Movable Point Frogs

[Anonymous]

While traveling through Nebraska along UP triple track I've seen numerous signs that say "Movable Point Frog" between the three tracks. I know what a frog is and I know what a movable point on a switch is but what is a movable point frog, why are they used and why is a sign placed by every one?

[mudchicken]

It is what it says it is. The frog point wingrail is made slender enough at the tip that it can be swung shut along the flangeway. Eliminates the banging over the gap, decreasing the impact damage to the point of frog and the wingrails in heavy tonage/ high speed applications.

Sign alerts train crews and others (*esp. hi-rails & shoved light cars) to presence of swing- nosed frog so they don't split the point running backwards througfh one , a la a run-through rigid switch. Really dangerous to hi-rails if derailed at speed. Increases speed in terms of eliminating unbalanced elevation shift in the high side of a curve. Swing nosed frogs/ movable point frogs re-introduced to the US in the late 1980's by Great Britain's Henry Boot Co.

(PRR had movable point frogs in the 1920's, the design fell out of favor)

[Anonymous]

MC--

So did the SP and SSW.

[mudchicken]

Not to be confused with spring frogs, which have also made a comeback.

[dehusman]

The sign reminds the crews because if they have to hand operate the switch, they have to line both the points and the frog.

Dave H.

[CSSHEGEWISCH]

Several of the diamonds at Kensington Junction, where the South Shore crosses over the IC main line to connect with the IC electric, are equipped with movable point frogs.

[CShaveRR]

Fortunately, those switches with the movable-point frogs are thrown automatically by the dispatcher--most of the time.

But if a dispatcher should tell you to operate the switch by hand, you'd have an amazing scenario to go through.

First of all, there are three machines to throw at each of these switches--one for the movable-point frog, and two for the points. And those point switches can't just be thrown in order--you have to open the switch nearest the point halfway, go to the other one and throw it, then fini***hrowing the first one. Then, go throw the frog.

And here's the kicker: these high-speed switches are usually used in pairs, at crossovers (where trains move from one main track to another parallel track--do not confuse crossovers with crossings!) So you have to do all of this twice. With the distance between track centers increased in many places, that could be a half mile or more of walking, just to throw a couple of switches. No, you can't throw one switch, hop on the engine and ride to the other one--both switches of a crossover have to be lined before movement can commence--it's the rule.

And then the dispatcher tells you to line 'em back after you've gone through them!

[jeaton]

And by that time, you could let everybody off at the Kensington Station and tell to walk if they want to get home sooner than waiting for the train.

Jay