In today's hobby, with DCC control systems so prevelent, the art of wiring a model railroad for multiple train operations with conventional DC power supplies isn't spoken about very often. DC block control remains a viable means of powering a layout however, and if done correctly can always be converted to DCC in the future. Whether using DC or DCC, there are still applications where having seperate track blocks can be an advantage.
BlocksWhat are blocks? Basically, it is a process of dividing the railroad into sections, in each of which a train can be controlled independently of a train in a neighboring block. Real railroads also often divide their mainlines into blocks, designated by signals, to keep traffic at a safe distance and on the right track.
By dividing your railroad into blocks, each section of track can be controlled by mulitple power packs or turned off entirely. On DCC systems, blocks are often used to operate signal systems and also to isolate problems.
How Many Trains Can I Run?
With DC controls, you will still be limited to running trains based on the number of power packs (cabs) you provide. The wiring shown here is for two-cab operation for clarity, but by substituting rotary switches for the toggles, you can add many more cabs if desired.
The number of blocks you need depends on your trackplan. Generally, mainline blocks should be as long as the longest trains you run, or a little longer. You'll also want to isolate passing sidings and places where you are likely to store trains like stations, staging yards and engine facilities.
It is easy to go overboard when adding blocks. The more you add, the more you have to manage.
Common Rail vs. Two-rail Wiring
When wiring blocks, you can either cut gaps in both rails, or wire one rail constantly and only cut a single rail. This is called common rail wiring.
Common rail wiring works fine for wiring signals and can be used for most blocks. Reverse loops will have to have both rails cut either way. The diagram shown here is for 2-rail wiring. All switches are Double Pole Double Throw (DPDT). With common rail, SPDT (Single Pole Double Throw) can be used instead.