Separate Power for Yards vs. Main Lines?

[nobullchitbids]

For whatever reason, the publishing wizard had no opportunity either to truncate lines and shift them down a slot or arbitrarily ignore spaces and just pile everything together; however, when I tried to do the eastern end, even though short enough to fit otherwise, MR's publishing wizard decided the spaces were irrelevant and bunched everything back together again.

Can't win them all!

[wccobb]

Gluefinger: I've assuming your restraints on both time and finances are rather rigid. Lemme continue from there.
In re yours of 18 June 2005, using a DPDT switch resolves the question of how your locomotive(s) get power. When the yard is "assigned" to the yard power pack, the mainline locomotive does not go into the yard. PERIOD. When the yard is "assigned" to the mainline power pack, it becomes electrically all one "block". The DPDT switch can be set only one way or the other and it's impossible to have the two power packs "cross-feed", short-out, or whatever. DO NOT use a common ground between the power packs. This can result in a 24 VDC potential in the track - which you don't need - not nohow !!!! (So much for all those imaginary "buggywhos").
Nobillchitbids is completely correct in his comments, even if his schematics do come thru a bit garbled. The single track "yard" on the "opposite side" of the mainline might also be viewed as a mainline passing track with all movement there controlled by the mainline power pack. This puts a very nice passing track on your mainline and greatly expands your operating possibilities. Might not be your first concept, but it's your model railroad and on this you can do just as you like (By the way, thanks for the great photos.)
Nobullchitbids yard "system" is also completely prototypical, but it might be a bit more that you want or need. Again, it's your model railroad. The CB&Q - BN - BNSF - Illinois RailNet - ONMITrax (pick your era) have switched LaSalle-Peru Illinois with basically no more tracks than you have there. Yes, they are a bit longer !!!!
Might be well to take a more complete look at the requirements of DCC. Nope, I ain't got DCC, but from what has been published in MR:
Tstage is right. Power busses & track feeders are very important. For every piece of rail on the top of the layout there should be a piece of 14 ga. wire (power bus) below the layout. There's a recommendation for a track feeder every second piece of rail. For a circle of 18 inch radius snap-track (12 pieces) that's about 20 feet of 14 ga. wire, 12 track feeders and 24 solder connections. I don't know the lengths of your tangent tracks and am assuming more snap-track. Why not? It works GREAT !!!! This means every 18 inches of tangent track needs 3 more feet of 14 ga. bus wire, 2 more track feeders and 4 more solder connections. I'll give you that soldering is not that hard, but it is time consuming; difficult to salvage for the next layout; and not needed for your DC system. In contrast, with screw termials on the track terminal sections, the DPDT switches and the power packs, everything is easily recycled to the next layout.
I would understand that none of your present locomotives are DCC ready and most are not DCC compatable. Guessing at $15 per locomotive, that's three times your present budget. So much for DCC for now !!!!!
Permit me one prediction. In 2009 - or thereabouts - after four years experience with this new layout, you'll have some very good, solid, etc. ideas about the next "new" layout. A better time to take a hard look at DCC. The DCC "stuff" available in 2009 probably isn't even imagined today and one of today's wimpy little 1 amp "cheapie thingies" may well be totally inadequate for what you want four years from now.
I suggest again - stay with DC for now. I don't think you'll ever regret getting this layout up and running on DC and letting any decision on DCC wait for your next layout. Again, Good Luck !!!!!

[oleirish]

QUOTE: Originally posted by tstage

Chris,

That does make a difference. Since you already have most of the stuff needed to run DC, that's probably the way to go.

I run a 4 x 8' layout, on DCC, only using two (2) wires. (Not the ideal, but it does work.) Once I nail down the layout design, I'll start running power busses and track feeders. The Bachmann EZ Command system only has 1 amp of power so I am limited to running a maximum of 2, maybe 3 locomotives simultaneously. (On a 4 x 8', 3 gets confusing enough.) I have newer locomotives so they don't draw much current.

If you are using this current layout as a learning experience, then I'd probably stick with the DC. Keep us abreast of your progess. Pics would be nice, too. [:)]

Tom

I also have a bachman EZ command and two engines on DCC,now bachman says they are comming out with a larger power supply w/on and off switch ,Have seen or herd anything on this yet??

JIM

BTW, I've heard that if you switch your layout from DC to DCC, you can keep much of the already existing wiring to run your layout on DCC.

[nobullchitbids]

Some closing notes on common rail:

IF you have one of those power packs which provides two throttles off of ONE transformer, e.g. an old Model Rectifier Dualpack, THEN you cannot use common rail; however, IF you are using two SEPARATE power packs, each with its own transformer, then the common-rail scheme does NOT result in pyramiding of voltage values. This is because each power pack in effect operates as an independent circuit, and all you are doing is providing a common ground. Like WC says, because only one of the packs can be connected to a particular block at once, it never can have more than 12 v. of potential no matter what is connected to the common rail. Think in terms of batteries: A wire from positive of battery "A" to negative of battery "A" makes a circuit; but, a wire from positive of battery "A" to negative of battery "B" does nothing unless the positive of battery "B" also is connected to the negative of battery "A." In the Dualpack, this connection exists; in separate, independent power packs, it does not. Yes, they both are plugged into the wall; but, the secondary currents are induced, not direct, so there really is no connection.

The principal problem with common rail is selecting which rail to be "common" -- you want the rail which requires the fewest number of gaps in it for purposes of control. This allows the common to be gapped instead for signaling, crossing gates, occupancy detection, whatever.