Optimum material for rails. Cost no object.

[McRhu]

If cost were removed from the equation, what would be the best material for rails? Given that resistance to wear and strength are important, what would do the job best? Depleted Uranium, Silver, Tungsten, pure Manganese?

 

[WatcherZero]

Its a tradeoff, if the rails are too hard the wheels will wear excessively and vice versa.

 

[quantinghome]

Vibranium.

 

[Master Cutler]

Adhesion between wheel and rail is achieved by micro welds forming at the wheel/rail interface.
Anything other than steel to steel would not perform as efficiently.

 

[ic31420]

Surely we should expand the question to

If cost were removed from the equation, what would be the best material for rails and wheels?

 

[McRhu]

Rails AND wheels it is then. What with all the nano science then, was it just LUCK that the early railways worked at all? Steel wheel on cast iron rail and such?

 

[D6975]

The rail used in long tunnels is my guess. They use that type to minimise the need to replace it.

 

[mcmad]

Its a tradeoff, if the rails are too hard the wheels will wear excessively and vice versa.

hopefully this is something that GBR will be able to influence as I feel the balance has swung to far towards favouring the wheels in recent years. The life of 'standard' rail is a fraction of what was previously achieved and the only significant change is wheels or profile of wheels.

 

[modernrail]

I noticed today that the southbound track at St P Thameslink seemed to have a lot of what looked to be honest to be damage inside the outer rail. Like shearing almost. The nearest pic I can find via Google seems to describe it as point wear. https://www.researchgate.net/figure...wear-mid-gauge-corner-checking_fig2_315475757

 

[edwin_m]

hopefully this is something that GBR will be able to influence as I feel the balance has swung to far towards favouring the wheels in recent years. The life of 'standard' rail is a fraction of what was previously achieved and the only significant change is wheels or profile of wheels.

Suspension and bogie dynamics too. Modern suspensions tend to damp the bogie rotation to prevent "hunting" oscillations, and this may mean that the bogies crab round on curves instead of running more parallel to the rails. The damper on Desiros (which are also very heavy which probably doesn't help) was changed to reduce this effect, but I'm not sure how well it worked.

 

[172007]

I noticed today that the southbound track at St P Thameslink seemed to have a lot of what looked to be honest to be damage inside the outer rail. Like shearing almost. The nearest pic I can find via Google seems to describe it as point wear. https://www.researchgate.net/figure...wear-mid-gauge-corner-checking_fig2_315475757

Have a closer look next time you are there for any rail greasers near by. Usually the build up of grease and dirt ends up overhanging the rail and looks like the moddle picture in the article linked but there is a lpt more overhang off the rail. This tends to be prominent in very slow speed areas such as major stations etc were there are curves nearby.

 

[HSTEd]

Well we could use superconducting bus bars in third rail installations, expensive but eliminates almost all the operational downsides of third rail!

[EDIT: I actually was going to seriously suggest superconducting earth return bars using technology being prototyped for aluminium smelter busbars, but I worry I would get laughed at]

 

[Master Cutler]

My guess is that if cost was no issue then ceramic wheels and rails would be the optimum material.
Some ceramic to ceramic surfaces stick like glue against sliding friction.
Strength wise, after seeing ceramic cutting tools I think this material would be more than capable of withstanding shock loads.

 

[modernrail]

Have a closer look next time you are there for any rail greasers near by. Usually the build up of grease and dirt ends up overhanging the rail and looks like the moddle picture in the article linked but there is a lpt more overhang off the rail. This tends to be prominent in very slow speed areas such as major stations etc were there are curves nearby.

Could well be it as there are some big curves in the underground Thameslink section which I presume use greasers?

 

[Tangent]

Have a closer look next time you are there for any rail greasers near by. Usually the build up of grease and dirt ends up overhanging the rail and looks like the moddle picture in the article linked but there is a lpt more overhang off the rail. This tends to be prominent in very slow speed areas such as major stations etc were there are curves nearby.

The curves at Borough Market between London Bridge and Cannon Street definitely display these signs.

 

[MattRat]

I think making the train's as light as possible would help the rails and wheels more. By light as possible I mean not too light of course. We don't want another Pacer on the railways.

 

[MarkyT]

If cost were removed from the equation, what would be the best material for rails? Given that resistance to wear and strength are important, what would do the job best? Depleted Uranium, Silver, Tungsten, pure Manganese?

Rearden metal.

 

[JohnElliott]

If cost were no object wouldn't the best solution be magnetic levitation?

 

[MarkyT]

If cost were no object wouldn't the best solution be magnetic levitation?

I believe hoped-for energy savings of high-speed maglev operation have proved illusory with the tech developed so far. Lack of mechanical contact clearly requires less frequent replacement of vehicle running gear and track components to account for wear over a system's lifetime, but I'm not clear if such savings balance out the greater energy use.

 

[edwin_m]

I believe hoped-for energy savings of high-speed maglev operation have proved illusory with the tech developed so far. Lack of mechanical contact clearly requires less frequent replacement of vehicle running gear and track components to account for wear over a system's lifetime, but I'm not clear if such savings balance out the greater energy use.

There is virtually no guided mode where junctions are as easy to make as on a railway, except perhaps rubber-tyre peoplemovers which are a very low-speed mode. Junctions on Maglev, monorails and similar normally involve moving some very large chunks of guideway to switch routes, and one route is probably useable only at slow speed. So they tend to be suitable only for loops or possibly end-to-end route, rather than the complex network that railways can do.

 

[AM9]

Well we could use superconducting bus bars in third rail installations, expensive but eliminates almost all the operational downsides of third rail!

[EDIT: I actually was going to seriously suggest superconducting earth return bars using technology being prototyped for aluminium smelter busbars, but I worry I would get laughed at]

Apart from icing issues, (the rails would actually be slightly cooler), and of course the safety issues of exposed high voltage
conductors at shin level.

 

[MarkyT]

There is virtually no guided mode where junctions are as easy to make as on a railway, except perhaps rubber-tyre peoplemovers which are a very low-speed mode. Junctions on Maglev, monorails and similar normally involve moving some very large chunks of guideway to switch routes, and one route is probably useable only at slow speed. So they tend to be suitable only for loops or possibly end-to-end route, rather than the complex network that railways can do.

Agree fully with that. While trying to remain open-minded, I've never been convinced by maglev arguments, not least because of the lack of compatibility with classic rail networks and the necessary additional changes between modes that would imply for many journeys that can be completed on one train today. Perhaps where an entirely new network was being built up from scratch where nothing existed before it might be different, say on a newly colonised planet!

 

[Grumpy Git]

How about making them out of unobtainium?

 

[Ken H]

How about making them out of unobtainium?

Or pandemonium.

 

[dm1]

Wheel-Rail dynamics get very complicated, very fast and many of the assumptions basic models make turn out to be invalid when looking at things in more detail. It boils down to everything being a compromise of some sort between strength, lifetime, adhesion and other factors, with the current setup being one that works fairly well empirically.

For example modern three-phase AC motors on trains are generally designed to maximise the amount of tractive effort they can apply to the rails under all conditions. Somewhat counter-intuitively this is not in fact when the wheel is not slipping on the rail at all, but rather at the point just below where the wheel loses traction entirely. Under wet conditions this can be quite a lot of slip and slip causes increased wear on both the wheels and rails.

 

[Irascible]

For example modern three-phase AC motors on trains are generally designed to maximise the amount of tractive effort they can apply to the rails under all conditions. Somewhat counter-intuitively this is not in fact when the wheel is not slipping on the rail at all, but rather at the point just below where the wheel loses traction entirely. Under wet conditions this can be quite a lot of slip and slip causes increased wear on both the wheels and rails.

This is also true of every train braking - albeit then you have extra fun of local heating too. ( Also true of rubber tyres, incidentally ). The ideal rail would I guess be extremely stiff to minimise rolling resistance due to slightly bending, but also sticky enough for traction. Maybe a composite? not up on material science at all these days.

What's the simplest solution tried so far for switching maglev? if there's outside guides ( especially plates ) then a fairly simple switch should involve dropping one pair of guides & raising another. Still not as simple as slewing rails, but way less involved than monorails traversing or rotating the entire track. A pair of double sided plate guides might make it easier still as you can gap one, but I guess something doesn't stack up somewhere...

 

[HSTEd]

Apart from icing issues, (the rails would actually be slightly cooler), and of course the safety issues of exposed high voltage
conductors at shin level.

I'm assumnig they would be bus bars connected at intervals to the track-side rails as opposed to actually being the conductors exposed to the train!

Ofcourse if you had superconducting out and return busbars you might be able to design a system with dramatically lower third/fourth rail voltage......

== Doublepost prevention - post automatically merged: 9 Apr 2022 ==

There is virtually no guided mode where junctions are as easy to make as on a railway, except perhaps rubber-tyre peoplemovers which are a very low-speed mode. Junctions on Maglev, monorails and similar normally involve moving some very large chunks of guideway to switch routes, and one route is probably useable only at slow speed. So they tend to be suitable only for loops or possibly end-to-end route, rather than the complex network that railways can do.

I'd argue that the ability to accelerate like maglevs can (0-500kph with accelerations limited only by passenger comfort) offers the ability to make a competitive transport solution even with only simple loops. Essentially imagine a tube line at 500kph.

 

[AM9]

I'm assumnig they would be bus bars connected at intervals to the track-side rails as opposed to actually being the conductors exposed to the train!

Ofcourse if you had superconducting out and return busbars you might be able to design a system with dramatically lower third/fourth rail voltage......

== Doublepost prevention - post automatically merged: 9 Apr 2022 ==

The OP question was about track/rails, so any idea of superconducting 3rd rail being fed with lower voltage (to be significantly safer the voltage would have to be reduced to less than 100VDC. That would meandrastic changes to the trains, e.g.:
collector shoes would need to carry 7.5 times their current levels, in-train wiring would need to be replaced and low-voltage motors would be a challenge, so the whole system would need changing.