Slip Switch Track

tracks? How do

Imagine an X-shaped crossing. Label the four branches A to D, clockwise from NW to SW.

Through routing is A-C and B-D. A single slip will also accommodate one additional movement, say A-D. A double slip will accommodate both A-D and B-C.

So, a single slip is equivalent to a crossing and two turnouts; a double slip is equivalent to a crossing and four turnouts.

This is kind of tough to do non-graphically, kind of like describing a spiral staircase without using your hands. :-)

-- Bill McC.

Slip switches are overlapping combinations of a crossing (a 'diamond') and a set of switches ('turnouts'). They are complicated and troublesome on both real railroads and models. They do save space, however, and are used in confined quarters where absolutely necessary. In prototype railroads, one common application is the lead-in trackage ('throats') to large passenger terminal yards. Being deeply imbeded in large cities almost by definition, space is at a premium in these yards. Vast arrays of slip (and other) switches are combined in VERY complex trackwork.

A 'double' slip switch can be though of as a 'routing' crossing. Choose any ONE of the four tracks to enter the switch, and you can choose to leave by either of the two OPPOSITE tracks (straight through, or branching). This is true no matter which of the four possible entrance tracks you begin from. Such a switch is very similar to a double crossover in function, with one crossing and four switches, but takes up only about 20% as much space.

A 'single' slip switch can be though of as a 'routing' crossing with fewer possibilities. On each side, ONLY one of possible 'entrance' tracks allow you to choose an alternate exit track (straight through, or branching). The remaining entrance track allows you only to pass straight through. It is equivalent to one crossing and two switches, but again takes up less space.

A similar arrangement is the so called 'three way' switch. It's NOT really one switch that allows you to take any one of three diverging routes as it appears (only a 'stub' switch can do that). Such a switch is really TWO overlapping switches. Together they allow the choice of any one of three routes.

"Slip' and 'Three way' switches are both examples of 'lap' switches. These are so arranged that the various components of one switch overlap those of adjoining switches saving space.

Model railroaders like these switches because they LOOK 'neat', and because they save space. They do require an unusual amount of maintenance to keep working well, and may cause problems with some equipment. Prototype railroads avoid them like the plague, but still are forced to use them in confined areas.

Dan Mitchell ==========

EDUPSHAW wrote:

"

" He also has some verbage on why most RTR double slips and double crossovers don't work very well.

Paul

The above is, in my view, misleading. A double slip does not have the functionality of a double crossover at all. The essential feature of a double crossover is that it allows trains to cross from one main track to another, in either direction, and most importantly it allows for two simultaneous parallel moves on those two main tracks.

A double slip allows for only one movement at a time and is functionally identical to two turnouts connected toe to toe. So identical that the wiring is the same. The lap analogy is correct just visualise those two turnouts pushed together so that they overlap,

A double slip is not equivalent to 4 turnouts and a crossing, its just equivalent to 2 turnouts, and is wired and operated as such. Keith Make friends in the hobby. Visit Garratt photos for the big steam lovers.

Before this erupts into a blaze, may I suggest that this sounds like a terminology problem, and that y'all may be talking about the same thing differently.

For my part, I was taught that a double slip is *four* turnouts and a crossover, integrated, and topologically and functionally the same as what you call a double crossover.

Thanks for your replies.

They help me decide about using one on my layout. I had planned to throw one in at a junction on a portion of my layout that looks kind of like the top of the Atlas N-16, "Atlantic Longhaul Lines" trackplan.

Thanks also for the link to the Teton Short Line site. It has been a while since I last visited Wayne's website.

Ed Upshaw

Anna Maria Island, a quaint drinking village with a fishing problem.

I was never much of a fisherman, but I remember the Stumble Inn...vaguely...

Jeff Sc. Native, Ga.

Don't bother to reply via email...I've been JoeJobbed.

Then you were taught wrong, terminology is not the problem, the functions and topology are very different in the two cases. Particularly that a double crossover allows for two through routes with simultaneous moves, a double slip does not. The double slip is two turnouts squashed together. Keith Make friends in the hobby. Visit Garratt photos for the big steam lovers.

Also known as a scissors crossover or scissors crossing.

Yes, definite terminology brane faht on this end. The thing I was missing in trying to visualize your description of the double slip was "frog to frog." A picture really is worth a thousand words.

In trying to find the simplest way to make the verbal distinction, how about, "the double slip necks down to a single track, while the double crossover has continuous parallel tracks."

Please do not post binaries (aka: pictures) to this newsgroup. rec.models.railroad is a text-only group. If you want to show pictures, please post just the link to a website or post it to a binary group like alt.binaries.pictures.rail.

Thank you.

Paul A. Cutler III Deputy Sheriff

************* Weather Or No Go New Haven *************

I agree with what you say, but find from experience that many modelers can't understand the notion of a 'lap' switch. A double slip IS the equivalent of a double crossover, so long as only ONE train at a time uses it. You are, of course. correct that a double crossover allows two trains to pass each other IN the switchwork, that cannot be done in a double slip (at least not without some excitement). :-(

The confusion over 'lap' switches is why most consider the common double lap switch to be a 'three way' switch. It's NOT.

Dan Mitchell ==========

Keith Norgrove wrote:

At NO location in a double slip switch does it neck down to a single track. It's more like a gantlet track, with overlapping but separate tracks.

Dan Mitchell ==========

John Miller wrote:

I don't think it can be done even with the excitement added I think you would have to get Ray Bradbury in on the project before it would work. He did something similar on Mars many years ago.

Congratulations! Now you can try explaining the difference between drills, drill motors and bits, and explain why there is no such thing as a "drill bit". Oh yeah, while you're at it you can also illuminate the masses regarding the incorrect use of the term "lashup" to mean "consist". Good luck!

....................F>

Etymology, GA.

When you select the through route it is as single track with lapped turnouts. The diverging routes are like gantlet tracks.

Keith, the double slip is indeed 4 turnouts and a crossing all wound up into a small piece of trackage. There are a set of points for each of the incoming tracks which indeed means 4 turnouts. Topologically, the double slip and the X crossing are the same basic thing but they are indeed doing somewhat different chores with the intent of the double slip to provide a crossing as the normal and the X crossing the not crossing as normal.

-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works every time it is tried!

True but a gantlet track is logically a single track, only one train at a time can use it. Keith Make friends in the hobby. Visit Garratt photos for the big steam lovers.

Bob, I thought I explained the difference fairly clearly, and tried to avoid causing confusion by using english English instead of american English.

Topology is probably a bad word to use as maybe none of us looked it up in the dictionary and so maybe are using it differently! (We'd probably have to agree on which dictionary to use anyway). Function is better. The double slip functions as two turnouts toe to toe, (not frog to frog). A train coming from either of two tracks can leave on either of two tracks. It differs from two turnouts in that it uses less space and two achieve this with acceptable radii you have two add two obtuse crossings (elbows?) and an extra four switch blades. Note that there are still two sets of switch blades, just that each set consists of 4 blades working together not the usual two. The double crossover (Scissors crossover in England) has the same function as the double slip and also the fundamental and most important function of allowing two trains to pass simultaneously on the parallel tracks. Keith

Make friends in the hobby. Visit Garratt photos for the big steam lovers.

Your message implies that a double slip switch is not restricted by the limitation that only one train at a time can use it as is a gantlet track. Is that what you mean to say? I should hope not. Never the less, the wording clearly implies that. A double slip turnout, when set to the diverging route is, in fact, very much the same as a gantlet tack. The difference being that the distance is much shorter and the points must be re-set to use the other diverging route. In a double slip turnout, one -and only one- route may be set at any instant in time. Perhaps this is what you meant?