Why didn't Brunel settle for 7 feet?

[ejstubbs]

Well if you consider Brunel to be ahead of his time, then he would already be looking at the metric system, and as the closest integer to 71/4 is 214 cm, I think this is why he would have gone for the slightly wider gauge.

 

That logic sounds completely backwards.  What's special about 214cm that he would choose that, and then turn it back in to feet and inches?  It makes no sense.  You might as well argue that, if you're starting off at 7ft but want a whole number of centimetres then the nearest integer number to that is 213cm,  which is 6ft 11⅞" to within a gnat's whisker.  So why didn't he use that?  Or why not 215cm, which is a much nicer, rounder number in metric?

 

The answer to the original question was given in post #2 in this thread, and hints at the possibility that, while Brunel was great at civils, he might not have been so hot at mechanicals.  Despite being a "genius".  Allegedly.

Edited March 30, 2018 by ejstubbs

[Steamport Southport]

Maybe it was to do with how long his stick was....

 

 

And no I'm not being funny.

 

http://www.bbc.co.uk/ahistoryoftheworld/objects/F5ZKtpQqSFWr7cHBXxCpuQ

 

 

 

Jason

[Salmotrutta]

Current Nuclear tech could make that work far safer than in the past 60 years.  Plus, it would allow electric traction without considerable infrastructure to power it reliably along many miles in areas less populated such as Middle America, Australia, Russia, etc.

Only problem is the past 60 years of poor nuclear planning havent done much to its image.  

Too true - it would be a great engineering solution. However making it safe and foolproof enough to satisfy society would be a challenge. Another "Lac Megantic" disaster that included a nuclear reactor just doesn't bear thinking about. 

Edited March 30, 2018 by Salmotrutta

[Salmotrutta]

Maybe it was to do with how long his stick was....

 

 

And no I'm not being funny.

 

http://www.bbc.co.uk/ahistoryoftheworld/objects/F5ZKtpQqSFWr7cHBXxCpuQ

 

 

 

Jason

Thanks for sharing! I wasn't aware of his walking stick! 

[Orion]

How tall was Brunel in his hat? That might give an alternative explanation.

 

[dibber25]

Thanks for sharing! I wasn't aware of his walking stick! 

 

The walking stick is one of STEAM's most treasured exhibits. If it goes anywhere, a senior member of museum staff has to accompany it.(CJL)

[Compound2632]

How tall was Brunel in his hat? That might give an alternative explanation.

 

 

He was 5'0" and the hat is estimated at 8". Allowing for crown overlap, say 5'6" - certainly short enough to lie down safely in the four-foot* in the path of an oncoming BG train.

 

*or should that be seven-foot?

Edited March 30, 2018 by Compound2632

[dibber25]

How tall was Brunel in his hat? That might give an alternative explanation.

 

Certainly not 7ft! The hat was apparently some compensation for his lack of 'physical presence'. (CJL)

[Pacific231G]

It's really the loading gauge not the track gauge that determines the length of P&C work, because the length of a lead from one track to the next depends on the track spacing, which in turn depends on the width of the trains not of the track. 

 

As to curves, it comes down to the fundamentals of the railway wheel.  The tread of the wheel is coned (inclined) and the track gauge is a bit wider than the spacing between the flanges (which I think is where we came in with that quarter inch...).  This means the wheelset can move a bit laterally on the track, but as it does so the effective circumference at the two contact points changes, so a rotation of one wheel will take it further than a rotation of the other.  As the opposite wheels are linked by axles they must rotate the same number of times, but on a curve the outer wheel needs to travel a bit further than the inner one. 

 

On a relatively gentle curve the wheel will actually "steer" so the ratio of effective wheel circumferences is the same as the ratio of the curve radii of the two rails.  The flanges are not in contact with the rail, unlike a road vehicle it doesn't need a differential and neither wheel is slipping on its rail.  However on a tighter curve the difference in effective circumference is not enough to compensate, a flange starts rubbing against the rail and potentially one wheel is slipping. 

 

This undesirable behaviour starts when the ratio of the useable taper of the wheel to the diameter is the same as the ratio of the track gauge to the curve radius.  Unless the wheels are made thicker or with a greater coning angle (which causes other problems) this ratio is fixed, and the minimum desirable radius is a certain multiple of the track gauge.  Hence if the track gauge is larger the minimum radius must be larger in the same proportion. 

Interesting stuff on wheel behaviour on curves Edwin but surely the length of a particular track formation will depend on both the gauge and the loading gauge. For a particular crossing angle,  If the gauge is larger you need more length to get the curve of the diverging rail from the switch heel  to the frog and if the distance between tracks is greater   you need more length, at a particular angle, to get between the tracks. In theory, because he was using the wider gauge more for stability than increased vehicle width. Brunel could have narrowed the distance between tracks but he would have been prevented from that by the minimum six foot way rule. Even now, the formations of former BG lines seem to include wider elements than those that were always SG. 

 

This does lead to something I'd never considered before. Until comparatively recently,  Britan's railways made far more use of bespoke track formations than railways in Europe and especially in North America who tended to make up even complex formations from discrete items such as turnouts, diamond crossings and slips which could be individually identified (and in documentation often were)  I'd always assumed that this was due to lack of space but would the narrower distance between tracks simply have made it more difficult to assemble formations from off the shelf items?

 

Due to a bridge strike a few months ago I had far more time than I wanted to contemplate this scissors crossover  just outside Waterloo

 

It's not clear in this aerial image but I was struck by how much of the formation was incorporated into single solid castings like the one I've highlighted. Would this have been a standard(ish) casting or one cast specfically for this location? 

Edited March 30, 2018 by Pacific231G

[JimC]

Certainly not 7ft! The hat was apparently some compensation for his lack of 'physical presence'. (CJL)

 

I think that has to be just another myth. When I look at that Great Eastern launch photo above, all the hats seem to me to be the same height.

[Compound2632]

I think that has to be just another myth. When I look at that Great Eastern launch photo above, all the hats seem to me to be the same height.

 

Brunel's seems taller because he was so short!

[Edwin_m]

Interesting stuff on wheel behaviour on curves Edwin but surely the length of a particular track formation will depend on both the gauge and the loading gauge. For a particular crossing angle,  If the gauge is larger you need more length to get the curve of the diverging rail from the switch heel  to the frog and if the distance between tracks is greater   you need more length, at a particular angle, to get between the tracks. In theory, because he was using the wider gauge more for stability than increased vehicle width. Brunel could have narrowed the distance between tracks but he would have been prevented from that by the minimum six foot way rule. Even now, the formations of former BG lines seem to include wider elements than those that were always SG. 

As shown in a previous post, broad gauge trains could be wider than standard gauge and the track centres would have had to be further apart to accommodate this.  The distance the train projected outside the rail either side seems to have been the same for the two gauges, which makes sense for a mixed gauge platform with the shared rail closest to the platform face.  So if the distance between the nearest rails of a double track was still six feet, the clearance between two passing trains would be the same on a broad gauge line as on a standard gauge one laid to minimum track centre spacings.  It follows that if the train dimensions given above are correct Brunel couldn't have narrowed the track spacing (between nearest rails of adjacent tracks) without reducing the separation of passing trains. 

 

The job of a crossover is to curve the train onto a different course, then move it sideways and curve it back to parallel to its original course but displaced across by one track centre spacing.  To my way of thinking the amount of lateral displacement depends on the train width not the track gauge, and the geometry of the curve depends on the speed and not the track gauge.  If you want the crossing to be on straight rather than curved rail then a narrower track gauge may actually lead to a longer crossover (at least if the train width is the same on the two gauges) because the length of the curve is shorter and the crossing angle is less. 

[Compound2632]

With the 'six foot' being 6'0" for both standard and broad gauge in practice (in general) and assuming the switches themselves are of the same geometry, a broad gauge 1:8 crossover will be (7'0.25" - 4'8.5") x 8 = 18'8" longer than a standard gauge one.

[Trog]

 

 

Due to a bridge strike a few months ago I had far more time than I wanted to contemplate this scissors crossover  just outside Waterloo

scissors crossover Waterloo.jpg

 

It's not clear in this aerial image but I was struck by how much of the formation was incorporated into single solid castings like the one I've highlighted. Would this have been a standard(ish) casting or one cast specfically for this location? 

 

For S&C on a curve I would expect the cast crossing to be a one off special. One of the reasons putting S&C on the straight is preferred these days, it makes finding spares in a hurry so much easier.

[jjb1970]

On nuclear trains, if you can make a nuclear aero engine, and given that very compact sealed reactors have already been developed, then technically I see no reason why you couldn't make a nuclear train engine. Whether it'd ever be accepted by regulators and the public is another question.

[PenrithBeacon]

There has never been a nuclear aero engine. Nuclear space engines yes but not for aeronautical use. In the fifties the USAF had a B-36 modified to carry a nuclear reactor but it didn’t propel the aeroplane

[jjb1970]

The US had a major program to develop nuclear aerospace engines in the 50's and 60's which reached the stage of testing prototype engines on static test beds. There were immense problems with radiation and safety but the engines worked. There have been a lot of rumours about possible Russian development of the idea.

[Steamport Southport]

Isn't Kim's "special secret train that is better than Donald's train" nuclear powered? If not, why not?

 

All evil Bond Baddies need nuclear trains.....

 

 

 

 

 

 

Jason

[PenrithBeacon]

The US had a major program to develop nuclear aerospace engines in the 50's and 60's which reached the stage of testing prototype engines on static test beds. There were immense problems with radiation and safety but the engines worked. There have been a lot of rumours about possible Russian development of the idea.

https://en.wikipedia.org/wiki/Aircraft_Nuclear_Propulsion

[Wickham Green]

With the 'six foot' being 6'0" for both standard and broad gauge in practice (in general) and assuming the switches themselves are of the same geometry, a broad gauge 1:8 crossover will be (7'0.25" - 4'8.5") x 8 = 18'8" longer than a standard gauge one.

........... two or three of them an' you'll need a bigger baseboard !

[Compound2632]

........... two or three of them an' you'll need a bigger baseboard !

 

The same argument applies to working in EM or P4 compared to 00. Although in this case the six-foot varies between the gauges (the track centre-to-centre is or should be the constant factor) the wider gauge results in longer pointwork, for the same geometry. 

[Reorte]

The US had a major program to develop nuclear aerospace engines in the 50's and 60's which reached the stage of testing prototype engines on static test beds. There were immense problems with radiation and safety but the engines worked. There have been a lot of rumours about possible Russian development of the idea.

I'd expect an aerospace nuclear reactor to have problems with radiation due to the issue of getting enough shielding around it without making it too heavy to fly. Shouldn't be as big an issue (but perhaps not a non-issue) on a train.

[Pacific231G]

I'd expect an aerospace nuclear reactor to have problems with radiation due to the issue of getting enough shielding around it without making it too heavy to fly. Shouldn't be as big an issue (but perhaps not a non-issue) on a train.

"This is  a Great Western Railway customer announcement Following a derailment at Temple Meads Station, the whole of Bristol has been evacuated and customers travelling to South Wales should travel via Hereford. We would like to remind customers who were intending to travel to Bristol that Great Western Railway offers an attractive range of alternative destinations."

Edited April 3, 2018 by Pacific231G

[Salmotrutta]

Customer announcement "Following a derailment at Temple Meads Station, the whole of Bristol has been evacuated and passengers to South Wales should travel via Hereford."

Oh dear what have I started? Sorry for de-railing the Broad gauge thread. I hope the OP doesn't go nuclear... 

[96701]

I tend to think that Brunel's broad gauge was one of those cases where a technically superior but expensive and minority solution lost out to a cheaper and more widespread "good enough" approach. That's the free market for you.

 

As for not envisaging the interconnection of railways, Brunel was hardly alone in this, although he was the most prominent and allowed to continue furthest before it was recognised as a commercial error.

 

And I say that as a compatriot of the Stephenson who regards Brunel as a bit of a Johnny Come Lately in the railway engineering field .

Deleted, point already made.

Edited April 3, 2018 by 96701