at that point. Speed signalling actually specifies the speed restrictions for the turnouts in the indications.
Back to the question.
If you go straight on one track, you can get a “clear” indication.
If you cross from one track to another, you’ll get a “diverging” (route) indication, or a reduced speed (limited (45), medium (30), or slow (15) depending on the design rating of the turnouts.
If you cross from one track and back to the first, you’re still going through those switches so you’ll basically get the same indication as a
