What's a Banjo Eye?
a...@hpfelg.hp.com
might be in some places) a round target with a hole in the center
that swung back and forth when activated. Looked somewhat like a
banjo being swung back and forth by its neck.
"Banjo eyes" must then mean moving ones eyes back and forth
like a banjo signal...in the context you refer, probably watching
people walk by.
Sometimes the banjo signals had red lights in the hole, for better
night visibility.
I can't remember when I last saw a wig-wag. Think it was in the LA
area 10 years ago.
Hope this helps.
Douglas W. Jones,201H MLH,3193350740,3193382879
> The banjo crossing signal, also called a wig-wag, was (and still
> might be in some places) a round target with a hole in the center
> that swung back and forth when activated. Looked somewhat like a
> banjo being swung back and forth by its neck.
>
> "Banjo eyes" must then mean moving ones eyes back and forth
> like a banjo signal...in the context you refer, probably watching
> people walk by.
>
NO! There was an early kind of searchlight signal called a banjo.
It consisted of a thick round body attached to the top of the signal
pole, so the overall shape of the signal was like a banjo. Inside the
body was most of a full sized semaphore mechanism, minus the blade,
and the light shone out through the "eye" in the cover of the banjo.
I gather the banjo had holes in both sides, so in daytime, daylight
was used to illuminate the signal lens. At night, an oil lamp was
lit in the signal, or something like that.
These were not wigwag grade crossing signals, they were used for train
control.
Doug Jones
jo...@herky.cs.uiowa.edu
Jon T. Adams
>From article <1770...@hpfelg.HP.COM>, by a...@hpfelg.HP.COM:
>
>> The banjo crossing signal, also called a wig-wag, was (and still
>> might be in some places) a round target with a hole in the center
>> that swung back and forth when activated. Looked somewhat like a
>NO! There was an early kind of searchlight signal called a banjo.
>It consisted of a thick round body attached to the top of the signal
>pole, so the overall shape of the signal was like a banjo. Inside the
>body was most of a full sized semaphore mechanism, minus the blade,
>and the light shone out through the "eye" in the cover of the banjo.
>
>I gather the banjo had holes in both sides, so in daytime, daylight
>was used to illuminate the signal lens. At night, an oil lamp was
>lit in the signal, or something like that.
>
>These were not wigwag grade crossing signals, they were used for train
>control.
When this whole discussion of "banjo" signals began I recalled that I
had seen a photo of such a thing, and as Doug points out, it should not
be confused with the traditional "wig-wag" signal, of which there are
still many locally (LA). Wig-wags are used for grade crossing protection
rather than for train control; at the center of the circular target on
the end of the wig-wag's pendulum arm is a red lens, reflector or
in the ones that I see there is a red light.
The photo of the banjo signal is in the book about the Mount Lowe Scenic
railway (I think; I'll have to check when I get back to my bookshelf); the
photo shows a "banjo" signal as described by Doug. However, this signal IS
a highway grade crossing protection device, rather than a train control
signal. It is quite possible that they were used also for train control,
but I have no proof of that use.
(BTW, the Mount Lowe Railway was a narrow-gauge line built in the 1890's
to provide service from the San Gabriel foothills above Pasadena (10 miles
north of LA) to an alpine resort atop Mt. Lowe. All that remains today is
the right-of-way, some ties and concrete footings. Must have been a pretty
neat thing back when...)
On signalling in general: the SP, Santa Fe and UP all use track circuit
occupancy detection, where a very big 2v wet-cell is connected across the
rails (i.e., one rail is connected to +, the other to -). A relay is
also connected across the rails, so that the relay is normally energized
when there is no equipment shorting the two rails together.
When a piece of rolling stock or a locomotive (or a wire or battery jumper
cable) bridges the rails, it creates a shunt circuit. The impedance of this
path is (hopefully) much lower than the relay circuit impedance; the relay
coil, in effect, is shorted out, causing the relay armature to relax. Then
the contacts close and the red lights come on, and everyone knows that the
block is occupied.
This is a very simple, failsafe (generally) technique; if the battery fails,
or the relay coil fails, the red light will stay on or just plain goes dark,
which in this part of the world means STOP. Obviously, it is a bit more
complicated than this, but not much...
How much current is available from this track circuit, you might ask? Well,
we put a Fluke DVM across the rails and measured both the track voltage and
the shunt current available. So there we were, on the Santa Fe Harbor Branch
that runs between LA (Hobart Yard) and Wilmington (LA Harbor); first we
measured the voltage, then we switched the meter over to amps and moved the
probes to the 10A sockets. Presto! we measured about 220mA of current
and at the same time heard the grade crossing bells start to ring. Not
realizing that we had indeed been the cause of the grade crossing event, all
three of us jumped about six feet vertically and 10 feet horizontally,
simultaneously looking both ways and expecting to see the sneering visage
of a blue and yellow Santa Fe loco creeping toward us (speed limit 15 mph).
Of course, there t'warn't nothing there but us... (BTW, this event occurred
11 years ago, well beyond the statute of limitations...).
In the desert east of LA, the roadbed becomes very conductive after any
rain; sometimes enough that the bulk resistance between rails via the
ballast is low enough that the relay gets shunted, setting the signals
to red (stop indication). Then all afternoon long you'll hear the dispatcher
verbally waving train crews past red signal after red signal, running
the railroad more like a DTC (Direct Train Control) rather than CTC
(Centralized Traffic Control) environment. The trains will generally run at
reduced speed, maybe 30mph or so.
And you'll also hear the DS calling out the signal maintainers; these guys
spend all day chasing ghosts in the 110 degree heat (and that's a cool day).
Lastly: to conserve signal lamp filaments, all block and intermediate signals
go dark if there is no train nearby to observe them; except, of course, the
signals protecting the two blocks immediately ahead of the train. Also,
interlocking signals and signals within yard limits generally never go
dark on purpose.
Better Railroading and Railfanning to All!
Jon
--
Jon Trent Adams, NW6H | "Per Aspera Ad Astra" A Dead Roman
J...@hydra.jpl.nasa.gov | Way-Rad : Opinionated : Single : Prevaricator :
"jpl don't know me from squat"| Raconteur : Engineer : President, Local Chapter
Ghenghis Khan Fan Club : Honorable Mention, "Calvin" Lookalike Contest
Steve Bjork
>I can't remember when I last saw a wig-wag. Think it was in the LA
>area 10 years ago.
I know of a couple of places in the SF Bay area with them. One is
just east (south) of the San Jose Caltrain/Amtrak depot, where the SP
Permanente branch starts (Vasona Block).
The other is in the Newark/Fremont/Centerville area, where the wye
for the Dumbarton main and the Mulford line is.
--Steven, who videotaped the Permanente Local *tripling* the hill Sunday,
with four Geep 9's and an SD9 lugging coal.
John Purbrick
>area 10 years ago.
I saw one near Rochester, New Hampshire, 2 years ago--on only-occasionally-
used trackage unfortunately. It was set up, as far as I recall, so that a
row of lights was covered/uncovered by the wigwag.
JBvB, can you comment?
John Purbrick
jp...@ai.mit.edu
carl.l.blesch
> The banjo crossing signal, also called a wig-wag, was (and still
> might be in some places) a round target with a hole in the center
> that swung back and forth when activated. Looked somewhat like a
> banjo being swung back and forth by its neck.
>
manually operated. I don't know much about it, but I saw a line-drawing
in an old Lucius Beebe (sp?) train book. Must've been the late 1800s
or early 1900s.
> I can't remember when I last saw a wig-wag. Think it was in the LA
> area 10 years ago.
I remember seeing wig-wag signals on the Chicago and North Western
and the Milwaukee Road in Wisconsin. The ones at the grade crossing
near my childhood home were pulled out back in 1981. The red light
was really too small for the kind of visibility required today
(same analogy with police cars - when I was a kid, all they needed
was a single bubble light on top of their cars. Today, they need
light bars with mirrors to make multiple flashing effects, or strobe
lights, and who-knows-what-else to call attention to themselves!).
I too haven't seen any recently.
Carl Blesch