Time to rewire

I would not use thinner than 14-gauge for track power, hot or ground.  Since good ground is essential and often overlooked, I would roughly have one ground drop to outside rails for every hot drop to center rails.

On my layout, which is L-shaped 30'x16', every switch (save an area where I have several switches back-to-back) is the end of 3 blocks.  It's convenient.  Also, every block is fed through a toggle switch so that (1) I can minimize stealth mode moves, (2) save lighted cars' bulbs, (3) keep running the rest of the layout if there is derailment, (4) when I have a lot of trains running, pinpoint where a derailment has occurred (5) cut off all other circuits to have a "programming track."

Running several engines on the same track in the same block.

Since you plan to run multiple engines it is important that your wiring be of sufficient gauge to reduce voltage drops. Also I would add circuit breakers or fuses on each feed to the track. A derailment or other short circuit fault could cause a "meltdown of wiring". I have individual circuit breakers on each feeder wire to my blocks.

Since my layout is compact I have very small block lengths. Since I need to remove power for blocks where engines are "parked" I use an individual toggle switch or my DCS to disconnect power. All wiring is #18 gauge shielded pairs where wiring is made to both the center and outside rails of each block. I isolate both the center and outside rails on all my blocks.  All track wiring uses "communication" type wire often used for household "alarm" systems.

Personally, I think a breaker on each feed is overkill.  A breaker on each TIU input should be adequate protection to all blocks fed from that TIU circuit.  I would not use any breakers above 10-amp rating.  On 5 of my 6 TIU circuits, I have 5-amp breakers to pop quickly on derailments (I do not use smoke).   On the 6th, since I often have 3 trains or more running, I use 7.5 amps.  Breakers & fuses take awhile to open on small overloads (say, less than 150% of rating)

Clem,

The DCS O Gauge Companion 2nd Edition has a 16-page section just related to wiring for DCS, including:

• TIU Channel Usage
• Wiring Considerations
• TIU Channel Assignment and Placement
• AIU Connection and Placement 
• Transformer Considerations

This section includes several wiring diagrams, as well.

I believe that, if you don't already own a copy, you would find it to be a good investment.

This and a whole lot more is all in MTH’s “The DCS O Gauge Companion 2nd Edition", available for purchase as an eBook or a printed book at MTH's web store!

Thanks for getting back to me everyone 

Barry I do have your book and will use it on this project, 2nd edition February 2011. Have any changes been made to this edition? 

    According to my track diagram how many blocks do you think I should have? Running two locomotive consist of five diesels each.

    What is the best way to get power and signal to the other side of a turnout, run jumper  wires from one side of switch to the other, or another set of wires from the terminal strip?  

    If i want more than one transformer powering a block or section of track how do I hook that into it?

   If I use fixed power bricks can I hook two apiece to each input side of each channel of the TIU?

Clem

Clem,

The book was last revised in September 2012. If you purchased the eBook, you can just download the newer copy the same way that you downloaded your current copy.

Regarding the number of blocks to use, the guidelines are present in great detail in the book's chapter on implementing DCS. If you follow the guidelines closely, you should do well.

Rough Idea for strictly command .  Red track...Fixed 1, one side . Fixed 2 other side

Blue track   Var 1 set to fixed

Yellow track  Var 2 set to fixed

Each color  should have blocks about 20 to  30 feet.

However... test as you wire with track signal test.

Re power past Turnouts:  See if your turnouts have wires under the base connecting all 3 legs; some do, some don't, even from the same manufacturer.  If you want three blocks to end at the turnout, which I do, sever the connections if any.  Then feed each leg separately.  Each block should be fed from as near to the center as feasible, unless very short.

Most of my blocks are under 6' long.  There are a few run a few feet longer, and many that run shorter.  I have 70 blocks.  Each dead-end or passing siding should be a separate block, and I strongly recommend each be toggled.

You should not be using more than one transformer to power the same block, or for that matter any single TIU circuit.  There are too many risks involved.  Why would you want to do so?  For 5 lashed up diesels, one decent transformer, like a Z4000 or a postwar ZW, should have no problem.

One item I don't think you mentioned is whether you'll also run conventional.  If you do, toggle switched blocks are a necessity if you want to run multiple conventional lcoops, or a mix of locos, at once.

Personally, I would used FIXED for the mains and variables for the yards, because my impression is that they have a b it more signal strength, which may or may not be so.