|
To: "oermsignal" Subject: Orange Empire Railway Museum Signals Update - 4/26/2004 This email is our semi-regular update about signals work (installation, maintenance and restoration) at the Orange Empire Railway Museum and is a collaborative effort -- the information for this e-news issue was provided by Allen Holliday and Gene Cranston. If you have information that would be of interest to others, please email it to me and we'll include it in our next newsletter. If you would like to be removed from this mailing list, please email me. Likewise, if you know someone who would like to be added to this list, please have them email me. If you receive duplicate copies of this email, please contact me and let me know your preferred email address. ------------------------------------------------------------------------------------------------ 11th St. Crossing - better but problems continue: If you remember from our last email, after disconnecting the impedance bond (which is no longer needed) at 11th St, the crossing "seemed" to be working better and no longer intermittently starting with no trains present. Gene checked the 11th St. track circuit again last Thursday and all was well. To save the very expensive strip chart paper ($30 per roll) Gene switched to a relay circuit that would have dropped and stayed down if the track circuit had been occupied or failed. No train has been in the area and the relay had not dropped, indicating there has been no failure for the days early last week. This indicates that maybe we had found and circumvented the problem. Mike's measurement of the audio track voltage last week at 0.8 volt and then 1.8 volt with the impedance bond disconnected showed a likely source of the problem with the 11th St. track circuit. Track circuit analysis is far from predictable. Track impedance looks like a mish-mash of small resistors and inductors across a series of resistors/capacitors and batteries to ground. The track circuit is considered good if the impedance is equivalent to four ohms per thousand feet from rail to rail under wet conditions. It can be measured but is difficult to predict. At AFTAC audio track circuit frequencies, the problematic impedance bond should not have had much affect on the circuit. By comparison, short [500 foot] 60Hz.track circuits are loaded much more heavily by impedance bonds. Audio track circuits are from about 500Hz to over 10KHz so the loading by the impedance bonds should be about one tenth as much (or less) than a 60Hz track circuit. In this case the loading by the impedance bond was very heavy. When one end of the impedance bond was disconnected the circuit once again looked like a typical audio track circuit. We assumed that the impedance bond was shorted (the resistance of an impedance bond is so low it cannot be measured with standard instrumentation). In this case the impedance bond had been connected but bonded around so operation of the circuit was otherwise not affected. In the week since we disconnected the impedance bond, the circuit has been monitored and has not failed once. Then late Sunday (yesterday) Gene checked the chart recorder tape and found some odd marks that has him concerned (but 11th St. and all else went fine for Railfest). In the near future, we need to go over the 11th St. track circuit and the power to the track circuit components "connection by connection" looking for anything loose or dirty. So as we've said before .... the saga continues. Rail Festival: Another Rail Festival took place this past weekend at OERM (April 24 and 25). The signals worked perfectly throughout both days. --------------------------------------------------------------------------------------------------- For additional OERM Signals information, visit the signals website at: http://gsee.sdf-us.org/signals. Previous editions of these email newsletters are at: http://gsee.sdf-us.org/signals/enews/enews.html . Questions or comments regarding OERM Signals should be directed to the Signals Superintendent Gene Cranston. |