Reversing Loops

[WIMorrison]

Chaps

 

This is the new h0e layout that I am about to start on which I will be controlling using the Z21 and Digikeijs DR5088RC for feedback to either Traincontroller or iTrains - decision to be made (any advice?)

 

My question is whether I am placing the auto-reverse modules (probably AR1) in the correct places to allow the operation of the layout - I think I am but best to check with the knowledgeable ones

 

 

I would object to any other suggestions on layout or thoughts in general - all advice will be gratefully accepted!

 

Iain

 

 

[Phil S]

if you have not yet bought the PSX=based AR1, then you may like to look at the LDT kit of an Auto-Reverser which AVOIDS the short-circuit, by using a short sense-track (of maybe <1cm) to pre-select the phase of the reversing section .... the same 'detection idea' but without the large current flowing

https://www.ldt-infocenter.com/shop/en/Reverse-loop-module/

 

\of course, in 009/N then it may be difficult supporting the short sense section of track

[WIMorrison]

Thank for the reply and please excuse my ignorance (or stupidity) but what is the advantage offered by the LDT unit? I used to use the Lenz module and never had any issues - excepting the price now - and was assuming the AR1 is the same.

 

I think getting the distance might be a challenge, but not impossible however I would like to know the advantages before deciding on the LDT as it seems more complex that the other auto reversers

[Brian]

If using any short detection reverser  - Reverse Loop Module or Dual Frog Juicer etc the length of track between all entrance pairs of Insulated Rail Joiners (IRJs) and all exit IRJs should be longer than the longest train to travel over that section. Train = Loco and all carriages or wagons.

[WIMorrison]

Brian

 

I have read that in various places but don’t understand why. I don’t have anything in any of the rolling stock, lights or sound, and I wonder why I need to have the whole train in the controlled section - any ideas?

[Dagworth]

Brian

 

I have read that in various places but don’t understand why. I don’t have anything in any of the rolling stock, lights or sound, and I wonder why I need to have the whole train in the controlled section - any ideas?

Are your rolling stock wheels metal or plastic? If they are metal then every single wheel crossing the joint approaching the reversing section will cause a short circuit.

 

Andi

[WIMorrison]

Now I see the logic, why did I miss it before I accept the need for the train length section and will reposition the reversing loop to meet that need - does the amended plan meet the requirement now? In other words, will this work?

My remaining question is what is the advantage of the LDT unit especially as it is twice the price of the AR1?

 

Edited December 27, 2017 by WIMorrison

[newbryford]

You still have a loop on the right and left.

 

Go back to your original plan and use the reverser to feed both lower legs of the wye, all the way round the loop and back up the main line on the left until just before the point into the sidings in the middle of the loop.

 

Similarly on the right.

 

Cheers,

Mick

[WIMorrison]

I was copying the wiring suggestions that I found on the web, here is a reasonably clear example https://www.dccshop.com/dcc-basics.html - do you not think that this will work?

 

Tracing it through on paper it would appear to work to me.

[Phil S]

41-58 Euro ?  (Kit, Built kit,  Built cased kit) for the LDT.   The MASSOTH version which also uses sense sections is much more expensive but then it is also designed for 10Amps (G Scale - then extra during a short) ..

 

The desirability of not having a short circuit - however short in duration - is greater with the larger gauges - hence Massoth (who made the electronics for LGB) were the first to release a Sensor-Section auto reverser ... in which there is NO short circuit current involved IF the sensor section has done its work.

LDT make the only kit / lower current /affordable version of a sensor-based module.   (The AR1 can be preset remotely too, I recall? ) 

 

If you are using a 'starter' dcc controller, with only 1 A output, then the short circuit current is relatively low - maybe 2A maximum ... but if you have a more common 3-5A normal maximum output  ( toy regulations create the limits) then the short circuit current could be as much as 10A ... and with dcc this may cause a dip on voltage across the layout affecting many other devices.  Best avoided if possible.  (Dividing into Power Districts each with their own power supply reduces / localised the problem.  The PSX breaker further protects sub-districts from problems in other sub-districts (using the same dcc feed)

 

The Sensor sections at each end of the Reversing section can be very short - a few millimetres -  just enough for the metal wheel to make contact as it bridges the gap between sensor section and the track where the train is coming from....  An instantaneous voltage comparison is now made between the sensor section and the upcoming Auto-Reverse section: if they do not match, then the A-R RELAY changes ... and the entry to the reversing section becomes correctly set.  Because the sensor section is not being used to provide current to power the loco, only to measure its voltage, there is no sudden, large, (short-circuit) current flow.  {This is also why the sensor section is as short as possible - hopefully more than 1 axle is powering the loco) 

The DIFFERENCE in method, is that WITHOUT the sensor section, BOTH pieces of track CAN SUPPLY a large current - because they ARE the source of power for the loco... and  current-sensing is probably used for detection - this sometimes means an adjustment for different sizes of locos as with the Lenz and Bachmann Auto Reversers (and others).

 

IF the sensor failed to detect correctly, for any reason, then the LDT/Massoth module will default back to a traditional autoreverse, and if it sees a short circuit, it will then change the relay 'as normal'.

 

ALTERNATIVES to the 2 methods above are variations of the 'sensor' idea:  either an optical detector or treadle in the track (Roco make such a track piece) to provide the trigger signal instead of the short-circuit or sensor-section-voltage -  and the PSX AR1 has this option I recall 'via dcc'.

(2 treadles needed at each end of the Auto-revering Section IF bi-directional running through it is permitted - 'inside' and 'outside' of the gap

Only 2 detectors/treadles are needed if running is ONLY 1 way:   entry-approach to the auto reversing section, and exit-approach from the Auto revering section..

[WIMorrison]

Mick

 

Is this what you are suggesting?

 

[newbryford]

Yes - and similar for the right hand side.

Feed from the bottom of the wye, include the sidings and round the right up to just before the point.

 

Doing that will completely remove any train length issues.

 

Cheers,

Mick

Edited December 27, 2017 by newbryford

[WIMorrison]

Mick

 

My issue with doing that on the right is that I will lose the ability to have multiple occupancy detectors as one will feed to the reverser reporting back that current is being drawn hence occupied and the reverser will sort out the track ‘polarity’ but this can only be done for one section. If there were no occupancy detectors then I agree that would be a solution.

[newbryford]

You never mentioned detectors. edit: oops - Digikeijs unit.....

 

Can you pick up sections within the reverse fed section with detectors?

It may be that you have to feed the (another?)  DR unit with the reversed feed.

It may be worth showing your detected sections.for that particular area of the layout.

 

As it stands, you still have a potential short at the point on the right- the one that is under the main line, marked with a small circle.

 

Cheers,

Mick

Edited December 27, 2017 by newbryford

[WIMorrison]

Mick

 

I see you spotted the mention of detectors - expecting the first one to arrive next week
 

Good spot on the point - do you think this version will work?

 

 

These images are filling up my Google Drive nicely

[newbryford]

As long as the reverse sections are longer than your trains, then I think that's OK. You can probably extend a bit deeper into the triangle - going as far as the other points at top left and bottom if needed..

 

If in doubt, put in more insulated gaps than you think you need. Far easier to wire round them afterwards than cutting another gap.

 

Cheers,

Mick