The Controls - Analog

When I first started planning for this railroad, in the early 1990’s, there was no electronic command control in N-Scale.

In that long ago analog day, the classic Arnold rapido model railroad layout allowed for the control of multiple locomotives with one transformer by using a clever combination of current routing turnouts and thoughtfully placed gap tracks.

Consider the placement of tracks, below:

The power pack which controls the railroad feeds power to the track at the lower right, marked “Feeders”. The track switches, marked “W1” and W2” allow track power only in the direction to which the turnout is set.  The gaps isolate a segment of track. 

When a train passing through W1 to the upper side track passes over the gap in that track, it either stops or continues depending upon the position of W2. If W2 is set for the straight position, then the train will continue.  If W2 is set to the curved position, then the power is off for the straight segment and the moving train stops after is passes over the gap.

A train moving in the opposite direction can be controlled in the same manner. And, theoretically, a third train can be operated from the stub siding in between the two through tracks.  Even the largest Arnold rapido layouts use this same control approach.

As noted earlier, this layout was started before command control, so there were at least two control issues. 

Train Speed Control

Control of the trains would have originally been through a conventional DC power pack, which controlled trains by increasing or decreasing track voltage. The higher the voltage, the faster the train.  Because this is a coffee table layout, the idea is to set the transformer for one “speed”, and then leave things alone.  In the analog situation, the power pack would have been set for one voltage and the train would be left alone. In this situation it would go one speed on level track, then it would go slowly uphill and very quickly downhill. 

There was an analog approach that would have improved upon this issue:

Minitrix manufactures an adjustable resistance unit, originally No. 6631 (now 66631).  This device has a sliding switch which lets you choose a voltage level for a segment of track.  They also manufactured a self contained diode, No. 6627 (now 66627).  Using the adjustable resistance unit, the layout operator could set the voltage to be lower for trains going downhill or higher for trains going uphill.

Fortunately, command control came to save the day with load compensation.  Briefly, with command control the command station tells a specific locomotive to operate at a certain speed and the locomotive’s decoder adjusts the locomotive’s motor speed to meet that speed requirement. This eliminated a lot of complicated wiring that would have been necessary if the railroad had been set up for analog operation.

Track Switch Control

The second issue simplified by the introduction of command control is the operation of the track switches (“turnouts”).  Conventional control of the track switches was with the Arnold 0721 (later 7220) switch controller. These illuminated controllers make for a professional looking control panel.

Because each has three wires for control purposes, and I anticipate putting the controls inside a drawer within the table, there will need to be a cable connecting things together.  I’ve done this before:

The way to do it is to make support surface for the transformer(s) and controls, then make the necessary wiring connections to the layout.  The idea is to guide the wires from the controls to a central point, then use a narrow spacer board to act as an alignment device for the individual wires.  This board is the length of the final cable. At the far end of the board is the train layout.

Once all the wires are connected, wire ties are used to group all of the wires together into a cable. If you’re resourceful, you may find a multi-pin connector that can be installed as you pull the individual wires so that you can disconnect the transformers and control buttons from the layout. It may also be possible to use a computer ribbon cable, but I have no experience with that.

Of course, as I look at this process, I realize that command control will make things considerably easier.  With command control, the control functions are handled by the command station.  The individual turnouts are connected to a decoder, which translates the command station signal and operates the individual track switches.

Next, a look at command control and coffee tables.

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