Bus Wire Configuration

Discussion in 'DCC & Electronics' started by 91rioja, Aug 3, 2006.

  1. kchronister

    kchronister Member

    I have one of those wire strippers, and that's exactly the case. On one side of the same-size hole it has stranded and on the other solid. And it's a variance of 2 - 22 solid and 24 stranded share the same hole, e.g.

    Personally I find solid easier to work with in every respect, and would only use stranded for something like a swing-up where you'll have regular, repeated flexing of the wire.
  2. nicknero

    nicknero Member

    for HO your gonna want to wire every 3 feet I did it and havent had a single problem with wiring since I did that including my switch machines
  3. Iron Goat

    Iron Goat Member

    What is the best way to rig your Bus Wire for an around-the-room layout? (One that follows the contour of the room's walls, with a lift out across the door way...)

    Should there be two Bus wire groups (one down each side of the room), or only one wire ?

    Thanks, Bob
  4. baldwinjl

    baldwinjl Member

    I'd put the command station opposite the lift out, run the bus both ways (two wires each way) around the room, have one of them power the left out. There is not need to specifically tie the bus together at the far end, theoretically it is better not to, so you don't need to tie the bus wires together at the liftout, just power the liftout with one set or the other.

  5. 60103

    60103 Pooh Bah

    I would go as far as to power the lift out - one rail from the clockwise feeders and the other from the counterclockwise feeder; and then power a couple of feet on the other side through the lift out. That gives you a safety break when the lift is out.
  6. baldwinjl

    baldwinjl Member

    Of course you still have to get the safety break from the other direction as well. So you probably need to run both of the buses onto the liftout, skipping a feeder and isolating the safety sections, the the buses come back off the liftout to pick up the skipped feeder. Choose one bus or the other to power the liftout itself.

  7. Iron Goat

    Iron Goat Member

    Thanks, guys.... that was the info I needed.

  8. railwaybob

    railwaybob Member

    If you read the manuals, you will find somewhere in the bowels of the manual that a minimum of 16 AWG wire should be used. Recent conventional wisdom has bumped that up to the thicker 14 AWG wire. And if you can handle 12 and even 10 awg wire, then go for it.

    As to the difference between stranded and solid, there isn't that much difference. The nit-pickers are still out on that one.

    More important than stranded or solid wire is the type of connection you use to connect your track feeds. Remember that a chain is only as strong as its weakest link. One of the weak links in the bus system is the type of connector between the bus and the track feeds. A lot of guys are using those mechanical "suitcase" connectors. So, you can have some nice 12 AWG wire but if you're using a mechanical suitcase connector, then you've lost the advantage of 12 AWG wire. The best means for connecting the track feeder wires to the bus wires is to solder the joints. This is where one of those 120 - 140 watt soldering guns comes in hand. And don't forget to shrink-tube the joint.

    Then there's also the AWG of your track feeds. Again, you can have nice 12 AWG wire but if you're using 24 AWG telephone wire, you've just lost the advantage of 12 AWG wire.

    And then there's the number of track feeds. Again, you can have nice 12 AWG wire but if you're track feeds are 12 feet apart, you've just lost the advantage of 12 AWG wire.

    There has been some discussion about inductance between the two bus wires on the digitrax@yahoogroups discussion forum. However, it doesn't seem to be a major issue for most of us. We've got other issues which are easier to correct.

    Bob M.
  9. baldwinjl

    baldwinjl Member

    I have to disagee a bit here. The advantage of the 12/14/16 gauge bus wire is that you reduce the voltage drop over the long haul out to the feeder(s). The short (say a foot of less) feeder of 22 or even 24 gauge wire can handle the current we are asking it to, it is just that over a long distance the voltage drop will be a problem, hence the need for the bus wires.

    A properly installed suitcase connector likewise can easily handle the task at hand. In a model railroad application I would be quite certain that almost all suitcase connector failures are due to improper installation. It isn't trivial to get a good soder connection in these cases either. Under the conditions that it is being done a cold solder joint or otherwise insecure connection is not going to be uncommon. I think here the key is to take care and do the installation properly, whichever method you choose.

    I will agree that every twelve feet is probably a bit too far between feeders, though that really means you are only counting on the rail for six feet. Again, more feeders is help from the reliability standpoint. Too few feeders are not negating the advantage of the 12 gauge bus, rather too few feeder increases the dependence on notoriously unreliable track joints to conduct the power.

    If people are worrying about the inductance between the feeder wires they have too much time on their hands. Theses are really slow signals at huge levels. If there is going to be a problem it is going to be in the contacts in a locomotive or in the wires (quite small, by the way) to the decoder.

  10. rfmicro

    rfmicro Member

    Bus Wire Connection

    Regarding type of wire, I would recommend shielded stranded cable as it is more resilient to twisting and movement, has greater current handling capability and less voltage drop than solid wire. Regardless, recommend shielded cable which ever is used.

  11. pgandw

    pgandw Active Member


    We're getting way over the top here. NCM railroad stated he had a 15ft bus run. Assuming a 5 amp power supply, 16 gauge is plenty for for his bus line. However, 14 and 12 ga is often cheaper and more available due to its use in house wiring.

    Unless the wire has to flex, I personally prefer solid wire as easier to use. But that's me. Either will work just fine.

    Shielding is unnecessary, as is wire twisting for the power bus - especially on a 15ft run. Both are nice to do, but given that the rails run precisely parallel for greater distances, taking precautions for the signal in the wiring is unnecessary.

    What is important is that the feeder to bus wire connections be made as reliable as possible, and that feeder connections be spaced close enough to overcome electrical connectivity issues with rail joiners (and impedance issues with rail if you are using code 40 rail or smaller).

    Overkill is very easy to achieve in this area. I know of a guy who has been successfully running a 5x10 ft layout with just 2 wires from his DCC unit to the track for over a year now. How long will that success last? Probably as long as he doesn't disturb his track. Suitcase connectors have been known to sometimes fail after several years in a hostile automotive or RV environment. How long will it take them to fail on a model railroad without the vibration and wetting that the automotive and RV installs get? And just how long does your layout stay intact before you move or change the layout anyway?

    What I'm saying is that feeders every 3-12 ft depending on how good you feel about your rail joiners is good enough. Soldered feeder to bus joints, suitcase connectors, crimped spade lugs and terminal screws, and wire nuts are all reliable enough (if done correctly) for the expected lifetime of the wiring of a not-large fixed layout.

    Modular layouts where modules are taken to shows have to take the wiring reliability a notch or two higher. Now, the subtle differences in reliability when being handled frequently and subjected to vibration during transport become important.

    Bottom line for NCMrail: If you are one of those guys who likes his wiring neatly bundled, all tagged and color coded, then you will probably feel better about leaning towards more feeders and heavier gauge wire. On the other hand, if you can live with spaghetti wiring under the layout, and use whatever color and type wire is cheap and available, then spacing feeders further apart and using suitcase connectors is probably for you. Both systems will work just fine, becasue the difference in reliability comes down far more to care during installation rather than the reliability of a given technique.

    my thoughts, your choices
  12. Iron Goat

    Iron Goat Member

    More great information... thank you.


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