A Frog by any other name, ... is maybe different?

[Tom Macrery]

Can anyone tell me why these two frogs are different? Maybe, is the fatter one perhaps for a high-speed point? Both are on our Hercules site.

[Stefan Andrzejewski]

Are these frogs not from a diamond crossing?

[Dylan Knott]

High speed turnout is the latter one.

[Gabor Kovacs]

Tom!

Basically, the only difference between the two sets of points, is there age, and probably purpose as well!

The first pic is of a standard 1 in 9 turnout, where the "frog" is constructed from several parts and adjoining rails.
In the second pic, the "frog" is a complete cast-steel casting with two replaceable "in-lays". These "in-lays" are replaced when worn out by train wheels crossing over the frog, thus eliminating the need to replace the entire frog when wore out! These cast-steel casting frogs are welded to the required rails, to complete a set of points, and they are far more durable and do not crack or break at the frog, as is the cast with the older type frogs.

Dylan's remark that the latter pictures are of high-speed frogs, is incorrect!
They are in fact a standard 1 in 9 frog, which can be used on main-lines, goods yards, and or sidings.
I believe (subject to correction) that this "frog" casting is similar in design and development to the ones used in the USA and Canada. Already, almost all the points that we use on the main-lines in and around Pretoria, and to Cullinan, have already been retro fitted with these cast-steel casting frogs. One needs to pay slightly more attention when crossing over these types of points – they give a far better ride over the points when crossing, than the older ones.

High-speed frogs have a "movable vee", which is located within the “vee” of a frog. High-speed points have either 1 in 12 or 1 in 20 (equal split) taper, and the frogs are a lot longer in length. High speed points can be identified by their length, with two point motors’ and or mechanical linkage connecting the "movable vee" to the main points motor. There is also the necessary signage alongside the track, indicating High-speed Turnout.

I know that within the Sentrarand (STQ) complex, certain cross-over points along the Union to Meyerton Section, Union to Heidelberg Section, Houtheuwel to Potchefstroom Section and certain sections along the RCL (Ermelo to Newcastle Section) are fitted with high speed points.

[Steve Appleton]

Good explanation, Gabbie. The newer frogs use managnese steel crossings (frogs) for increased wear resistance. There are several types.
This from the VAE website at: http://www.vaeafrica.co.za/ :

One of the most problematic areas is the crossing. Normally made up of a combination of rails, blocks and bolts, this is a potential trouble spot and frequently, under the duress of worn or badly damaged wheels, tends to break up quickly. Over the years manufacturers have moved away from normal bolts, flame cutting and welded construction and is more in favour of huck-bolting and machined components. Recently, manganese inserts are also preferred. The number of manganese inserts available is however limited due to the initial high pattern costs and are therefore normally only available competitively on the more popular turnouts. It is true to say however that this hard wearing unit outlasts normal rail by at least three times and the possibility of the crossing breaking up is minimal.

VAE describe the fancy crossing frog, pictured by Tom, as a "compound crossing with high-manganese steel in the overrunning area". It is also worth saying that all newer points and crossings are now mounted on customised concrete sleepers rather than wood. Their alignment seems to be much more accurate and the ride over them is much smoother than for the older types mounted on wood.
Here is a high-speed crossing with moveable vee lifted from the VAE website:

highspeed_points.jpg (92.99 KiB) Viewed 3435 times

[Steve Appleton]

Much more info here on the main VoestAlpine website http://www.voestalpine.com/vae/en .

[Tom Macrery]

Thanks, Gabbie and Steve, fonts of knowledge, both of you!