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To: "oermsignal" Subject: Orange Empire Railway Museum Signals Update - 4/27/2004 This email is an quick update to yesterday's newsletter about signals work (installation, maintenance and restoration) at the Orange Empire Railway Museum. 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. ------------------------------------------------------------------------------------------------ Signal Garden: The Cox Bell controller circuit board failed several months ago due to a blown FET and Timer IC (the root cause was never able to be determined). After repair by Barry Todd, it was placed back in service last month. But once again the FET has failed -- this time it is visibly burned and cracked. More investigation is now needed to determine what is killing it -- the suspicion is that the Cox Bell coil is partially shorted and drawing excess current --- we'll be checking it out in the coming months. Also the Lower Quadrant Wig-Wag is still sluggish at times. Originally it was thought that the supply voltage was too low but after adjusting the supply last month, the sluggishness continues. The latest thought is that it is not level and this is hampering it's starting ability. Our plan is to shim the entire case to get the entire mast, arm, and wig-wag closer to level. Member's Xing Wig Wag: The member's wig-wag repair done by Paul Khoury several weeks ago started getting "sluggish" again. Paul went back up the ladder again and found a broken contact. He corrected it and once again it's working great. 11th St. Crossing - a little education: Gene was asked for additional information regarding the track circuit at 11th St. crossing. The question and answer are included below: Question: Things have come a long way since the pure DC signal circuits. The 4 ohms per mile doesn't seem unreasonable under wet conditions. Is the impedance significantly higher than the DC resistance and, as the [audio track circuit] frequency is increased, does the impedance continue to get higher? Answer: Good ballast is more than about four ohms per thousand feet WET or about 3/4 ohm per mile. A coded DC track circuit (ElectroCode) was operated experimentally by the Southern Railway on a track circuit that was 14,000 feet long -- I do not know the actual ballast condition or resistance. DC track circuits are normally limited to about 7,000 feet steady or 12,000 feet coded with AC and audio track circuits much less. Frozen or VERY DRY track circuits are usually thousands of ohms per thousand feet. Impedance for audio track circuits would be lower due to the capacitive component of the ballast. Series inductive reactance is higher and becomes predominant enough that it results in the ability to end an audio track circuit with no insulated joints or other termination - one of it's advantages. The FRA specifies a shunt (short from rail to rail) of 0.06 ohm to simulate a train when testing. By the way, in the 70's some railroads used blast furnace slag as a low cost ballast. Due to the iron content it made signal track circuits nearly impossible. A friend informed me that the Southern Pacific Colton hump yard had to be reballasted after the first heavy rain due to the fact that the track circuits could not be made to work when wet. In another instance I once cleared a failed track circuit by kicking a gap in some wet salt like material that ran from rail to rail. Even with the extreme variation of ballast resistance, in most places there is no need to readjust track circuits with changes in the moisture. I have heard that in some northern climates they have to adjust some longer track circuits fall and spring year to compensate between frozen ballast in the winter and wet ballast in the summer. --------------------------------------------------------------------------------------------------- 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. |