Hi
I found this diagram last approved in 1908. What was the purpose of a sliding frog? Are there any still in use? Would it be linked to the points? How was it guarded? I can picture all kinds of gauge problems. http://prr.railfan.net/standards/standards.cgi?plan=56687-D
Thanks
Pete
Pete,
The diagram looks like a frog with a ‘dashpot/spring’ to hold one of the wings tight against the frog. This is quite common where a spur connected to a mainline and they did not want the frog hammered from the passage of high speed trains. The big issue was maintenace of the dashpot/spring part. I have seen them in the last 20 years, but I suspect most are now long gone.
Jim
Dunno what the correct term is, but frogs with a moving rail that keeps the frog gap closed for main line trains are the usual thing on the SP main line San Francisco to San Jose. Lots of #20 x-overs, a few #14s, a couple of #10 turnouts-- all installed in the last five years or so.
The proper term is ‘Moveable point frog’. And they are not uncommon in todays main line railroad operations.
I would call it a spring frog. I think the moveable point frogs, at least in modern terms, are active points generally lined by a switch machine. The spring frog is passive. It is forced open by the inside of each flanged wheel on the secondary route and movements are at slow speed. The guard rail acting on the other wheel holds the flange well clear of the actual point. The frog automatically springs back to resume the mainline position. That PRR plan has a rather different mechanism from the ones I have seen on CP, where only the one rail moves.
John
That’s the proper term for a frog with a point that can move. Nothing to do with this thread.
LOL
I’d also call the linked plan a ‘spring frog’. There’s still a few on secondary lines and industrial sidetracks where they were reinstalled, but are prone to being damaged beyond repair by derailments - even if not caused by them - so that tends to reduce their number.
I interpret it as only having 1 moving rail - the top one, which carries the straight-side traffic, and would be moved for the curved-sdie traffic.
Note also the ‘Anti-Creep Device’ linkage bar at the right end of the wing rails, and in Section C-C and some of the details at the far right side of the plan. That’s to keep the closure and wing rails from ‘running’ under traffic and causing all kinds of grief - from binding on the frog point, to widening the gauge a little, etc.
This is what we called a “spring frog”. The diverging side wing rail is held closed, that is against the point, to provide a continuous running surface for straight side moves. In a diverging move the back of the wheel flange forces the wing rail open to create a flangeway.
When I worked for an Eastern Washington Short line we had one former NP branch that was infested with the things. Ours were 85# rail #9 frogs. They were high maintenance and we had typically low budgets. The FRA inspector made a point of closely examining every one of them on every trip. We finally got tired of his attentions and replaced them all over the course of a year or two, which I am sure was his intent.
CX500’s description of a swing nose frog is correct. IIRC they are used in high speed crossovers with frog numbers greater than #20. They are a relatively new item in US practice and are relatively rare.
Mac
Spring Frog, complete with horn (never heard dashpot used before in this application, Eastern thing?)
NOT a movable point or “swingnose” frog - that’s a totally different animal. - And they are now showing up again in high tonnage area with an improved horn adjustment system.
The Union Pacific is installing the modern day version of them right now in certain locations on the Sunset Route high speed mainline in California and Arizona.
Look at the “Sunset Route Two-Tracking Updates” thread for pictures of them.
http://cs.trains.com/trccs/forums/t/120779.aspx?PageIndex=44
locoi1sa (2-22):
These are some spring frog photos as in the “Sunset Route Two-Tracking Updates” thread …
New spring frog on a new switch pre-installation in Pomona, CA
Colton, CA: A new West Colton Yard switch …
… in action too …
In the above photo, notice how the flange moves the closed rail over.
Hope these photos visually have helped convey the idea.
OK, it was late last night, and I wasn’t as sharp as I should have been -
First, K.P. - thanks much for providing these illustrative and informative photos above ! especially the ‘before-and-after’ open/ closed action sequence [tup] Fortunately, it looks like you had a tank car that didn’t obstruct your view too much.
The principle difference here is that the P.R.R. Standard plan that is linked in the Original Post - No. 56687 dated Nov. 15, 1900, Revision D June 19, 1908, ''Sliding Yard Frog for 85 & 100 Lbs. Rails’’ - shows a frog where both wing rails slide to the side in the same direction whenever a wheel traverses the secondary route. Note the details of the Plate in Section B-B and below it, and that the plates and springs, etc. are symmetrical about the centerline of the frog. (Note also the ancient dates and the comparatively light rail sections involved.) That’s why it had to have the ‘‘Anti-Creeping Devices’’ that I pointed our previously, and which are not seen on modern spring frogs - this thing was so loose that the rails could have easily run longitudinally. Note also that the details of the necessary ’
Spring frogs are quite common.
Well, I’ll be darned - I found a 34-page, approx. 1.64 MB in size, ‘PowerPoint’ presentation in ‘PDF’ format titled ‘‘Inspection & Maintenance of Spring Rail Frogs’’ by Leslie Strezo of BNSF Railway from the 2005 AREMA Conference at -
It’s pretty interesting, if you’re ‘into’ such things as I am.
And by golly, I owe an apology to Jim/ jrbernier - for sure, there’s a ‘dashpot’ shown on page 20 of 34, with comments on inspecting and checking them on pages 21 and 22 of 34. It looks just like a shock absorber, and seems to serve much the same function - ‘‘Proper closing time of wing rail between 30 seconds and 3 minutes’’ (page 20 of 34, though is says ‘‘3 seconds’’ instead on page 21). The other comments about the variable speed operation of the thing underscore my previous concerns, though.
What can go wrong, will.
Are these similar to a spring switch?
It is indeed a spring rail frog. Here in the east, they have pretty much been replaced with conventional railbound manganese frogs because they are high maintenance items. There are just too many parts to wear or become loose. The critical part to maintain is the vertical clearance between the horn and its housing. The FRA limit is 3/8 inch. If this clearance is excessive, during a trailing move on the main track, the lead axle of a truck can depress toe end of the wing rail, lifting the heel end up. The trailing wheel could then catch the gage side of the uplifted wing rail, spread it at the toe end and fall into the gage of the track.
Although these are high maintenance frogs, Amtrak has used them at “outlying turnouts” along the Northeast Corridor high speed mains, to provide a smoother ride for the passenger trains and reduce battering of the frog point. The diverging move thru sring rail frogs has always been limited to 10 or 15 MPH.
Yes and no. A spring switch is equipped with a manual throw mechanism so it can be hand thrown for facing point diverging moves. The sprung switch point is useful at the ends of passing sidings and double track, to allow trains to enter the single track without having to stop to throw the switch. They also simplify things for the dispatcher in TCS territory and eliminate the power switch machine and its circuitry. In a trailing point move, they may be traversed at the speed dictated by the turnout frog number. For example, a turnout with a No. 10 frog is good for 20-25 MPH throughout, including the switch points.
Thank you guys.
I can understand the closing of the frog gap to save the rail and wheels from pounding. Let me understand this. The flange of the wheel going through the frog is what opens the flangeway? Manganese steel was probably too expensive back in the day to have on every switch.
Thanks for all the responses.
Pete