Where a rail of the diverging route crosses a rail of the straight route, the frog provides flangeways for the wheel flanges and a point that carries the wheel across the gap. Frogs are numbered by their angle: a number 10 frog spreads one unit for every ten units of length, and higher numbers give gentler, faster diverging routes. Main line turnouts use rail-bound manganese or spring frogs built to take enormous impact, and a battered frog point is a common source of slow orders.
That number 20 frog at the west end is battered, they want to swap it out the next time MOW gets a window.
Manganese frogs are rebuilt in place by welding, so a battered frog does not always mean a new casting.
Also heard as
- frog casting
Related terms
Switch points
The pair of movable, tapered rails in a turnout that steer wheels onto one route or the other.
Gauge
The distance between the inside faces of the two rails, 4 feet 8.5 inches on standard-gauge track.
Line
To throw a switch so it routes a train or car onto the intended track.
MOW
Maintenance of way: the department and crews that build and maintain track, bridges and roadbed.