Flange bearing crossing speed

[naveen.1994]

Hello,

I am Naveen, uni student working on investigation of speed over the flange bearing crossings. Most standards state its 15 kmph but do they have any analysis backing up or is it jus a conservative speed to keep it on track.

Thank you,
Naveen.

[Beeyar Wunby]

Originally Posted by naveen.1994

Hello,

I am Naveen, uni student working on investigation of speed over the flange bearing crossings. Most standards state its 15 kmph but do they have any analysis backing up or is it jus a conservative speed to keep it on track

Hi Naveen, and welcome to the forum.

I don't know exactly what the definition of a flange bearing crossing is, but here in the UK, 15 MPH is the default speed of turnouts and crossings. That's another way of saying that if a crossing doesn't have speed board, the driver must take it at 15 mph or less.

Hope this helps, BW

[aussiesteve]

G'day Naveen and BW,
Yes, I was likewise bamboozled by the term.
But, there is some info re flange bearing frogs at Wikileaks.
https://www.google.com/url?sa=t&rct=...rAs7hZzocW-pmE
And if that link works, a PDF file apparently details the H type crossing.
I haven't downloaded the PDF, so don't know exactly what it details.
Steve.

[aussiesteve]

G'day,
I have finally managed to google some info about the flange bearing frog.
This technique is something that I had not heard of previously.
I can now see the benefits of this concept, though it generally imposes a speed restriction upon one or both routes.
Plus, High Rail vehicles can have problems when encountering a flange bearing frog.
I had assumed a technique applied for tramways, but this is also being trialed for heavy rail by companies like the BNSF.
The principle being to reduce the impact of wheel treads rolling through the standard frog gaps in the rail.
Four distinct designs exist for the flange bearing frog.

1; Lift frogs, where the designated main route rail is continuous through the frog and permits high speed on the main route.
The diverging rail lifts the flange up and over the main route.
Here a normal gap in the rail does exist for the diverging route imposing a reduced speed limit.
The wheel treads sides of the diverging train being guided by guard rails, but no guard rail is necessary for the main route.
Lift frogs cannot be utilized on curved track sections due to potential derailment on the diverging route.

2; Combination tread and flange bearing frogs, which are similar to normal frogs, with a slight gap in the rails for both directions.
Upon approach to combination frogs the flanges of either direction train are lifted to proceed over the gaps.
Guard sections are necessary for both directions to direct the wheel tread sides through the frog.
Becoming tread bearing again upon the outward side of those gaps in the frog.
Speed restrictions apply to either direction through this frog.
But, as with normal frogs, heel and toe impacts cause ongoing damage, though reduced to that of a normal frog.
This is especially the case with worn wheel treads which actually produce a higher flange depth as opposed to new treads.
As the combination frog wears it becomes tread bearing for new wheels and flange bearing for worn wheels.
Combination frogs are utilized in yards where speeds are normally restricted.

3; One Way Low Speed crossings are utilized at diamond crossings.
The OWL provides continuous tread bearing rail though the main line, and the opposing slow speed route lifts the flanges.
Contact is made on the head of the straight route rail by the cross route flanges and will eventually wear a groove.
Hence the OWL is only useful for locations with limited cross traffic running a slow speed.

4; Full flange bearing crossings, again utilized at diamond crossings, this time both routes are flange bearing.
Hence, here speeds can be higher but similar for both routes.

The FRA mandated speed for flange bearing frogs is 10 mph on the diverging route, or both routes for combination frogs.
Therefore, in regard to tramways, yes I can see the benefit of flange bearing frogs to provide a smoother high speed ride.
Though, at the disadvantage to the slow speed route.
I will need to do more googling to discover just how wide-spread the flange bearing frog is here in Australia.

Back in the early 1990s the appearance of an 80 kph high speed turnout in smog hollow did give us the challenge to test it.
This turnout located at Glenfield suburb on the main South line necessitated the use of a moveable frog.
Yes, it was fun zooming through at 80 kph.
This turnout no longer exists having been replaced with a fly-over.
But, as with any set of points (switch), there is also the switch and stock rail wear and damage sustained during endless usage.
Maybe we should revert to the old timer Stubb switch.
No frog or switch rail, both of the stock rails are slid across to align with the chosen route rails.
Definitely no trailing through Stubb points permitted.
And, you also go bush if the stock rails are not exactly aligned.
But, if we no longer hear that clickety clack of wheels hitting the frog gaps, what is there left for us to enjoy.
No clickety clack with continuous weld rail.
Steve.