Over the last few years,I have acquired most of my trackwork from different Ebay sellers,benefitting from decent prices when possible.Among these items,I’ve set hands on a pair of double-slips that I’m incorporating in my layout design to maximize the use of the limited space I have available.I will use them just the same but I have two question about the prototypical use of these…
First,are double-slips exclusively used in yards or some can be found on mainlines,sidings or industrial spurs,etc?
And then,did double-slips exist during the steam era?If so,were they restricted to smaller engines as I can imagine Challengers having a hard time going through them?Just curious,thanks.
Have seen double-slips on the mainline e.g. at the North end of the B&P Tunnel on the Northeast Corridor in Baltimore. Also in yards e.g. a pair of hand operated double-slips in the coal yard in South Philadelphia. IIRC the Hoboken Shore (a switching line in NJ) had one or more slip switches. but not sure if they were double-slips or single-slips.
They had double-slips in the steam era. Not a Challenger, but the slips at the B&P Tunnel handled a lot of GG1s and they were 4-6-6-4s (sort of)
The PRR had a double slip on a urban industrial that served 4 industries.This was the only way these industries could be served because of the tight space-more like a brick canyon actually
Double slips are old technology - they were connected to, and `powered’ by, armstrong interlocking linkages before the development of electric and pneumatic switch motors.
One very unusual `out in the boondocks’ application saw a double slip at one corner of a somewhat asymmetrical diamond crossover. The through route ran southeast-northwest (upgrade) across a high bridge, straight through the double slip, across the diamond, then straight into a rather long tunnel. The points of the turnout opposite the double slip were almost inside the tunnel. There were two dead-end spurs with a platform between to the east of the diamond, and one spur extended to the west. The spurs were long enough to accept a standard-length train, and the whole occupied a rather narrow ledge on the side of a steep mountainside. Through trains blasted across the diagonal of the diamond at speed. Any train that stopped had to switch off, stop on a spur, then back across the diamond before starting again. Theoretically, three trains could take siding to clear a fourth through schedule, but the maneuver would call for some careful choreography to prevent everything from getting totally snarled up. The station was Higashi-Shiojiri on the JNR Chu-o Hon Sen, and it was used by well over 100 trains daily.
The same track configuration, but a somewhat less hectic schedule, will be found on my layout, at the Yamamoto Station of the Tomikawa Tani Tetsudo.
I have a detailed track diagram from 1953 that shows a double slip immediately east of Cermak Road and just south of Canal Street where the ICRR and ATSF tracks both crossed and joined each other on their way to and from Alton Junction at 21st Street in Chicago, just a few yards away. This would still be considered mainline track at this point.
Double slips were frequently used in passanger station yard throats to save space and to enable many routes to the various platform tracks from the few tracks coming into the station. Take a look at the tracks going into St. Louis terminal. There are an amazing amount of double slips there.
In my previous post I mentioned St Louis as having alot of double slips in the approach to their terminal. Well just my luck this Fall Issue of Classic Trains has a view of the approach tracks that I had mentioned with a view brom a blimp. I count at least 20 at first glance. You may want to take a look at that Birds Eye View image to see how they would be used.
Whe I got up to come to work on the 29th of July at 9:30 p.m., my wife said it was my lucky day as I had received a Classic Trains, Model Railroader and a Trains magazine. Today I received my NMRA Bulletin. I work midnights so I can not vouch for when it got put in my mailbox. My wife sometimes picks the mail up then forgets it in her car for a day or two. If it were me I would be watching for the letter carrier to put them in the mailbox, then retrive them right then.Then I would get no sleep, as I would be up reading them all afternoon.
The only limitation to slip switches vis a vis motive power was the frog number used for each leg of the double slip. I’ve never seen on in prototype service with frogs less than number 8, but their is no limit to the frog number than can be used with a double slip switch. If it had to handle large steam locomotives; the double slip switch would be designed for it’s intended purpose with the correct size frogs (i.e.; switch numbers; switch sizes; whatever). The only real limitation to the size of a double slip switch is the available real estate.