Scissors (elec)trickery

[Izzy]

9 hours ago, Grovenor said:

If Ian's scissors is built as per the Templot plan he showed then this approach is not practical, it needs to be looked at as an integrated whole to avoid the need for rail gaps in very awkward places. The required wiring has already been provided by Suzie.

See

Regards

 

Ian is working in 2mm/2FS using soldered track, as do I, so I am aware of the difficulties of arranging isolating gaps, which I agree is far from easy, as well as the wiring needed for either/both DC or DCC, it’s the same really. I hope what I propose will answer all the questions that do often arise. I will post the diagram/s sometime in the next day or so, just got to draw them out today.....

 

Izzy

[Pete the Elaner]

On 10/03/2019 at 01:29, AndyID said:

 

You could try this. There are really only two "states". All straight or all crossing. You can set the points for other combinations but none of them make much sense.

 

I'm assuming you are using live frogs. There are six of them (indicated by the circles) but you only need to gang the diamond's frogs from two of the turnout frogs.

 

(from a former Paisley Buddy)

 

 

 

 

 

 

 

 

 

 

 

I fully agree that only 2 states need to be considered: All straight & all crossed. Any others involve running in to a point not set.

With all points set to straight, the crossing needs no power at all, so I would isolate all rails. YOu only then have to consider how the crossing needs to be wired when the points are set to use it.

You do not need to take power from any switched frogs. If you only consider the crossing with the points thrown, you can take the feed directly from one of the main line feeds. If you have cab control, you could choose which circuit to include the crossing in.

So I would ignore the feeds from the frogs to the crossing, which are wrong anyway.

[Suzie]

1 minute ago, Pete the Elaner said:

I fully agree that only 2 states need to be considered: All straight & all crossed. Any others involve running in to a point not set.

With all points set to straight, the crossing needs no power at all, so I would isolate all rails. YOu only then have to consider how the crossing needs to be wired when the points are set to use it.

You do not need to take power from any switched frogs. If you only consider the crossing with the points thrown, you can take the feed directly from one of the main line feeds. If you have cab control, you could choose which circuit to include the crossing in.

So I would ignore the feeds from the frogs to the crossing, which are wrong anyway.

 

The polarity of the crossing frogs has to be changed depending on which crossover is being used. It is not possible to set 'all crossing' when using a live frog diamond in the middle. There are three states!

 

The feeds from the point frogs to the crossing frogs are quite correct when using Andy's scheme which requires twelve isolating breaks on the six frogs.

[Izzy]

11 minutes ago, Pete the Elaner said:

 

You do not need to take power from any switched frogs. If you only consider the crossing with the points thrown, you can take the feed directly from one of the main line feeds. 

So I would ignore the feeds from the frogs to the crossing, which are wrong anyway.

 

How can this work when the diamond frogs need to change polarity depending on which way the crossing is made? Same as with the points. I feel I must be missing something obvious here, but I can’t see what.

 

Izzy

 

Oh, sorry, Suzie beat me to it...

Edited March 12, 2019 by Izzy

[Pete the Elaner]

19 minutes ago, Suzie said:

 

The polarity of the crossing frogs has to be changed depending on which crossover is being used. It is not possible to set 'all crossing' when using a live frog diamond in the middle. There are three states!

 

The feeds from the point frogs to the crossing frogs are quite correct when using Andy's scheme which requires twelve isolating breaks on the six frogs.

3 states?

All points set to straight. The crossing can be dead for this. As long as it is isolated, does it matter which way it is powered?

All points set to crossing. Top rail needs to be the same polarity as top rail & bottom needs to be same polarity as bottom rail.

1 crossover straight & the other to crossing. Why bother? Every usable scenario has just been covered.

[Suzie]

1 hour ago, Pete the Elaner said:

3 states?

All points set to straight. The crossing can be dead for this. As long as it is isolated, does it matter which way it is powered?

All points set to crossing. Top rail needs to be the same polarity as top rail & bottom needs to be same polarity as bottom rail.

1 crossover straight & the other to crossing. Why bother? Every usable scenario has just been covered.

 

The problem with your scenario is the crossing frogs - the polarity reverses between crossing one way and crossing the other way. There is no way round it other than switching in conjunction with crossing one way or the other - or separately switching those frogs.

[Grovenor]

3 hours ago, Suzie said:

2-pole switches will require breaks around the four point frogs (eight of them) so that you can just link the crossing frogs to the point frogs and have one pole per point frog.

 

I tried very hard to rework it but DPDT + TPDT is the best I could get either way while maintaining the structural integrity as far as possible with breaks just on the crossing frogs.

Depends on the sectioning, if its DCC or all in one section then a DPDT for each crossover will do it. If the tracks are in different sections then extra switching will be needed depending on how the sections are arranged.

I thought I had one all drawn out but have failed to find it so far.

I'll make a new one if its not resolved shortly.

Regards

[Ian Smeeton]

Sobriety has returned, hower, work is now getting in the way.

 

Thank you all for your input.

 

I hope to have a full day on this at the weekend, but as the weather is improving (says he, looking out at driving rain and howling winds), I may end up volunteering at 'Rocks By Rail' on Saturday. Pray for rain on Sunday, please otherwise the Boss will have me on Gardening Jankers.

 

This hobbby lark keeps getting pushed down the pecking order, much to my chagrin.

 

If divorces were cheaper, it might be an option.

 

Regards

 

Ian

 

 

[Izzy]

The requirement for the OP, is for DC ( it is in the DC section), just using the DPDT slide switches that work the individual point tie-bars via tube/wire if possible, which it is, to keep it simple and easily produced. 

 

Izzy

 

added - actually this general question has been asked here before, in 2015, and clearly and simply answered by Clive Mortimore. The details are here: 

https://www.rmweb.co.uk/community/index.php?/topic/86612-home-made-scissor-crossing-and-control/

 

read his post, about halfway down the first page. Pretty much what I will be posting with specific details about the Templot configuration Ian will be building.

 

 

Edited March 12, 2019 by Izzy

[Suzie]

5 hours ago, Izzy said:

The requirement for the OP, is for DC ( it is in the DC section), just using the DPDT slide switches that work the individual point tie-bars via tube/wire if possible, which it is, to keep it simple and easily produced. 

 

Izzy

 

added - actually this general question has been asked here before, in 2015, and clearly and simply answered by Clive Mortimore. The details are here: 

https://www.rmweb.co.uk/community/index.php?/topic/86612-home-made-scissor-crossing-and-control/

 

read his post, about halfway down the first page. Pretty much what I will be posting with specific details about the Templot configuration Ian will be building.

 

 

 

Clive ignored the OP's requirement to keep the frog triangles intact (only four isolating breaks in the whole scissors) and provided the same solution that AndyID has already proposed above (which has twelve isolating breaks).

 

[Grovenor]

There should be 16 isolating breaks, not including seperation of DC track sections (which Clive included). Of course using Peco turnouts and not isolating the frog from the switch blades does reduce it by 8, but I would not expect to do that on hand built track.

Quote

The requirement for the OP, is for DC ( it is in the DC section), just using the DPDT slide switches that work the individual point tie-bars via tube/wire if possible, which it is, to keep it simple and easily produced. 

OK, Ian, assuming this is one slide switch per point, then you will have to manage manually the operation of one crossover at a time to avoid shorts on the diamond. The wiring can be biased to allow use of one crossover but not the other if both are reversed.

Can you confirm that it can all be in one power supply section as it is in the yard?

In this case one slide switch per point will do.

 

So far as isolating gaps go there should be 16! Not 4 or 12.

Each turnout needs 2 gaps to isolate the frogs from the switches, that is 8.

Each of the 4 rails across the diamond needs a gap to prevent a dead short, another 4.

And the two common crossings in the diamond need to be isolated from the adjacent stock rails, another 4.

Regards

 

[Suzie]

 

On 10/03/2019 at 12:22, Suzie said:

There are three states in practice which makes the wiring a bit more intuitive:-

 

• All straight
• Crossing bottom left to top right
• Crossing top left to bottom right

I am assuming that you will feed both routes from one end and not require power routing and that you can operate the two points of each crossover with a single switch. DCC would have made this a lot easier, but you should be OK.

 

Note that the frogs of points 1 and 3 are connected together as are the frogs of points 2 and 4 to make life easier.

 

I could not do it all with DPDT switches, so you might have to add a microswitch to point 1 to get the extra pole.

 

If you need power routing you will need extra poles for that too. Wiring is common return with the black feed being the common.

 

 

 

15 minutes ago, Grovenor said:

There should be 16 isolating breaks, not including seperation of DC track sections (which Clive included). Of course using Peco turnouts and not isolating the frog from the switch blades does reduce it by 8, but I would not expect to do that on hand built track.

OK, Ian, assuming this is one slide switch per point, then you will have to manage manually the operation of one crossover at a time to avoid shorts on the diamond. The wiring can be biased to allow use of one crossover but not the other if both are reversed.

Can you confirm that it can all be in one power supply section as it is in the yard?

In this case one slide switch per point will do.

 

So far as isolating gaps go there should be 16! Not 4 or 12.

Each turnout needs 2 gaps to isolate the frogs from the switches, that is 8.

Each of the 4 rails across the diamond needs a gap to prevent a dead short, another 4.

And the two common crossings in the diamond need to be isolated from the adjacent stock rails, another 4.

Regards

 

 

Keith

 

You might like to count the isolating breaks on my diagram above from halfway down page 1. It does show five breaks but that was before I found out that only a single track feed was required eliminating one of them (blue, green, red and orange feeds are all the same). The only isolating breaks required apart from the obvious are on the two diamond frogs. 

 

Only one slide switch per crossover is required (both points of each crossover operated from one switch) but one does need to be a three pole one for this scheme.

 

I will leave it to the OP to decide which scheme to use - simple track configuration with minimal rail cuts (my method) versus simple wiring using two DPDT switches (AndyID/Clive method).

 

 

[Grovenor]

Suzie,

There are actually 16 isolating breaks in your diagram, you are just ignoring the breaks at the frogs.

 

ian,

Attached is a wiring diagram using one slide switch per point and a single section.

Contacts are shown for the two straight routes, ie all normal.

Operating points 1 and 3 or 2 an4 will switch the polarity of the 4 frog sections (A, B, C, D) for the revevant crossover route.

Operating all 4 points the 2 & 4 route will be energised correctly, the 1 & 3 will not so will short if run through.

Regards

Edited March 12, 2019 by Grovenor

[Suzie]

I just don't count flangeways as isolating breaks - they have to be there!

[Silver Sidelines]

As I have already noted  https://www.rmweb.co.uk/community/index.php?/topic/142950-scissors-electrickery/&do=findComment&comment=3491535, the Peco insulfrog diamond offers a simple and very elegant solution.  Of course I did have to modify one of my engines so that it didn't stall on the plastic frogs https://www.rmweb.co.uk/community/index.php?/blogs/entry/16797-dead-frogs-and-a-2p/ - but again another simple and elegant solution.

 

Cheers Ray

[Grovenor]

45 minutes ago, Suzie said:

I just don't count flangeways as isolating breaks - they have to be there!

Flangeways have to be there, but in hand made finescale track they are not usually insulated. IMHO its always best to be explicit about the required gaps.

Regards

[AndyID]

It is possible with 2 two-pole switches, but not quite the way you might expect.

 

 

The top switch determines the polarity of the two triangular sections A and D. I'm assuming all the points are either straight or turning out but it would also be possible to arrange for the switch to throw mechanically if either crossover (f for facing, t for trailing) is selected. The bottom switch feeds A and D to B and C depending on facing or trailing operation.

[Suzie]

The lower switch can work in conjunction with a point, but the top one can't unless a second DPDT switch is interspersed to reverse the feed connected to the other crossover so that if both points are normal there is no reversal, and if either is reversed the feed will be reversed (ignore the scenario when both crossovers are set!) Probably not too hard to gang an extra DPDT switch to give four poles on one of the crossings - it certainly simplifies the wiring at the cost of an extra pole.

[Harlequin]

I was intrigued by this problem but while I was working it out AndyID had already posted the solution I arrived at (which might not quite meet the OP's needs but is electrically very simple).

 

So that my evening wasn't completely wasted (!) here's my version:

 

(Different naming scheme and slightly different isolator positions than AndyID.)

 

Edited March 13, 2019 by Harlequin

[AndyID]

31 minutes ago, Suzie said:

The lower switch can work in conjunction with a point, but the top one can't unless a second DPDT switch is interspersed to reverse the feed connected to the other crossover so that if both points are normal there is no reversal, and if either is reversed the feed will be reversed (ignore the scenario when both crossovers are set!) Probably not too hard to gang an extra DPDT switch to give four poles on one of the crossings - it certainly simplifies the wiring at the cost of an extra pole.

 

The top switch essentially says "either or both crossovers active". I'm assuming all the points are ganged mechanically or the top switch is thrown mechanically if the points are thrown for one or other crossover. The bottom switch isn't mechanically connected to any of the points. It's just a "route selector".

 

It's not as slick as your method

 

[Ian Smeeton]

My goodness, I seem to have started an all out war, here. Not my intention at all.

 

My original intention was to use DPDT slide switches to physically switch the points, and , somehow, to energise the requisite crossings.

 

Standing working a plastic injection moulding machine for 8 hours is physically and mentally undemanding, hence the original pondering.

 

It could be possible to throw all 4 points from one switch, rather than using two 'ganged switches for each route. Perhaps that is the way to go. After all, there will only be 'one engine in steam' over the scissors, so either all straight, or all diverging would be feasible and acceptable.

 

Being hand built, the crossings were all built as discrete units before being soldered to the copperclad.

 

I will upload a (bad ) scan of the actual beast tomorrow morning, marked up with exactly where all the rail breaks/gaps are. Of course, these can be bonded to each other, as and where required, and if I have missed any, the dremel will come in handy.

 

Please bear with me as antisocial working hours are getting in the way of any modelling this week.

 

Regards

 

Ian

[AndyID]

Ian,

 

I hope you are moulding useful bits for model railways :)

 

Not so much a war, more a case of extreme nerdiness. Personally I wouldn't use any of these methods. I'd do it with one three position switch, four servos, two relays and some diodes. Another way to do it is with "frog juicers", but they are too expensive for anyone from Paisley.

 

Cheers!

Andy

[Ian Smeeton]

Quite correct re the frog Juicers, servos, diodes etc.

 

Clive Mortimore on another topic (I should have searched more diligently) and Izzy have come up with what I feel is the best solution.

 

For myself, I was trying to work out how to switch, effectively 3 common crossings at a time, when in actual fact it is only 2. The two k or obtuse crossings on the diamond do not need to be switched at all, as they can be fed with the track polarity. This is where I was coming a cropper.

 

My thanks to all who have had input, and apologies to Suzy, particularly, as I used the catch all "Gentlemen" further up thread. Being an old fart, my gender definitions can sometimes be confused by the slightest wandering.

 

I will ask Izzy to put up his proposal for critique, but he might prefer to keep his head below the parapet.

 

Regards

 

Ian

[Ian Smeeton]

10 hours ago, AndyID said:

Ian,

 

I hope you are moulding useful bits for model railways

 

<snip>

 

Cheers!

Andy

 

Sadly, no. My definition of my work, is that we are not even a widget factory. We make parts that other people turn into widgets.

The work is second only to the painter & decorators apprentice detailed with watching paint dry.

 

We make all sorts of things from airport security trays to the stems and stamens of the British Legion Poppies, and from the ends which are made into lobster pots to KitKat display stands and humbrol paint display stands.

 

I would love to see us making model railway bits, but as I am a humble machine operator/driver, I suspect that it will be a long time before we start bringing Hornby's tools up from Margate or back from China.

 

All the best,

 

Ian

[Izzy]

 

Okay, this is the wiring/operation suggestion that I have made to Ian. The actual rail breaks are where Ian has already made them, with question marks where I have queried what exists or doesn't, the trackwork already having been built, so he can make whatever adjustments he feels necessary.

 

Please bear in mind that this is intended to fit in with his original request of just using the four DPDT slider switches which change the points/frog polarity if it was possible. These being worked manually using wire/tube/rodding in conjunction with the switches. It is indeed the system I have returned to in recent times, after trying various motorized ways and finally ending up with hacked servos, although I use DCC power rather than the DC that is Ian's preference. But the wiring is exactly the same whatever save for the lack of sections with DCC.

 

 

As it is DC, and to provide the greatest flexibility with running moves I have suggested that the scissors unit is split into three sections, the central diamond crossover, which of course can remain live at all times irrespective of the chosen route, and the two straight routes, A1/A2 and B1/B2 forming single powered sections.

 

Which pair of points power the diamond frogs C1/C2 is down to personal preference and ease of operation, A1/A2, B1/B2, A1/B2, B1/A2. The particular location and main route might play a part here I feel. In this particular case, and looking at the Paisley St James general trackwork design, I have again suggested in the diagram, B1&B2. This is for ease of use in remembering that these can both be set straight - obviously - but both must not be set to crossover at the same time, to ensure the correct diamond polarities whatever route is used, A1/B2, or B1/A2. The setting of A1/A2 is immaterial -  except of course when choosing the correct one for a crossing route!

 

regards to all,

 

Izzy

 

 

 

 

 

Edited March 15, 2019 by Izzy
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