Maybe my brain isn’t working right on this (not an uncommon occurance [:)]), but I’m having a little trouble distinguishing the difference between a double crossover and a double slip switch. So I have to questions for y’all:
What’s the real difference between them?
Where would you use each?
Thanks!
—joe
A double crossover is comprised of 4 turnouts and a crossover so trains can cross from one track to the other from any direction on parallel lines. You can also arrange the 4 turnouts so you cross from one track to the other in either direction, but not through a crossover. This arrangement takes up a lot of linear footage with #6 turnouts.
A double slip is for a situation where two tracks come from different directions instead of running parallel, and you have the option of going straight through like a crossover, or switching to the other track, from either direction. A double slip is more compact than a double crossover.
Peco makes both single and double slip switches. Now that I’ve opened a new can of worms, let me explain what a single slip switch does. A single slip looks a lot like a double slip, but you can change from one track to the other from only one end, not both. From the other end, you can only go straight through on the line from which you enter.
Thanks! So, if I’m designing a dogbone-type layout, and I want the blobs to also serve as reversing loops, it sounds like a double-slip switch will do what I want without taking up a lot of space.
Sound right?
No, the other way around, if I’m understanding you correctly. Two parallel tracks need a crossover to form a reverse loop. A double slip would be used if you wanted to have access to two mains from a yard. A regular switch would come off the far main, a double slip would cross the near main and then go into the yard.
A picture is worth a thousand words. Your track plan is at the bottom right?
You’re right – the picture makes it very clear! Yes, that’s about what the plan would be, except I’m trying to keep the two crossovers close together since the actual track plan will end up more like a folded dogbone, with the loops on top of each other. It’ll be a little tough to have a crossover on the upper loop, since the ‘inside’ track will be climbing the hill while the ‘outside’ track after the loop will be sort-of level while it skirts the edge of the mountain. So a double crossover just outside the bottom loop would do the trick.
Thanks again, folks!
Thanks for the explanation, Big_Boy_4005 - I’ve always been curious. In terms of incident-free operation (e.g. no derailing, stalling or other issues) is one superior to the other? Can both be powered for remote operation? Are there any other considerations in choosing between the two solutions?
Thanks.
In general a crossocer is a connection between separate parallel tracks, a slip switch provides connections between tracks which cross at a shallow angle.
I have read that slip switches are more common in Europe than in the US.
The only use I have seen of slip switches in the US is the throats of major passenger terminals to make connections between the many track involved. Crossovers could be used instead but then the throat would have to be much longer.
Yes both crossovers and slips can have motors mounted to move the points.
Both the double crossover and the double slip are space saving track arrangements. Both are costly and complex in real life and modeling. It is not unprototypical to avoid using these specialty tracks if at all possible. These two configurations are not really interchangable. Their use is specific to the task.
A double slip has 8 points and 4 frogs, but only performs the work of two regular turnouts. That’s a lot more moving parts, which means more maintenance, and more possibility for derailment for a real railroad. For a modeler, there are electrical issues in addition to all of that. Of course they can be made to work, and they look really cool. A double slip needs 2 motors to be thrown. Four points on one end and four on the other.
Maybe the best application for a double slip is where you have 3 or more parallel tracks, and you need a route across all of the tracks. The outermost tracks would have regular switches, but to make a nice smooth path, double slips would be used to cross the interior tracks. This arrangement would allow trains on the inner tracks to cross as well.
The double crossover is only used in conjunction with 2 parallel tracks. The added complexity comes from the diamond used to connect all four switches. It represents a right crossover and a left crossover, but to save space they are on top of one another. Again 2 motors can power this piece, though special linkages will be required. One motor and linkage for each crossover.
A question occurred to me – if you’re wiring for DCC and using a double-crossover (or a DIY with switch combos and a crossing), where is the actual reversing loop? Do you have to isolate the switchs and the track beyond together? Or do the switches count as one RL, and the loop beyond them another?
I think you have to insulate both rails once on each crossover, because either path forms the reverse loop. That part stops the electrical short circuit. I forget what you have to do for DCC reverse loops and wyes, because you still have to tell the train it needs to go east instead of west. That part may be more like the traditional DC, where you need to have a transition section.
I think you do something like this, both rails all the way across, four locations. Try this topic for DCC reverse loops:
http://www.trains.com/community/forum/topic.asp?TOPIC_ID=19721
I have to confess that I cheat and do 3 rail trains, so this aspect of a reverse loop situation doesn’t exist.
On real railroads a double crossover would be a left hand and a right hand crossover one right after the other (also called a “universal” crossover). What is being called a double crossover here I have seen referred to as a “scissors” crossover, for obvious reasons.
Dave H.
On the prototype indivdiual crossovers are preffered but space isn’t an issue. The only time a double slip switch is used is when space and route selection are critical like in major terminal trackage. I don’t recall ever seeing a prototypical double crossover. In my opinion that would be the rarest of the three.
Yea, if I had miles to do it, I’d use two crossovers – but since I only have about 15 linear feet, I’m willing to sacrifice prototypical for space-saving. [:D]
OK guys, even real railroads can have space constraints. Of course with the disappearance of most passenger service, and all of the mergers, that is usually no longer the case.
When I think of double slips and complex trackwork, this photo stands out in my mind as the ULTIMATE example. This was the Jersey City passenger terminal of the CNJ. The photo has no date, but it is probably from the late 60’s. It shows what lengths railroads were willing to go to for passenger service in it’s day. Note the right side of the photo, one double slip has already been partially dismantled, and some of it’s frogs lay discarded between the tracks.
But look at the flexibility it offered the towerman for putting a train on any track in the station if a regular assigned track wasn’t available for any reason. AND right in the foreground is a double crossover with double slip switches on the ends!!! That could be the only set up like that ever built.
If you look carefully, there wasn’t just one double crossover, there were FOUR!!! Three of the diamonds are visible, and the fourth was removed, as it would have been connected to the partially dismantled double slip. Flexibility, you bet!!! There are two parallel paths crossing every main track in both directions.
Imagine ten tracks running through the quad diamonds at Rochelle, because this is what it might look like. That signal bridge at the top of the photo is quite the piece of work as well.[swg]
Hey Elliot,
Enlighten me. What is the purpose of so many tracks and switches in one area. I opened
up the photo to full size and got a headache [:D]. Dave
Well Dave, I wish I knew more about the terminal myself. Jersey City is located due west across the Hudson River from the southern tip of Manhattan. The caption from the photo says there was a ferry opreation from New York. This was probably a very busy place twice a day serving commuters.
The view in the photo is looking away from the terminal building. This facility served at least three railroads in it’s day. Passenger trains from the B&O, Reading, and the Jersey Central all used these tracks.
Perhaps we are looking west into New Jersey, and the piers are behind the building. Maybe the tracks going off in one direction belong to the Reading leading to their mains. The B&O tracks would run off in the other direction, leaving the Jersey Central to run off straight into the distance. It is also possible that there were coach yards nearby, and perhaps engine facilities too.
Where ever the tracks went, they must run off in a number of different directions. The point of this mess is to allow a lot of simultaneous movements without blocking up the entire terminal. Imagine all of the arrivals in the morning and departures in the afternoon on weekdays.
This was all abandoned in 1967.
Elliot,
Thanks.
It must have been one hell of a job keeping order. One misaligned switch and you would be headed
off to God knows where! [8D] Dave
All that routing is necessary so more than one train can move across the entire interlocking plant at the same time. Picture if you will the need to get loaded commuter trains out of the station while replacing the trains with empties for the next movement. Now picture something stalling or derailing on the only route and the need becomes pretty obvious. In fact reduction of the redundancy at Union Station in Chicago has caused massive delays for commuters and a lot of angry people.