Thanks guys for the explanations and photos of movable point frogs.
Rich
Alton Junction
Moveable point frog
Standard Frog
Never too old to have a happy childhood!
richhotrainWhat is a "movable-point frog" and how does it differ from a normal frog?
BNSF installed a movable point frog in the interlocking in my old hometown of Toluca IL, along the ex- Santa Fe, west crossover (from south to north track using Santa Fe nomenclature). There are two frogs and sets of points on each crossover, but they had only installed one movable point frog (out of a total of four in the interlocking) at the time I was there. It looks sort of like a spring switch frog if you have seen one of those, only it is controlled by pipes radiating from the switch to the frog, sort of like a manual interlocking at a tower, so that when the switch points move, so does the point in the frog, making the rail the point is now part of continuous rather than with a one or so inch gap as in a normal frog. The result is just fantastic in terms of noise: it is much, much quieter, and I must imagine that the maintenance is reduced also.
On a side note, the east crossover was just a mess when I was there in the fall of 2012, one frog was in the mud, bolts were loose, etc. I think BNSF needs to pick up the maintenance there. I also noticed something I thought I would never see on that line: a contractor was welding in a section of rail, hard to believe they would let one of those guys out there, I wonder if BNSF is farming out their maintenance of way operations. If so, it is too bad, I would think they would want to keep it in house for accountability.
There's a much more recent shot of this location over on Trainorders.com today:
http://www.trainorders.com/discussion/read.php?4,3403496
Carl
Railroader Emeritus (practiced railroading for 46 years--and in 2010 I finally got it right!)
CAACSCOCOM--I don't want to behave improperly, so I just won't behave at all. (SM)
A movable-point frog can croak while he hops.
All seriousness aside, a normal fixed-point frog is a solid casting that includes a gap in the rail tread to allow for passage of the wheel tread. A movable-point frog has several parts, one of which is a tread that can move in either direction to close the gap in the rail tread, allowing a smoother ride and less hammering action.
Perhaps some of the railroaders on this forum can explain this a bit better.
CSSHEGEWISCH Movable-point frogs are not common.
Movable-point frogs are not common.
Please help me out with terminology here.
What is a "movable-point frog" and how does it differ from a normal frog?
but worked this time for me
but I am a TRAINS -and CLASSIC TRAINS subscriber
CShaveRRI was able to bring up the picture without difficulty. Perhaps if I warmed up the link...http://trn.trains.com/Interactive/Photo%20of%20the%20Day.aspx?id=%7b955D6395-49E6-40C5-8A8D-36A5D6FAC8B8%7d
Nope, still "subscriber-only content" on my end.
I was able to bring up the picture without difficulty. Perhaps if I warmed up the link...http://trn.trains.com/Interactive/Photo%20of%20the%20Day.aspx?id=%7b955D6395-49E6-40C5-8A8D-36A5D6FAC8B8%7d
Another reason for such a crossing would be that the angle is too acute to assure a safe straight route across the other track. Batter a frog a little bit, and you could have problems. The crossing between Metra and UP at Western Avenue has a number of diamonds like this (as well as double-slip switches...definitely a different animal). I'll have to check again sometime and see whether it's only the UP's main tracks that have them (and not the tracks moving stuff to or from the coach yard to the station). At high speed or low speed, something like this would reduce the amount of wear in the vicinity of the frogs by eliminating the gap. This would be especially useful at a spot like this, where diamond replacement would cause a major disruption to traffic. (Again, though, the tracks do cross at a fairly sharp angle.)The premise would be the same as a movable-point frog on certain switches...although these switches permit higher speeds for the diverging routes, the frogs usually protect the main lines (where speed is not affected). What makes them higher-speed switches is the acuteness of the angle. I suspect that anything with a number higher than 20 would be likely to have a movable frog. And that would apply to switches or diamonds.
DwightBranch Edit: If you click open the link and then login as a magazine subscriber you can make the photo open, I can't put a hot link in that way. You must be a magazine subscriber, but it is a puzzle switch in Milwaukee, the caption says at a point where an industrial line diverts from the pacific coast main, with a Milwaukee Road steam engine passing on an adjacent track.
Edit: If you click open the link and then login as a magazine subscriber you can make the photo open, I can't put a hot link in that way.
You must be a magazine subscriber, but it is a puzzle switch in Milwaukee, the caption says at a point where an industrial line diverts from the pacific coast main, with a Milwaukee Road steam engine passing on an adjacent track.
As far as I know there weren't any slip switches in Milwaukee on the Milwaukee road. The spot the OP is referring to is Grand Ave. interlocking.
Randy
Nomenclature, definitions, terminology, geography, cultures and what we are talking about cause confusion. I looked at the Wikopedia article and I don't think it is describing switch styles but rather junctions, crossovers, turnouts, etc. as all diagrams except one are single lines depicting a single track. It is also based on English railroading rather than American. And it also negates what I described as slip and double slip switches and their uses. Instead they are showing different kinds of junctions, crossovers, turnouts and the respective interlocking. So, now that you know the picture is not of a switch but of an interlocking or junction or crossover, you can analyze it from a different perspective.
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Movable-point obtuse-angle frogs are very common as parts of slip switches. Less common as stand-alones in standard crossings, but hardly unknown.
Closed acute-angle frogs with spring-loaded wing rails are quite common.
CSSHEGEWISCH Movable-point frogs are not common. Kensington Junction included several crossings where the South Shore crossed the IC main line to connect with the IC suburban line that were equipped with movable-point frogs. I haven't seen them anywhere else. Double-slip (puzzle) switches can be found by the dozen in the approaches to any major passenger terminal. It would be quite unusual to see one by itself outside of a terminal area.
Movable-point frogs are not common. Kensington Junction included several crossings where the South Shore crossed the IC main line to connect with the IC suburban line that were equipped with movable-point frogs. I haven't seen them anywhere else.
Double-slip (puzzle) switches can be found by the dozen in the approaches to any major passenger terminal. It would be quite unusual to see one by itself outside of a terminal area.
My favorite stand-alone double slip switch was at one corner of an asymmetric diamond crossover, at a place called Higashi-Shiojiri on the JNR's Chu-o Hon Sen. It was needed because there was a meet-pass signal box/station on a narrow ledge between a tunnel portal and the abutment of a bridge over a deep canyon. Over 100 trains a day were scheduled across it - every train that passed that point. The need (and the station) went away when a second tunnel was driven through for the down main track. The new Shiojiri tunnel is on a completely different alignment, and its eastern portal is a couple of kilometers away from the old tunnel.
Chuck
It would be nice to see a picture of what the OP is referring to. I don't find any photo of a "switched diamond" online. There is a schematic in the Wikipedia link, and a photo of a switched frog. I assume that a switched diamond would have all four frogs that have a rotatable bridge section that lines up one route or the other. They would not have points, but just match rail end-to-end. I don't recall ever seeing one.
All major terminals in New York:: GCT, NYP, Hoboken, and Jamaica plus in many places along the subway systems employ slip and double slips switches. It is one of the major wonders many of Ridewithmehenry's first time riders remark about, in fact.
Actually and to my surprise , wilkapedia has a good explanation.
http://en.wikipedia.org/wiki/Switched_diamond#Switched_diamond
Not a slip switch for there is no divergent route and as was stated slip switches are LOW speed devices rarely found outside of terminals.
Shooshie,
I can't open your link, but are you referring to one of these?
http://www.google.com/imgres?imgurl=http%3A%2F%2Fi155.photobucket.com%2Falbums%2Fs309%2Fmsibnsf%2FP1000581.jpg&imgrefurl=http%3A%2F%2Fwww.subchat.com%2Freadflat.asp%3FId%3D645350&docid=LkXkptBCPHMn0M&tbnid=kM8yAaeNK2UvJM%3A&w=973&h=1024&ei=cB9qU7e7CtCUyAT_m4LgCA&ved=0CAIQxiAwAA&iact=c
A common name for that is a “puzzle switch.” It is an actual crossing diamond for the crossing function, but it also has divergent capability.
Upon approach from any of the four directions, it offers a choice of crossing straight through or diverging into the other track.
Actually instead of calling it a poor mans crossing it should be considered a rich mans crossing. The moveable point crossings were for higher speeds. They were common when trains ran on fast schedules like the Hiawatha.
The interurban ,North Shore line also used them on the main line where they crossed the Milwaukee or the CNW.
http://trn.trains.com/Interactive/Photo%20of%20the%20Day.aspx?id=%7b955D6395-49E6-40C5-8A8D-36A5D6FAC8B8%7d
The link is to an Al Kalmbach photo from 1949 in Milwaukee, " beneath Milwaukee’s arched Wisconsin Avenue bridge." To the left of the locomotive there are some apparent switch points. Closer inspection reveals that this is no switch, but a mechanical crossing. Does anyone know if these were common back then? Is it a poor man's crossing? Perhaps the machine shop never got around to grinding some points at that angle. I see a tower nearby; maybe the points were interlocked and could only assume one of two positions. Otherwise, I see a recipe for derailment when a distracted switchman throws one of those sets of points the wrong way.
Does anyone know the story on this? Or more about such crossings in general?
Thanks,
Shooshie
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