Railway Gauge

[denmarks]

Are the flanges of railway wheels exactly 4 feet 8.5 inches apart to match the rails or is there some leeway? Why don't the wheels constantly squeak?
What is the maximum width of an Amtrak car? I read that the maximum width for a railroad car is 10 feet 6 inches but they can be up to 11 feet wide with no problems. It always intrigues me as we pass a freight train.

 

[Qapla]

Ever use a 2x4 to build something? They are not all 2 inches by 4 inches ... that is the "nominal" dimension.

Taking heat, cold, weight and movement into consideration, I would imaging that the 4'8.5" dimension of "standard gauge" rail is also nominal - since it will change as the temperature, weight and friction of day-to-day operation has it's inevitable effects on it ... there would have to be some sort of built-in allowances for such fluctuations.

 

[zephyr17]

Are the flanges of railway wheels exactly 4 feet 8.5 inches apart to match the rails or is there some leeway? Why don't the wheels constantly squeak?
What is the maximum width of an Amtrak car? I read that the maximum width for a railroad car is 10 feet 6 inches but they can be up to 11 feet wide with no problems. It always intrigues me as we pass a freight train.

Wheel treads are a conical section. Around a curve one side rides up the tread's cone, the other down. In a ideal world, the flange should never touch the rail, although in practice they do on tight curves causing flange squeal. Flanges are slightly less than track gauge.

The point of contact with the rail is actually a very small part of the wheel tread (and a small part of the rail surface, too. Rails aren't flat, either).

 

[TinCan782]

Google train wheel profile, or something similar to read about what is going on.
Wikipedia has this short entry ... Train wheel - Wikipedia

 

[TinCan782]

Without needing special approval, UP states: Lading must not exceed maximum width of 10 feet 6 inches
https://www.uprr.com/aboutup/maps/graphics/grossweight_limits.pdf

 

[zephyr17]

AAR Clearance Plate F, which is the most common on Western US railroads, is a maximum loading gauge of 10' 8" wide from 3'4" above the railhead to 16' above the railhead including handrails. It narrows at the top and bottom, 7'4" wide at 2.5" above the railhead and 8'10" at 16'6" above the railhead.

Now you know why the Superliner Roomette upper "coffin" curves in on the side.

 

[zephyr17]

Also, if the flanges were designed to be in contact with with the inner side of the rail it would increase friction, rail wear, wheel wear and the energy required to move the train tremendously, negating one of the biggest efficiencies steel wheel on steel rail has.

 

[mcropod]

Also, if the flanges were designed to be in contact with with the inner side of the rail it would increase friction, rail wear, wheel wear and the energy required to move the train tremendously, negating one of the biggest efficiencies steel wheel on steel rail has.

As sadly in evidence in a key piece of railway infrastructure for all regional trains on my line just before their arrival in the CBD terminal station. In order to speed their arrival and increase traffic on the affected regional lines, where previously trains had to cross a large number of tracks used by suburban traffic, designers came up with a flyover arrangement. But because of the small space they had to work in and likely also the need to get it done quickly, it required two very tight radius turns to be used.

Within a short time they had to work out how to reduce the severe friction which was damaging wheels as well as the track. A combination of very slow speeds and constant manual rail greasing was used, then later the track was replaced and the turns made slightly wider at huge cost and service disruption. I suspect the whole flyover will later be re-engineered.

https://www.theage.com.au/national/...-be-torn-up-this-weekend-20160212-gmsude.html

 

[Devil's Advocate]

Wheel treads are a conical section. Around a curve one side rides up the tread's cone, the other down. In a ideal world, the flange should never touch the rail, although in practice they do on tight curves causing flange squeal. Flanges are slightly less than track gauge. The point of contact with the rail is actually a very small part of the wheel tread (and a small part of the rail surface, too. Rails aren't flat, either).

This video helps show how conical wheels work, why they're used, and why flange contact is best avoided.

 

[fdaley]

I recall reading that when the original Erie Railroad route was built across the Southern Tier of New York in the 1840s, the track had a 6-foot gauge. Apparently in those early days no one understood the interchange potential of railroads, and the builders -- and the state of New York, which was backing the effort -- didn't want anyone else using their railroad. I have often wondered if any of the rolling stock from that 6-foot-gauge railroad was preserved. Imagine the capacious sleeper rooms you could have had. Of course, I think at that stage they were still having everyone get off the train somewhere en route to eat and sleep.

 

[PeeweeTM]

Just a picture in our shop of a wheel on a straight rail.
Gives you an idea about the clearance between the parts...

 

[willem]

AAR Clearance Plate F, which is the most common on Western US railroads, is a maximum loading gauge of 10' 8" wide from 3'4" above the railhead to 16" above the railhead including handrails.

Should that be 16 feet above the railhead rather than 16 inches? If not, I don't understand.

 

[jis]

I recall reading that when the original Erie Railroad route was built across the Southern Tier of New York in the 1840s, the track had a 6-foot gauge. Apparently in those early days no one understood the interchange potential of railroads, and the builders -- and the state of New York, which was backing the effort -- didn't want anyone else using their railroad. I have often wondered if any of the rolling stock from that 6-foot-gauge railroad was preserved. Imagine the capacious sleeper rooms you could have had. Of course, I think at that stage they were still having everyone get off the train somewhere en route to eat and sleep.

Whether the cars were capacious or not would depend on what their loading gauge was. Just a wider track gauge does not imply wider loading gauge.

For example Indian Railways mostly uses UIC loading gauge on their Broad Gauge tracks, exceptions being the suburban EMUs which are much wider, and the more recent double stacks on select routes which are almost ridiculously tall, much taller than the US double stacks because they put the containers on more or less standard height flat cars and not on well cars like in the US.

Conversely British loading gauge is much smaller than AAR loading gauge, while both run on standard gauge tracks. There are a few routes in the UK cleared for the Continental UIC loading gauge, but none for any AAR loading gauge AFAIK.

 

[west point]

There are limitations for wider gauge train cars and locos. The wider gauge especially comes up for each wheel loadings. For the same length of cars the loading becomes enough that 3 axel trucks are necessary. However the dynamics of of 3 axel are not well understood for HrSR much less HSR.

A bigger problem for bulk freight would be need for much shorter cars. That then effects bridge loadings. Longer span bridges would need much higher Cooper ratings. There are a few bridges that are built for short ore cars but if wider cars carry the same 253k loads then car trucks would be even closer than present cars . Again bridge loadings get all messed up

 

[jis]

There are limitations for wider gauge train cars and locos. The wider gauge especially comes up for each wheel loadings. For the same length of cars the loading becomes enough that 3 axel trucks are necessary. However the dynamics of of 3 axel are not well understood for HrSR much less HSR.

A bigger problem for bulk freight would be need for much shorter cars. That then effects bridge loadings. Longer span bridges would need much higher Cooper ratings. There are a few bridges that are built for short ore cars but if wider cars carry the same 253k loads then car trucks would be even closer than present cars . Again bridge loadings get all messed up

Just because a car is wider does not imply that axle loads will be significantly higher necessarily. It depends on what is being carried in the wider cars. For example axle loading is a complete non-issue in standard length but 12' wide suburban EMUs in India (on 5'6" broad gauge track, normal Indian trains are more or less UIC loading gauge), since the additional 100 or so standing passengers added to each car does not cause the axle load to go past the standard axle loads used for cars in India. Similarly for the wider than normal UIC or AAR loading gauge widths used for the Japanese Shinkansen.

As it turns out though it is uncommon for wider tracks gauge to imply significantly wider loading gauge, for various reasons, so in general it tends to be not as much of an issue.

 

[George Harris]

As JIS said for much of this. There is complete confusion on many people's part concerning the relationship between track gauge and loading gauge, and axle load limits. Over a fairly wide range there is none. As JIS said, the Indian railroads on lines having clearances built for double stacks allows higher loading than US double stacks. Here is where track gauge does come into play. There is a practical limit in the ratio between height of the center of gravity of the loading and track gauge. Hence, on the Indian 5'-6" track higher loading can safely be carried than on the North American 4'-8 1/2" track gauge. But, when you do get high you cannot stop on highly superelevated curves. Hence in the US, at least, most railroads reduced their allowed maximum superelevation from 6 inches to 4 inches after the introduction of piggyback and tri-level autoracks. For the most parts of the world average heights of loading does not approach these limits. Since being off-center is also a factor, width of equipment does come into play for high loadings, but not really that much for normal passenger equipment heights. For example, the Taiwan passenger equipment used on their 1067 mm (3'-6") gauge railways is as wide as the UIC allowable limits on standard (1435 mm = 4'-8 1/2") gauge tracks. In fact, most North American equipment cannot operate on European or other railroads built to UIC requirements as it is too high, too wide, and too heavy.

There is this story going around that the diameter of the space shuttle boosters was limited by track gauge which comes from the original wagon wheel spacing used by the Romans which was determined by the width of a horse's butt. This story is completely bogus.

As to the original question on this thread about the relationship between wheel gauge and track gauge, I can give specific answers, but don't have time to look it up right now.

 

[Devil's Advocate]

Are the flanges of railway wheels exactly 4 feet 8.5 inches apart to match the rails or is there some leeway? Why don't the wheels constantly squeak?

As shown in the image above the direct contact area is only a small sliver of the total wheel width. The contact point varies depending on the state of the track and the movement of the train but generally avoids the flange.

 

[zephyr17]

Should that be 16 feet above the railhead rather than 16 inches? If not, I don't understand.

Feet. I'll correct it

 

[cirdan]

there is of course the story about Hilter's plans for a new system of railroads with a gauge of 4 meters (more than 13 foot) with super luxury trains linking the main cities providing hotel-like sleeping suites and dining cars high enough to have real chandeliers.

But track gauge doesn't even stop there as there are cranes and crane gantries that run on even wider gauge (but typically don't go around curves or have switches).

 

[George Harris]

Ever use a 2x4 to build something? They are not all 2 inches by 4 inches ... that is the "nominal" dimension.

Actually, the current defined dimensions of a 2x4 are 1 1/2 x 3 1/2. They have gradually shrunk over the years. Those in my parent's house which was built in the earl 1950's were 1 3/4 by 3 3/4. There was a period of time somewhere in the 60's to 70's that the defined dimension was 1 5/8 x 3 5/8. The original 1 3/4 x 3 3/4 was somewhat legitimate in that the large lumber mill saws were 1/4 inch thick.

 

[George Harris]

Something I wrote concerning the source of our standard 4'-8 1/2" standard gauge to another site that was not railroad related, simply copied verbatim:

This one (their statement of the origin of track gauge comes from the width of a horse's butt) comes up often with variations. Think wagon wheels set on 5 feet centers with 4 inch wide iron treads. That leaves you 4 feet 8 inches. Put a vertical flange on the inside of the wheel Make the rails an additional 1/2 inch further apart so that you have a little play, and guess what! You get 4 feet 8 1/2 inches. I suspect this to be the most likely origin. Then there is little thing that this "standard" gauge is far from universal. In Russia, Ukraine and most of the former Soviet Union countries the railroad gauge is 5 feet 0 inches. In Ireland the railroad gauge is 5 feet 3 inches, which is also used in Argentina, Chile, and part of Australia. In India and Brazil it is 5 feet 6 inches. Spain and Portugal are at 1668 mm, which is essentially 5 feet 5 5/8 inches. Then there is a lot of 3 feet 6 inch gauge track, like Japan, Taiwan, New Zealand, part of Australia, etc. Thailand, Malaysia, the narrow gauge lines in India and surroundings and most of the former French colonies in SE Asia have meter gauge track (3 feet 3 3/8 inches), (Vietnam, Cambodia, etc.) There has also been some 3 feet 0 inch gauge track in mountainous regions in quite a few places, like in Colorado and Yukon and probably a few other places.

By the way, the extrapolation that the Space Shuttle booster diameter is based on track gauge is completely bogus. The space between rails has nothing to do with it. It is the space to walls, adjacent tracks, bridge piers, overhead bridges, tunnels, etc. Even though the track gauge in the US is the same as it is in most of Western Europe, there is no way you could haul the space shuttle units on their railroad system because of their much closer and lower clearance standards.

 

[joelkfla]

Actually, the current defined dimensions of a 2x4 are 1 1/2 x 3 1/2. They have gradually shrunk over the years. Those in my parent's house which was built in the earl 1950's were 1 3/4 by 3 3/4. There was a period of time somewhere in the 60's to 70's that the defined dimension was 1 5/8 x 3 5/8. The original 1 3/4 x 3 3/4 was somewhat legitimate in that the large lumber mill saws were 1/4 inch thick.

Gee - just like cartons of OJ & rolls of paper towels. Rolls of paper towels and TP have shrunk so much that now we have double, triple, and even MEGA rolls to make up for it.

 

[ehbowen]

Track gauge also can vary (slightly) with the condition/deterioration of the track, and that measurement is one of the factors used to "classify" track by the FRA. That classification determines the allowable maximum speed of operation over the track. See page 5.25:

https://railroads.dot.gov/sites/fra.dot.gov/files/2020-08/2008_Track_Safety_Standards.pdf

 

[Willbridge]

These diverse gauge and load factors are one reason why European rail cars had a mind-boggling amount of info displayed on them. My favorite was the stenciled anchor indicating that it was equipped for car ferries. A restrictive box around the anchor meant that it was small enough to meet British clearance standards.

Note that this boxcar met "European" standards for international pool service in those days. Numerous countries did not participate.





Same railway administration, different profiles.



This sort of appearance also occurred on Spanish and Russian railways that purchased passenger cars from Germany. A big step from a German carbody to a Russian platform.

 

[Willbridge]

We weren't exempt.