Help wiring a single slip

[woodbine]

 

Hopefully I've uploaded the image correctly!

I think I've worked it out, but I need reassurance, as I wasn't expecting it to be so odd.

 

I'm OK with Common Crossing #1, which is controlled by Switch #1.

 

I'm OK with Common Crossing #2, which is controlled by Switch #2.

 

It seems to me that Common Crossing #3 has to be controlled by Switch #1 (using the 'other' terminals on the DPDT).

 

Which seems to leave Switch #3 not wired up or controlling anything, as Switch #1controlling Common Crossing #3 has to be favourable in order to allow that movement?

[hayfield]

Why noy use the accessory switch within the point motor on switch 3 to change the polarity in crossing 3 as this controlls which way the traffic flows into the crossing I think you are spot on there

[jamie92208]

I would agree with using the auxiliary switch on the point motor for switch 3. It looks fine to me.

 

Jamie

[woodbine]

Why noy use the accessory switch within the point motor on switch 3 to change the polarity in crossing 3 as this controlls which way the traffic flows into the crossing

There is no point motor, as the turnouts are all wire-in-tube. However, this is driven by DPDT slide-switches at the baseboard edge.

The point I was making ( ) is that surely the route through CC3 is NOT controlled by S3. It doesn't matter which way S3 is set, a movement from the DOWN into the SIDING or vice-versa could be required, and permissable, even if S3 was set for the straight road, in which case the polarity of CC3 would be wrong.

 

So the polarity of CC3 is only dependant upon whether S1 is set for straight or diverging.

If set for straight it permits straight through working of the UP and DOWN lines. If set for diverging it permits working from the DOWN onto either the UP or the SIDING.

[hayfield]

Switches 2 and 3 have to be thrown together, but when they are thrown the polarity on both common crossings alternate. you can do this from one switch if you want, however there is no problem in using each switch to change a common crossing.

[The Stationmaster]

There is no point motor, as the turnouts are all wire-in-tube. However, this is driven by DPDT slide-switches at the baseboard edge.

The point I was making ( ) is that surely the route through CC3 is NOT controlled by S3. It doesn't matter which way S3 is set, a movement from the DOWN into the SIDING or vice-versa could be required, and permissable, even if S3 was set for the straight road, in which case the polarity of CC3 would be wrong.

 

So the polarity of CC3 is only dependant upon whether S1 is set for straight or diverging.

If set for straight it permits straight through working of the UP and DOWN lines. If set for diverging it permits working from the DOWN onto either the UP or the SIDING.

 

Hmm, switch 1 and switch 3 would normally be worked by a single lever as together they make a crossover. Thus the polarity of CC3 would depend on the position of Switch 3 - just, at this stage, think of Switches 1 and 3 as a crossover.

 

The next step is most readily followed from the prototype as Switch 2 could only be operated after both Switch 1 and Switch 3 - you would not be able to operate Switch 2 without first operating the other two. Now do a rethink from that situation and see how it comes out.

 

I think it is a common problem for modellers when looking at the wiring of slips that they aren't aware of the prototype 'logic' in the working of the switches. What this means is that at least one end of the slip will be worked in conert with (mechanically by the same lever as) another point in another line, or one end of a slip in another line. And the other end of the slip will be worked by another lever - again possibly in concert with another point end in yet another line. This logic starts to make even more sense when you have two or more slips forming a 'ladder' of pointwork - and it makes working out the wiring a lot easier I find (my last layout had a ladder started by a point, followed by a single slip followed by a double slip but working out teh wiring didn't strike me as a difficult task as it was just a series of crossovers in my mind (with aneed to watch the feed points of course).

[woodbine]

Hmm, switch 1 and switch 3 would normally be worked by a single lever as together they make a crossover. Thus the polarity of CC3 would depend on the position of Switch 3 - just, at this stage, think of Switches 1 and 3 as a crossover.

 

The next step is most readily followed from the prototype as Switch 2 could only be operated after both Switch 1 and Switch 3 - you would not be able to operate Switch 2 without first operating the other two. Now do a rethink from that situation and see how it comes out.

 

I think it is a common problem for modellers when looking at the wiring of slips that they aren't aware of the prototype 'logic' in the working of the switches

 

Yes, you are quite right, and I hadn't considered that.

However, on the prototype there wouldn't have been a baseboard joint between S1 and the rest of the formation :-), and with wire-in-tube I think it would be a bit awkward, to say the least, to operate S1 and S3 both from one DPDT, so couldn't this be 'represented' by S1 and it wouldn't matter which way S3 was set, since I can't throw it at the same time anyway?

I suppose it does go against the grain, but the desired end result would be achieved with one less switch to throw on my part, and it doesn't set up any conflicts, does it?

[The Stationmaster]

Yes, you are quite right, and I hadn't considered that.

However, on the prototype there wouldn't have been a baseboard joint between S1 and the rest of the formation :-), and with wire-in-tube I think it would be a bit awkward, to say the least, to operate S1 and S3 both from one DPDT, so couldn't this be 'represented' by S1 and it wouldn't matter which way S3 was set, since I can't throw it at the same time anyway?

I suppose it does go against the grain, but the desired end result would be achieved with one less switch to throw on my part, and it doesn't set up any conflicts, does it?

 

 

I think you've raised the critical aspect of the modelling area (as with your double slip idea which is at least one solution - hopefully). What I did when using wire-in-tube many years ago was exactly what you were originally planning to do, it was not easy to get both ends of a crossover working together off one lever, but I did try .

 

So the simple solution is perhaps - short of power point operation of course - to just remamber the logic when working your individual point ends. So 'pull' No.1 then No. 3 before you 'pull' No.2. Put back 2 before 3, and 3 before 1.

 

Possible simple answer on your dpdt switches when they are next to each other - put a 'bar of some sort fixed to the back of No. 3 and going behind No.1. You then have very simple interlocking which means you can't move 3 to reverse unless 1 is already reverse and you can't put back 1 until you have put back 3. And if 2 & 3 are on the same board you can apply that principle to them, and it might be easier to do it this way than the way you proposed for your double slip?

[woodbine]

]it was not easy to get both ends of a crossover working together off one lever, but I did try[/i]

 

You should see my Heath-Robinson cat's-cradle attempts to get just ONE turnout at a time working!

Well at least I have the excuse of it being my first layout (and probably the only, the time I have left!)

Maybe I'll string some piccy's together in a blog, as a warning to others! One day....

 

All this linking of points across baseboards throws into relief the limits of the wire-in-tube method.

Certainly it seems to me now that it would be easier to adopt 'creative' solutions to interlocking using power-operated points.

Having said that, it is quite satisfying to see the blades move gently across in tune with a finger on the lever...

[woodbine]

Stationmaster said:-

Hmm, switch 1 and switch 3 would normally be worked by a single lever as together they make a crossover. Thus the polarity of CC3 would depend on the position of Switch 3 - just, at this stage, think of Switches 1 and 3 as a crossover.

Ultimately, the logic of that is inescapable.

I tried on paper all the possible combinations of the frog polarities for the different roads and nothing actually made anything easier.

Electrically I should have regarded the slip as just that, with its own logic and wired accordingly SW2 - CC2 and SW3 - CC3, and mentally separated the LH turnout from it altogether, as I would have done had it been further away physically.

Then as long as it is all operated first as a crossover (in my case from two levers as explained above), then set SW2, as Stationmaster said, all is well.