Practicality of Rubber Tyres

[Up_Tilt_390]

Rubber-tyred trains are present throughout the world on several metro systems, such as Mexico City, Lusanne, and most famously the Paris Metro. I don't think they've ever been used on a national railway network, and in fact I would be surprised if they were given the higher speeds and greater distances, but true to the nature of the forums someone will correct me if I am wrong. In this thread though I want to talk about the practicality of them. Are they worth the time, money and maintenance and for their advantages and disadvantages?

Compared to steel wheels, some advantages are:

• Smoother rides, likely because of the rubber handling vibration better than steel.
• Faster acceleration and higher speed as well as greater handling of steep gradients.
• Shorter braking distances, allowing trains to be signalled closer together than normal.
• Quieter rides for both people inside and outside the train, particularly in open air.
• Greatly reduced wear and tear on the rails, thus reducing maintenance costs.

However, some disadvantages are:

• Higher energy consumption, which would likely cost more in energy supply.
• Possibility of tyre blow-outs, which obviously doesn't happen with steel wheels.
• Hotter operation, though I'm not quite sure what this means if I'm honest.
• Weather variance effects when above ground, such as loss of traction in snow and ice.
• Same expense of steel rails for switching purposes, and to provide electricity or grounding.
• Tyres would need to be replaced more often, unlike steel wheels which are replaced less.
• Tyres break down when in use and turn into potentially hazardous and pollutant dust.

(Information was obtained and reworded from the Wikipedia article of 'Rubber-tyred metro' in the 'Technology' section of the article)

During my engineering course, I did a few evaluations in my time, and in this case I'd say that rubber tryes are helpful for high-capacity metros which wish to run frequent trains, or elevated metros that wish to reduce noise and vibration to everybody around them. Though in the case of the former, the London Underground does well without rubber tyres, so perhaps it's a hit and miss.

But aside from that, the maintenance cost that was reduced in regards to wear and tear on the rails is only replaced with the need to bring in more tyres and replace them more often, which costs money in itself, along with the potentially hazard and pollutant particulate matter as well as higher energy consumption and the need to build more steel rails for switching purposes.

For what you get, it doesn't sound much like a bargain, and in fact new modern metros such as the Dubai Metro opted for steel wheels instead of rubber, which to me says a lot about their efficiency. So in my evaluation, I think rubber-tyred aren't as practical as steel-wheeled metros, but I want to know what you all think. It doesn't have to be a long case study like mine seemed to be, so do not worry. Thanks in advance, and I welcome any new information and opinions.

 

[Bletchleyite]

A hybrid wheel having a rubber layer between the metal tyre and metal wheel has been used in places (not sure about the UK[1]), but one of those delaminating caused the Eschede ICE crash and they have fallen out of favour since as a result.

Lausanne has "proper" rubber tyres due to the severe gradients, it would otherwise have to be a rack railway or a funicular (indeed part of it used to be the latter). It's more like an oversized airport people mover really. And I'm not sure why they are so popular on said airport systems - some have steep gradients but most don't.

As to Paris, the influence of Messrs Michelin probably play a big part rather than it being a good technology for that application.

[1] *Possibly* APT?

 

[Billy A]

In answer to the question....the increased heat comes from the high rolling resistance of rubber as compared to steel tyres. As the tyre flexes the energy involved has to go somewhere and so it's released as heat which I'm told then impacts on temperatures in the train. In addition of course the increased rolling resistance means that electricity consumption by the train is higher. Having converted to and built some lines as rubber tyred I think the RATP, operators of the Paris Métro have decided not to convert any more although I'm unsure about new builds (four new lines are being built).

 

[Clansman]

In terms of the Paris Metro, it seems that the rubber tyres are great for the extremely ridiculous tight curves which exist on the network in terms of track wear, speed, and the ride quality. Couldn't envisage them being of any benefit over here though.

 

[physics34]

seeing as the ride quality doesnt seem to be a concern anymore or the general comfort of passengers, im not sure why theyd ever be used here.

 

[AndrewE]

Rubber-tyred trains are present throughout the world on several metro systems, such as Mexico City, Lusanne, and most famously the Paris Metro. I don't think they've ever been used on a national railway network, and in fact I would be surprised if they were given the higher speeds and greater distances, but true to the nature of the forums someone will correct me if I am wrong. In this thread though I want to talk about the practicality of them. Are they worth the time, money and maintenance and for their advantages and disadvantages?...

They have been tried:
Discussed here:https://www.ianvisits.co.uk/blog/20...ved-experiment-with-rubber-tires-on-railways/

...The special pneumatic tyres, fitted with metal flanges in order to keep the coach on the rails, had a wooden hoop inside them so if they punctured, they only deflated slightly to prevent derailment. ... There were other attempts — the Coventry Pneumatic Rail-Car, built by a Coventry car manufacturer for example. Which did have the advantage of looking exceptionally sleek as well.

Despite all the claims at the time of long life for the tires, they did wear out quickly, and also where a train carriage of the time needed just four wheels, a comparable carriage fitted with pneumatic tyres could need as many as 20 wheels.

The extra cost of building the carriage, and the ongoing maintenance meaning the concept was doomed. It was the wrong sort of wheel on the tracks...

and here http://mikes.railhistory.railfan.net/r146.html too

 

[edwin_m]

In terms of the Paris Metro, it seems that the rubber tyres are great for the extremely ridiculous tight curves which exist on the network in terms of track wear, speed, and the ride quality. Couldn't envisage them being of any benefit over here though.

Interesting point as the "coned" profile of steel wheels them to traverse modest curves without slipping. On tighter curves one wheel effectively slips, which is possible because of the moderate coefficient of friction. Rubber tyres have a higher coefficient of friction and the wheel-rail interface is effectively horizontal.

Do rubber-tyre metros have differentials to counter the effect of one wheel having to go faster than the other on curves?

 

[Bletchleyite]

I would expect there will be a diff, yes. It's not like that feature is rare on road vehicles or difficult to come by!

 

[AndrewE]

Good deduction. This page http://www.emdx.org/rail/metro/principeE.html says

"Notice the two axles with differential gears and their traction motors.

 

[WatcherZero]

I'll let you in on a secret, the reason there's rubber tired rail vehicles in France is because Michelin successfully lobbied local and national government that freight moving from roads to rails post WW2 would put the tire industry at risk.

 

[hooverboy]

I didn't say developers, but house building interests. Which the local authorities certainly are!

In terms of the Paris Metro, it seems that the rubber tyres are great for the extremely ridiculous tight curves which exist on the network in terms of track wear, speed, and the ride quality. Couldn't envisage them being of any benefit over here though.

really?
see the island line thread. might work...it is a bit on the bouncy side!not sure about impact of saltwater corrosion though, but should be cheaper that planing down wheel flats.

 

[FenMan]

Older readers may remember this wonderfully entertaining piece by John Redwood MP. It's from 2002. Yes, he was pro-rubber tyres for trains because reduced braking distances would mean more trains could run at peak hours.

http://www.independent.co.uk/voices...-taking-a-more-rational-approach-5362620.html

His arguments amply demonstrated that "a little knowledge is a dangerous thing" and I recall the piece attracting plenty of ridicule!

 

[edwin_m]

Good deduction. This page http://www.emdx.org/rail/metro/principeE.html says

Interesting link and the pictures there show one of the problems with the Paris rubber tyre system. As well as a full set of steel wheel running gear (only used at junctions and if there is a flat tyre) the bogies not one but two extra sets of wheels (as well as differentials, thanks for pointing out). The weight penalty must be fairly significant.

Smaller-scale systems such as the VAL and airport peoplemovers don't have this level of duplication (though I guess they must still have differentials) and rubber tyres make more sense in these applications. I don't know what happens with a tyre burst on these systems but the vehicle is contained within a concrete channel so is unlikely to "derail" outside it.

 

[AndrewE]

Interesting link and the pictures there show one of the problems with the Paris rubber tyre system. As well as a full set of steel wheel running gear (only used at junctions and if there is a flat tyre) the bogies [have] not one but two extra sets of wheels (as well as differentials, thanks for pointing out). The weight penalty must be fairly significant.

I would have thought that if rubber tyres were worth using then modern engineering could easily arrange independently-motored wheels running on either stub axles (like the Talgo) or turning on fixed axles, so removing the need for a diff.

 

[Western Lord]

Enthusiasts for rubber tyres should be aware that they are a significant contributor to urban pollution.

 

[AndrewE]

I don't think there are any enthusiasts here, we are considering the merits and demerits in answer to the original question "about the practicality of them. Are they worth the time, money and maintenance and for their advantages and disadvantages?"
I can see that there might be situations (like a roller coaster metro squeezed in and around an existing city) where their adhesion makes them the only viable option on the gradients needed. Equally I would have thought that the smooth polished concrete running surfaces I think I remember seeing in Paris would be a problem on gradients outdoors in drizzle or sleet. It's possible that they would be no worse than steel on steel in that situation, but I thought rubbber was selected to get up gradients that a conventional railway can't manage anyway.

 

[coppercapped]

I don't think there are any enthusiasts here, we are considering the merits and demerits in answer to the original question "about the practicality of them. Are they worth the time, money and maintenance and for their advantages and disadvantages?"
I can see that there might be situations (like a roller coaster metro squeezed in and around an existing city) where their adhesion makes them the only viable option on the gradients needed. Equally I would have thought that the smooth polished concrete running surfaces I think I remember seeing in Paris would be a problem on gradients outdoors in drizzle or sleet. It's possible that they would be no worse than steel on steel in that situation, but I thought rubbber was selected to get up gradients that a conventional railway can't manage anyway.

There was a lot of coverage in enthusiasts press (which consisted of Trains Illustrated and the Railway Magazine!) in the 1950s about the rubber tyred metros. As I recall one of the arguments for its selection was that Metro Line 1 in Paris is very close to the surface and rubber tyres were selected to reduce vibrations to the neighbouring buildings.
And, of course, Michelin was an important lobbyist...
In practice only a couple of other lines were converted and the idea was only sold to places where France had an influence - hence Montreal in Quebec.
It's limitations were:

• higher rolling resistance of the rubber tyres, the heat released warmed up the tunnels
• limited weight carrying capacity of rubber tyres compared to steel wheels so the stock was made narrow to limit the loads carried
• very heavy and complex bogies

so no other country used the idea except for special purposes.

 

[jamesontheroad]

Glad that Montréal has been mentioned, because it is a notable use of rubber tyres in North America. In fact, in the last year they've introduced the first new trains to the system in about years, the MPM-10 (aka "Azure") built by a consortium of Alstom and Bombardier.

The advantages and disadvantages have been discussed already, but the characteristics of the Montréal Métro are closely bound up with the use of tyres. Compared to other systems, it is relatively quiet, with no screeching of steel wheels on steel rails. The ride is bouncy, but not noticeably so. By specifying rubber tyres from the outset, the construction of the whole system was able to take advantage of a number of energy-saving and cost-saving features. For much of the network, stations are cut-and-cover and built near the surface (saving construction costs and passenger entry/exit time). Between stations, the bored tunnels (generally) drop down to a deeper depth before rising up to the next station. This allows departing trains to save energy by using gravity to pick up speed and save energy that would be wasted by braking be slowing on the incline to the next station.

I recall that at the time of construction, these gradients between stations would have prevented the subsequent conversion to steel rails. While technology has moved on, and the steel wheels/rails could work, the impracticality of closing the system for a lengthy conversion and the decision to order the MPM-10 has committed Montréal to at least another 40 or 50 years running on rubber.

 

[edwin_m]

The practice of grading the line up on the approach to the station and down again on departure is well known and certainly not confined to rubber tyre metros. In London it's perhaps most obvious on the Central Line but I believe even Crossrail does it - though perhaps not at all stations as there may be constraints such as other tunnels above or below that make it impossible. It may be that the gradient selected in Montreal is optimised for rubber tyre and too steep for a steel wheel system.

 

[twpsaesneg]

A hybrid wheel having a rubber layer between the metal tyre and metal wheel has been used in places (not sure about the UK[1]), but one of those delaminating caused the Eschede ICE crash and they have fallen out of favour since as a result.

Lausanne has "proper" rubber tyres due to the severe gradients, it would otherwise have to be a rack railway or a funicular (indeed part of it used to be the latter). It's more like an oversized airport people mover really. And I'm not sure why they are so popular on said airport systems - some have steep gradients but most don't.

As to Paris, the influence of Messrs Michelin probably play a big part rather than it being a good technology for that application.

[1] *Possibly* APT?

Class 86's had SAB resilient wheels fitted to some if not all in the '80s. Think this was mainly a reaction to the rough riding characteristics of the original suspension system and the 100mph running requirement for passenger services. I'm not sure if they made it into the later classes of AC traction.

 

[furnessvale]

Class 86's had SAB resilient wheels fitted to some if not all in the '80s. Think this was mainly a reaction to the rough riding characteristics of the original suspension system and the 100mph running requirement for passenger services. I'm not sure if they made it into the later classes of AC traction.

They were certainly rough on the track.

I remember installing new crossing noses at Euxton Jcn one weekend, and going back the weekend after to build up the battered noses with weld!

 

[Taunton]

Smoother rides, likely because of the rubber handling vibration better than steel.

I take it you haven't ridden in Paris. The "pneus" bang, thump and jolt their way along. Lateral positioning on the flat running beams is provided by further horizontally-mounted rubber wheels sprung against the conductor rails. These have their own version of 'hunting', particularly as power goes on or off.

Faster acceleration and higher speed as well as greater handling of steep gradients

Steel wheels have always been able to handle this, look at tramways for gradients. Performance is almost wholly determined by installed power rather than coefficient of friction. The thing about the Paris pneus is they were replacing the classic old metro stock, with 50-year old technology. The limits nowadays are generally what the passengers inside can handle, especially with the move to mostly standing passengers on urban systems.

Shorter braking distances, allowing trains to be signalled closer together than normal

A function of the signalling system, the key determinant is not braking performance but Platform Reoccupation Time. Look at the DLR, which can have trains stopped right behind, like buses.

Quieter rides for both people inside and outside the train, particularly in open air.

Not noticeable inside, where motor noise dominates both, and outside on open sections, such as on Paris Line 6, tyre swish seems to carry just as much. The one thing you do not get is the penetrating noise hammer from a steel wheel car running with small flats.

Higher energy consumption, which would likely cost more in energy supply.

Apparently considerable.

Weather variance effects when above ground, such as loss of traction in snow and ice.

Paris was concerned about this on the first open air sections on Line 6, but apparently not a problem in the end.

Same expense of steel rails for switching purposes, and to provide electricity or grounding

The reason why the rails inside the running beams in Paris are notably shiny is because the trains have to carry skids which run along the rails, both for return current and for track circuiting. It was also the basic spec of the system that conventional trains could continue to run. This is well worthwhile during the conversion, which is extremely costly and extensive; the Line 6 conversion in Paris in the 1970s took over 3 years, service continuing throughout. That was the last line Paris converted, because conventional technology had caught up.

Tyres break down when in use and turn into potentially hazardous and pollutant dust.

The whole of the Paris pneu system smells like a tyre depot. This has to come from somewhere.

 

[Taunton]

Class 86's had SAB resilient wheels fitted to some if not all in the '80s.

One of the first applications of resilient wheels was in the USA, with the first of the PCC tramcars, which became a US standard in the 1940s, and then spread elsewhere. They certainly contribute to a far better and quieter ride. They have a rubber ring inserted between the wheel centre and the (steel) tyre. Manufacturing this must be interesting.

 

[Up_Tilt_390]

I take it you haven't ridden in Paris. The "pneus" bang, thump and jolt their way along. Lateral positioning on the flat running beams is provided by further horizontally-mounted rubber wheels sprung against the conductor rails. These have their own version of 'hunting', particularly as power goes on or off.

Steel wheels have always been able to handle this, look at tramways for gradients. Performance is almost wholly determined by installed power rather than coefficient of friction. The thing about the Paris pneus is they were replacing the classic old metro stock, with 50-year old technology. The limits nowadays are generally what the passengers inside can handle, especially with the move to mostly standing passengers on urban systems.

A function of the signalling system, the key determinant is not braking performance but Platform Reoccupation Time. Look at the DLR, which can have trains stopped right behind, like buses.

Not noticeable inside, where motor noise dominates both, and outside on open sections, such as on Paris Line 6, tyre swish seems to carry just as much. The one thing you do not get is the penetrating noise hammer from a steel wheel car running with small flats.

Apparently considerable.

Paris was concerned about this on the first open air sections on Line 6, but apparently not a problem in the end.

The reason why the rails inside the running beams in Paris are notably shiny is because the trains have to carry skids which run along the rails, both for return current and for track circuiting. It was also the basic spec of the system that conventional trains could continue to run. This is well worthwhile during the conversion, which is extremely costly and extensive; the Line 6 conversion in Paris in the 1970s took over 3 years, service continuing throughout. That was the last line Paris converted, because conventional technology had caught up.

The whole of the Paris pneu system smells like a tyre depot. This has to come from somewhere.

I actually have been on the Paris Metro, though this was seven years ago, so my knowledge is limited. I did think that the advantage of closer trains were more down to signalling, and in fact the tube a year before I went to Paris was just as, if not more frequent.

 

[edwin_m]

Steel wheels have always been able to handle this, look at tramways for gradients. Performance is almost wholly determined by installed power rather than coefficient of friction. The thing about the Paris pneus is they were replacing the classic old metro stock, with 50-year old technology. The limits nowadays are generally what the passengers inside can handle, especially with the move to mostly standing passengers on urban systems.

The coefficient of friction does have an influence, particularly in low-speed acceleration/braking and hill climbing (the maximum gradient is related to the coefficient of friction and the proportion of axles motored). Rubber tyre systems can get to about 15% gradient but for steel wheel the maximum is about 10% and for most vehicle types much less. However I do agree that these sorts of gradients and accelerations are at the limit of what is acceptable for comfort (the Paris Metro cars contain notices warning about severe braking).

A function of the signalling system, the key determinant is not braking performance but Platform Reoccupation Time. Look at the DLR, which can have trains stopped right behind, like buses.

Platform reoccupation time includes how long it takes to accelerate the first train out of the platform and brake the second one in. Also, with a fixed block signalling system with a train stop, the distance a following train can approach depends on the braking rate. So a train with better acceleration and braking will have a better platform reoccupation time. But capacity also depends on dwell time and other factors such as train length, so acceleration/deceleration doesn't have a huge effect.

 

[Mikey C]

For what you get, it doesn't sound much like a bargain, and in fact new modern metros such as the Dubai Metro opted for steel wheels instead of rubber, which to me says a lot about their efficiency. So in my evaluation, I think rubber-tyred aren't as practical as steel-wheeled metros, but I want to know what you all think. It doesn't have to be a long case study like mine seemed to be, so do not worry. Thanks in advance, and I welcome any new information and opinions.

Much of the Dubai metro runs on the surface (on viaducts), I imagine the temperature in summer must be fearsome, which might affect the tyre efficiency?

 

[edwin_m]

Much of the Dubai metro runs on the surface (on viaducts), I imagine the temperature in summer must be fearsome, which might affect the tyre efficiency?

Doesn't seem to bother the 12-lane highway alongside it, or the world's largest airport nearby. Tyres need to withstand the heat they generate internally (due to their high rolling resistance) so probably aren't that sensitive to ambient temperature.

 

[AndrewE]

Doesn't seem to bother the 12-lane highway alongside it, or the world's largest airport nearby. Tyres need to withstand the heat they generate internally (due to their high rolling resistance) so probably aren't that sensitive to ambient temperature.

Plane tyres have an extreme loading on landing then not much stress afterwards (and I bet they are subject to much more demanding specification than road vehicle tyres anyway) and road traffic - cars - don't put much of a load on their tyres (in contrast to the 8 wheeled bogies needed to carry a single lightweight passenger railcar.)

 

[edwin_m]

I believe the tyres used on rubber-tyre trains are actually aircraft tyres or a variation thereon.

 

[Shimbleshanks]

There have been some attempts to use rubber tyres on monorail systems too, notably the Brockhouse Uniline system that was tested in the 1950s. This used what amounted to a rubber-tyred diesel shunter running on a concrete track with a steel guide rail in the middle. The idea was to allow railway-like systems to be built quickly in developing countries without the need for expebnsive earthworks. As far as I know, the idea never progressed beyond the prototype stage. https://www.britishpathe.com/video/road-rail-line
There was also a strange Russian experiment which involved putting rubber-tyred road wheels under a mainline diesel loco. I'm not sure that they were thinking of: https://fotki.yandex.ru/next/users/masterokst/album/333797/view/783989