Broad gauge -v- Standard gauge

[tom73]

George Stephenson originally used 4 ft 8 in so where did 4 ft 8½ in come from?
IKB favoured broad gauge, initially 7 ft and then 7ft ¼ in.
What were the advantages of broad gauge?
What would the implications have been if broad gauge had been chosen for nationwide use and the
4 ft 8½ in abandoned?

 

[hexagon789]

George Stephenson originally used 4 ft 8 in so where did 4 ft 8½ in come from?

Eased by 1/2in for curves. The same happened with Brunel's broad guage, Eased from 7ft to 7ft 1/4in to improve running in curves.

Broad guage was supposed to allow greater stability at speed and larger more comfortable carriages, presumably with higher capacity than standard guage ones.

 

[edwin_m]

With hindsight broad gauge was the wrong choice. There's nothing it could have done that hasn't since been done with standard.

 

[brstd4260]

Standard gauge was based on a the gauge of some of the pre existing plateways in the North East. The gauge for some of these was based on the width of the wheels on carts in common use in the area. These in turn were based on the width of the pre-existing ruts in the surviving Roman roads. Standard gauge is thus in effect based on the gauge of roman waggons and chariots!

 

[krus_aragon]

What would the implications have been if broad gauge had been chosen for nationwide use and the
4 ft 8½ in abandoned?

A lot depends on when broad gauge might have been chosen. By the time the Regulating the Gauge of Railways Act came along in 1846, there were already a lot more narrow (standard) gauge railways than broad, partially because Stephenson started first, and had been very prolific in advising other railways.

If the broad gauge had been closer in route mileage, or its advocates had persuaded Westminster that it was clearly better, then I'd have expected similar stipulations that (bar some exceptions) all new railways were to be build in the broad gauge, and that narrow gauge railways would later be expected to lay mixed gauge track, or convert to broad gauge. This would have required significant expense when it came to widening bridges and tunnels, and if Parliament was going to mandate all these private companies (which many MPs had shares in) to do this, it may have required some funding from the Government to do so. This would have been quite a departure from existing policy of leaving everything in the hands of private capital where possible.

 

[swt_passenger]

Broad guage was supposed to allow greater stability at speed and larger more comfortable carriages, presumably with higher capacity than standard guage ones.

Broad gauge carriages and locos were apparently little or no larger than standard gauge. The wheels were still within roughly the same overall body width, the carriages were never ‘scaled up’, indeed if they had been, any alleged greater stability would have been gradually reduced...

 

[swt_passenger]

Standard gauge was based on a the gauge of some of the pre existing plateways in the North East. The gauge for some of these was based on the width of the wheels on carts in common use in the area. These in turn were based on the width of the pre-existing ruts in the surviving Roman roads. Standard gauge is thus in effect based on the gauge of roman waggons and chariots!

One of the very oldest railway myths, I believe, except for the first bit...

 

[Taunton]

Broad gauge was supposed to allow … larger more comfortable carriages, presumably with higher capacity than standard gauge ones.

Track gauge has nothing to do with rolling stock dimensions - look at the locos and trains in South Africa, larger than anything in Britain but on 3'6" gauge. Or the vast double-stacks in the USA, way beyond what old Hastings Size rolling stock was restricted to in Britain, but on the same gauge tracks.

The BART trains in San Francisco had every design aspect in the 1960s gone into by "experts", so they ended up with non-standard 5'6" track gauge, cars no larger than the rest of the USA because the air resistance expert pointed to minimising piston pressure effect in the tunnels, and the inability to be able to use any of the standardised track maintenance equipment from the various US contractors, so they have to buy their own specialist kit for everything. They really regret going for a silly gauge.

 

[Indigo Soup]

Broad gauge carriages and locos were apparently little or no larger than standard gauge. The wheels were still within roughly the same overall body width, the carriages were never ‘scaled up’, indeed if they had been, any alleged greater stability would have been gradually reduced...

The supposed advantage of the broad gauge was that it would allow locomotive boilers to sit between wheels, rather than over them, thereby lowering the centre of gravity and improving stability. In response, the LNWR argued that stability wasn't the limiting factor on speed - it was the quality of the tracklaying.

In the later days of broad gauge, the stock was basically just standard gauge bodies with unreasonably wide running boards, since everyone knew it would be converted sooner or later. Removing running boards and swapping bogies was much easier than building new bodies.

Track gauge has nothing to do with rolling stock dimensions - look at the locos and trains in South Africa, larger than anything in Britain but on 3'6" gauge. Or the vast double-stacks in the USA, way beyond what old Hastings Size rolling stock was restricted to in Britain, but on the same gauge tracks.

Coming the other way - the standard North American loading gauge, AAR Plate B, is about the same size as the loading gauge on the GWR's broad gauge lines. Slightly narrower, but higher and with a fatter top. And AAR Plate B is their minimum gauge, exceeded on virtually all lines.

The BART trains in San Francisco had every design aspect in the 1960s gone into by "experts", so they ended up with non-standard 5'6" track gauge, cars no larger than the rest of the USA because the air resistance expert pointed to minimising piston pressure effect in the tunnels, and the inability to be able to use any of the standardised track maintenance equipment from the various US contractors, so they have to buy their own specialist kit for everything. They really regret going for a silly gauge.

In a particular stroke of genius, the 'experts' were from outside the railway industry, and insisted on doing everything from scratch. Whatever the theoretical advantages of the 5'6" gauge may have been, they didn't understand the rail-wheel interface and specified cylindrical, rather than coned, wheels. As a result, BART has major issues with flange wear.

 

[Lucan]

Broad gauge carriages and locos were apparently little or no larger than standard gauge. The wheels were still within roughly the same overall body width, the carriages were never ‘scaled up’, indeed if they had been, any alleged greater stability would have been gradually reduced...

I understood the original GWR loading gauge was significantly larger. So never mind whether the rolling stock took advantage of it at the time, it would have been a big advantage today nationwide. Those broad gauge trains in photos look a bit ridiculous, as if they are stretching to reach the rails, but I believe that Brunel was thinking ahead, unlike Stevenson Senior. Today, a UK rail freight wagon looks ridiculously small next to a large HGV - no wonder rail has lost most freight to road.

I read a story (sorry, can't find a ref) that Stevenson was asked in later years if he wished he had built his railways to a larger track gauge. He replied "Perhaps a little larger". I guess he might have been thinking of 5'6", or at least 5'.

A broader track gauge has the advantage of greater dynamic stability. The quasi-static stability (ie against rolling over onto the side on a sharp corner) is obviously not an issue with railways as it is with road vehicles. Dynamic stability was one of the issues that limited simple 4-wheel wagons to 40mph to avoid wheelset hunting (hammering from side-to-side between the flanges) and made freight so slow until the modern era - another reason for losing freight to road. Rolling stock on a narrower track gauge requires more exotic (ie expensive) suspension to reach a given high speed than on a broader gauge.

Brunel's 7ft was OTT. 6ft would have been nice, say 1.8m if we could start again today - combined with a Channel Tunnel loading gauge.

 

[Altfish]

Infrastructure is more expensive on broad gauge; bridges, tunnels, cuttings and general land take for yards and depots are increased. Turning circles must also be greatly increased.

 

[krus_aragon]

Infrastructure is more expensive on broad gauge; bridges, tunnels, cuttings and general land take for yards and depots are increased. Turning circles must also be greatly increased.

As a counter-example, narrow gauge lines (as opposed to standard) were often built narrow to reduce the infrastructure costs.

 

[edwin_m]

I understood the original GWR loading gauge was significantly larger. So never mind whether the rolling stock took advantage of it at the time, it would have been a big advantage today nationwide. Those broad gauge trains in photos look a bit ridiculous, as if they are stretching to reach the rails, but I believe that Brunel was thinking ahead, unlike Stevenson Senior. Today, a UK rail freight wagon looks ridiculously small next to a large HGV - no wonder rail has lost most freight to road.

But that's an issue about structure gauge, not track gauge. With hindsight we adopted a structure gauge that was too small, but as mentioned above there are many other countries that demonstrate how a much larger structure gauge can be compatible with the standard track gauge.

A broader track gauge has the advantage of greater dynamic stability. The quasi-static stability (ie against rolling over onto the side on a sharp corner) is obviously not an issue with railways as it is with road vehicles. Dynamic stability was one of the issues that limited simple 4-wheel wagons to 40mph to avoid wheelset hunting (hammering from side-to-side between the flanges) and made freight so slow until the modern era - another reason for losing freight to road. Rolling stock on a narrower track gauge requires more exotic (ie expensive) suspension to reach a given high speed than on a broader gauge.

The dynamics of hunting oscillations are complicated (Wikipedia has pages of maths on the subject) and I'd welcome a simple explanation of how you think broad gauge makes it better. My suspicion is that the tendency to oscillation is related to the ratio of wheelbase to track gauge, so a larger track gauge would require a longer wheelbase for equivalent stability, and the same wheelbase is less stable on a broader track gauge.

Widening the gauge reduces by the same proportion the radius at which flange contact occurs, so effectively constrains the ability to have tight curves.

 

[Taunton]

Infrastructure is more expensive on broad gauge; bridges, tunnels, cuttings and general land take for yards and depots are increased. Turning circles must also be greatly increased.

Again, most of that is about the size of the vehicles, not particularly related to the track gauge. The one thing that is relevant is the curve radius, which allows sharper curving around hillsides etc and reduces the expense of earthworks to overcome these. There's nothing particularly to stop running small sized trains, to avoid tunnel etc expenditure, on standard gauge track, as the London Tube demonstrates well.

Trams (and double-deck ones to boot) running on standard gauge and having right-angled turns at road junctions shows even this is not all exclusive.

 

[hexagon789]

Broad gauge carriages and locos were apparently little or no larger than standard gauge. The wheels were still within roughly the same overall body width, the carriages were never ‘scaled up’, indeed if they had been, any alleged greater stability would have been gradually reduced...

Fair enough, I assumed that as some broad guage trains are wider that GWR ones might've been too.

CIE had some 10ft2in wide on its 5ft 3in.

Track gauge has nothing to do with rolling stock dimensions - look at the locos and trains in South Africa, larger than anything in Britain but on 3'6" gauge. Or the vast double-stacks in the USA, way beyond what old Hastings Size rolling stock was restricted to in Britain, but on the same gauge tracks.

I'm just going by what I've read heard, I personally don't know one way or the other whether the GWR actually built wider carriages than the standard guage railways of the time.

 

[jimm]

I understood the original GWR loading gauge was significantly larger.

No it wasn't.

Just look at all the original Brunel-designed overbridges that are still in use today. They have wider lateral clearances than other structure of the time, due to the need to allow for the extra width of the broad gauge track, but the vertical clearances under these bridges were scarcely any different to those on other railways that were being built in Britain in the mid-19th century.

The lateral clearances have allowed the use of wider dimensions than usual on some passenger rolling stock operating on former GWR routes over the years, such as the Super Saloons built by the GWR in the 1930s for Plymouth boat trains and the current Class 165 and 166 turbo diesel units

 

[krus_aragon]

Just look at all the original Brunel-designed overbridges that are still in use today. They have wider lateral clearances than other structure of the time, due to the need to allow for the extra width of the broad gauge track, but the vertical clearances under these bridges were scarcely any different to those on other railway.

I doubt that any railway of the time would have seen a need to go for a greater vertical clearance: with nothing of note to fit under the floor of a railway carriage, and the TEU container nowhere near being dreamed of, why build something significantly taller than a person? (Platforms were generally very low back then, too, as people were used to clambering up onto a stagecoach.)

 

[PeterC]

Standard gauge was based on a the gauge of some of the pre existing plateways in the North East. The gauge for some of these was based on the width of the wheels on carts in common use in the area. These in turn were based on the width of the pre-existing ruts in the surviving Roman roads. Standard gauge is thus in effect based on the gauge of roman waggons and chariots!

If he had been from the Forest of Dean coalfield instead then standard gauge would have been 3ft 6. On the other hand if he had worked for Bailey of Nantyglo we would have had 4ft 4. There was too much variation in plateway guages to attribute any ancient measurement based on the width an Italian horse's backside to our modern railways.

 

[edwin_m]

If he had been from the Forest of Dean coalfield instead then standard gauge would have been 3ft 6. On the other hand if he had worked for Bailey of Nantyglo we would have had 4ft 4. There was too much variation in plateway guages to attribute any ancient measurement based on the width an Italian horse's backside to our modern railways.

The Forest of Dean one seems rather narrow - did the wagons also go down the mines or something? Generally the gauges of the old wagonways tended to be between 4' and 5', which is about the same as a typical cart. I don't know if all carts in a particular region had the same "gauge" from time immemorial and those elsewhere had a different one, or whether they just had to be "standardised" if they wanted to take advantage of the wagonway.

 

[Taunton]

I doubt that any railway of the time would have seen a need to go for a greater vertical clearance: with nothing of note to fit under the floor of a railway carriage, and the TEU container nowhere near being dreamed of, why build something significantly taller than a person?

Because the dominant height feature then was the chimney of the locomotive. If Brunel wanted a tall chimney for draughting purposes on top of a big boiler, on top of the axle of big driving wheels (Brunel favoured single drivers with large wheels) that would drive the height specification.

 

[krus_aragon]

Because the dominant height feature then was the chimney of the locomotive. If Brunel wanted a tall chimney for draughting purposes on top of a big boiler, on top of the axle of big driving wheels (Brunel favoured single drivers with large wheels) that would drive the height specification.

A good point, though

The supposed advantage of the broad gauge was that it would allow locomotive boilers to sit between wheels, rather than over them, thereby lowering the centre of gravity and improving stability.

would mitigate it somewhat.

I'm now regretting not taking a tape measure with me when I went to the museum in Swindon!

 

[Lucan]

dynamics of hunting oscillations are complicated ... and I'd welcome a simple explanation of how you think broad gauge makes it better.

They are indeed complex and many factors are involved; I have worked in this area. Basically a wheelset with conical wheels on its own will seek centralisation, a good thing as far as it goes because it steers the flanges away from grinding against the rail, but it will overshoot, leading to oscillation. Put that wheelset into a suspension system and that tendency to oscillate can be damped out and otherwise constrained at lower speeds, but can get the whole suspension vibrating in resonance as the train goes faster. A broader gauge slows the centralisation effect (ie lowers the natural wheelset hunting frequency) because the difference in rolling radii between the wheels is smaller in proportion to the gauge, while still allowing the desirable centralisation, and therefore pushes the critical speed out higher.

Of course the ability of the wheelset to centralise on curves is lower on broad gauge, but that does not matter on the easy curves of a high speed line. You could argue that the same effect could be obtained by reducing the conical angle, but then you would sooner lose the conicity entirely as the wheel treads wear, so more frequent re-treading would be needed. I have seen pronounced negative conicity accompanied by very worn flanges on worn-out LU wheelsets.

 

[edwin_m]

They are indeed complex and many factors are involved; I have worked in this area. Basically a wheelset with conical wheels on its own will seek centralisation, a good thing as far as it goes because it steers the flanges away from grinding against the rail, but it will overshoot, leading to oscillation. Put that wheelset into a suspension system and that tendency to oscillate can be damped out and otherwise constrained at lower speeds, but can get the whole suspension vibrating in resonance as the train goes faster. A broader gauge slows the centralisation effect (ie lowers the natural wheelset hunting frequency) because the difference in rolling radii between the wheels is smaller in proportion to the gauge, while still allowing the desirable centralisation, and therefore pushes the critical speed out higher.

Of course the ability of the wheelset to centralise on curves is lower on broad gauge, but that does not matter on the easy curves of a high speed line. You could argue that the same effect could be obtained by reducing the conical angle, but then you would sooner lose the conicity entirely as the wheel treads wear, so more frequent re-treading would be needed. I have seen pronounced negative conicity accompanied by very worn flanges on worn-out LU wheelsets.

Thanks for the explanation - so a narrower gauge presumably needs more damping to get to the same critical speed. This might to a small extent cancel out the extra costs of broad gauge infrastructure, but the curve tracking issue exacerbates the worse minimum radii of broad gauge.

 

[furnessvale]

I understood the original GWR loading gauge was significantly larger. So never mind whether the rolling stock took advantage of it at the time, it would have been a big advantage today nationwide. Those broad gauge trains in photos look a bit ridiculous, as if they are stretching to reach the rails, but I believe that Brunel was thinking ahead, unlike Stevenson Senior. Today, a UK rail freight wagon looks ridiculously small next to a large HGV - no wonder rail has lost most freight to road.

<SNIP>

Today, a UK rail freight wagon looks small next to a German rail freight wagon, and something more than ridiculous next to a US doublestack. Both those countries use standard track gauge.

It is nothing to do with track gauge and everything to do with structure gauge.

 

[PeterC]

The Forest of Dean one seems rather narrow - did the wagons also go down the mines or something? Generally the gauges of the old wagonways tended to be between 4' and 5', which is about the same as a typical cart. I don't know if all carts in a particular region had the same "gauge" from time immemorial and those elsewhere had a different one, or whether they just had to be "standardised" if they wanted to take advantage of the wagonway.

The Severn and Wyke was 3ft 6 as was the series of wagonways that linked Hereford with the Brecon and Mon at Govilon which between them accounted for a lot of milage on the Welsh border. However Bailey's tramroad from Nantyglo to Govilon was 4ft 4 while Hill's from Blaenavon to Llanfoist was only 2ft. My point being that four and a half feet plus or minus a bit certainly wasn't universal.

 

[edwin_m]

The first railway coaches were essentially several stagecoach bodies mounted on a chassis, so while a wagonway might take its gauge from a cart a passenger railway would take it from a stagecoach, and these were probably much less variable in their dimensions. Anything much narrower than 4ft would probably look pretty unstable unless the stagecoach body was lowered and possibly narrowed as well.

 

[krus_aragon]

Followers of this thread may be interested to read what Robert Fairlie (of Ffestiniog Railway fame) had to say in 1872 when he was trying to persuade people that narrow gauge railways were superior to either standard or broad gauges. Arguments proposed include reduced costs of constructing the railway and its rolling stock, the ability to traverse sharp curves, and greater stability without having to use bogie stock. There's also a good bit of promotion of his Fairlie Engine design, of course.

 

[edwin_m]

Followers of this thread may be interested to read what Robert Fairlie (of Ffestiniog Railway fame) had to say in 1872 when he was trying to persuade people that narrow gauge railways were superior to either standard or broad gauges. Arguments proposed include reduced costs of constructing the railway and its rolling stock, the ability to traverse sharp curves, and greater stability without having to use bogie stock. There's also a good bit of promotion of his Fairlie Engine design, of course.

Not sure about the stability, as a NG carriage would be intrinsically less stable than a SG one of the same body dimensions. That's one reason NG carriages tend to be more low-slung.

 

[krus_aragon]

Not sure about the stability, as a NG carriage would be intrinsically less stable than a SG one of the same body dimensions. That's one reason NG carriages tend to be more low-slung.

The stability Fairlie mentioned was with regard to the length of stock (i.e. the distance between the axles), but I forget the specifics. He also believed that the use of bogies was an unnecessary expense, one that the Americans used because of the low quality of their trackbed laying.

These are all his arguments, and he clearly had a vested interest in promoting the construction and use of narrow gauge lines!

 

[martinsh]

These are all his arguments, and he clearly had a vested interest in promoting the construction and use of narrow gauge lines!

Did he ? Fairlie locomotives were built for standard gauge as well