Why Not Rubber?

[BigBoyFan4006]

I know I'm probably missing some obvious reason as usual, but why have railroads not used rubber to help increase the grip for the wheels on a locomotive? I've seen it used for model trains, but never heard it being used by full scale trains. I know, there's a BIG difference between the two. But still, why?

 

[bendorsey]

Considering the weight on the drivers it wouldn't last a microsecond under power. Peel it off like a banana, lol.

Ben

 

[Dinorius_Redundicus]

I'm certainly no expert, but guess it's because rubber would not be stiff enough to keep the train stable against sideways forces (as when it goes around a bend or through some tricky points at speed). Also, it would wear down quite quickly given the huge loads.

Having said that, I have seen rubber tires on trains in both the Paris and Santiago (Chile) metro systems. Maybe these are special cases. In any case, rubber tires on trains are not unknown.

.

 

[deneban]

Steam locos, being of variable horsepower and constant torque, could have used them because that high torque at start caused slippage. But there was no elastomer technology that would work in that era. Diesels are constant horsepower and variable torque, so the wheels do not slip regularly because of the torque control they have (just like cars). For the limited time diesels do need to increase friction, sand is a lot cheaper to use than adding a new high maintenance item which is under wear all the time needed a small fraction of the time. Also as the name implies, elastomers are elastic and would stretch when torque is applied, causing all kinds of problems as you can imagine.

You mean you don't use sand on your model railroad?

 

[cascaderailroad]

Anyone who has HO trains knows that rubber traction tires: CSX (they reduce electrical contact, spread grease & grime, accumulate dust, and generally gum up the works).
Even hard rubber (like on solid tire bicycles) would pit, and get flat spots, inside of no time, and a 200 ton loco would squeesh the rubber tires.

 

[mezzoprezzo]

~snip~ .. rubber tires on trains are not unknown.

They are used in UK for light passenger loads, e.g. the Shuttle train which links Gatwick Airport's two passenger terminals.

No wheels on rails though. No driver either!

http://www.bbc.co.uk/news/10473241

 

[teddytoot]

And don't forget the 1930s Michelin railcars. Although not a complete failure they were not found really suitable for the railway environment.

 

[Pendolino]

In the 1930s, several experimental rail vehicles with rubber wheels were built, mostly by Michelin in France:

Very few of them still run in exotic places (Madagascar) as tourist trains:

I also found an experimental Budd Railcar built in 1932 and tested by PRR and Reading:

All the above vehicles ran on normal railway tracks, and all of them were plagued by excessive wear of the rubber wheels. If this happened with very light vehicles, you can only imagine what can happen with a heavier freight locomotive.

Another kind of rubber wheel railway vehicles used a special concrete+rail right-of-way. Here is an example, which ran in my home town from the 1930s to the late 1960s, climbing gradients up to 12%:

The concept is still used by the French VAL automated subway: this is a picture of the Turin subway. I tried it and it has impressive acceleration rates .

 

[Bill69]

Actually, the Paris metro uses rubber pneumatic tires as used on trucks but with no tread.

http://en.wikipedia.org/wiki/Rubber-tyred_metro

Bill69

 

[SharkNose]

Re: the Budd railcar that Pendolino mentioned: It was involved in some near-misses at railroad crossings because due to the rubber tires, the metal of the car was not in contact with the rails enough to set off the crossing mechanisms. Same with block signals. They tried to fix this by adding wire brushes to the car that would stay in contact with the rails.

 

[deneban]

The topic was really the use of rubber to assist steel wheels for traction, not rubber wheels

 

[mezzoprezzo]

Rubber tracks could be interesting!

 

[kws4000]

FWIW the German ICE had rubber in the wheels themselves before a wreck eliminated them. You have a steel tire, and a steel hub, with a rubber liner between the two. Supposedly improved ride quality. But at some point, the tire broke, straightened itself, nearly impaled a passenger. He ran to get the conductor, and started the train to slow down but it was too late; it accordianed into a bridge.

 

[Pendolino]

The topic was really the use of rubber to assist steel wheels for traction, not rubber wheels

All of the above vehicles (with the possible exception of VAL light subway) have steel wheels (rubber flanges wouldn't work too well on turnouts ). Tires were used to increase adhesion, exactly as in scale models.

This document provides a clear view of the arrangement used in the Budd railcars (page 1, figure 4):

http://www.prototrains.com/patents/2129235.pdf

 

[cascaderailroad]

In short ... Don't expect to see it on heavy freight trains or high speed trains in your lifetime (unless it is in Japan, China, Disneyworld, or on light rail vehicles).

 

[deneban]

All of the above vehicles (with the possible exception of VAL light subway) have steel wheels (rubber flanges wouldn't work too well on turnouts ). Tires were used to increase adhesion, exactly as in scale models.

This document provides a clear view of the arrangement used in the Budd railcars (page 1, figure 4):

http://www.prototrains.com/patents/2129235.pdf

Good point, Ok let me rephrase more precisely:

The topic was really the use of rubber to assist steel wheels for traction only, and not the use of rubber on steel to afford wheel elasticity, compression, noise reduction, or pressure distribution.

 

[cascaderailroad]

Manganese steel wheels, on manganese steel rails and frogs, gets stronger, and stronger, with wear and tear (until they eventually wear out) ... I don't see too many 35,000 ton freights stalling, and slipping their wheels, with 3 locomotives, each weighing 200 tons, pressing down on the rail for tractive effort (unless there happens to be a locomotive malfunction en-route).

Rubber is about as good as Flubber :hehe:

 

[BigBoyFan4006]

Even hard rubber (like on solid tire bicycles) would pit, and get flat spots, inside of no time, and a 200 ton loco would squeesh the rubber tires.

That's true. But IF you COULD make the rubber hard and strong enough to withstand the weight and excessive wear, yet left it soft enough to make it a little bit "squeeshy", wouldn't it increase traction by increasing the amount of contact between the wheel and the rail? Just a thought.

 

[BigBoyFan4006]

Good point, Ok let me rephrase more precisely:

The topic was really the use of rubber to assist steel wheels for traction only, and not the use of rubber on steel to afford wheel elasticity, compression, noise reduction, or pressure distribution.

Precisely! Thanks for trying to make my question more clear.

 

[kws4000]

A

That's true. But IF you COULD make the rubber hard and strong enough to withstand the weight and excessive wear, yet left it soft enough to make it a little bit "squeeshy", wouldn't it increase traction by increasing the amount of contact between the wheel and the rail? Just a thought.

The only thing we're looking at modifying here is the coefficient of friction between the wheel and rail. Steel on steel is about .16-.80 by Wikipedia, but rubber and concrete is listed .3-1.0 .
According to here, http://hypertextbook.com/facts/2005/steel.shtml rubber on steel is about .7 . (EDIT: coeffriction is NOT dependent on area of contact, but IS on materials involved) But what you are proposing, a thermoset polymer with sufficient strength to support a locomotive, is NOT rubber, and therefore would have a different coef-friction, thereby changing the argument. Most polymers that would even come close in supporting the load, simply cannot stand up to the wear and abuse, not to mention require completely different brake and truck and wheel designs.

Why? Due to poor strength, they need larger contact areas. Which leads to bigger wheels and wider rails, which also lead to new bogie designs. Due to their low melting temperature and propensity to char at high temps, standard clasp brakes do not work and disc brakes need to be worked up. Where to put them becomes a problem due to limited space needed for the traction motor, and outboard mounting is precluded by large bearings/thick frames and the loading guage.

If there was a way to make a polymer with high friction, high strength, high wear reisistance, and high melting temp, it would have been done a long time ago. But then again, get a degree in chemical engineering and material sciences, and prove us wrong.

FWIW, Matthias Baldwin made bronze tires for a few of his first locos due to their higher friction on the iron rails of the day. But they wore too rapidly, and were replaced by tires cast in a chilled steel mold. This made the edge harder and stronger by conducting the heat away more rapidly, producing a better product than by sand-mold casting.