Bus Wiring

[davefoxx]

Forum,

Our vacation on the Outer Banks is coming to an end, and I'm looking forward to returning home and working on the new layout.  My only Digitrax throttle is presently in the hands of the manufacturer for repairs and an upgrade.  While I await its return, I can go on with wiring the layout.

I have a few questions about bus wires (please note that I have a Digitrax DCC system and I plan to install one UR92 Duplex Radio Tranceiver/IR Receiver from which to run my upgraded DT402D throttle):

1) Do I need bus wires on a HCD layout?

2) If so (or even if just recommended), I believe I recall that someone recommended the bus wires being a closed loop.  Is this correct?

3) Do I really need 14 gauge wire for the bus wires?  On my last layout, my soldering iron could just barely heat this large wire enough to allow me to solder the feeders to it, so can I get by with 16 gauge since the bus wires won't be that long?

4) For DCC signals, what's better: solid or stranded wire?  Personally, I prefer working with stranded, which seems more flexible, and I can tin the end to make it solid at the connections.

5) Oh, and for others' thoughts on this subject, I'm considering punching holes in the bottom of the HCD and trying to fish wires through the cardboard honeycomb inside the door.  This would keep the fragile wires and connections from being exposed to being snagged during construction and moves.  Whatcha think?

Thanks,
DFF

[John]

I have a few questions about bus wires (please note that I have a Digitrax DCC system and I plan to install one UR92 Duplex Radio Tranceiver/IR Receiver from which to run my upgraded DT402D throttle):

1) Do I need bus wires on a HCD layout?    - I don't think you do.  If you put a terminal block somewhere around the center of the door, run the connection from there to the DCC booster using #16 wire - (about 2 feet), and then drop #18 feeders from there to the 4 points of the compass, you are going to be just fine

2) If so (or even if just recommended), I believe I recall that someone recommended the bus wires being a closed loop.  Is this correct? That is incorrect - you don't want a closed loop

3) Do I really need 14 gauge wire for the bus wires?  On my last layout, my soldering iron could just barely heat this large wire enough to allow me to solder the feeders to it, so can I get by with 16 gauge since the bus wires won't be that long?  See my answer above

4) For DCC signals, what's better: solid or stranded wire?  Personally, I prefer working with stranded, which seems more flexible, and I can tin the end to make it solid at the connections. I also prefer stranded wire .. it makes little difference ..

5) Oh, and for others' thoughts on this subject, I'm considering punching holes in the bottom of the HCD and trying to fish wires through the cardboard honeycomb inside the door.  This would keep the fragile wires and connections from being exposed to being snagged during construction and moves.  Whatcha think?    I think it's a good idea ..

[davefoxx]

Thanks, John.  I really appreciate your input, and, in the case of question #2, I'm glad that I asked.  Should I gap the rails in my roundy-round to avoid a closed loop in the track, too?  I assume that this has something to do with the clarity of the DCC signal.

DFF

[peteski]

+1 about what John stated and yes, it would be a good idea to gap the track if it forms a closed loop.  However on such a small layout, I really don't think that a closed loop would cause much of a problem.    It becomes a problem on much larger layouts where the inductance and capacitance of the DCC bus becomes large enough to affect DCC signal quality.

[Scottl]

How much larger would be a problem?  My roundy-round is pretty big when you stretch it out...

[peteski]

If your layout is DCC and you aren't having any problems then I say don't worry about it.  Unless you have an oscilloscope or maybe a DCC signal analyzer, there is no way to tell how degraded (if at all) the DCC signal is.  But if your engines are already acting funny or you lose control from time to time then cut a gap in your loop of track (and make sure the bus is open-ended) and see if things get better.

[mmyers]

Normally when the layout gets to a size that would require cutting a closed loop it also requires additional boosters for power districts. Since each power district needs to be isolated, the closed loop separation is taken care of at the same time.

16ga stranded bus wire will be plenty large for a HCD layout. Assuming the largest HCD slab I've seen locally measures 3-0 x 6-8. just pick two colors of wire; one for each rail, and stick to that color code. Black, red, and white are colors that will always be available even in the future. Pick two. BTW, 18 ga two conductor thermostat wire will always have a red and a white wire. I like to use that for feeders.

Martin Myers

[Scottl]

Thanks, all good to know.

[BCR 570]

I have a few questions about bus wires (please note that I have a Digitrax DCC system and I plan to install one UR92 Duplex Radio Tranceiver/IR Receiver from which to run my upgraded DT402D throttle):

1) Do I need bus wires on a HCD layout?  This is really determined by the length of your feeder wires, which ideally should be as short as possible, and how often you plan to insert them.  Put another way, if your feeder wires are going to exceed 12", then you will likely require bus wires.

2) If so (or even if just recommended), I believe I recall that someone recommended the bus wires being a closed loop.  Is this correct?  As already stated, this is incorrect.  Your bus wires can have branches leading off but cannot close back on themselves.

3) Do I really need 14 gauge wire for the bus wires?  On my last layout, my soldering iron could just barely heat this large wire enough to allow me to solder the feeders to it, so can I get by with 16 gauge since the bus wires won't be that long?  Probably depends on the length of the run - 14 AWG seems to be the recommended standard but for a small portable layout, 16 AWG might work fine.  For joints to 14 AWG you will want to use a chisel tip on your iron with the blade flat to the wire for increased heat transfer.  It also helps if you can avoid two things:  (1) other items plugged into the same circuit as the iron (ie. fan, light) which reduces the power to the iron (2) the coiled metal iron stands, whic hactually contact the tip and draw heat away from it.  For bus wire connections I use a Weller 35 watt iron with ST2 chisel tip.

4) For DCC signals, what's better: solid or stranded wire?  Personally, I prefer working with stranded, which seems more flexible, and I can tin the end to make it solid at the connections.  I am using stranded for bus wires as it is more flexible for feeding through holes in benchwork, etc.

5) Oh, and for others' thoughts on this subject, I'm considering punching holes in the bottom of the HCD and trying to fish wires through the cardboard honeycomb inside the door.  This would keep the fragile wires and connections from being exposed to being snagged during construction and moves.  Whatcha think?  Any wiring beneath a portable layout is susceptible to damage when moving, so any attempt to move the wiring inside the HCD would be beneficial in my opinion.

Good luck!

Tim

[davefoxx]

Thanks, Tim.  I really appreciate the information, as I close in on the permanent wiring of the layout.  At this point, I am just trying to absorb as much information from experienced modelers as I can, so any comments from fellow asshats are welcome.

DFF

[MichaelT]

Forum,
5) Oh, and for others' thoughts on this subject, I'm considering punching holes in the bottom of the HCD and trying to fish wires through the cardboard honeycomb inside the door.  This would keep the fragile wires and connections from being exposed to being snagged during construction and moves.  Whatcha think?
Thanks,
DFF

Dave,

If you drill through the HCD and then insert a drinking straw through the hole, will make pulling wires much easier. Once you're done, pull the straw out and cut it away from the wiring, or just leave it in if it's not noticeable.

mdt

[davefoxx]

Good idea, Michael.  What I have done in the past is to use a piece of a coat hanger wire (cut the end on a 45 degree angle) to drill through the foam and door.  By then drilling a slightly larger hole with a standard drill bit where the coat hanger penetrated the HCD, wires can then be fished back up through the door and foam.  In other words, a piece of coat hanger wire is a long drill bit and the fish tool.

This time I plan to use a hole saw to cut large access holes in the bottom veneer of the door, so the soldered connections can be recessed into the door.  I'll fish the wires from hole to hole within the hollow core of the door.  Hopefully a piece of coat hanger will penetrate the cardboard honeycomb structure in hollow interior of the door.

DFF

[Chris333]

I've done similar with past door layouts. I take an old 1/8" round file and put in in the drill, since files are longer than drill bits. This gets me through 2" of foam and the door. Then I poke the same 1/8" brass tube I use for my turnout linkages through the hole. Once through stick the wires down the tube and pull the tube out.