Baseboard Track Bus best-practice?

[Damo666]

I'm rewiring my layout from DC to DCC and am seeking advice on Track Bus best practice.

 

The length of each baseboard is 1,200mm and the depth is 700mm.

 

In the examples below I have only shown one line to represent the principle. Also, I haven't shown connections to all sections of track.

 

Track Bus option 1:

One cable somewhere central along the board, (avoiding point motors etc)

Some droppers could be about 400mm long.

 

A Bus Suppressor would be at each end of the track bus.

 

Track Bus 2:

One cable located in an ideal position for most of the track, with a 'spur' off to another same sized track bus to feed sidings etc.

Would the Bus Suppressor just be needed on the main Bus, or also at these spurs too?

 

Track Bus 3:

One cable which zig-zags across the layout providing power to the track to ensure the droppers are of minimal length.

Edited February 26, 2021 by Damo666
Silly typo error

[brossard]

Main thing is to put dropper wires (20 - 22 gauge) on EVERY single piece of track.  Do NOT rely on rail joiners for electrical conductivity.  Over time they tarnish, get dirty with paint and glue and loosen.

 

After that a largish wire (18 gauge) from one end of the board to the other.

 

I used 18 ga speaker wire:

 

 

The buss is the copper coloured wire.  I used choc blocks to connect the droppers and daisy chained them to the buss.  Board interconnections are white extension cords cut up.

 

Best practice?  I don't know, others may do it better.  However, it all runs.

 

John

 

Edit:  you might want to have a read of this:

 

http://www.wiringfordcc.com/

 

 

Edited July 4, 2020 by brossard

[John ks]

Here is a slight modification to your second plan

By having a terminal strip between your track bus & your local sub busses a fault will be easier to locate 

If you have a short then disconnect a sub bus, if the short goes away then the short is in that sub bus

This needs all sub busses to be insulated from each other( a bit like DC blocks)

 

John

[Jeff Smith]

I provide droppers from every piece of rail and then provide a bus under each rail.  Effectively duplicating the rails under the baseboard.  With DCC, if you ever want to use sound, ie an idling diesel, you cannot use isolating points as you might for DC.  The danger exists that you can drive a loco into an incorrectly set point but it will just short rather than derail!

[Damo666]

9 hours ago, Jeff Smith said:

I provide droppers from every piece of rail and then provide a bus under each rail.  Effectively duplicating the rails under the baseboard.  With DCC, if you ever want to use sound, ie an idling diesel, you cannot use isolating points as you might for DC.  The danger exists that you can drive a loco into an incorrectly set point but it will just short rather than derail!

 

19 hours ago, Damo666 said:

Also, I haven't shown connections to all sections of track.

 

Good advice which I have noted. Thanks

[Damo666]

9 hours ago, John ks said:

Here is a slight modification to your second plan

By having a terminal strip between your track bus & your local sub busses a fault will be easier to locate 

If you have a short then disconnect a sub bus, if the short goes away then the short is in that sub bus

This needs all sub busses to be insulated from each other( a bit like DC blocks)

 

John

 

Thanks John, that's a really good solution.

 

I was reading the link @brossard had provided to Allan Gartner's site 'Wiring for DCC' where he discussed choc blocks to trouble-shoot shorts and was suggesting (unless I read it wrong, it was very late last night / this morning) that every dropper is connected to the bus via a screw terminal. I thought that this was OTT complicated, but your suggestion is a very neat adaptation. Thanks.

[Ron Ron Ron]

I'd definitely go along with the advice that it's "optimal" to feed each individual piece of track and not to rely on rail joiners, but that doesn't necessarily mean an individual track feed from the track bus.

 

WiringForDCC is a very useful guide, which is essential reading IMHO.

A key point in that guide, reiterated elsewhere, is that the Power Bus is the whole of the "circuit", including the track. 

i.e. the Rails also form part of the Power Bus.

 

Providing a feed to each piece of track does not mean you have to have masses of complicated wiring links.

It should also allow you to have the minimum of wiring at the same time, without adding multiple spurs and "sub-busses".

The suggestions above appear to be making it unnecessarily complicated.

 

It's also possible to connect a piece of track to another using a short jumper wire, rather than providing a separate feed (dropper).

This would be useful at the end of a long siding or remote part of the layout, where an extra run of track bus wires would be difficult to provide, or would be OTT.

 

Of course when it comes to specific examples, such as the one you've drawn for us here, there's more than one way to skin a cat.

Personally, I'd just take 2 or 3 spurs off the main track bus run, running perpendicular to the track bus (front to back on your drawing).

I would then simply run droppers off these spurs to each track above.

Where there's an awkward, or odd bit of track that needs an extra feed, if running an individual dropper isn't really necessary, just bond this piece of track to the adjacent (joining) rails with a jumper wire.

 

Isolation for fault finding introduces another angle to this.

Chock blocks?

Other screw connectors?

Plug and socket connectors?

Simple isolation switches?

Note that Power District and Sub-District wiring can resolve some of the isolation planning  issues.

 

 

.

Edited July 5, 2020 by Ron Ron Ron

[Gavin Liddiard]

Option one works fine.

This is the underside of a fiddle yard board from Mauch Chunk, the most recent layout built by Barrowmore Model Railway Group:

 

 

We use the main conductors from 2.5mm² domestic mains cable for the track bus and thinner stranded wire for the droppers.

The droppers are soldered to the underside of each individual rail before the rail is laid and then wrapped around and soldered to the track bus. The pic shows two track buses as we use PSX circuit breakers to protect the two halves of the fiddle yard  and also two on the scenic section.

Our P4 layout Mostyn is wired in a similar way although each rail has two droppers for redundancy and the layout, being much larger, utilises nine PSX circuit breakers to protect the separate power districts.

Edited July 5, 2020 by Gavin Liddiard

[DCB]

You need droppers to each piece of rail if you use non conductive cosmetic fish plates on scale track such as most P4. Lots of folk get away with using fishplates for continuity with code 100 rail others need droppers to each piece of rail even with DC and code 100.  What all have in common is a need to be able to electrically isolate chunks of the layout for fault finding.  Otherwise the whole thing shorts out and nothing runs and you have no idea where the fault is, especially if the train you are watching is not the one at fault.  Its bad enough on a 8 X 1 BLT with 6 points but when you get into the 20 locos/ lit coaches and 40 points range it can become challenging.  Chunk it up into sections with DPDT switches of about 6 to 8 points and 6ft X 2ft then you can flick the sections off and back on one by one until the general area can be located.   I have had loads of weird shorts almost all on  post 2010 locos but with 40 odd switched sections narrowing down the fault to a few feet and points saves a huge amount of time.  The alternative is lying on your back with a screwdriver or wire cutters when something goes wrong. Very embarrassing when you have your mates round for a running session.

[Andy Reichert]

 

My 4 track DCC test layout was wired as above. Everything is set on the top surface so no crawling under baseboards, neither initially nor later.

 

All the wiring is bare metal to ensure flatness for buses to pass under easily and safely intervening tracks. The 0.001" thick brass strip above is one of many set down at around 15" intervals. Two round the layout (also bare) 22 ga buses are laid, one on each edge of the 4 track route, one for "+" and one for (-). Each brass trip is connected at one end only, alternately linked to the + and - buses.  Very short bare 30 ga feeders are taken from the brass strip and soldered to the underside of the appropriate rail. Electrically, this system supports the full 5A of most DCC boosters and has worked flawlessly for a decade along a full scale mile of track.

 

 

Apart from easy access, the system allows the surface wiring, including both + and - buses to be completely hidden by laying the ballast directly over the wiring.

 

Andy

 

Edited July 8, 2020 by Andy Reichert
duplicated picture removed

[WIMorrison]

This thread is a good as it shows that my wiring is just as untidy as everyone else's wiring