[N&W] Re: Rock Slide Detector Fences

Tue May 25 22:52:36 EDT 2004

As VGN had no signals Matoaka to South Branch, is it safe to
say VGN had no slide fence protection in this territory ? I mean
we're talking the palisades of the New River and the rock out
croppings at Perrow here.
Harry Bundy
___________________________________________________________
I expected some expert to comment on this before now, but I'll relate my
understanding of slide detector fences on the N&W.  First, it is unrealistic
to expect a woven wire fence to keep boulders or large rocks off the tracks.
Depending on the size of the rock and the momentum it picks up before
striking the fence, the rock could tear right through the fence.  Instead,
each end of the fence has a cable running to a switch that is tied into the
signal system in such a way as to set the appropriate signals at their most
restrictive aspect whenever the cable is pulled due to a lateral
displacement of the fence.  If too many rocks were allowed to accumulate
behind the fence, they could push against the fence with sufficient force to
keep the switch at the end tripped, and the signals set against traffic.

Many years ago I remember hearing that some track-side residents would
somehow push hard enough on the fence to set the signals and stop a coal
train, after which they would clammer onto the tops of the cars to throw off
coal for use in their homes.  Probably a Great Depression era happening.

Gordon Hamilton

----- Original Message -----
From: "N&W Modeling List" <mailing-list at nwhs.org>
To: "N&W Mailing List" <mailing-list at nwhs.org>
Sent: Sunday, October 19, 2003 8:12 PM
Subject: Rock Slide Detector Fences

 > ROCK  SLIDE  DETECTOR  FENCES
 >
 > Some years ago while visiting a model railroad, one
 > of the members asked me about slide detector fences.
 > Locked in a not unusual model railroad mountain
 > predicament, the modeler was faced with very steep
 > -- almost vertical -- high embankments paralleling
 > his nicely curving mainline.
 >
 > Rather than mumble onward, I showed him several
 > slide detector fences in N&W and Clinchfield photo
 > books. For a modeler, I thought this was perfect as,
 > for me, there is no way better to model than directly
 > from proto photos.
 >
 > And he did.
 >
 > I was back there a month later and his slide fences
 > looked excellent, very close to the photos. Some were
 > in place while several others were formed and just
 > about ready to install. Nice job!
 >
 > Well, not so nice.
 >
 > I dropped in a few weeks later and about lost my lunch. All the slide
 > fences were in place and sceniced -- they looked great -- but between the
 > fences and the steep walls, the modeler had poured in enough rock scraps
to
 > fill in the space about half way up his rock detector fence and all along
 > the full length of his excellent detecting wire web.
 >
 > Whaaaa?
 >
 > The modeler was thrilled with his work and merrily showed off all the
 > details, even including "... all the rock that over the years had
 > accumulated ..." behind the fence. He said he believed such a rock pile
was
 > prototypical.
 >
 > Hummmm ...
 >
 > So, I asked him to show me a proto photo of slide detector fence holding
 > back that much rock. Of course, no such photo came to the limelight.
 >
 > However ...
 >
 > The situation stimulated an excellent debate (in which I mostly did not
 > partake) and which would have made cable TV's "Hardball" sound wimpy.
There
 > were several interesting points made ... or should I say, powerfully
 > elucidated! The spit was flying ...
 >
 > Some swore the rock pile was realistic. Others made funny noises.
 >
 > Associating in favor of the rock pile theory, one said that railroads used
 > the fences to keep the rocks off the tracks ... And that no one ever
 > cleaned out the rock piles behind the fences.
 >
 > One fellow thought that to key the sensor a rock or slide had to break a
 > wire. Another said the rock hit the wire and it pulled a spring that
yanked
 > a solenoid and set off the sensor. Most really didn't know.
 >
 > The voting was about even regarding the output. Maybe half said that when
 > hit the fence sensors triggered only red lights on the two nearest signals
 > guarding either direction through the slide area. But then, the other half
 > felt that the sensors sent a specific "fence-been-hit" signal direct to
the
 > dispatcher. Futhermore, the other half didn't know this one either.
 >
 > The fence takes a slant near the top and there were several opinions as to
 > why the slant and which way it slants -- toward or away from the track --
 > photos be damned.
 >
 > There was more, such as how the fences look on each end, how many types of
 > sensors a given fence might have, how strong is the fence vs. the size of
 > the rocks that might fall, and are the fences typically painted and what
 > color? I'm sure there was more, but I'll cut it here so I can make my
point
 > before I lose everyone.
 >
 > The modelers' discussion in reality was great. It brought up a variety of
 > railroad aspects that some had never heard of and in which virtually all
 > had some interest. I mean, this is the way railroad knowledge and interest
 > gets advanced. In spite of the shouts, the defending of turf and even the
 > volleys of misinformation, the debate was great.
 >
 > Years later we have email lists such as the one we are on now and on which
 > we can carry forth with the same sort of debate ... For the most part,
sans
 > the red faces and with time to do a bit of research before opening one's
 > mouth ... Errrr ... Hitting the send button.
 >
 > What I'd like to do is to spread that debate here amongst this group. As
 > you read the material above you likely had an opinion or two on several of
 > the differing points. And I'm hoping you'll take the time to offer here
 > your knowledge and questions for both the modelers amongst us who really
 > would like to get it right and for the 1:1 fans here who just like the
warm
 > fuzzies of learning more about real railroading.
 >
 > What do you all know about slide detector fences? Among several such
fences
 > that I've seen are those up on the bluffs north of Clinchfield's Copper
 > Creek Viaduct (or was it a bridge? ... or a trestle?) and beside the
 > Norfolk & Western's Pokie mainline as it climbs the miles leading to
 > Maybeury (is that Ennis?). I only presume that the Virginian and B&O had
 > the rock stopping fences, too. What do you know?
 >
 > Frankly, I've never seen a slide fence back filled with rock. I've never
 > seen anyone carting away all the fallen stones. I've never seen a train
 > stopped by a red board induced by a slide fence. Heck ... The ones I saw
 > ... Well ... They were just standing there minding their own business when
 > I saw them.
 >
 > Sooooo ... What do you guys know? Spill your guts on this one ... Let it
 > all hang out. What's the low down on railroad slide detector fences?
 >
 > As a kickoff, why not check out this link to view a "Standard Rock Slide
 > Detector Fence (new type)" of May 8, 1975, on the D&RGW. But please do not
 > limit yourselves to modern era slide fences ... This is an "era limitless"
 > experiment.
 >
 > Click here:
 >
http://users2.ev1.net/~swmeier/DRGW/MOWBooks/1966Book/images/Page%20156.1.jpg
 >
 > And here's a definition I found. Do you all agree with it? Does someone
 > have a better or corrected definition?
 >
 >  >>>>>
 >
 > What is a slide detector fence?
 > To prevent train accidents due to falling rocks or earth slides in hilly
or
 > mountainous regions, electrically charged wire fences are made to serve as
 > detectors. If a falling rock or an earth slide breaks one or more of the
 > wires in the fence, a relay is released and "stop" signals are set up to
 > halt a train approaching from either direction.
 > <<<<<
 >
 > Anyway, tonight I was thinking, "The Cubs lost ... Might as well do slide
 > fences." What do you say?
 >
 > Thanks and later ... Bob Loehne
 >