St. Mary Hoo - P4 Southern Region third rail

Simon Glidewell

Western Thunderer
I did a test today with the third rail; I wanted to see if I could run a loco just using the third rail and one live running rail; normally I just use the third rail as an additional source of power in conjunction with two rail running. The results were astounding; the class 73 happily buzzed up and down the entire length of the layout as though it was on two rail! I was amazed. Not only that but the tandem point it passed over had all its polarity switches disconnected... can you see where this could be leading? Yes, that blasted bisected point is still giving me electrical problems despite Dave's kind assistance; I've checked all soldered joints; all section breaks and wired it just as per the diagram but I am still getting weird and frustrating results. My fault really for attempting something rather too complex for a bird brain like me. If all else failed, the third rail might be the answer. Obviously it would restrict movement to EMU's and ED's/electrics only, plus normal two rail locos over the CEGB bisection. The latter works perfectly and is the most complex part of the point by far, with loads of tiny lengths of rail and a maze of wiring. I had thought that this part of the set up would cause most problems. It is hugely annoying, as all my stock passes through the entire point (all the crossings) very nicely with no derailments. An alternative would be to make a normal point for the junction and add the bisected point after this and restrict it to electrics only on the normal roads. I've always loathed electrics and always get them wrong.
 

Neil

Western Thunderer
Sorry to hear that you're having problems with the electrical bit of the pointwork Simon. I've spent some time staring at the diagram I did and am fairly sure that I haven't boobed. It's difficult to trouble shoot at a distance, but I wondered if you could post a trackplan of the layout so that I could see how the bisected point fits into the scheme of things, it's just possible that it's getting some weird back feed from some other bit of track connected to it.

Could I ask a couple of questions to clarify how the wiring is arranged. Are the wires colour coded? I make no judgement here as I often end up setting out with good intentions and then having to improvise with another colour when I run out. Also are the wires run directly from switch to rail or do you joint them at a choc block connector or solder tag strip?
 

Simon Glidewell

Western Thunderer
Many thanks for your assistance Neil; I doubt there's anything wrong with your original plan; it's far more likely that I've done something wrong. All the wires are colour coded (as per the colours on your plan) with appropriate Humbrol paint. The point isn't connected to the layout yet so is stand alone. The wires are connected directly to the switches with no connector blocks. I've changed the polarity switches too, to see if I was using dud switches, but they are all OK too. Everything is wired in colour code order and each section break is properly isolated so there are no shorts in that way. As Dave suggested, it appears to be a conflict between the yellow and magenta crossings. But something else I noticed is that the main polarity switch (not the independent one) is only working in one switch position; if I switch it the other way there is a short. It works if switched to the right but not the left. When this switch is to the right and the independent one is down, track C works, but A and B only work (in these switch positions) on the switch blade side of the point. If you place the loco on the other side of the point, on the frog, the loco starts moving again on track A but on track B the loco runs in the opposite direction! Quite a mess.
 

Simon Glidewell

Western Thunderer
CIMG000A.jpg A photo I forgot to post when I was realigning my tandem point (with a makeshift track spacing device). It obviously shows the removed plastic slide chairs, but also gives a nice view of the two side exit ramps (essential items for working third rail, to lift the pick up shoes onto the main conductor rail, and lower them off). You hardly ever see these modelled on third rail layouts; I can only think of a handful of other layouts where I have seen this feature. This morning these were in full electrified use as I was testing third rail only operation (most successfully). You can also see one of my own hybrid isolators below the first ramp; all the isolators on the layout use scale etched metal cradles (that the conductor rail sits in - not attached to as is sometimes mistakenly thought) supplied by the Scalefour Society shop. You need good eyesight for these! The unballasted area around the switch blades will eventually be ballasted in, and scale cosmetic tiebars added.
 

Peter Insole

Western Thunderer
Ah, Simon, that trackwork looks good, and hearing that the third rail worked perfectly has warmed the old cockles no end! I have many times sat and cogitated collector shoes in 4mm and upwards, and of course coupling them to the noisiest motors available!

I don't want to intrude on your present modelling tasks or break a train of thought, but please would you sometime describe how you achieved it?

All the best, Pete.
 

Yorkshire Dave

Western Thunderer
Hi Simon

I've redrawn Neil's wiring diagram here at home so I can trace the switching and current flow in my simple way...:oops: and as I can see it should work.

The only thing I can suggest is to break the independent switch into two 'centre off' switches - one wired for the yellow and the other for the magenta frog. It could be that there is something funny happening within the existing independent switch.
 

Colin Parks

Member
Hi Smon,
Only a thought...
I have never wired up a tandem point, but could there could be issues if the polarity of the third rail? Perhaps the conductor would need to change from positive to negative to match the crossings.

All the best,

Colin
 

Steph Dale

Western Thunderer
Simon,
It has been my pleasure to follow this thread as an observer, but seeing your conundra with your crossing I thought I'd see if I could help more and I'm afraid I came to the same conclusion as (Yorkshire) Dave. The logic seems good from here.
I have to confess I didn't consider any effects from your working third rail or any returns.

Colin,
It's really good to see you here and I've been following your threads on the other place about your EMUs. I've done a few more carriages since I was a regular poster there, so should probably update one of my threads!

Steph
 

Simon Glidewell

Western Thunderer
Many thanks Pete, Dave, Colin and Steph! What a great bunch you are and thanks for all your suggestions! The bisected point doesn't have any conductor rail on it yet; that would come once it is located on its baseboard. So that's not an issue here (the tandem point works fine and that has full conductor rail in place). I think I will try Dave's new suggestion and see what happens; as it's such an unusual arrangement as a piece of track I've never come across any others who have wired one up; I'm sure someone out there has built one, but I'll never find them! I think I will have another thorough look at the way the wiring is behaving, plus double check all my electrical breaks again. Pete; in answer to your question, I will definitely describe how I build my third rail, and I will use the bisected point as my example... so watch this space! This is something I do know how to make function very efficiently, if nothing else!!

All the best
Simon
 

Neil

Western Thunderer
Thanks for the clarification Simon; I have some further suggestions.

Before altering the switching arrangement I would check again that the right wire goes to the right bit of track. Getting the loco to run in reverse over part of the formation sounds like you may have swapped over the wires feeding the red and blue rails beyond the switch rail section. Often worth getting a friend to check with you as I know from experience that sometimes it's possible to overlook the same mistake time after time.

If no success from that I wonder if you could take a photo of the point and its wiring, clear of stock, directly overhead which might enable me to trace out the wires and maybe work out why things are not working as they should.
 

Simon Glidewell

Western Thunderer
Many thanks again Neil; I will get a photograph for you but it probably won't help as half the wires are currently sitting below the temporary baseboard. Because there are so many (vis a vis the number of small rail sections) there wasn't room above and it would be impossible to disguise them later on.
 

Neil

Western Thunderer
You're quite right then Simon, I doubt that will be any use then. A further thought occurred, looking at the diagram I have only shown the switched connections, did you common up all the red rails together and all the blue rails together? I can't remember if I said this at the outset, implied it or forgot to mention it at all. It's one of those possible errors of omission where it would seem natural for me to do so, but with hindsight it may not have if you were doing your best to follow the instructions to the letter.
 

J_F_S

Western Thunderer
Some excellent looking track here - very well done!

Just on side entry ramps, I am a bit concerned to see that you seem to be using LUL pattern ramps - much better than nothing but not correct for the Southern. James Moorhouse posted some useful details of the SR pattern in Colin's thread here:-

P4 conversion work - Page 4 - Scalefour Forum

They are fairly easy to make out of plain metal strip, but even easier if you have some left over etches from building the S4 society lever frame which has the correctly shaped bit of waste fret!



Side Ramp Small.jpg

Side Ramp Top Small.jpg


I was confused when you talked about "isolators" but presume you mean "insulators" or, more commonly "pots"!

Great stuff, keep up the good work!

Best wishes,

Howard
 

J_F_S

Western Thunderer
Simon,

I am not sure if you have or have not solved the problem of wiring your crossings yet, but there is an "error"* in the original diagram. If you look at tjhe "A/B" changeover switch, the Blue and Red feeds are both connected to one common feed. However, they should be connected separately - the "top" red and blue should come from the diagonal road as drawn. However, the bottom red and blue should be connected to the red and blue rails at the toe and of the point. As drawn, you might get a short or no feed depending on how the diagonal road is fed in relation to the feed to the toe of the point.

Hope that makes sense. Although a crossing through a point looks a bit nasty, it is actually no different in principle to any other diamond crossing, and this means that it is sometimes possible to replace the A/B switch by one driven from a suitable point controlling the routing through the crossing (I do this on my layout) but this will not be so if the two routes are completely independent of each other. You also would really need to have full interlocking between your point levers if nasty things are not to happen...

Hope that helps.

Howard

Edit:- * not an error if all the reds and blues are commoned together as Neil suggests in his later post.
 
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