I just purchased a double slip turnout for my layout and upon examining it,I find it quite complex in design,which got me wondering…are any used in prototypical railroading?Just curious…
Yes.
They are common in large passenger stations. Toronto has a large number at the west end, many of them built into double crossovers.
There’s a thread somewhere with a picture of another yard full of slips.
Do you mean like this?
The prototype editions are complex, and can be confusing to operate. Hence the railroad slang term “puzzle switch.”
Actually, until recently, I thought the real ones only had 2 sets of 4 points that needed to be moved. This is how the models work. The real ones, and I’m not sure if all are this way, have an interior set of points which close the low angle frogs near the center. This extra movement does indeed make them puzzling, because in addition to having your entrance and exit routes set, you have to make sure the proper flangeways are open.
The simplified model versions, take much less getting used to.
Big Boy’s photo says it all. The prime area of use was the passenger terminal. Look at any of the large commuter terminals and you will see them. They fill the void needed to move trains across lines.
If I recall correctly, the throat of Jamica station on the Long Island Rail Road is a mess of switches and looks not unlike that picture Big boy posted.
Hey guys, that’s my favorite photo of complex trackwork. It is of the Jersey City passenger terminal during it’s dying days. I love sharing it whenever someone says “double slip”.[swg]
It is quite rare to see only two or three double-slip switches in one sighting, you’re more likely to see them by the dozen. One location that has only a handful is the O’Hare terminal of the Chicago Transit Authority Blue Line.
The prototype uses double (and single) slips:
- Where the S-curve through two standard turnouts would cause an unacceptable slow spot on what should be (and is, through the slip switch) tangent track.
- Where, as in the Jersey City photo, standard turnouts would stretch the yard throat half way to the Pennsylvania state line.
- Where something really strange requires it - such as a track on a sustained, unbroken grade having to connect (and interchange trains with) a level track in the space between a bridge abutment and a tunnel mouth. (Japan National Railway, Chuo Main Line. Can’t recall the station name, and it may have been rebuilt in the forty years since I saw it.)
Number three, above, is the only case I’ve ever found where only one double slip was used, but there are probably lots of others.
As for the ‘interior’ movable points at the obtuse-angle frogs, the prototype also uses closed frogs on ‘standard’ turnouts. The object is to avoid pounding the frog to death with repeated slams from passing wheels (which doesn’t help the wheels any, either).
Since this is hardly an issue with our models (except, possibly, rideable live steam), and the low number acute frogs we work with severely restricts working space, very few modelers outside the Proto 83 camp need be concerned with those ‘extra’ points.
In chicago at the Union station platforms there are 22 double slips in less than a fourth of a mile . You will also see in very large freight yards double slips so that yard jobs can easily get through there mess of tracks.
James
Since my initial post,I’ve received the double slip turnout and,although I suspected it,I’ve found out that these types of turnouts are a most interesting piece of trackwork to install on a layout.I’m used with a double crossover turnout at the club,which only needs two switching sequences to be fully exploited,meaning either bypass or crossing.All the four motors are wired in parallel on one single SPDT switch and that’s all there is for any leg of the turnout you’re coming in from.
Now the double-slip…hummmm…much different indeed.Although only two motors flick the turnout tracks,there are four different switching sequences possible,depending on which track you’re coming from and to which track you want to go.I sure can’t wait to have it installed on my future layout,must be fun…
Jacktal: does your slip have all the points at one end on a single operating rod? I use the “probe and stud” operating method and I draw the slip on the track diagram and put a stud in each track coming out. All I have to do is touch the entry and exit track and the points are lined up. The wiring, of course, goes to the switch machine at the opposite end.
Mine is the Peco N scale code 55 Electrofrog double slip turnout no:SL-E390F.It does have two drawbars which each actuate one end of the double-slip,thus setting one turnout for straight route and the other one for diverging route.What then happens is that the other end has to be set to match or you otherwise get a derailment.
On a double crossover,you have two switching sequences,meaning going straight or diverging,and all switching motors are actuated simultaneously for both options.Now the double slip is a different story…I have four different switching sequences possible depending on where the train comes from and where I want it to go.
Let’s say I have eastbound/westbound trackage,I then have a north and a south track and the switches could then be called east sw. and west sw.Sequence 1:if a train comes from NE and the E sw. is set straight,then the W sw. HAS to be set straight also to direct the train to SW.If it’s not,derailment is on order.Sequence 2:the train comes from NW and the W sw. is set straight,you HAVE to set E sw. straight too.Two different switching sequences for going across depending if you’re going NE to SW or NW to SE,and in both cases,the drawbars are actuated in opposite directions.
Now more…sequence 3:if a train comes from NE and I want it to go to NW,then the drawbars both have to be drawn towards south while keeping the train on the south track (4th sequence) you need to draw both the moving rails assemblies towards north.It makes for a very interesting piece of trackwork as I will need two DPDT momentary switches to control both the diverging and bypass pairs of sequences independently,but that’s not bad,just more thrilling to operate…
Maybe it would be simpler with the help of electronics (or computer) but wiring I can handle better.I’ve got it all figured out,now what’s left is testing.
jacktal: the way I look at it, you have two switches to work. If you are coming from the west, the points set you to go either NE or SE, whether you come in from NW or SW. Then you look at the east end and you set the points to receive you from either the NW or SW.
It may be simpler to think of it as two switches points to points, but overlapped.
(I’m using Peco slips but in HO.)
Indeed…this double slip works like two turnouts end to end,but with the advantage of using considerably less layout space than the two TO’s or the double crossover.Layout space being gold to me,I might buy more of these space saving devices.
I forgot to ask…I’ve seen a much interesting picture (on this post) of double slips being widely used in yard operation.Are there any occurences where slips have been used to join mainlines?
The US prototype uses movable points, instead of fixed “K” frogs, in the center of all crossings where the crossing angle is shallower than a #6. This is because at those shallower angles the center guard rails of the K frogs cannot safely steer the wheels in the correct path.
Ouch, reviving a 7 year thread for your first post. [:(!] LOL
It is a little confusing, but welcome the the forum.[:D]