DCC Track problem

[geochoice]

Hiya

 

I have rebuilt my layout and changed from a couple of ovals etc that had sidings etc and worked fine.

 

I have put a link across the oval to give me a reverse loop but the select is giving an error (flashing 12)reading, should there be

 

an isolator somewhere help please.

[poliss]

You need isolated rail joiners at each end of the link (which must be longer than your longest train). You will also need a reverse loop module or there will always be a short circuit.

[geochoice]

poliss said:

You need isolated rail joiners at each end of the link (which must be longer than your longest train). You will also need a reverse loop module or there will always be a short circuit.

thanks for that but a bit

techhy for the old fella here.

so isolated rail joiners at each end ok

the longer than longest train bit I presume is just the engine not including the carriages

reverse loop module does that connect to track then?

sorry very new

to this and not very intelligent :-( on model railways

[poliss]

No, the longest train includes carriages. When using a reverse loop the left rail meets the right rail causing a short circuit. To overcome this you need an electronic module which is connected to the piece of track connecting the loops. This changes the

 

polarity of the track.

See https://www.hornby.com/shop/digital/r8238-hornby-dcc-reverse-loop-module/

[geochoice]

Thanks for explaining that, I can understand that with a DMU with lighting front and rear etc but surely with a simple hornby carriage there is no electrical transmission through it, this still applies does it?

 

Problem is I only have about 900mm

 

across the centre of the loop from point to point branch, would I then be better off isolating from the inlet side of the point and continuing round to the outlet of the opposite point? does that make sense to you? sorry

[poliss]

As Flashbang will tell you, the metal wheels on a coach, waggon etc. can breach the insulated joiners and cause the short circuit. See the section on reverse loops on Brian Lambert's website.

http://www.brian-lambert.co.uk/DCC.htm#Reversing Loops.

[Flashbang]

Hi

As Poliss correctly states the distance between the entrance pair of IRJs and the exit pair of IRJ ofr the reverse loop rails MUST be longer than the longest loco plus all its carriages or wagons ever likely to travel on the reverse section.

When

 

using a Reverse Loop Module any metal wheel (Loco, carriage or wagon) will cause the bridging of the entrance or the exit IRJs. So its important to have the section longer than the longest train.

The module flips its loop rails polarity upon detecting

 

a short occurring at either ends IRJs. If the distance between IRJs is less than the longest loco and all stock you seriously risk causing the main console to shut down or even RL module failing due to the continually occurring shorts as each metal wheel rim

 

bridges the IRJs.

So keep the distance between the four IRJs longer than the longest train and only feed the rails of the loop (between the IRJs) from the RLM output terminals.

 

[geochoice]

Thanks. So if I provide IRJs over a greater section than the actual link between ovals thus increasing the isolated section that would be ok, not just between the the point "legs" ? Then a greater section would be isolated and reversed polarity and I would

 

br ok with longer carriage and loco.

[geochoice]

Do I need isolating track or can isolating fishplates be used to the same conclusion ?

[Fishmanoz]

Isolating fishplates are what you need. As you have 2 at each end of the section, this isolates the track in that section from the rest of the layout. Then you connect the RLM to this section and it corrects the polarity each time a loco enters.

[hosh]

Flashbang said:

Hi
As Poliss correctly states the distance between the entrance pair of IRJs and the exit pair of IRJ ofr the reverse loop rails MUST be longer than the longest loco plus all its carriages or wagons ever likely to travel

on the reverse section.
When using a Reverse Loop Module any metal wheel (Loco, carriage or wagon) will cause the bridging of the entrance or the exit IRJs. So its important to have the section longer than the longest train.
The module flips its loop

rails polarity upon detecting a short occurring at either ends IRJs. If the distance between IRJs is less than the longest loco and all stock you seriously risk causing the main console to shut down or even RL module failing due to the continually occurring

shorts as each metal wheel rim bridges the IRJs.
So keep the distance between the four IRJs longer than the longest train and only feed the rails of the loop (between the IRJs) from the RLM output terminals.

So RL Modules don't like

to be called into action too many times over a short period.

Can they overheat in the scenario where carriages at the front keep flicking it one way and then moments later the rear carriages flip it the other, etc, etc?

[geochoice]

Right thanks to all.

 

Ordered the Reverse Loop Module and the isolating fishplates.

 

Decided to use the short loop only and restict traffic to maximum length of three carriages so no overhanging into adjacent section. This can be used simply

 

to reverse direction of engine for returning up a slope to storage yard. Any additional carriages forcing over length can be dropped in station yard and collected on way past again. (modelling licence). By working this way only occasional use of RLM required,

 

in fact using it as a turntable to switch direction occasionally.

 

Job done, well if the parts arrive soon and I can work it out.

[geochoice]

Right have got the RVL and the isolating fishplates, copied the very poor illustration I think and the isolated section remains isolated when loco enters it

 

Have red light on RVL set to select but the loco stops on entry

 

Please help me.

[poliss]

You have put the 8 insulated joiners in the positions shown on Brin Lambert's website here?

http://www.brian-lambert.co.uk/DCC.htm#Reversing Loops.

[geochoice]

Hi mate, slightly different layout to that, simply described I have an oval with points at opposite ends and track diagonally between them so making a sort of figure of eight.

 

I have put insulating joiners in each point going in the direction of

 

the diagonal four insulators in total

 

 

[geochoice]

I presume I still need the little links in the frogs

[poliss]

Did you scroll down to the part where it says '

Where a reverse loop does not return back to its input point, but instead it cuts across the layout diagonally and uses two separate points'.

I think that's the same as your set up. You will need to

 

fit 8 insulated joiners in the places illustrated.

 

The point clips? I don't think you'll need them. Try it with and without them.

[geochoice]

I think you are a star poliss, will need pull the track apart and fit more insulators as that layout is the same as mine apart from opposite hand, shame I stopped reading at the first section and didn't go farther down the page. Will try that when I have

 

time (being shouted out to go out !) and report back, sounds most likely tho, cheers. :-)

[geochoice]

and it works. wey hey ..... thanks poliss nice one

[poliss]

Any time geo. :-)

[BobStan]

I love these answeres Been wondering how to do that myself cus I don't want a turntable on my layout but I do want to change direction of some locos without removing then from the track Now I an apply this method and simple change tracks with my points

Bob

 

[Flashbang]

Just remember a dcc reverse loops track between the entrance pair of IRJs and the exit pair of IRJs MUST be longer than the longest train ever likely to travel over the loop. This 'longest train' includes loco and all carriages or trucks etc.