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Dual Gauge track - Mixing DCC and DC


-missy-
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Hello. I am after some advice.

 

Currently in the design works I have some dual gauge track.

 

image.png.bfdc0b19931d77d82943809008accf13.png

 

The thing is, my standard gauge engines are DCC whilst my narrow gauge engines are DC. Is it possible to do such a thing? I dont plan on running both SG and NG at the same time but there will be times when both SG and NG engines will occupy different parts of the layout. I am a bit worried that the DC engines will interfere with the DCC engines or am I over thinking this?

 

Thanks

 

Missy.

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There are risks to your DC locos if they might be exposed to DCC power.  DC motors really hate the DCC waveform and will burn out fairly quickly (how do I know?).

 

The turnout pictured looks very good.

 

My advice is to start installing decoders in your NG locos then there is no issue.

 

John

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9 minutes ago, brossard said:

My advice is to start installing decoders in your NG locos then there is no issue.

John

 

Thank you John.

 

Installing decoders into my NG engines isn't an option I'm afraid.

 

M.

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11 minutes ago, brossard said:

There are risks to your DC locos if they might be exposed to DCC power.  DC motors really hate the DCC waveform and will burn out fairly quickly (how do I know?).

 

The turnout pictured looks very good.

 

My advice is to start installing decoders in your NG locos then there is no issue.

 

John

 

That was my thought but I suspect that the NG here is 4mm track gauge (2ft) so the locos will be tiny.

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1 minute ago, Tricky-CRS said:

 

That was my thought but I suspect that the NG here is 4mm track gauge (2ft) so the locos will be tiny.

 

I am struggling to fit motors into some engines, let alone decoders Richard.

 

M.

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You just need to be VERY careful that the DC and DCC never meet and think carefully about how everything is isolated and switched when operating.

 

The upper most rail in your picture, for example, is common to both circuits (gauges).

 

Personally, I wouldn't do it :(

 

Having seen the standard of your work, however, you might make it work ... :) 

 

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Presumably on the dual gauge sections you will have to switch between standard and narrow gauge running as they share one common rail throughout and both at junctions. If you used something like a DPDT switch, so the dual gauge bits are either entirely DC or DCC but cannot be both, this would eliminate any risk of cross contamination.

 

Depending on the arrangement you could switch it by a two coil latching DPDT relay driven from a point motor circuit so the track would be energised based on whether SG or NG routes were selected.

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Julia

 

I have done this for my DJLC I did it by switching  sections  of track via interlocked relays  took a fair bit of head scratching to make it work.    Relays are wired so the  NO  connection is DCC  the common feeds a rail and NC connection is 9v DC,   to keep it simple I used single pole relay boards so a track with a point needs 3  relays (2 rails and  the V)  plus V switching relay(s)

 

20200331_165045.jpg

 

Phil Himsworth  must have posted at the same time  the same idea I use relays because of the current  involved 

 

Nick B

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You can use DCC and DC at the same time, as long as you follow a few key points:

 

1. There must only be one common rail. There must be no change from right to left rail as a common rail.

 

2. There must be 2 separate electrical circuits. There must also be 2 separate power supplies.

 

3. The power supply units must be galvanically separated from each other.
This means that at least one of them must have an isolating transformer (the old coil types) and a bridge rectifier. Under no circumstances 2 switching power supplies (laptop type) can be used.


4. All frogs that do not touch the common rail only, must be completely isolated and supplied with the appropriate voltages when throwing the point.

This is likely to become the biggest problem because when crossing an uncorrectly set point the two voltages can connect which can cause severe damage to DCC components.

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1 hour ago, Phil Himsworth said:

If you used something like a DPDT switch, so the dual gauge bits are either entirely DC or DCC but cannot be both, this would eliminate any risk of cross contamination.

 

 

Unfortunately not.  It could be fairly easy to inadvertently knock the switch! 

 

Making the switch fairly difficult to access or using a plug and socket arrangement where only one or the other can be plugged in reduces the risk of unintended change of supply, but neither eliminates the risk of simply forgetting to change the supply when required.

 

This problem is essentially the same as a big standard gauge layout part of which is DC and part DCC, or one is switchable between two runnings with complete removal of locos before changeover.  Some clubs do this, but there's still a risk of somebody forgetting and putting the wrong stock on the track.

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28 minutes ago, Michael Hodgson said:
2 hours ago, Phil Himsworth said:

.... If you used something like a DPDT switch, so the dual gauge bits are either entirely DC or DCC but cannot be both, this would eliminate any risk of cross contamination.

 

Unfortunately not.  It could be fairly easy to inadvertently knock the switch! 

 

 

I think a changeover can be done, with adequate safety against accidents.  But but it requires more sections to protect against trains accidentally crossing isolation gaps.    

 

dualgauge.png.f2bc6b12bb7ce569b14f36f7127e3872.png

The above is a simplified model of track.  Black for one gauge, green for the other.   Two position, 6-pole switch required (may be cheaper with switch operating relays).   If switched to "black", then E is connected to black, and A+B are disconnected, protecting the black line from trains accidentally running into them from the green part of the layout.    If switched to "green", then E is connected to green, and sections C+D are disconnected, providing equivalent protection. 

 

Its similar to protecting programming "sidings" from locos creeping out of the siding and accidentally doing things to the entire layout.   

 

 

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2 hours ago, Michael Hodgson said:

 

Unfortunately not.  It could be fairly easy to inadvertently knock the switch! 

 

Making the switch fairly difficult to access or using a plug and socket arrangement where only one or the other can be plugged in reduces the risk of unintended change of supply, but neither eliminates the risk of simply forgetting to change the supply when required.

 

This problem is essentially the same as a big standard gauge layout part of which is DC and part DCC, or one is switchable between two runnings with complete removal of locos before changeover.  Some clubs do this, but there's still a risk of somebody forgetting and putting the wrong stock on the track.

on my modest example DCC / DC is selected via route selection of the point(s)  so far so good    agree with Nigel on splitting to smaller section if on a bigger  layout  ( DJLC  are only 600 long )

 

Nick B

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2 hours ago, Michael Hodgson said:

Unfortunately not.  It could be fairly easy to inadvertently knock the switch! 

Presumably there are two problems we are trying to avoid; the easy bit, what a DPDT switch would fix, is accidentally connecting the DC and DCC supplies together. The hard bit would be avoiding a DC train being supplied with DCC or vice versa.

 

What happens in that scenario? I assume a DCC train just won't do anything given straight DC as there's no carrier, and a DC train will hopefully just buzz a bit given DCC, as long as you don't leave it too long?

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Nigel's layout is potentially simpler than the OP's, and I see it as a special case - the fact that it is essentially two independent railways not sharing a common station.  It's basically the same as a standard gauge section with two tracks interlaced over a short section.  I see the risk to the locos as being greater if you are going to leave a loco standing on the mixed gauge section E whilst the power is switched to the other system than it is  if you run from A to B whilst C & D are isolated and vice versa.

 

As to what happens if you do connect a loco to the wrong power supply, I suspect that depends on the decoders.  Some decoders do support one decoder-fitted loco running on DC. If you have several such connected all at once, hopefully the DC controller will cut out.

However I think you could burn out a DC motor if it is fed by a DCC supply for any length of time.

 

My concern is not that the the wiring can't be done - it clearly can, rather it's the risk that you do the unintended, especially if both power supplies are live at the same time.  I am thinking in terms of a beer can across the rails in the wrong place, or perhaps a screwdriver or stray wire, a metal object across one of the isolating rail joints.  You can be careful to avoid such things, but sod's law applies.

 

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Thanks for the replies and suggestions guys.

 

It does all sound quite complicated but not impossible. As a result I have a couple of questions.

 

1. Is the consensus to use a common rail then isolate the DCC and DC rails from each other or to have a common rail, leave the NG and SG rails electrically joined, then switch the supply so its either DCC OR DC?

2. If there is either a DCC or DC engine left on the track when operating the opposite type, will I have to totally isolate that engine from both the 'common' track AND the supply rail?

 

Thank you.

 

M.

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So far, folks seem to be concentrating on the risk to the DC locos' motors.

 

My concern would be that you could damage the output transistors on your DCC controller if there was any way that the DC supply could be fed back in to the DCC circuitry. This could happen if there was a derailment. So I'd be looking to make sure that when running on DC in the mixed gauge section that the DCC rails were totally isolated from the DCC supply, and when on DCC that the DC rails were totally isolated from the DC supply, and that there were clear dead sections between the mixed gauge and the DC and DCC sections so that any sort of overrun of points or derailment could not possibly result in the DC and DCC non-common rails being bridged by wheels or metal chassis or body parts. I know that Nigel's covered this, but I thought it was worth emphasising.

 

Getting decoders to fit is an art especially in smaller locos, so I appreciate your problem. Have you considered permanently coupling a coach or wagon to each narrow gauge loco and putting the decoder in the coach or wagon and abandoning DC altogether? Not ideal I know, but it would let you run Standard and Narrow Gauge simultaneously, and I can't help thinking that at some stage you will want to do that.  

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20 hours ago, Phil Himsworth said:

Presumably there are two problems we are trying to avoid; the easy bit, what a DPDT switch would fix, is accidentally connecting the DC and DCC supplies together. The hard bit would be avoiding a DC train being supplied with DCC or vice versa.

 

What happens in that scenario? I assume a DCC train just won't do anything given straight DC as there's no carrier, and a DC train will hopefully just buzz a bit given DCC, as long as you don't leave it too long?

It's an incorrect assumption that a DCC train won't move because there's no "carrier" as you put it.  Most, DCC decoders will run quite happily on DC provided that CV29 has been set to allow running on analogue, and the DC voltage is high enough as DCC decoders need a certain minimum voltage before they start working on DC. 

 

The "bit of a buzz" from a DC loco on DCC powered track is a big risk. The longer a DC loco sits stationery on DCC powered track the greater the risk of the motor overheating and burning out. This may well be a particular risk for the Narrow Gauge locos in question because it sounds like they're equipped with pretty small motors which will be less able to absorb heat into their structure because of their size, and thus run a greater risk of overheating and burning out than a larger motor.

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3 hours ago, GoingUnderground said:

 

 

Getting decoders to fit is an art especially in smaller locos, so I appreciate your problem. Have you considered permanently coupling a coach or wagon to each narrow gauge loco and putting the decoder in the coach or wagon and abandoning DC altogether? Not ideal I know, but it would let you run Standard and Narrow Gauge simultaneously, and I can't help thinking that at some stage you will want to do that.  

not obvious is the gauge of the track 9.42mm and I believe 4mm so you can imagine how small the NG loco is

 

Nick B

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1 hour ago, nick_bastable said:

not obvious is the gauge of the track 9.42mm and I believe 4mm so you can imagine how small the NG loco is

 

Nick B

Lots of people have 009 DCC layouts - I personally have a large h0e layout which at 1:87 is actually smaller than 00 gauge and I have decoders in all my locos. I know people that have fitted a decoder with sound into a 'tin turtle' and much RTR 009 is now supplied DCC Ready, or even DCC Fitted.

 

Think of a N Gauge steam loco which is smaller than most 009 locos, yet they can fit DCC, sound and stayalive into them - plus, people do DCC Z gauge so fitting into a 009 loco means you have lots of space ;)

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3 minutes ago, WIMorrison said:

Lots of people have 009 DCC layouts - I personally have a large h0e layout which at 1:87 is actually smaller than 00 gauge and I have decoders in all my locos. I know people that have fitted a decoder with sound into a 'tin turtle' and much RTR 009 is now supplied DCC Ready, or even DCC Fitted.

 

Think of a N Gauge steam loco which is smaller than most 009 locos, yet they can fit DCC, sound and stayalive into them - plus, people do DCC Z gauge so fitting into a 009 loco means you have lots of space ;)

 

I think the point being made is that the narrow gauge is not 009, but something smaller than Z gauge.  The standard gauge being 2mm finescale (or effectively N gauge) is the DCC railway.  It's the smaller than Z gauge narrow gauge railway that is DC.

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Further up thread it refers to track gauges of 9.42 mm and 4 mm - I understand that it is a 2mm finescale layout where the mainline locomotives are effectively N gauge, but the narrow gauge line represents 2' gauge prototypes in 2mm scale, hence the 4 mm track gauge.  That therefore places the narrow gauge stock somewhere between T Gauge and Z Gauge, so I can appreciate why trying to fit a decoder in the narrow gauge locomotives is not an option.  By comparison, H0e locomotives are huge.

 

I think the confusion probably stems from the fact that the point photographed in the original post is a very fine piece of craftsmanship (or should that be craftswomanship) which may lead you to think that it's 00 and 009.

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