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Trip Report - Sunset Limited
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[QUOTE]Originally posted by George Harris: [QB] [QUOTE]Originally posted by PaulB: [qb]I don't know about signals freezing, but switches can freeze if the heaters are malfunctioning. Switches have lots of moving parts, and if they freeze it becomes difficult to impossible to move these parts. So, there are heaters for each switch. These may be electric, or propane if the switch is out in the sticks.[/qb][/QUOTE]Given the location of the Sunset Route, it could weel be that only a small portion of it or even none of it actually has switch heaters. These things are expensive to install and maintain, so in areas where freezing is a rare event, they usually are not installed. In those cases, then it is necessary for the maintenance of way forces to get out and chip out the ice or put kerosene burning smudge pots under the points, which this far south they may not even have. The only part where ice usually causes a problem is if you get ice between teh switch point and the stock rail it is supposed to close against so that when you throw the switch it will not close completely. In that case, you can not get a clear signal for any movement over the switch. Mostly they are propane because you want something that does not require commercial power to function, as ice and snow storms frequenly cause power failures. The standard AAR switch machine is required to have a closing force of not less than 2,500 pounds, so snow, slush, small limbs and small rocks, hands and feet are not a problem. There is enough force to squeeze out the slush and snow and crush other objects, but ice is strong enough to stall the machine. In the normal switch arrangement, there are rods between the switch rails to keep them in proper relation to each other. At the point itself will be the swtich machine, which normally has three rods connecting to the switch points. A drive rod which actually moves the swtich, a detector rod which follows and must make contact with one of two postions within the switch machine, and a locking rod which has a notch inside the switch machine into which a "key" fits when the switch is properly closed. The position of these rods must be in agreement for the signal to clear. On large turnouts, there is frequently a second drive point which is moved by a rod and crank arrangement from the one machine at the point. Most of the other moving parts are enclosed in the switch machine housing so they are not subject to interference from ice and snow. For the very high speed turnouts on the Northeast Corridor, there are multiple switch machines, but these you will not see on the Sunset Route or much of anywhere else outside the NEC. [/QB][/QUOTE]
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