The placement of towers would depend on the way switches were operated. The early ones were operated by long runs of pipe and there was a practical limit of 500 yards. There were also considerations of whether the towerman could see all the track he was controlling. A double ended station could have a tower at both ends.With the coming of electric track detection and powered switches, fewer towers would be required, down to today's railroads which may be controlled by one (not-so-)central point.
On lower density lines, there might not be a full interlocking, but remote switches would be controlled by the train crew.
--David
Mondo - I have both books they mentioned. Remind me to bring them over next time I see you...
Randy
Not a tower, but a classic mechanical interlocking, seen in 1960:
Single track main, with one turnout to a long spur to a mine complex about a mile away. The turnout and three signals (two-position lower quadrant) were controlled by four long, heavily-weighted levers in a lever frame on the platform adjacent to the station building (passenger platform on main, on the trailing end of the turnout.) The points were connected by rods, while the signals were cable-operated. The interlocking bars were located in a box on the end of the point throw bar - point position controlled which signals could be cleared, and clearing a signal locked the points until the signal was reset to stop. When the levers were in normal position (points lined for main, all signals stop) they lay flat on the platform. When reversed, they had been pulled through about 120 degrees and stood tall!
In less-clement climate, the levers wold probably have been inside a structure of some kind.
Short answer on the original subject. Interlocking systems (usually housed in towers) controlled turnout points and railroad signals. Watch towers controlled crossing gates and traffic signals at grade crossings. If the interlocking was at a point where two railroads crossed, the "junior" railroad (second to be built at that point) would have to build and maintain the interlocking (prototype reason for a 'non-standard' interlocking tower, if the tower was built and maintained by the Podunk and Northern at its crossing with the Pennsy.)
Chuck
Mondo,
Interlocking tower are usually placed at busy locations where they do not want to have to stop and align the switches. The entrance or exit to a freight classification yard is a good example. Many times cross-overs are just 'hand throw' switches, used for emergencies or to allow a local to cross over to switch an industry on the other main line. When I worked for the Burlington, we had a trailing point cross-over in virtually every small town along the double track main.
Yard towers typically do not control switches or signals. They provide a place for the Yardmaster and the yard clerks to do their paperwork. They range from small wooden structures, to large multi level buildings with the classic glass tower on the roof.
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
nbrodar wrote: Widely spaced interlockings would each have their own tower. Several closely spaced interlockings could be control from the same tower. Later as more and more towers fell to CTC, some roads adopted a sort of mini-CTC where one tower would control the interlockings over 20 or 30 miles. Nick
Widely spaced interlockings would each have their own tower. Several closely spaced interlockings could be control from the same tower. Later as more and more towers fell to CTC, some roads adopted a sort of mini-CTC where one tower would control the interlockings over 20 or 30 miles.
Nick
Yep... For the most part the PRR started with each set of crossovers governed by its own tower, but by the 50s, usually one tower controlled several sets of crossovers. If you have a few crossovers close together, you can have them consolidated. The NH was much like the PRR in that it had a multi-tracked main with lots of interlocking towers. Other than the expense (there are two companys that make kits for NH pagoda-style towers) there is nothing but benefit to having many towers on your layout. It screams prototype, since NH had such distinctive towers, and it screams infrastructure, something northeastern railroads had a lot of. For the PRR and NH (and pre-CTC NYC), there were upwards of 4 mainline tracks, so each set of crossovers had 10 switches to control, as well as any number of home and distant signals showing the alignment of routes through the interlocking.
Modeling the Rio Grande Southern First District circa 1938-1946 in HOn3.
An interlocking is really a type of control system that prevents trains from being routed onto conflicting routes. It can be as simple as one turnout leading into a siding. Or as complex as Philadelphia Zoo where PRR's four track east west main, met the four track north south main.
Take a Ride on the Reading with the: Reading Company Technical & Historical Society http://www.readingrailroad.org/
Mondo,If you are still planning on doing the NH, be advised that the NH had fairly unique towers. The NH's typical tower was the "pagoda roof" style, in either brick or concrete/terra cotta. But the NH did have lots of wood framed towers as well...most if not all were the 4-sided roof variety. Kingston Tower (wood) was featured in MR April 2002, with drawings.
This is New London Tower, a brick pagoda roof type.http://photos.nerail.org/photos/2006051521080914718.jpg
(Of course, the catenary isn't supposed to be there for a NH fan...LOL)
BTW, if one wants to model the early 1900's and before, towers were not just at interlockings. They also were wayside towers that controlled signals in the days before automatic block signals.
Paul A. Cutler III*************Weather Or No Go New Haven*************
cwclark wrote: interlocking towers are generally located at crossovers ..yard towers can be at either end of a yard or right in the middle of one...The englewood tower in Houston was located at the top of the hump yard while the tower at the East yard in San Antonio was a very high structure right in the middle of the yard..i've even seen some yard towers to the far left and middle of the yard tracks or the far right of the tracks in the middle of a yard...chuck
interlocking towers are generally located at crossovers ..yard towers can be at either end of a yard or right in the middle of one...The englewood tower in Houston was located at the top of the hump yard while the tower at the East yard in San Antonio was a very high structure right in the middle of the yard..i've even seen some yard towers to the far left and middle of the yard tracks or the far right of the tracks in the middle of a yard...chuck
Hi Chuck,
Now I've got to ask you.....What's the difference between an interlocking tower and a yard tower? Certainly, I can get excited about buying and building some new towers, but I need to buy the right ones.
Thanks again,
Mondo
Hi Dave, Mike and Jim,
Thanks for the helpful information and I will check out the books mentioned.
Now, based on the input you've provided, am I correct that I need a tower at each end of the yard? Also, I have a double-track mainline with about 7 single cross-overs and 2 double-crossovers along the mainline. Do I actually need an interlocking tower at every cross-over? It seems to me that it would have been a pretty simple job for some guy to sit in the tower and just throw the switches for a cross-over every once in a while. However, with that said, I'm forgetting that the mainline I'm modeling in New London, Connecticut would have seen many freights per day and around 30 passenger trains. Maybe all the traffic would have kept a guy busy with those cross-overs.
Thanks again guys,
Here's one of my interlockings, protecting a crossover and junstion together:
Interlocking tower control interlockings. Although most of these have given way to CTC and relay sheds.
Here's my Atlas Tower protecting Lack Junction:
The tower didn't have to be a stand alone structure. It could be incorporated into a station or yard office. Before the interlockings around my yard were automated, we had an operator, next to the yardmaster, in the tower.
Yard towers are generally placed at either the arrival and departure point, or at the busiest swithing lead. A Hump Tower will be placed at the apex of the hump.
Watch towers protected grade crossings. Belive it or not, the Main Street crossing in Lansdale, PA is still protected by a watch tower. Sorry, I don't have any pictures.
Interlocking Towers - Control switches/trackage at crossings/juctions, or the entrence/exit to a yard. The original towers were two story and had 'armstrong' levers to move the switches/signals via a pipe/rod system. The levers were interlocked by a 'frame' so the operator could not align conflicting movements. Most have been replaced by CTC installations, but many time the tower is used as the 'instrument shed' to house the electronic gear.
Watch Tower - I suspect this is the small tower on a post that one used to see at street grade crossings in urban areas. Most of them controlled the 'gates' at the crossing via a pnumatic air sustem(many had a hand pump in the tower). Tfhe crossing operator was elevated so he could see(many times controlled 3-4 crossings in a row), and he operated the gates. I remember seeing one in Mankato, MN about 1972 that was still manned and controlled 3 or 4 crossings in town.
Wow! You're in luck! Two recent publications by Kalmbach should be just the ticket.
1. How to Build Realistic Layouts - explains interlockings, where they go, and what they do
2. Modeling Railroads of the 1950s - shows how and where watch boxes were located and how they looked in the 1950s.
I have both. Great references. Although I have two shelves of books on the PRR and its specific practices from the 1950s, I still use the aforementioned Kamlbach books for references as well.
Short answer: Interlockings were located at junctions and where two reailroads crossed, as well as (like on PRR) where crossovers on multi-tracked mains were located. The controller in the tower operated the switches and signals, which were machanically "interlocked," hence the name.
Watch towers, boxes, shanties, and shacks were typically at grade crossings (roads crossing tracks), and a watchman stayed there and -- ahem -- watched for trains. When one was coming, he either manually lowered the gates or flagged traffic to stop. This practice was dying out in the 1950s (replaced by automatic gates and signals), although I still have a manual crossing with watch box on my July 1956 layout.
Hope this helps!
Hi Guys,
I'm trying to get the details right on my layout. I have built several interlocking towers made by different manufacturers in HO scale as well as several watch towers and have no idea where they should be placed on the layout. Anybody out there who can give me an explanation? By the way, I'm modeling the late 1950's, if that matters.
Thank you,