Reverse Loop wiring

10309 Views 14 Replies 10 Participants Last post by Campaman, Jan 5, 2015

icornish

Discussion Starter · May 27, 2005 (Edited by Moderator)

I've laid out my oval(s) of track, and have just put a new reversing link line across the middle of the board joining the two inner loops. the reverse loop track is fully insulated from the main track - don't want a short circuit!

Now, the question I have is how have other's who have done this (In DC, not DCC) wired them up ?
I've tried the basic DPDT switch, and that works OK. But, I've also seen other options using bridge rectifier (http://rail.felgall.com/rlt.htm for example), which does not appear to work (why?)
Any other ideas ? (And don't say "Use DCC", because I can't afford the decoder modules for all the loco's I have)

TIa,

Ian

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RightAway

· #2 · May 27, 2005

Hi Ian,

Having looked at the illustrations on the web page you mention, I have a couple of comments:

The uppermost illustration is confusing in that it does not show both rails. To which rail should the single diode be soldered? (I think it should be the right rail in the direction of travel). Should the other rail be isolated at this point? (I think not)

I would also query the lower illustration. Notice that two of the diodes point North West. I think it would work if these were to point South East. This would ensure that one rail of section B always gets positive current and the other rail always gets negative.

The trade off is that trains in section B will never be able to reverse. Whichever way the reversing switch is set, they will only ever go forward (or stop).

The above comments are based on theory alone, let me know if it works in real life.

Regards

RightAway

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Gary

· #3 · May 27, 2005 (Edited by Moderator)

This is an interesting and important topic as reverse loops enable continuous running (of sorts with the use of a manual switch if its not automated) and at the same time permits a shelf type layout between the loops allowing locomotives to run continously around the perimeter of a room on an "L" type base (for example) with loop baloons at each end.

Now I am not an expert and complexities of this subject has always put me off even thinking about using reverse loops, but if we can work things out to make this idea easy for folk to grasp, then I am confident more will give it a go because of the space saving advantages when compared to continous running on an oval circuit which has to be placed in the centre of a room or at one side on a base with a depth of 1000mm or more which can make access on the far side of the layout difficult.

How does the information at this link look. The design requires a manual switch to change the polarity but if the switch is not thrown the loco comes to a halt automatically. If it is thrown whilst the loco is between the breaks then the loco continues on its merry way without stopping. All that it needs is something to automate the polarity switch for the whole process to be automatic:-

http://www.geocities.com/loggingloco1/dctramway/reverse.htm

Happy modelling
Gary

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RightAway

· #4 · May 28, 2005

Yes Gary, excellent link.

A two-rail diagram is so much more useful. You could possibly get away with using a single diode on the exit section, but for the price of a diode, using two as shown makes the process easier to understand.

Regards

RightAway

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Sarah Winfield

· #5 · Dec 31, 2014

http://www.geocities.com/loggingloco1/dctramway/reverse.htm

This is a subject with which I am wrestling with at the moment. The above link no longer works for what, presumably it was intended. Instead you are directed to a yahoo site.

I have wired in the switch (I am using DC) as per the many examples on the web.

Now it is a question of how do I use the switch?

I have placed isolating fishplates at each end of my loop and there is about 5' of track between them so there is plenty of space and time for me to change the DPDT switch.

Do I have to have the locomotive stationary and change the switch or can it be done with the train moving please?

Do I also have to change the controllers direction switch?

I know without the DPDT switch the locomotive stops because of a short due to the rails coming back on themselves but the opposite polarity.

The switch changes this but when do I use the switch?

I have looked at diodes but fear that will be too complicated although I do have plenty of these.

Any assistance would be appreciated please?

Sarah Winfield

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Suzie

· #6 · Dec 31, 2014

Sarah

If you use a bridge rectifier it is very simple to wire, just connect the + and - terminals to your reverse loop, and the ~ terminals to the rest of the layout. You will be limited in that you can only drive the train in one direction around the loop, and you will have to remember to flick the reverse switch on the controller while the train is in the 5', but it really is that simple and there is themn no need to stop.

If using the DPDT switch you will have to make sure that the switch is in the correct position before entering the loop, stop the train in the loop, flick the switch and reverse the controller, then restart the train. It is all a bit of a faf really.

Richard Johnson

· #7 · Jan 1, 2015 (Edited by Moderator)

*** Suzie's approach is excellent for hidden loops that are just for turning trains, especially if you have a spring-switch point that does not need changing.

But...

There is actually no need to stop even with reversing switches only - and you can keep entry-direction flexibility.

two switches are used, one for main, one for the loop area.

orient the switch on the loop so it indicates polarity vs entry direction for clarity (up for enter top of loop, down for entry bottom of loop for example)

While the loco is in the loop, change the mainline switch. No need to stop.

View attachment rev_loop.pdf

this is from the web

Richard

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kristopher1805

· #8 · Jan 2, 2015

Just for completeness Roco produce an item number 10767 which is both digital and analog and this it also works with Z21 or multimaus and this does what you want automatically, perhaps your bespoke solution above is good enough but for many a ready made item may be of interest.

Richard Johnson

· #9 · Jan 2, 2015

*** it is not brand spe3cific and will work with any DCC system, but like many train brand accessories it is hellishly expensive... more than double the PSX-AR which is an excellent product.

Sarah Winfield

· #10 · Jan 2, 2015

The suggestion using 2 x DPDT switches, is that suitable to a DC controller please?

Sarah Winfield

16A

· #11 · Jan 2, 2015

QUOTE (Sarah Winfield @ 2 Jan 2015, 16:56) <{POST_SNAPBACK}>The suggestion using 2 x DPDT switches, is that suitable to a DC controller please?

Sarah Winfield
Yes Sarah. Doing this creates two separately powered sections and, as Richards states, you have to make sure the polarity is correct as the train enters the loop section, whilst it is in the loop you change the main line switch (thus reversing the main line's original polarity) and the train will run straight off the loop at the other end without it having to stop. The problem is that you have to be aware the controller knob now shows it running in a different or opposite direction eg if it was in the forward (or right) position when running onto the loop, it will also be in the forward (or right) position as it runs off as you have effectively altered the direction when you threw the switch, you'll have to remember which way it is set.

Sarah Winfield

· #12 · Jan 2, 2015

Thank you for that further explanation.

I was going to ask a question about how others identify the direction a particular locomotive is going to go.

It seems to me what ever I do the first few millimetres of travel are always a bit of a lottery as to which way the locomotive is going to go. How do other members identify the direction of travel for a particular locomotive please?

Sarah Winfield

Sol

· #13 · Jan 3, 2015

For DC locos - from the NMRA standards & all model locos normally follow this http://www.nmra.org/sites/default/files/st...s-9_1984.08.pdf

Positive potential applied to the right hand rail shall produce forward motion

The term "right hand rail" as used herein means the rail to the right of the observer standing between the rails with their back to the front of the locomotive.

In a good wired layout, direction control usually would be a centre off switch that can go left or right, so the direction switch is a good indicator of which way the loco will go.

DCC of course is different - direction is determined by the direction the front of the loco is facing - in steam, the smokebox is always forward.

16A

· #14 · Jan 3, 2015 (Edited by Moderator)

QUOTE (Sarah Winfield @ 2 Jan 2015, 18:14) <{POST_SNAPBACK}>Thank you for that further explanation.

I was going to ask a question about how others identify the direction a particular locomotive is going to go.

It seems to me what ever I do the first few millimetres of travel are always a bit of a lottery as to which way the locomotive is going to go. How do other members identify the direction of travel for a particular locomotive please?

Sarah Winfield
Not sure I can explain what I would have done given this situation when I used DC, but I'll have a go:-

Install the 'main line' switch oriented horizontally rather than in the usual vertical alignment so that you switch it left to right or vice versa, not up and down. With the switch positioned left, turn the controller left and see which way the loco goes - with the switch positioned right the loco will travel in the opposite directions.

There are only four possible combinations of switch & controller position which would be relatively easy to learn and remember. A quick visual check of their positions would have you making 100% correct decisions - not 'a bit of a lottery as to which way the locomotive is going to go'.

Personally I'd start with the switch positioned right and use this as my default setting. If I ran a loco round the loop it would result in the switch being 'left' as the loco came off the loop - continue until the loco is stopped and then flick the switch back into its default position. ie you only have it in the left position when exiting the loop and only until you bring the loco to a standstill. You'll soon pick it up

Hope that's clear.....

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Campaman

· #15 · Jan 5, 2015

Sarah's reversing loop isn't just a standard loop, its a loop coming off an oval into the centre to a station complex if she is still looking at the same track plan that has been discussed and designed in her other thread.

I think it will need more that two switches.

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