Signals For Double-Slip Switches

Let me look in my archives, but the signal placement library from the old Custom Signals website may have had a placement schematic for this. (It will be a few days before I can get to it.)

Maybe something like this Don, I'm still figuring out where things are going to go through my DSS pair!

There is really no such thing as a signal for a slip switch.  They are always part of an interlocking and standard interlocking signal rules apply.

For signaling logic, a double slip is the same as four ordinary switches and a crossing pushed together so the points overlap.

I can't imagine a slip switch that isn't part of an interlocking with a bunch opf other switches.  The indications on the interlocking home signals will include the route through the slip switch.

I have to agree with mlaughlinnyc above.  I have a very early (but post-1925) photo of the entrance to Chicago Union Station that shows at least 6 double-slip switches in a 4-track throat outside the station.  None of them are individually signaled.  As I stated in another post, slip switches (single or double) are ordinarily going to be used in slow speed situations like terminals, freight yards, industrial switching or ports.  Thus, outside of interlocking rules and controls, there is little need to provide signals for those switches.

Chuck

Yep, my double-slip switches certainly are at a busy spot.

Great diagram John. That answers all my questions...

I am all for not signaling these things. They are at one end of my yard and it is a cramped area. If these were commonly found as part of an interlocking and under control of that interlocking then so much the better. I would be delighted not to have them individually signaled.

Don

Confusion headquarters here.  I have three overlapping 72" radius curved switches exiting a tight staging area and when I change trains quickly the points can get camouflaged by all the rail so I just follow my finger as I trace / align the points.  Need to carefully follow through the various 3 way turnouts also.  Maybe it's just me, but it can be easy for me to incorrectly route a train.  And this is with only two rail, three rail can be a real visual challenge.

Not sure but the OP may be referring to panel or switch machine type of point position indicators like the red / green LEDs on some control panels.  The engineer is primarily concerned if they have the permission to proceed and at what speed.  The control tower aligns the switches to permit passage and to direct engineer action.  The confusing point is that as sole operators we are both.  Perhaps the Z-stuff switch machine indicator lights boil down to the DSS "signals".

Signature Switch Company

Signature sub assembly units        

Tom Tee, can't imagine trying to build this switch assembly in 3Rail. What are the curve radii for the three track switch pictured in the second photo.  I assume these assemblies are hand laid.  Quite a space saver.  Are you using floating points for these? 

These switches are the product of Brad Strong t/a Signature Switch.  He has made dozens of custom one off turnouts for me at  a little more than atlas  switches.

The outside radius is 72.  Due to needing to power the frogs,  floating points are not used here.  I drill a hole in the tab & use a d.p.d.t. slide switch like this:

I prefer hand throws because I walk around with my RR.  

Even where I use Tortoise switch machines,  I mount the Tortoise toggle at the layout edge adjacent to the  turnout.

If you really wanted signals to indicate switch path / direction of travel, you would have to use one dwarf/ground signal at each switch entry location (4 of them).  Each signal would tell the engineer if he was routed straight through (green, I suspect) or routed to change direction (probably yellow).

Chuck

That is information that the engineer does not need for passing through the slip switch.  The home signal at the interlocking will indicate whether the train may proceed at normal speed or must reduce to medium speed through the interlocking.  If any switch in the trains path is set for a diverging route, there will be a medium speed signal entering the interlocking.  That speed applies to the whole train from when the engine passes the home signal until the caboose clears at the other end of the interlocking.

It is possible (but I do agree that this is most unusual) to have a slip-switch not part of an interlocking, but my explanation above was to assist those modelers who might want to use signals to indicate turnout/path direction solely for distant visual purposes.  Not prototypical, but possibly useful.

However, what the modeler will see using dwarf signals varies, of course, by his point of view.  In most cases, only 2 of the 4 required signals will be visible from any set location.  To solve this, a modeler might build a small red-yellow-green light panel next to each entry point of the slip switch.  The signal controller would only permit entry from one point at a time (either green for straight thru or yellow for changing track) and all other signals would change to red to prevent collisions.

Again, this is just a modeling "thought," not meant to be prototypical operation.

Chuck

Ok, a chance to test my signaling knowledge, awesome. I find signaling the most fascinating part of real railroading

I’ll use Gunner John’s example;

This entire drawing is a single interlocking, also known as a control point. Today pretty universally called a CP in North America followed by a mile marker. The signals only govern entry into the CP. The individual aspects describe the path through the CP. The signals are all absolute. Red means stop. Do not pass a red signal without the express permission of a dispatcher and then only at restricted speed.

D-D and E-E are double slip switches.

There are no signals for individual turnouts, just for the CP itself.

My guess is the only signals that would have a green aspect would be A and I on T3. All the remaining signals would have only yellow and red aspects because of the possibility that some thing really bad will happen if there is an oops meaning all trains entering the CP on the other tracks do so at approach or restricted speed.

The top aspect describes the straight through path.  The center aspect describes the diverging track.  The lower aspect describes the next distant turnout.  I'm really a bit fuzzy about all that.

So, signal D on T4 describes the path through the CP.  The top aspect turnout A-A and the lower would describe turnout B-B.  It is stop or go only as there are no alternative paths.

But signal G on track T6 has 3 aspects.  The top for turnout C-C, center for turnout D-D and the bottom for turnout E-E.  They describe both the position of the turnout and the status of the track block beyond it.

Double slip switches inside yard limits would be either unsignaled or have dwarf signals indicating the position of the turnout.

Now aren’t you sorry you asked

Anyone with real knowledge please retort.

Sounds good to me, except that I know that some railroads (like the PRR) used a combination of overhead signals and dwarf signals at complex interlockings to give the engineer proper guidance through the switches.  That's I subject about which I still have a lot to learn.

Chuck

@rdunniii posted:

Ok, a chance to test my signaling knowledge, awesome. I find signaling the most fascinating part of real railroading

I’ll use Gunner John’s example;

You've just used up my entire signal budget on that one spot on the layout!

@rdunniii posted:

My guess is the only signals that would have a green aspect would be A and I on T3. All the remaining signals would have only yellow and red aspects because of the possibility that some thing really bad will happen if there is an oops meaning all trains entering the CP on the other tracks do so at approach or restricted speed.

Interlocking trackwork like this is controlled either by a dispatcher or a tower operator.  When a train approaches, the operator lines a route through the interlocking, throwing switches as needed.  This causes ALL signals on tracks approaching the thrown switches to display STOP.  After he has lined the route, he sets the signal on the track where a train is approaching and presses a button on his panel.  If a valid route is selected and the outgoing track on the route is unoccupied, the signal will display an aspect other than STOP.

If the operator did not line a proper route or if the route leads into an occupied track, the signal will not move off STOP.  The system is designed to prevent oops.  Trains run at reduced speed through switches (slower on switches with more curvature) to reduce risk of derailments.

The top aspect describes the straight through path.  The center aspect describes the diverging track.  The lower aspect describes the next distant turnout.  I'm really a bit fuzzy about all that.

Western railroads tended to use this type of signalling.  On eastern roads the signals told the trains what speed to run at, not what route they would be taking.  Multi-head signals were used so that many different speed aspects could be displayed, such as clear, medium clear, slow clear, approach, medium approach, slow approach, restricting, etc.).

@PRR1950 posted:

Sounds good to me, except that I know that some railroads (like the PRR) used a combination of overhead signals and dwarf signals at complex interlockings to give the engineer proper guidance through the switches.  That's I subject about which I still have a lot to learn.

Chuck

PRR signals were speed signals, telling the engineer what speed to run at and whether to plan to stop at the next signal or not.  An interlocking out on the main would typically only have signals on the tracks approaching the interlocking, there would be no signals within the interlocking itself.  Mainline tracks would have signal bridges or mast signals while passing sidings and spur tracks would typically have dwarfs.

Multiple dwarf signals were found in complex yard throats of passenger stations and sometimes in freight yard throats.

@PRR1950 posted:

If you really wanted signals to indicate switch path / direction of travel, you would have to use one dwarf/ground signal at each switch entry location (4 of them).  Each signal would tell the engineer if he was routed straight through (green, I suspect) or routed to change direction (probably yellow).

Chuck

But you would not want to locate one of those dwarfs where it would cause a train to stop with its cars blocking other possible routes through the interlocking -  a reason for having the signals clear a route all the way through an interlocking.

@gunrunnerjohn posted:

Yep, my double-slip switches certainly are at a busy spot.

We have an arrangement similar to that at our club.  There is a simple way to display the route lineup on the control panel.  Here is the layout.

This one uses two slip switches on a double track mainline at the east station entrance.  I've shown route lights for main line tracks 1  (1W and 1E) and 2  (2W and 2E), a freight bypass (B) and an alternate route (4E) to the east.  Also the crossover (XO).

The logic for he route lights is very simple.

If XO is lit, meaning a train using the crossover and no other possible movements, then  ( B or 1W )  and ( 2E or 4E) are lit.

If XO is dark then two routes are lit

   - on track 1 - (B or 1W)  and 1E.

   -  on track 2 - 2W and (2E or 4E).

Note that the pair of double slip switches is logically equivalent to a crossover and two single switches..

Our layout is

@Bob posted:

 

Three correct paragraphs followed by:

The top aspect describes the straight through path.  The center aspect describes the diverging track.  The lower aspect describes the next distant turnout.  I'm really a bit fuzzy about all that.

Western railroads tended to use this type of signalling.  On eastern roads the signals told the trains what speed to run at, not what route they would be taking.  Multi-head signals were used so that many different speed aspects could be displayed, such as clear, medium clear, slow clear, approach, medium approach, slow approach, restricting, etc.).

There is no such thing as top or bottom aspect, only lights.  Aspect is the name for the combination of light colors.  If the top lights is green, that says nothing about path, simply that the train may proceed at track speed as authorized in the timetable.  A middle green (red on top) indicates that the train may proceed at medium speed within interlocking limits and then resume track speed.  If the second block ahead is blocked (occupied or a swatch against it, The middle light would be yellow.

There were no "speed aspects".  Only speeds named in the Book of rules could be displayed - usually proceed, medium, slow and restricted.  The rules for these were

Proceed - run at track speed as authorized in the timetable

Medium - A speed not to exceed 30 mph. (Most main line turnouts were designed for that speed.)

Slow - A speed not to exceed 15 mph. (Most likely a sharper curved turnout at a yard entrance.)

Restricted - Speed such that the train/engine could stop short of any obstacle, not to exceed slow speed.

15  and 30 were the numbers on most railroads, but could differ although I don't know of any such case.

Later a Limited speed (usually 45 or 50) was added.  This was indicated by having the signal flashing.  For example, when CTC was installed on NYC main lines in the 60's, switches had a longer frog angle that permitted 50 mph.  This was a failsafe system in that if the flashing mechanism failed, the indication would be medium rather than limited.

I am not aware of any differences in that essential  logic between eastern and western railroads.

@rdunniii posted:

Ok, a chance to test my signaling knowledge, awesome. I find signaling the most fascinating part of real railroading

I’ll use Gunner John’s example;

This entire drawing is a single interlocking, also known as a control point. Today pretty universally called a CP in North America followed by a mile marker. The signals only govern entry into the CP. The individual aspects describe the path through the CP. The signals are all absolute. Red means stop. Do not pass a red signal without the express permission of a dispatcher and then only at restricted speed.

D-D and E-E are double slip switches.

There are no signals for individual turnouts, just for the CP itself.

My guess is the only signals that would have a green aspect would be A and I on T3. All the remaining signals would have only yellow and red aspects because of the possibility that some thing really bad will happen if there is an oops meaning all trains entering the CP on the other tracks do so at approach or restricted speed.

The top aspect describes the straight through path.  The center aspect describes the diverging track.  The lower aspect describes the next distant turnout.  I'm really a bit fuzzy about all that.

So, signal D on T4 describes the path through the CP.  The top aspect turnout A-A and the lower would describe turnout B-B.  It is stop or go only as there are no alternative paths.

But signal G on track T6 has 3 aspects.  The top for turnout C-C, center for turnout D-D and the bottom for turnout E-E.  They describe both the position of the turnout and the status of the track block beyond it.

Double slip switches inside yard limits would be either unsignaled or have dwarf signals indicating the position of the turnout.

Now aren’t you sorry you asked

Anyone with real knowledge please retort.

Signals A,B,C,H,F and I would all have a high green aspect allowing normal track speed through the interlocking.

" remaining signals would have only yellow and red aspects because of the possibility that some thing really bad will happen if there is an oops meaning all trains entering the CP on the other tracks do so at approach or restricted speed"

This is not a normal factor in railroad signal design.  It is expected that engineers will obey signal indications.  Many have been fired for not doing so.

Signals do not actually indicate the position of any turnout.  They simply display permission to enter the interlocking, the maximum speed allowed in interlocking limits, and they perform the usual block signal function for blocks beyond the interlocking.

These might be helpful.