Richard: If the points are SET to just clear the Check Gauge then it will be impossible to short the back side of any wheel set with an open point rail. This also assumes that the wheel set is correcly set to the check gauge. If a wheel set is shorting the first thing to check is the wheel check gauge, front side of one flange to the rear of the opposite flange. NOTE: the wheel check gage and track check gage MUST BE EQUAL!!!!! If they are not, all bets are off and shorts could occure. I agree that a point should be the same polarity as the adjacent stock rail and this will also stop any shorting. This requires a PC throw bar be gapped. This brings me to my statement; DC or DCC requires a reversable frog politiarty. Therefore No such thing as DCC compatable/friendly. Paul
________________________________ From: Richard Karnes <[email protected]> To: "[email protected]" <[email protected]> Sent: Friday, September 28, 2012 3:36 PM Subject: {S-Scale List} Re: PC Switches Michael Eldridge -- Prototype turnout points are made in various lengths according to the frog number. Turnout Nos. 5 and 6 have 11-foot points. Nos. 7 through 10 have 16'-6" points. No. 11 through 14 turnouts have 22-foot points. And so on. These are AREA (American Railroad Engineering Association) standards. Note that they are all derived from optimal use of 33-foot rail lengths (by now obsolete). Paul Vaughn -- Both you and Ed Loizeaux make the point that there is no such thing as a DCC-compatible turnout. I totally disagree with both of you, although I prefer to call them "DCC-friendly." It is always possible, particularly with larger-number turnouts, for the backside of a metal wheel to contact the open point's railhead, even though the point spread conforms to the NMRA standard. This is because the open point's nearest location to the adjacent stock rail is not at the tip of the point. It is at the place where the taper begins from the full-width railhead. Not all wheelsets will rub the back of the open point, but some may. With ordinary DC, such momentary rubbing causes no discernable performance degradation. But DCC systems are designed such that their primary response to any situation is to protect themselves from damage. Any momentary short circuit will shut down the system for some discernible fraction of a second, causing every locomotive in the same power district to hiccup. The best practice -- for ANY split-point (not stub) turnout -- is to ground the closure rails to their adjacent stock rails, use an insulated throwbar, and isolate (gap) the frog from the closure rails. The frog can be powered from auxiliary contacts on, or actuated by, the switch machine; or by some electronic device like an automatic polarity (phase) reverser (e.g., "Frog Juicer"). Dick Karnes
