Throwing single slips

[jim s-w]

Hi all

A thought has crossed my mind on single slips. On a double slip both ends need to be thrown to set the route but on a single slip, you can throw one end and not necessarily the other. From a model point of view with traditional wiring you do need to throw both ends but I wonder, on the prototype what do they do?

Jim

[Tim V]

Not necessarily true on the GWR/WR. The two sets of switches on a double slip were worked independently. Only 'other' railways were perverse.

For information, here is the Mells Road diagram. Note the different numbers on each end of the slip.

IMG__ (1).jpg

[jim s-w]

Thanks Tim

May not have been clear enough. On a double slip you have to ensure the correct route is set at both ends. On a single slip you don’t. For example if the straight road is set one end. The other, where the point blades are not on the route that’s set can be left at whatever they happen to be. Im curious if that’s what happened.

Jim

[Tim V]

The diagram shows that the interlocking precludes that kind of thing happening.

Say I want to go from the down main onto the branch. Reverse 24, 26, releases 23 or 27, but not 25 or 28.

[Noel]

Presumably Normal for 26 is to the curved road [platform and siding respectively], 24 Normal locks 26 Normal and 26 Reversed locks 24 Reversed?

[Tim V]

That would be the general idea, I'm merely giving this diagram as an example.

[PeteT]

Interesting observation Jim - at Embsay the double slips were worked from 1 lever, but the single slip wasn't. I would assume 9 would be locked unless 6 was thrown?

The crossover would be thrown as a pair though, but the left hand end needs to be independant (not that the right hand couldn't, in model terms, be put back to straight if 9 was thrown - but wouldn't happen on the prototype).

http://www.davidheyscollection.com/user ... ulleyn.jpg

[grovenor-2685]

Interesting observation Jim - at Embsay the double slips were worked from 1 lever, but the single slip wasn't.

No, the double slips are not worked by one lever, in each case one end is worked by the lever as numbered, the other ends are hand points. ie a second lever but not in the frame. The numbered ends are acting as traps protecting the running lines from the yard, the other ends are just available for yard shunting. The single slip is fully in the interlocked area and each end has its own lever, both being parts of crossovers.

I would assume 9 would be locked unless 6 was thrown?

Yes, normally written as 9 released by 6.

The crossover would be thrown as a pair though, but the left hand end needs to be independant (not that the right hand couldn't, in model terms, be put back to straight if 9 was thrown - but wouldn't happen on the prototype).

Not quite sure what you mean here. crossover 6 can be reversed to allow moves between up and down lines, to access the yard from the down both 6 and 9 need to be reversed.

It is normal for the 4 blades at one end of a double slip to be operated by one lever**, whether from the frame or a hand lever. A double slip is the equivalent of two turnouts toe to toe. Depending on the required route neither, either or both levers may need to be pulled. A single slip is the same except that one of the routes is not possible.

** Note this applies to 99% of cases but in the past, for esoteric interlocking reasons, some double slips had seperate levers for the 2 sets of switches at the same end, hence the double slip may have 3 or 4 levers. I have seen this in complex layouts on the GWR and the LNWR but never managed to follow the logic as the interlocking could have been done the conventional way and the same railway did so at other places.

In railways with germanic influence double slips in yards often had just one lever that set the slip either as a diamond crossing or as the two slip routes, and there are suggestions that there were one or two such installations in yards over here although Its only hearsay, I have never seen evidence. This is the arrangement favoured by german model suppliers, eg Maerklin and Fleischmann.