[N&W] Rock Slide Detector Fences

[nw-mailing-list at nwhs.org]

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