Western Railroad Discussion > Slide Fence Question

At MP 220 on the UPRR in the Truckee River Canyon, Calif just west of Floriston is a rather impressive boulder catch fence and slide fence.  

There's also a manual crossover and old cantilever signal bridge still in place right there which is unseen from Hwy 80 as it's all behind a hill. 

Questions about slide fences. How many volts DC is running through the wires? 

The wires are pretty stretchy and close together what size rock does it take to bust through and show a red signal?

Looks like this years long stormy winter tested the boulder catch system with some big rocks.

Pretty impressive setup.  

Chuck

I was told once by a signal maintainer the the rails had 7 vdc. I would think the same for the wire. I'm sure there are experts here that will weigh in.

Slide fences normally have 12vdc. All they do is hold up a relay until a wire is broken or end cap is pulled out of it's socket, then said relay drops putting the signals to stop. That's the real simple answer. I had to test one in Soledad Canyon twice a month while working for Metrolink and to make sure the cap pulled out was to stand on the ballast shoulder and run into it. You could just pull the cap out, but that wouldn't give it a real test of something bouncing off of it.

Old type c track circuits put out 6vac with a resistor at the feed end and had a diode at the other end of the circuit making half wave dc. Track relays had a resistor in series with it and that dc was dropped to around .8 volts. The combined voltage on the track was roughly 3vac, 3vdc.

On the UPRR do the slide fences normally trigger a trackside signal?

Heading EB downhill there in Floriston the signals aren't far at all from the slide fence. No time to stop. 

Maybe other signals get triggered too?

The boulder catchers caught some rocks that would have for sure put a train into the Truckee. 

There are some stretches that keep the UP busy.  They do a good job it seems to be quite the challenge. 

Chuck

 

I would think they still do if the fence is from the SP days. The signals probably got moved around when the UP took over but should still go to stop, but being an old SP guy and they way the UP does things, who knows.

No point in a fence if the signals don't stop you. 

Perhaps more than one set of signals in a direction from the fence will go red giving the crews more advance notice?

Otherwise trucking down the Truckee you come around the bend seeing a red signal and a few hundred feet beyond that a rock the size of a truck on the tracks. 

Very unstable rock. Huge round river-rock boulders. Definitely some train-stoppers. 

Always thought slide fences were a cool part of railroading.  

Chuck

 

RailDawg Wrote:
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> Perhaps more than one set of signals in a
> direction from the fence will go red giving the
> crews more advance notice?
>

Depends when the rock came down. If they were by the signal that would have been yellow because the rock came down, the red will be a surprise (among the reasons folks are suppoed to keep looking out the window).

TAW

Don't know how they work on Donner but on UP's former WP Canyon Sub (Feather River Canyon) a tripped fence will cause an indication on the dispatcher's board. I have been given radio instructions on the fly to comply with a sudden slide fence indication per rule 6.21.3 because we were already past the governing signal. 

Some slide detectors may "talk on defect."  One that I was familiar with years back, on a un-signalled branch, would broadcast a radio warning on the road channel  if the slide fence was broken--something like, "Slide detector tripped at Milepost 123.4."  This message would repeat two or three times initially, then would repeat about every 5 minutes or so after that, until the detector was reset.  Sometimes that could go on for hours, because the signal maintainer had a huge territory and could be up to 150 miles away from the detector on another call.