Running multiple trains on a single track presents powering requirements decidedly different from running multiple trains on separate tracks.

Automatic operation means no engineer to adjust train speed. All trains have to re-start in any track block after a stop and traverse the entire track plan with the voltages assigned each track block. Track blocks require different voltage assignments for curves or track switches and for effect. Some blocks may have different voltages assigned, say so a following train can be given a slower speed.

Additional transformers are needed for accessories, lighting, and controllers.

The K 'N G Railplex Train Layout was originally powered by four Lionel KW transformers, four Lionel ZW transformers, and one Mainline Industries "The Max" transformer. A Mainline Industries "Sub-Station" Transformer powered lights and operating accessories. Commercial transformers powered controllers.

Each KW transformer provided two circuits; the ZW transformers provided three circuits (four consumed too much power;) the "Max" transformer provided two hefty circuits, for a total of 22 separate train powering circuits. The layout has thirty-eight track blocks; twelve track blocks allow for selecting from two voltage levels, creating a need for fifty separate, adjustable transformer circuits. Fifty transformer circuits were, obviously, too many to give each track circuit a separate transformer.

Transformer circuits were set for different voltage outputs and each of the thirty-eight separate track blocks and twelve alternate powering circuits were connected to an appropriate voltage.

The train transformers were all connected to a line-powered variable auto-transformer so power to all track circuits could be adjusted with one control. This served to compensate for different line voltages and to set train speed for good visitor appeal. We also learned that trains run faster after running for a while and could use the auto-transformer dial to slow trains down after a while.

Another problem developed. Postwar transformers exhibit up to a five volt drop as current draw varies from no-load to full-load. A fully loaded transformer would drop its output voltage enough so train speed would vary noticeably as trains moved into track blocks powered from the same transformer. Sometimes a stopped train would have trouble re-starting until trains moved out of track blocks sharing the same transformer. Trying to "balance" track block assignments across the train transformers was a constant task. Perfection was never achieved.

Weight was a serious problem. The array of transformers pictured weighed over two hundred eighty-five pounds; too much to conveniently lift into the bed of a pickup truck.

The train transformers have been replaced with two custom wound "tap" transformers. Each transformer can supply 20 secondary amperes with eleven taps providing nominal voltages from 12.0 to 18.4 volts. Both transformers are connected to one line-power variable auto-transformer to permit adjusting the nominal voltages of all taps with one control. Two of these custom transformers are overkill; one would power the entire layout.

These transformers exhibit a voltage drop of less the 1/2 volt from no-load to full-load. No more need to try and "balance" track block assignments.

Transformers are arranged on two carriers: one for train power and one for accessory and controller power. Total weight went from 285 pounds to about 105 pounds. Each carrier is manageable.

Each transformer powers the track blocks in half the layout (four panels.) Tap wires from the transformer winding are connected to a quick-disconnect array block. Bus wires are connected to the quick-disconnect array and form a cable for connection to the layout panels. Connections for the thirty-eight separate track blocks and twelve alternate powering selections are connected to an appropriate bus wire within the eight panels.

Since all the track blocks are protected for "power passing," there is no shorting of transformer taps as an engine's pickup rollers pass over track block powering changes.

Separate cables connect to each half of the layout. Cables are made from #14 stranded wire. A #10 stranded wire supplies the "track common" connection. This wire carries the sum current of all track power, so needs to be rather heavy.

The wall plug is powered from the power strip on the accessory transformer carrier. One switch turns the entire layout off and on.

Train accessories, track switches, and outside-rail detect are powered by two 150 watt Lionel pre-war Type "K" transformers. Commercial transformers power the controller boards.

The Lionel Type "K" train transformers were made from 1913 to 1938. A moving lever selected a "tap" for train power. This technique could not be used with E-Unit reversing trains, since the E-Unit would drop out as the lever was moved between taps.

The Type "K" has a binding post for each transformer tap. A plate on the side shows connections for voltages from 2 to 25 volts. The transformer is rated for 110 volts input, so adjustments need to be made for modern 115 to 120 volt line power.

The binding posts make the Type "K" perfect for powering accessories. The variety of tap voltages allow just the right voltage for any accessory. We carefully inspected and tested the two transformers used. We did have to replace the line cords and provide circuit breakers, but otherwise they are as they were when they were made over sixty years ago.

Additional commercial transformers (in the box on the left) provide power for the controllers used for train control and accessory activation.

All powering is AC; no regulated DC power is needed.

A split cable supplies controller and accessory power to the layout panels.

A power strip distributes line power for the accessory and train power carriers. A single line switch turns all layout power off and on.

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