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Old April 9th, 2010, 07:01 PM   #1
railzilla
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MISC | Effects of axle load and speed on performance and maintenace

Japanese trains be it commuter, regional or Shinkansen have a very low axle load compared to Europe and especially to North America. The success of Japanese railway and the reliability of them suggest this is one of the key factors. Axle load is also discussed in the sources about Japanese railways i could find on the web. Many improvements in Japanese railways where to keep the axle load low to an extend that they even use EMUs to transport containers.
However i haven't found a formula to calculate the effect of axle loads and speed to the wear of the track. For example if a train with 10 tons axle loads traveling at 100km/h, how will an increase of speed or axle load affect the wear on the track.
I think it increases with the square of the speed so a 200km/h train does four times the damage of a 100km/h one.
For the axle load t increases with the cubic so a 20tons trains does eight times the damage a 10ton axle load train does .
Is this correct. If somebody has the exact formula it will be very welcome.

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Old April 10th, 2010, 02:30 AM   #2
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Be careful what you wish for Here's a formula for the cost of track wear recently quoted in a Bombardier article:

k1 * sum(Qtot ^ 3) / nz
+ k2 * sum(sqrt(Qtot ^ 2 + Yqst ^ 2)^3) / nz
+ k34 * sum(f(FvV)) / mz

with
k1: cost coefficient for track wear
k2: cost coefficient for component wear
k34: cost coefficient for rolling contact wear
Qtot: vertical axle load
Yqst: static lateral force
nz: number of axles per wagon
f(FvV) energy dissipation function for rolling contact

...which didn't really enlighten me too much. There's no way to tell which of the three components dominates. Speed's not in there, might be hidden in f(FvV).
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Old April 10th, 2010, 12:47 PM   #3
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Quote:
Originally Posted by alphorn2 View Post
Be careful what you wish for Here's a formula for the cost of track wear recently quoted in a Bombardier article:

k1 * sum(Qtot ^ 3) / nz
+ k2 * sum(sqrt(Qtot ^ 2 + Yqst ^ 2)^3) / nz
+ k34 * sum(f(FvV)) / mz

with
k1: cost coefficient for track wear
k2: cost coefficient for component wear
k34: cost coefficient for rolling contact wear
Qtot: vertical axle load
Yqst: static lateral force
nz: number of axles per wagon
f(FvV) energy dissipation function for rolling contact

...which didn't really enlighten me too much. There's no way to tell which of the three components dominates. Speed's not in there, might be hidden in f(FvV).
Ok thanks, i think it was to promote their steered bogies thus the lateral force which increase with the square of the speed. And the track cost is the cubic to the axle load interesting.

No wonder there is so much focus to reduce axle load in Japan as it is the dominant term.

BTW the reason i am asking for this is that the Swiss Federal Railways are going to Order double decker trains which a light tilting function. My point is that they have to pay lots of infrastructure maintenance going with so heavy trains so fast around corners. What ever smart bogies are used they are going to be rail eaters. In the long run the Japanese approach would save Billions. Just weeks ago swiss railways announced 60% more demand of money because of excessive track wear. Yet the still order SUVs on rails.
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Old April 10th, 2010, 03:39 PM   #4
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Originally Posted by railzilla View Post
BTW the reason i am asking for this is that the Swiss Federal Railways are going to Order double decker trains which a light tilting function. My point is that they have to pay lots of infrastructure maintenance going with so heavy trains so fast around corners. What ever smart bogies are used they are going to be rail eaters. In the long run the Japanese approach would save Billions. Just weeks ago swiss railways announced 60% more demand of money because of excessive track wear. Yet the still order SUVs on rails.
They're not really ordering SUVs on rails. SBB has been only been buying relatively light trainsets in the last years.
A Swiss Ic2000 car has an axle load of around 12t, so they aren't exactly heavy, even by Japanese standards. The new FLIRT trainsets also set about 12t on the rails. Same for the tilting ICN trainsets.
Compare that to the max axle load of a Shinkansen, which is 17t.
I'd expect the new SBB doubledeckers to have an axle load of around 13/14t, but we'll know more about that next month.
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Old April 10th, 2010, 06:18 PM   #5
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You are rigth with your notes but your axle loading are for the empty cars. Also IC2000 are only trailers where Shinkansen has all axles powered except in the driving vans. Add 2.5 tons for a fully laden car. An N700 Shinkansen has only 11.2 t axle load with full passenger capacity. It can tilt and top speed is higher than an ICN. An European version would even be lighter due to the narrower loading gauge. The E4MAX double decker is only used on some lines. It is also built to the wider Shinkansen loading gauge.
A FLIRT might be lightweight here in Switzerland but would be considered as heavy in Japan, for commuter rolling stock the axle load is around 10 tons. And a Stadler GTW has 20 tons axle load for the power container.
The increased disruption of service due to breaking rails and other infrastructure defects and increased demand for maintenance funds speak for themselves. When S-Bahn Zürich started there where not many such incidents.
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Old April 11th, 2010, 01:19 AM   #6
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i guess one bonus of the uk having small light dmu and emu trains then
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Old April 11th, 2010, 03:05 AM   #7
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Before bashing heavy US rail cars, remember the FHA takes a different approach to all passenger rail traffic safety: it aims to make collisions survivable, hence the strong structural requirements for their rail cars.
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Old April 11th, 2010, 10:18 AM   #8
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A TGV is relatively light and has a very good safety record during crashes. The problem is also if the trains are heavier you gain nothing in safety as more potential energy is involved. What you need are crash absorbers and defined crumble zones.
The point is that to travel fast the requirements on the track geometry are high, and the faster you get the more precise it needs to be. Heavy trains damage the tracks much more than light ones. Thus it is needed to realign or grind the tracks frequently. US railroads are here to transport freight. Just look at the tracks, they are never really straight and there are gaps between the short rails rails. Just listen to all that clickety clack when a train is running over it. For low speed it is all rigth but you cannot go fast over those tracks. Continuous welded rail, concrete sleepers or even slab tracks are used to provide a very good track for high speed.Conclusion it is not wise to run high speed and heavy freight on the same tracks. Germany wanted to use its high speed lines for freight during night, but the newest lines have such gradients that freight or even old generation ICE cannot run on it. Simply because it is cheaper to have separate high speed and freight tracks than to combine them.
Multiple units are indeed the best for the tracks thus we see loco hauled trains slowly disappearing. Alstom with the TGV was the last company to produce a loco hauled high speed train. The successor AGV is also a EMU.
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Old April 11th, 2010, 11:53 AM   #9
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Quote:
Originally Posted by Suburbanist View Post
Before bashing heavy US rail cars, remember the FHA takes a different approach to all passenger rail traffic safety: it aims to make collisions survivable, hence the strong structural requirements for their rail cars.
The FRA safety regulation based on "Crash Worthiness" is economy driven and has nothing to do with any philosophy.
Think about it, to obtain global standard of "Collision Avoidance", all tracks and train-sets within US will require to install state of the art digital in-cabin signaling system with automated train stop system(ATS), something freight operators will not comply since they own the tracks and it will be they who would have to pick up the bill for such investment.
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Old April 11th, 2010, 01:10 PM   #10
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It might economy-driven (it's pretty reasonable to think so), still it is a philosophy: make crashes survivable rather than, at exponentially increasingly costs, avoid crashes. Whether it is a good approach or not I can't exactly say, because as you pointed, the US rail network is optimized for 2-mile-long bulk freight, in non-electrified tracks.
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Old April 11th, 2010, 06:28 PM   #11
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Quote:
Originally Posted by railzilla View Post

You are rigth with your notes but your axle loading are for the empty cars. Also IC2000 are only trailers where Shinkansen has all axles powered except in the driving vans. Add 2.5 tons for a fully laden car. An N700 Shinkansen has only 11.2 t axle load with full passenger capacity. It can tilt and top speed is higher than an ICN.
Do you have a few references? I've been looking for this data online and couldn't find much.

Quote:
A FLIRT might be lightweight here in Switzerland but would be considered as heavy in Japan, for commuter rolling stock the axle load is around 10 tons.
Commuter rail in Japan is narrow gauge., and almost always single level. The correct comparison would be with a company like RBS, not SBB...

Quote:
And a Stadler GTW has 20 tons axle load for the power container.
And that's on purpose, to increase traction. However i think that for estimating wear more factors are involved. In the end what matters is probable weight per seat.
Using more axles to distribute weight also has a cost...


Quote:
The increased disruption of service due to breaking rails and other infrastructure defects and increased demand for maintenance funds speak for themselves. When S-Bahn Zürich started there where not many such incidents.
I've been commuting to Zürich for a year and a half now. In that period I have only been affected by one infrastructure related incident. That was when the catenary came down in Dietikon. That wouldn't have been avoided with lighter trains.

SBB indeed needs more money. In my opinion they should increase the price of the GA and tickets on the most travelled sections. That would could raise a lot of money.
(For most of you who don't know what the GA is: It's a pass that allows unlimited travel on the entire swiss public transport network. It's extremely good value for money. I have such a pass because it is a lot cheaper than driving. It could even double in price and it would still be cheaper than driving...)
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Old April 11th, 2010, 07:34 PM   #12
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Quote:
Originally Posted by K_
Do you have a few references? I've been looking for this data online and couldn't find much.
jrtr.net is a good source in general
Many manufacturers have websites in english
Wikipedia is also a good source
Data for N700 is here: http://www.japantransport.com/seminar/JRCENTRAL.pdf and yes i know it is marketing

Quote:
Originally Posted by K_
Commuter rail in Japan is narrow gauge., and almost always single level. The correct comparison would be with a company like RBS, not SBB...
It is not really the loading gauge in Japan is similar to Europe and actually larger than in UK which uses standard gauge. Some Japanese private railways and subways also use standard gauge. More important is the use of DC traction which saves the heavy transformer, but even AC stock is lighter in Japan as 60Hz allows much smaller transformers than 16.7 Hz. And the use of shorter cars. Japanese commuter stock is only 20m long compared to Switzerlands 25 meters. If Swiss railways would use single deck 20m cars they would be in the same range like Japan. But as long as cargo trains even pass through the Bahn Tunnel and the first series of S-Bahn stock is actually a Loco hauled train maybe it just doesn't make sense to reduce axle loading. Japan switched to EMUs more than fifty years ago. And even for freight the maximum is 17 tons. Maybe they just think in longer terms. Nobody here really cares if you have to replace the track after 10,20 or 50 years.

Quote:
Originally Posted by K_
And that's on purpose, to increase traction. However i think that for estimating wear more factors are involved. In the end what matters is probable weight per seat.
Using more axles to distribute weight also has a cost...
Thats why i started this thread. It seems Japanese favor more axles over higher axle load. The also distibute propulsion to more axles and use relative weak motors. It is a trade off between vehicle maintenance and track maintenance.

Quote:
Originally Posted by K_
I've been commuting to Zürich for a year and a half now. In that period I have only been affected by one infrastructure related incident. That was when the catenary came down in Dietikon. That wouldn't have been avoided with lighter trains.
Other have been affected by more incidents which where mostly due to broken rails for example several incidents at Harbruecke.

Quote:
Originally Posted by K_
SBB indeed needs more money. In my opinion they should increase the price of the GA and tickets on the most travelled sections. That would could raise a lot of money.
(For most of you who don't know what the GA is: It's a pass that allows unlimited travel on the entire swiss public transport network. It's extremely good value for money. I have such a pass because it is a lot cheaper than driving. It could even double in price and it would still be cheaper than driving...)
I agree. Single tickets are rather expensive while yearly tickets are too cheap. Actually most passengers on the crowded Zurich Bern relation use the GA. Many students live at home and travel across Switzerland every day instead of searching a flat where the study. Same for office workers and of course civil servants which have an even lower price. At the end cheap public transit leads to the same effects like cheap car travel. But for politicians it is easier to buy more trains than double the GA price. Which as you say would still be a fair price. The tender is still not decided but SBB asked for a complicated and expensive solution.
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Old April 12th, 2010, 07:16 PM   #13
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heavier axle load allows for better freight effeciency.

Japan places much more emphasis on passanger travel.
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Old April 13th, 2010, 07:31 AM   #14
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Quote:
Originally Posted by railzilla View Post
Data for N700 is here: http://www.japantransport.com/seminar/JRCENTRAL.pdf and yes i know it is marketing
Good info, however it quotes half a ton per seat for the N700, many modern Swiss trainsets are as light. For a full 8 car train they quote 365t and 636 seats. I doubt however you could put in that many seats in an 8 car train and fit both the Swiss loading gauge and comfort standards...


Quote:
It is not really the loading gauge in Japan is similar to Europe and actually larger than in UK which uses standard gauge. Some Japanese private railways and subways also use standard gauge. More important is the use of DC traction which saves the heavy transformer, but even AC stock is lighter in Japan as 60Hz allows much smaller transformers than 16.7 Hz. And the use of shorter cars. Japanese commuter stock is only 20m long compared to Switzerlands 25 meters. If Swiss railways would use single deck 20m cars they would be in the same range like Japan. But as long as cargo trains even pass through the Bahn Tunnel and the first series of S-Bahn stock is actually a Loco hauled train maybe it just doesn't make sense to reduce axle loading.
That is the big difference: Japanese commuter railroads only transport passengers. That is why I made the comparison with the RBS. The point I'm trying to make here is that the reason for the differences between the practices of the SBB and Japanese commuter rail have more to do with the environment they each operate in than an unwillingness in Switzerland to adopt best practices from elsewhere.
When you remove the constraint of having to accomodate freight Swiss railways end up buying very light trains too. The RBS is a very efficient operation.

Quote:
Japan switched to EMUs more than fifty years ago. And even for freight the maximum is 17 tons. Maybe they just think in longer terms. Nobody here really cares if you have to replace the track after 10,20 or 50 years.
European railways are switching to EMUs en masse too. The Re460 is probably the last locomotive SBB passengers will every have bought. This switch is however not without its critics.
However there are two things that are very different in Europe:
- There is more freight on the rails, and the governements want to encourage rail to transport even more freight.
- Infrastructure is no longer the railway's main problem.
One could of course encourage the use of lighter trains by penalizing heavy axle loads more in the formulas used to calculate track charges. That makes sense, but would go against the aim of getting more freight on the rails. Lighter axle loads also mean that you need more locomotives to get your train over the Gotthard.


Quote:
Thats why i started this thread. It seems Japanese favor more axles over higher axle load. The also distibute propulsion to more axles and use relative weak motors. It is a trade off between vehicle maintenance and track maintenance.
Looking at the formula the other poster gave I get the impression that weight distribution has a big influence. It's not so much average axle load, but having the same weight on each axle. The GTW 2/6 suddenly looks a lot less attractive.

However, replacing a Re460+IC2000 consist with a trainset with the same weight per seat, but distributed power is a good idea when it comes to reducing wear. So I don't realy agree with you that SBB is "ordering SUVs".

Quote:
The tender is still not decided but SBB asked for a complicated and expensive solution.
SBB has decided they don't want the active tilt compensation immediately yet. In stead they now are talking about fitting one trainset as such, so the technology can be tested. If it proves workable it will be retrofitted to the other sets.

You never now what might happen. Switzerland might experience an economic boom so that suddenly building more new lines becomes feasible :-)
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Old April 13th, 2010, 07:34 AM   #15
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Originally Posted by alphorn2 View Post
Be careful what you wish for Here's a formula for the cost of track wear recently quoted in a Bombardier article:

k1 * sum(Qtot ^ 3) / nz
+ k2 * sum(sqrt(Qtot ^ 2 + Yqst ^ 2)^3) / nz
+ k34 * sum(f(FvV)) / mz

...which didn't really enlighten me too much. There's no way to tell which of the three components dominates. Speed's not in there, might be hidden in f(FvV).
One interesting aspect of this formula is the sum(Qtot^3) factor. This looks like axle load distribution having a big impact.
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Old April 13th, 2010, 11:12 AM   #16
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European railways are switching to EMUs en masse too. The Re460 is probably the last locomotive SBB passengers will every have bought. This switch is however not without its critics.
However there are two things that are very different in Europe:
- There is more freight on the rails, and the governements want to encourage rail to transport even more freight.
- Infrastructure is no longer the railway's main problem.
One could of course encourage the use of lighter trains by penalizing heavy axle loads more in the formulas used to calculate track charges. That makes sense, but would go against the aim of getting more freight on the rails. Lighter axle loads also mean that you need more locomotives to get your train over the Gotthard.
First freight loses money in Europe, IMHO as long as outdated screw couplings are used it wont change. If you calculate the damages the freight does to the track it gets even worse.
Second it is correct that the companies which do not own the track simply do not care about it. So they buy cheap raileaters instead of expensive sophisticated locos which are nicer to the track. Thats true for passenger as well as freight. So pricing should not only include tonnage but also some damage factor. There must be a benefit if better rolling stock is used.
Third freight needs a lower track standard than passenger.
So it would make sense to ban freight from the most traveled passenger corridors. Track prices are kilometer based but if you price a longer less direct route with a lower track standard is cheaper, the cargo companies will use it. It doesn't matter if a train with bulk takes a few minutes longer. Fast freight would have to use EMU or DMU just like passengers. See the M250 super cargo express form JR freight.
http://en.wikipedia.org/wiki/M250_series


My opinion is that at the end taxpayer has to pick up the tab anyway. But there would be ways to reduce the cost by giving the right incentives. A part of the problem is that of course the decision makers in rail are railfans and thus often like big, heavy and fast locomotives. And even it is a Lexus Hybrid a SUV is still a SUV.
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Old April 13th, 2010, 11:42 AM   #17
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First freight loses money in Europe, IMHO as long as outdated screw couplings are used it wont change.
there are quite a few pricate freight railways in Europe at the moment. I don't think they are losing money (maybe right now because of the economy, but not structurally). And I don't think the screw couplers are that much of a disadvantage. Sure, it limits the maximum tractive effort in a train, but few freight trains in Europe operate near the limit of what the coupler will handle, and that for entirely different reasons (like siding lenghts)

Quote:
... it is correct that the companies which do not own the track simply do not care about it. So they buy cheap raileaters instead of expensive sophisticated locos which are nicer to the track.
Well, there's one place in the world where the freight railways do care a lot about what their trains do to the track. That is the US, where the roads own the track, and lots of it, that carries a lot less tons/track mile than in Europe. You'd think that they would have switched to low axle loads long ago if that was the main solution to lowering track maintenance.
Remember that freight doesn't travel at high speeds. I think Japan Rail freight would be happy not having to used complicated BoBo-BoBo axle arrangments. I wouldn't be surprised that from their point of view the maximum axle load of 17t on the Japanese network is a bug, not a feature. (Notice how they build their locomotives to exactly the maximum allowed...)

Quote:
Thats true for passenger as well as freight. So pricing should not only include tonnage but also some damage factor. There must be a benefit if better rolling stock is used.
It's a lot more for passenger trains. Passenger trains travel at higher speeds. Track wear increases rapidly with speed. So it makes sense to make passenger trains lower. However there are ofcourse trade offs. More axles will mean more wear also.

Quote:
Fast freight would have to use EMU or DMU just like passengers. See the M250 super cargo express form JR freight.
http://en.wikipedia.org/wiki/M250_series
Interesting concept. Notice how they only have two such sets though. Most of JR freight's trains are pulled by locs that eat as much rail as the infrastructure owner will allow them.... 17T is not that much lighter than 20t...

Quote:
My opinion is that at the end taxpayer has to pick up the tab anyway. But there would be ways to reduce the cost by giving the right incentives. A part of the problem is that of course the decision makers in rail are railfans and thus often like big, heavy and fast locomotives. And even it is a Lexus Hybrid a SUV is still a SUV.
This is where I have to disagree strongly. At the moment there is no category of people less satisfied with the railway decision makers than the railfans. Railways keep on buying light trainsets, whereas the railfans would indeed like heave locomotives.... As I seaid elsewhere: The Re460 is the last locomotive SBB passengers bought. Come back in 20 years and you'll only see trainsets on the passengers services in Switzerland.

I'm not saying that we can't learn from the Japanese. I'm just saying that the Japanese are operating in a different environment than the Europeans, with a network build according to a different set of compromises.
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Old April 13th, 2010, 12:23 PM   #18
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there are quite a few pricate freight railways in Europe at the moment. I don't think they are losing money (maybe right now because of the economy, but not structurally). And I don't think the screw couplers are that much of a disadvantage. Sure, it limits the maximum tractive effort in a train, but few freight trains in Europe operate near the limit of what the coupler will handle, and that for entirely different reasons (like siding lenghts)
Screw coupler take twice the man power for any shunting operation, thus making car load operations ineffective. It is also more time consuming to decouple or couple screw couplers. Also it is a very dangerous job. Of course for unit trains it is not so important but as now the couplers are the limit of locomotive power. For gradients pusher or midtrain helpers are needed to not break the couplers. Again distributed power can solve the problem.

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Originally Posted by K_ View Post
Well, there's one place in the world where the freight railways do care a lot about what their trains do to the track. That is the US, where the roads own the track, and lots of it, that carries a lot less tons/track mile than in Europe. You'd think that they would have switched to low axle loads long ago if that was the main solution to lowering track maintenance.
Remember that freight doesn't travel at high speeds. I think Japan Rail freight would be happy not having to used complicated BoBo-BoBo axle arrangments. I wouldn't be surprised that from their point of view the maximum axle load of 17t on the Japanese network is a bug, not a feature. (Notice how they build their locomotives to exactly the maximum allowed...)
US roads can live with a bad track quality. If a good track is needed Amtrak has to pay for it. Again it shows that freight and passengers shouldn't mix.


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Originally Posted by K_ View Post
Interesting concept. Notice how they only have two such sets though. Most of JR freight's trains are pulled by locs that eat as much rail as the infrastructure owner will allow them.... 17T is not that much lighter than 20t...
Yes a locomotive needs to be as heavy as allowed to have maximum tractive effort. Thats why modern electrics actually have steel or concrete ballast. If a higher axle load is permitted like in Skandinavia they just add more ballast.
Thus axle load and other wear factor need to be penalized in the track fees.
Actually the axle load for most of Europe is 22.5t
17.0^3= 4913
22.5^3=11390.625
So a 22.5 ton axle load makes 2.31 more track damage than a 17t axle load.
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Old April 13th, 2010, 02:25 PM   #19
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As K has mentioned, axle-weight is not the only factor. It used to be that railway engineers only thought in terms of axle loads, but experience has shown otherwise. (A good example is the British Rail class 86 experience, link on wikipedia but can't access it here but easy to find, BR made 100 locos, then on the next 100 - class 86 - decided to hang the motors on the axles unsprung - caused massive unexpeted wear on the track)

Unsprung weight is also a significant factor, i.e. the proportion of the axle-load that has no suspension at all. There is also the stiffness of the suspension, and many other factors.

Depending on suspension, at any given speed one train can produce less wear on the track even though it has a higher axle load than another train, but at different speeds the advantage is reversed. It is extremely complicated.

Basically high frequency vibrations (or high impact undamped pulses, to use describe it from the other side of the coin) damage metal locally more than low frequency vibrations, even if the lower frequency vibration contain more energy. However, suspensions do not behave in a linear fashion, and become stiffer or looser depending on speed and the tuning of the dampers (the Virgin class 390 pendolinos have been re-tuned sinceit was decided they wouyld only go 125mph, as it was found tuning for 140mph provided too stiff a ride at the operational max of 125mph)

Imagine how long it would take to damage the track if you went at it with a hammer, which has an equivalent axle weight of 0.0007 tons

But with rubber aeroplane tires the same track would be fine to probably over 100 tons per axle, not that the sleepers and ballast would though.
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Old April 13th, 2010, 03:35 PM   #20
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The Re 6/6 loco is BoBoBo because the Ae6/6 CoCo was a rail killer, but this is only a issue on curved track. Also steering Bogies and the like are especially useful in curves. The issue with unsprung mass makes sense and i guess this is where speed comes into the equation as the forces would increase with speed. Wheel slip and spin also contribute to wear. I just wanted a relative simple formula to understand how it is working, even it is only for straight track .

A heavy, slow moving with appropriate suspension might be easier to the track than a fast moving lighter train.

Continuous welded rails would prevent hammering so it lasts longer than conventional track.


So at the end the only way would be to test different bogies at different speed and loading. Then make a table of the damage coefficient. This way a pricing system could be established to reduce track wear.

The worst is the track even detoriates with the time even it is not used at all.

Last edited by railzilla; April 13th, 2010 at 03:43 PM. Reason: typo
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