reversing loop on a single track?

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Builder
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reversing loop on a single track?

Postby Builder » Thu Feb 15, 2018 9:15 pm

I Have been trawling through a lot of the posts on track layouts, and what i have an idea to do is a return loop to turn the loco and on going back to the loop will go the opposite way to turn again! Clear as mud , hey? so i may do two, one each end, instead of a oval or continuous run, This will be 0-16-5 peco track , My question is ,would it be easier to modify the point to allow the loco wheels to `move` the direction each time it passes , or would an electrical sensor type setup for a point motor be better? I was thinking if the spring pressure on the point is reduced, the weight of the loco will move it without a derail? Any thoughts? Jim.

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End2end
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Re: reversing loop on a single track?

Postby End2end » Thu Feb 15, 2018 9:25 pm

I'd say the latter. The former sounds like a definate short circuit to me.
Perhaps with "Hall" sensors in the track and magnets attached to the loco and perhaps the end of the train too as Pendon does to switch the points (and signals) and train location. I.e. the system "see's" both ends of the train.

Also, from the depths of memory this layout shape may be described as a "dumbell" style.
Hope it helps.
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Paul-H
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Re: reversing loop on a single track?

Postby Paul-H » Thu Feb 15, 2018 9:58 pm

On my clubs n-gauge layout they have the same thing, a single track with a reverse loop at each end bad they use infrared sensors to detect the approaching loco and switch the points automatically, next time I go I will ask what system they used.

Paul

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Mountain
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Re: reversing loop on a single track?

Postby Mountain » Fri Feb 16, 2018 12:37 am

The irdot things? I have the predecessors to those devices which were made by a man who didnt make many a year. Mine were intended for either train detection or automatic control of a train rather then point control, but they are fairly similar. One has to paint the underside of the locomotives silver or white to make them work as you have an infra red emitter shining a beam upwards from the centre between the rails of the track and when it reflects the beam on the underneath of a passing locomotive, an infra red detector will then set off to trigger the electrical relay or similar which controls whatever it is you want it to do. Basically, the bits that do the work look like two 5mm light emitting diodes (LED's) which protrude through holes in the layout so they sit at something like sleeper height in between the rails.
Enjoying 7mm narrow gauge.

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Flashbang
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Re: reversing loop on a single track?

Postby Flashbang » Fri Feb 16, 2018 12:00 pm

Hi
I would be inclined to use a couple of IRDOT-P units. These are infra red detectors and can operate a solenoid point motor too, hence the -P suffix. One is placed between sleepers before the point on the approach side and sets loop point to the straight route the other further around the loop so as the rear of the train is clear of the point and this sets the point for the exit route.
See this example http://www.heathcote-electronics.co.uk/irdotp.html Infra red means it will work with all stock passing over it and no magnets etc are needed. :D
Broken? It was working correctly when I left it.

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Bufferstop
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Re: reversing loop on a single track?

Postby Bufferstop » Fri Feb 16, 2018 4:03 pm

In DCC you'll need a reverse loop module and all four rails insulating at the ends of the loop. In DC either wire it through a DPDT (Reversing) switch or if you are happy for trains to always run in one direction use a bridge rectifier, either way the DC controller will need to be reversed when the points are changed, otherwise you'll get a short circuit at the exit when the loco bridges the insulating gap..
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Flashbang
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Re: reversing loop on a single track?

Postby Flashbang » Fri Feb 16, 2018 6:53 pm

DC or DCC you need a minimum of 4 IRJs. 2 at the beginning of the entrance of thd loop and two more at the exit. Plus two IRJs for any other tracks entering or leaving the loop.The distance between any entrance and exit IRJs needs to be longer than the longest train. I.e.the whole train - loco,carriages or wagons needs to fit inside the loops IRJs.
A Switch (DPDT) can be used on DC or DCC power . This can be a manual switch or point operated one.
A DCC reverse loop module will work automatically on DCC layouts . It cannot be used on DC layouts though.
Broken? It was working correctly when I left it.

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Emettman
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Re: reversing loop on a single track?

Postby Emettman » Fri Feb 16, 2018 7:12 pm

Does this have to be automatic for continuous running, or could it be - train enters loop, stops and waits to be released?

This in DC would be pretty simple for one loop (running in one direction only), needing
4 diodes,(return loop conflict eliminated)
2 momentary push-buttons and CDU to work point (or mechanical linkage is fine!)
1 DPDT operated by point tie-bar to change main-line polarity.

This could also operate two loops, as long as only one train is involved.

(I've actually done a variant on this to get a one switch operation of a bidirectional passing loop.)

Chris
"It's his madness that keeps him sane."

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Ironduke
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Re: reversing loop on a single track?

Postby Ironduke » Fri Feb 16, 2018 8:06 pm

Some brands of points, e.g. Atlas, have a fairly weak spring so that a train coming into the point just pushes the blades aside if the points are against them. That doesn't take care of the rail polarity though.
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Rob

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Mountain
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Re: reversing loop on a single track?

Postby Mountain » Fri Feb 16, 2018 8:15 pm

Of corse, you could make a standard dogbone in that the centre piece has two rails.
I seem to remember someone who used Fleishmann points with a standard loop (Not a reverse loop) for an outdoor layout as they had weak springs so that locos and stock would be able to push through the point if it was set to the wrong direction and the blades would spring back to the set route. He was able to uncouple with a ramp, run round and couple up the other end with no electrical or mechanical control other then the 12v track power. Add this idea to a reverse loop and also add diodes to ensure the loco current is sorted out and all should work well, as long as one changes controller direction when train goes back onto the single line.
Enjoying 7mm narrow gauge.

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Emettman
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Re: reversing loop on a single track?

Postby Emettman » Fri Feb 16, 2018 10:28 pm

Mountain wrote:Of corse, you could make a standard dogbone in that the centre piece has two rails.


You can then get the reversing with one, or preferably two, straight lengths of track.
(would make a nice 4 platform station)
Polarity shift would be automatic, and only ordinary point control would be required for 4 points (self isolating).

...He was able to uncouple with a ramp, run round and couple up the other end with no electrical or mechanical control other then the 12v track power.


I've done this in LGB of the 11 points on the layout, only 4 need to be controlled, the other seven being spring-loaded.

Add this idea to a reverse loop and also add diodes to ensure the loco current is sorted out and all should work well, as long as one changes controller direction when train goes back onto the single line.


Exactly. Works for return loops and passing loops with no switches at all, with the right track plan.

Chris
"It's his madness that keeps him sane."

Builder
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Re: reversing loop on a single track?

Postby Builder » Fri Feb 16, 2018 10:33 pm

Lots of interesting solutions here! , I have now started to understand a few shortcomings on my idea`s , but following advice from Flashbang, the IRDOT p system will work, and appears good value too, they also show several types of systems in DC and DCC.
http://www.heathcote-electronics.co.uk/ ... loops.html
I am at preliminary planning stage, so a way off yet still. I am busy finishing off the 009 layout at the moment,but `gathering up` what i need for 0n30. That is when i get rid of the cough/cold/sneezing fits currently endured! thanks again, Jim.

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Mountain
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Re: reversing loop on a single track?

Postby Mountain » Fri Feb 16, 2018 11:04 pm

It looks an exciting project. I hope you get the 009 gauge layout successfully running and finished first.
I dont know why, but I find that working in 7mm narrow gauge to be liberating.
Enjoying 7mm narrow gauge.


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