resistence is the issue

[SteamGene]

It dawned on me that I could eliminate about nine feet of buss wire by running drops from the upper helix track to the buss wire already there.  This would mean that some of the 18 gauge drops would be on the order of two feet long.
Which would be better - buss the upper level and have shorter drops to it or cut off nine feet of buss wire?
Gene

[Atlantic Central]

I'm not the DCC expert by any means, but I would say simpler is better and eliminate the the nine feet of buss. 18" vs 24" of 18 guage should not be a measurable difference/problem.

Sheldon

[SteamGene]

Having asked the question, I finally cut a buss wire striping wire for a drop attachment point - right at the entrance to the helix.  Now the buss is splice instead of one continuous wire.   
Gene

[WoundedBear]

The splice shouldn't be trouble....mine is all done like that....solder the joints and heat shrink, or equivalent, to seal them up.

Sid

Mind you....I am using 14 guage stranded copper for all my power connections.

[SteamGene]

This wire is 14 gauge stranded.  I used a wire nut - I have a bunch of them from somewhere or other. 
It stands to reason that each connection is going to drain a little.  While I don't have an enormous layout, it's not a 4x8 either. 

BTW, the upload your picture gods are against me all the way.  My latest attempt tells me I don't have Javascript, when I know I do. 
Maybe Sheldon knows enough to post the layout plan to the board.  I can handle the modifications easily enough.
Gene

[r.cprmier]

Gene;
the drain on each connection is miniscule, of any.  I don't think, in this case, that the question is about the drops; but rather what your total load is going to be, in amps on your buss.  On 14 gauge;  The ampacity for single conductors in free air is going to be greater that it would be for those in conduit, cabling, etc.  I assume your buss is run as a single conductor in (mostly) free air.  I will hazard a guess that you will not load that wire up appreciably, unless you are running a replication of South Station in Boston, circa: 1944!

Rich

[SteamGene]

Rich,
I assume the greatest number of locomotives would beL
east and west switcher in South River Yard - 2
2 east bound through trains
2 west bound through trains
1 mine run
1 local freight
1 ad hoc switcher
This would be max capacity for the entire layout.
Gene

[r.cprmier]

Gene;
A rule of thumb  I would use would be that given the average draw for an HO scale DCC decoder would be roughly 1 amp, I would use that as a reference.  of course, you are also going to be limited by the parameters of the power pack you use; and most of those I have seen wouldn't overload #14 Stranded; #18 stranded pigtails is a non-issue. 
All in all, the average model rail would be pretty safe with 14, or 12.  I used 12, basically because it was what I grabbed out of the storage barn.
No...I am really just more comfortable wit h12 THHN.

I have run separate conductors for any power requirements for lighting, switch machines, etc.



Rich

[rogertra]

RESISTANCE IS FUTILE.

Sorry, couldn't help myself.

[Jim Banner]

On my own layout, I use .5 amps as the average draw of operational locomotives.  This takes into account that some operators are running their trains slow, some fast, some up hill, some down hill, and some may even be stopped waiting signals or orders.  We operated the layout for several years with five operational locomotives using a 2.5 amp MRC Command 2000 and later a 2.5 amp Digitrax Zephyr.  The only overloads were shorts from running turnouts.  But if you are running sound equipped locomotives, 1.0 amp per locomotive would probably be more realistic.

There is no way a 5 amp booster or a 5 amp output of a power manager can overload either 12 or 14 gauge wire.  And a 50 foot bus has only .25 ohms resistance even with #14 wire, so the voltage loss would be only 1.25 volts if all 5 amps were being drawn at the far end of the bus.  This voltage drop is negligible and in any event could happen only in very unusual circumstances, like ten locomotives all at the farthest end!  More realistically, imagine a 50 foot long track with five double headed trains on it, each drawing 1.0 amp.  Suppose these trains are 10', 20', 30', 40' and 50' from the supply and all the power is carried by a #14 gauge bus with no power carried by the rails.  Then the voltage drop at the far end would be only 0.375 volts.

Having said all that, I have to admit that like Rich, I used #12 for buses.

If voltage drop and resistance were the only considerations, we could use #20 wire for buses up to 50' long.  We would not even exceed its ampacity of 9 amps in free air.  The reason for the heavy #12 and #14 buses is a whole nuther story.

[r.cprmier]

Jim;
Yeah, the difference in twelve or fourteen in this case is pretty much moot point.  We could stretch this out to the nines with Ohm's law, Kirchoff's law, etc and so on , ad nauseum, and accomplish absolutely nothing.

In the case of voltage drops V. distance; we are operating (ostensibly) DCC, which, of course, is 16 or 18 VAC; so again, the effect that DC has on length wouldn't really apply.

As said, I found it just plain convenient to use 12.  I also use it for powered projects-like my harbour sounds.  man, this is way cool!!   Out of the rear horn, out behind the bascule bridges, is the seagulls and wave action; and in the harbour is the sounds of tugs, the "putt-putt" of steam engines, and the whistles, clanks, and general cacauphony ala a scene from "Tugboat Annie".  As a matter of fact, one of the tugs will be named the "Narcissus".  How far back does your mind travel, my boy?...And above of course, is the City...
...Good ol' Greenway...

Rich

[SteamGene]

I remember Tugboat Annie!  Great stories. 
Gene