Dale G. Kraus, MMR

Continuing this sporadically produced screed …

Myth #3: Track switches must be “DCC Friendly”

This is perhaps the most persistent myth in all of digital command control. Somehow, the word has gotten out that all of the all-rail-frog (i.e., Shinohara™) switches are unusable and that older insulated (dead) frog switches, such as the Atlas Custom Line™ must have their frog castings powered. Prospective DCC converts at my old shop often voiced this concern. The modeler was reluctant to take the leap into DCC for fear he would have to rip out and replace all his old turnouts. I don’t want to put too fine a point on this, but …rubbish!

This myth stems from two characteristics of the commercial all rail switch: First, since the points are connected together with all metal tie bars and a pivot bar, both point rails carry the same polarity as whichever stock rail the points are touching. This means that the frog also has that polarity. From these characteristics, a fear has developed that loco and/or car wheels will short out the command station when rolling through the points. Not possible! If both the wheelsets and the switch points are built to NMRA standards there will be a substantial air gap between the wheels and the open point rail. If you experience shorts, check the wheelset back-to-back and the point-to-stock rail clearance using your NMRA standards gauge. One of these is seriously out of tolerance.

Second, because the frog polarity changes with the point position, the open end of the frog rails must be insulated from the inner rails of the attached track. Two insulated rail joiners are the easy fix. The outer rails of the diverging tracks need not be insulated from the stock rails of the switch. Regular metal joiners may be used there. If you do not insulate the inner rails, you will have a short! It is also necessary to assure good electrical contact between the points and the stock rails. Keep the inside surface of the stock rail clean (use a Bright-Boy) and make sure the point closes completely and firmly. Be sure no bits of ballast or glue interfere.

Lastly, the Custom Line switches need not have their frogs powered unless you are using really small, two- or three-axle locos. Occasionally one of these frogs is installed one- or two-thousandths of an inch higher than the metal rails. A few strokes with a fine cut mill file laid flat on the frog will cure this.

More later.