Posts by 34C
1 - 8 of 28 Posts
There are so many strange features to this project. Why the decision to base it on a BR5 chassis is just the first. If they were truly serious about re-imagining steam for railtour purposes you would imagine that form would follow function. Presumably that's why they have gone reciprocating instead of the natural choice of turbine for the much greater efficiency on offer: it has to go chuff to appeal to the rail tour market.
So OK it's going to be reciprocating, now put in all the other 'best in class' technologies to deliver the required functionality, and let that define the form. Particular aspects that seem to have been ignored in my totally unhumble opinion.
Mechanical limitations of 2 cylinders for high power output. It is acknowledged in the design spec that 2 cylinders are pretty brutal for high power outputs with the all-up mass typical of a UK loco. Three cylinder, simple, or compound on the Smith system, have proved their worth for this class of operation, due to the much superior mechanical balance intrinsic to these types. One of the under-recognised benefits of three cylinder simple is the potential for continuous steam flow through the circuit, much kinder on the boiler than two or four cylinder simple.
Exhaust clearance and aerodynamic efficiency. The 'Bugatti' front on the A4 class was outstandingly successful in obtaining excellent exhaust clearance, combined with reduction in wind resistance, and is very similar to what is still the choice for diesel and electric traction. So why not use it?
The spec correctly acknowledges the need for large consumable supplies, and a large bogie tender is provided for . But this places a constraint on the loco length to stay within the 70' turntable limit. Here's where completely rethinking the traditional steam loco format would really pay off. It is going to be oil fired, so provide full servo automation of all controls, and abandon the traditional cab as the driving position. Place driving positions both ends, just as on a diesel or electric. The improved forward outlook alone justifies this. That means the length restriction is far less severe, as with the loco fully reversible there is no need for turning. With a compatible control system the loco could also push a DVT equipped set. The advantage for rail tours with pressure on minimising turn round, and integration with the other motive power should be obvious.
Integrate all that, and a UK version of the Hiawatha 4-6-4 suggests itself, 4,500 dbhp, six axle tender, roughly 100 ft long, good for 120mph with a 300T payload - roughly an HST equivalent. Now that would be exciting.
So OK it's going to be reciprocating, now put in all the other 'best in class' technologies to deliver the required functionality, and let that define the form. Particular aspects that seem to have been ignored in my totally unhumble opinion.
Mechanical limitations of 2 cylinders for high power output. It is acknowledged in the design spec that 2 cylinders are pretty brutal for high power outputs with the all-up mass typical of a UK loco. Three cylinder, simple, or compound on the Smith system, have proved their worth for this class of operation, due to the much superior mechanical balance intrinsic to these types. One of the under-recognised benefits of three cylinder simple is the potential for continuous steam flow through the circuit, much kinder on the boiler than two or four cylinder simple.
Exhaust clearance and aerodynamic efficiency. The 'Bugatti' front on the A4 class was outstandingly successful in obtaining excellent exhaust clearance, combined with reduction in wind resistance, and is very similar to what is still the choice for diesel and electric traction. So why not use it?
The spec correctly acknowledges the need for large consumable supplies, and a large bogie tender is provided for . But this places a constraint on the loco length to stay within the 70' turntable limit. Here's where completely rethinking the traditional steam loco format would really pay off. It is going to be oil fired, so provide full servo automation of all controls, and abandon the traditional cab as the driving position. Place driving positions both ends, just as on a diesel or electric. The improved forward outlook alone justifies this. That means the length restriction is far less severe, as with the loco fully reversible there is no need for turning. With a compatible control system the loco could also push a DVT equipped set. The advantage for rail tours with pressure on minimising turn round, and integration with the other motive power should be obvious.
Integrate all that, and a UK version of the Hiawatha 4-6-4 suggests itself, 4,500 dbhp, six axle tender, roughly 100 ft long, good for 120mph with a 300T payload - roughly an HST equivalent. Now that would be exciting.
QUOTE (steamrailuk @ 15 Aug 2008, 23:42) <{POST_SNAPBACK}>Are you suggesting a loco similar to the Leader class loco built by Oliver Bullied?
Oh no, heaven forfend! There was just too much 'new and untried' in that rethinking of the format to be successfully developed when steam was still in mass production and operation, with thousands of men daily practising the related engineering expertise. Not a chance of developing anything that far from the basic Stephenson format now. This lack of mass experience and the developed expertise that results is a serious issue for any such project, as the Tornado build demonstrated. Even the best people, when they are few in number, need a lot of time to simply get all the work done right.
So, this is about making the absolute best of the Stephenson format. If you want a fast reliable and powerful steam loco, start from the existing 'best in class' examples and develop that. No doubt about it, for really fast powerful and reliable simple locos, best in 2 cylinder were machines like the Niagara 4-8-4, and Hiawatha 4-6-4. In shrinking these to British loading gauge, an extra cylinder is required. (I have spoken to enginemen who worked Britannias, and while they all regarded it as a good tool, the hammering it handed out to them was not well liked!) BR discovered that the cheapest big engine it had (build, maintenance and operating cost) was the Peppercorn A1. There's your base platform for development - and BONUS! there is current experience of building one. An extra trailing truck wheel might well be a good idea to keep the axle loads low enough (and it will help in another way), so probably a 4-6-4.
The one big new factor that has emerged since the steam loco went out of regular service in the UK is ubiquitous automation and computing. That's the element to explore to improve the basic Stephenson loco. A real benefit of this is that the traditional cab can be abandoned as a driving position, which eases restraints on the external firebox shell: no longer do the crew need to see forward past it, so it can fill the full moving loading gauge. (That's where the extra length at chassis rear by having a four wheel truck helps.)
None of this is new thinking apart from the automation; JF Harrison, who was effectively BR's last steam CME was deliberating on 'where next' with guidance from Andre Chapelon, back in the late 1950's. In addition to what has already been mentioned, he would have insisted on Caprotti valve gear based on his experience with DoG, which showed unmatched engine efficiency for a simple locomotive. This came too late for general use, and in some ways it is a shame that Tornado has not been fitted with this gear.
But this really is the stuff of dreams. Short of an individual with serious wealth deciding to make it happen, there's not a prayer of building such a thing!
Oh no, heaven forfend! There was just too much 'new and untried' in that rethinking of the format to be successfully developed when steam was still in mass production and operation, with thousands of men daily practising the related engineering expertise. Not a chance of developing anything that far from the basic Stephenson format now. This lack of mass experience and the developed expertise that results is a serious issue for any such project, as the Tornado build demonstrated. Even the best people, when they are few in number, need a lot of time to simply get all the work done right.
So, this is about making the absolute best of the Stephenson format. If you want a fast reliable and powerful steam loco, start from the existing 'best in class' examples and develop that. No doubt about it, for really fast powerful and reliable simple locos, best in 2 cylinder were machines like the Niagara 4-8-4, and Hiawatha 4-6-4. In shrinking these to British loading gauge, an extra cylinder is required. (I have spoken to enginemen who worked Britannias, and while they all regarded it as a good tool, the hammering it handed out to them was not well liked!) BR discovered that the cheapest big engine it had (build, maintenance and operating cost) was the Peppercorn A1. There's your base platform for development - and BONUS! there is current experience of building one. An extra trailing truck wheel might well be a good idea to keep the axle loads low enough (and it will help in another way), so probably a 4-6-4.
The one big new factor that has emerged since the steam loco went out of regular service in the UK is ubiquitous automation and computing. That's the element to explore to improve the basic Stephenson loco. A real benefit of this is that the traditional cab can be abandoned as a driving position, which eases restraints on the external firebox shell: no longer do the crew need to see forward past it, so it can fill the full moving loading gauge. (That's where the extra length at chassis rear by having a four wheel truck helps.)
None of this is new thinking apart from the automation; JF Harrison, who was effectively BR's last steam CME was deliberating on 'where next' with guidance from Andre Chapelon, back in the late 1950's. In addition to what has already been mentioned, he would have insisted on Caprotti valve gear based on his experience with DoG, which showed unmatched engine efficiency for a simple locomotive. This came too late for general use, and in some ways it is a shame that Tornado has not been fitted with this gear.
But this really is the stuff of dreams. Short of an individual with serious wealth deciding to make it happen, there's not a prayer of building such a thing!
QUOTE (steamrailuk @ 16 Aug 2008, 11:44) <{POST_SNAPBACK}>So what your suggesting would be like the other locos i've posted on this link, SLM class 52 and the red devil. Start with an existing donor engine such as a 5MT/ Black 5/ or any other BR Standard and by using as many parts as possible, modernise the design.
The same process, but start from the absolute best in class for the type of work envisaged. The BR5 was a very lacklustre design: poorer than both the Black 5 from which it was developed, and the much cheaper B1 (BR's own data). If the intention is to build a steam loco for high speed service capable of integration into current scheduled operations it will need a lot of power to take a realistic payload: 4,000 drawbar horsepower would be a minimum. The proven express designs to study are the final generation of US express superpower which actually demonstrated this capability, and the best in class the UK can offer which would be the Peppercorn A1 and DoG as development platforms. It's a lot easier to do a 100% stretch from these 2,000dbhp designs, than 200% from the 1200dbhp of a BR5.
The same process, but start from the absolute best in class for the type of work envisaged. The BR5 was a very lacklustre design: poorer than both the Black 5 from which it was developed, and the much cheaper B1 (BR's own data). If the intention is to build a steam loco for high speed service capable of integration into current scheduled operations it will need a lot of power to take a realistic payload: 4,000 drawbar horsepower would be a minimum. The proven express designs to study are the final generation of US express superpower which actually demonstrated this capability, and the best in class the UK can offer which would be the Peppercorn A1 and DoG as development platforms. It's a lot easier to do a 100% stretch from these 2,000dbhp designs, than 200% from the 1200dbhp of a BR5.
QUOTE (steamrailuk @ 18 Aug 2008, 13:39) <{POST_SNAPBACK}>That does make sence about using the best in class as a template. surprised that the BR 5MT was a poor design as i though it was a more robust version of the black 5 and the B1 ..
The point about the BR standard 5 is that it should have been better in performance than either of the black 5 and B1 (which performed very similarly when tested by BR), and cheaper than the B1. That would be justification for a new design: at least equivalent (and for preference better) performance, for less capital expenditure. It was more expensive than the B1, and BR trialled it against the black 5 and discovered it wasn't as good in terms of boiler evaporation and power output. After draughting experiments they improved it to within 98% of the power output, for 5% more coal consumption as compared to a black 5, and left it there as that was adequate for the duties it had to undertake.
By no measure can that be called a success, and what that may be pointing at is that for a simple locomotive of that size and general characteristics, the optimum point in performance had been achieved; there really wasn't anymore stretch potential, unless the engineers were prepared to increase working pressures and temperatures, as the 5AT project proposes. To obtain the output specified for 5AT requires a 200% increase in the conversion of steam to mechanical energy in the cylinders. I wish them luck with the idea because despite advances in materials science, the weight increases required for higher boiler pressure, higher superheat, improved thermal insulation, and roller bearings, and the physical space required to accomodate the much larger superheater in a relatively small loco are all going to be very challenging. A further challenge will be the frame strength, rod sections and bearing areas required to stand the 200% increase in piston forces: US design to handle these sort of power densities resorted to a cast steel frame with integral cylinders; and that came with a mighty weight penalty. Every single one of the advances proposed for 5AT has to work for the project to succeed, it is an awful lot to ask for, particularly when working off a base platform that was apparently pretty much on the limit.
QUOTE ..I thought LNER locos were generally very refined, finely tuned machines, not very easy to maintain but that may only be true about gresley locos and not thompson or peppercorn.
When BR got down to doing equivalent costing for loco maintenance it caused a lot of surprise. The most expensive element to maintain is the boiler. My memory of the figures is that in the class 8 category the LNER A4 and SR Merchant Navy boilers respectively cost 0.8 and 0.6 pence a mile in classified repairs, compared to the Duchess at over 2.5 pence per mile (When this was done the Merchant Navy boilers were significantly newer than those on the A4 and Duchess which were similar in working life, and so the MN boilers should be a bit cheaper.) When you bear in mind that a round top boiler as on the A4 is cheaper in first cost than a belpaire type as on the Duchess and MN you have to ask some hard questions. One of the big differences is three cylinders against four. Three cylinders are far 'kinder' to the boiler than four (or two) because you get six gentler exhausts per revolution which 'work' the firebox sides in particular rather less fiercely.
It is worth knowing that the LNER through most of its' existence was near broke as a business: the depression hit its' freight revenue worst of all the groups, and it was the biggest freight mover as a total percentage of its business of all the groups. This drove them very hard toward getting costs down. That is one of the reasons why they stuck with the cheaper round top boiler: and when 'the chips were down' during WWII it was Doncaster's experience that persuaded Riddles that the Austerity 2-8-0 should have a round top boiler for economy, instead of the belpaire used on the 8F. And it worked just as well! The obsession with the more expensive belpaire boiler in the UK shows the force of habit: in all the other countries that pushed steam development hard, USA, Germany, France, round top boilers were the norm. All these countries produced locos with far greater power output than any UK class.
QUOTE ..the idea about using locos such as DoG and the A1 as development platforms with american practise incorperated into the designs is a good idea, but i'm not so sure if they would have problems with route availabilty. wouldn't a scaled down version of those locos be better?
Absolutely, you have to 'scale down'. The Great Northern A1 was largely inspired by the Pennsylvania Rail Road's immensely successful K4 pacific: Gresley took the key features which delivered this loco's performance and effectively scaled it down to produce a loco capable of fitting in the UK loading gauge. This became the platform to develop the A3, A4, and Peppercorn A1 pacifics, and was also where Bulleid learned his craft before leaving Doncaster for the SR to build further pacific developments. This pacific chassis stretches naturally to a 4-6-4, and maybe a 4-8-4 or 4-6-6 chassis, and definitely has the potential: in the US 4-6-4's could achieve over 5.000 dbhp, Chapelon had 5,500 dbhp out of a 4-8-4 (still too big for UK loading gauge) but somewhere in the 4,000 to 4,500 dbhp range should be achievable on a UK 4-6-4.
The point about the BR standard 5 is that it should have been better in performance than either of the black 5 and B1 (which performed very similarly when tested by BR), and cheaper than the B1. That would be justification for a new design: at least equivalent (and for preference better) performance, for less capital expenditure. It was more expensive than the B1, and BR trialled it against the black 5 and discovered it wasn't as good in terms of boiler evaporation and power output. After draughting experiments they improved it to within 98% of the power output, for 5% more coal consumption as compared to a black 5, and left it there as that was adequate for the duties it had to undertake.
By no measure can that be called a success, and what that may be pointing at is that for a simple locomotive of that size and general characteristics, the optimum point in performance had been achieved; there really wasn't anymore stretch potential, unless the engineers were prepared to increase working pressures and temperatures, as the 5AT project proposes. To obtain the output specified for 5AT requires a 200% increase in the conversion of steam to mechanical energy in the cylinders. I wish them luck with the idea because despite advances in materials science, the weight increases required for higher boiler pressure, higher superheat, improved thermal insulation, and roller bearings, and the physical space required to accomodate the much larger superheater in a relatively small loco are all going to be very challenging. A further challenge will be the frame strength, rod sections and bearing areas required to stand the 200% increase in piston forces: US design to handle these sort of power densities resorted to a cast steel frame with integral cylinders; and that came with a mighty weight penalty. Every single one of the advances proposed for 5AT has to work for the project to succeed, it is an awful lot to ask for, particularly when working off a base platform that was apparently pretty much on the limit.
QUOTE ..I thought LNER locos were generally very refined, finely tuned machines, not very easy to maintain but that may only be true about gresley locos and not thompson or peppercorn.
When BR got down to doing equivalent costing for loco maintenance it caused a lot of surprise. The most expensive element to maintain is the boiler. My memory of the figures is that in the class 8 category the LNER A4 and SR Merchant Navy boilers respectively cost 0.8 and 0.6 pence a mile in classified repairs, compared to the Duchess at over 2.5 pence per mile (When this was done the Merchant Navy boilers were significantly newer than those on the A4 and Duchess which were similar in working life, and so the MN boilers should be a bit cheaper.) When you bear in mind that a round top boiler as on the A4 is cheaper in first cost than a belpaire type as on the Duchess and MN you have to ask some hard questions. One of the big differences is three cylinders against four. Three cylinders are far 'kinder' to the boiler than four (or two) because you get six gentler exhausts per revolution which 'work' the firebox sides in particular rather less fiercely.
It is worth knowing that the LNER through most of its' existence was near broke as a business: the depression hit its' freight revenue worst of all the groups, and it was the biggest freight mover as a total percentage of its business of all the groups. This drove them very hard toward getting costs down. That is one of the reasons why they stuck with the cheaper round top boiler: and when 'the chips were down' during WWII it was Doncaster's experience that persuaded Riddles that the Austerity 2-8-0 should have a round top boiler for economy, instead of the belpaire used on the 8F. And it worked just as well! The obsession with the more expensive belpaire boiler in the UK shows the force of habit: in all the other countries that pushed steam development hard, USA, Germany, France, round top boilers were the norm. All these countries produced locos with far greater power output than any UK class.
QUOTE ..the idea about using locos such as DoG and the A1 as development platforms with american practise incorperated into the designs is a good idea, but i'm not so sure if they would have problems with route availabilty. wouldn't a scaled down version of those locos be better?
Absolutely, you have to 'scale down'. The Great Northern A1 was largely inspired by the Pennsylvania Rail Road's immensely successful K4 pacific: Gresley took the key features which delivered this loco's performance and effectively scaled it down to produce a loco capable of fitting in the UK loading gauge. This became the platform to develop the A3, A4, and Peppercorn A1 pacifics, and was also where Bulleid learned his craft before leaving Doncaster for the SR to build further pacific developments. This pacific chassis stretches naturally to a 4-6-4, and maybe a 4-8-4 or 4-6-6 chassis, and definitely has the potential: in the US 4-6-4's could achieve over 5.000 dbhp, Chapelon had 5,500 dbhp out of a 4-8-4 (still too big for UK loading gauge) but somewhere in the 4,000 to 4,500 dbhp range should be achievable on a UK 4-6-4.
QUOTE (steamrailuk @ 18 Aug 2008, 16:35) <{POST_SNAPBACK}>Is that the reason why american loco's have very large coupling rods compared to british loco's?
Yup. On the final US maximum power designs the power that had to be transmitted, is at about a 3:1 ratio: 6,000hp as compared to 2,000hp in the UK.
Yup. On the final US maximum power designs the power that had to be transmitted, is at about a 3:1 ratio: 6,000hp as compared to 2,000hp in the UK.
QUOTE (steamrailuk @ 18 Aug 2008, 20:59) <{POST_SNAPBACK}>thanks for that, always wondered about that on american locos. What do think about my suggestion for a combined Tornado design with the advances made in Duke of Gloucester as a development platform for a modern steam loco
A step in the right direction. Now all you need is years of academic and practical engineering experience, a dozen or more people with similar qualifications, and a large wodge of the folding stuff. An outline concept is one thing, developing this to a credible project proposal a serious business, the design process a severe test of ability and stamina: and then you have to build the thing...
If you have that kind of ability and energy, while building an example of an obsolete form of railway traction would be fun, I cannot help but feel that working on power generation might actually be more useful for society.
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Oh yes, something I didn't mention about the rods on US locos, the late designs had roller bearings on the crankpins, which need much larger housings compared to the plain bearings used in UK steam practise; that also pushed up the size of the rod cross sections.
A step in the right direction. Now all you need is years of academic and practical engineering experience, a dozen or more people with similar qualifications, and a large wodge of the folding stuff. An outline concept is one thing, developing this to a credible project proposal a serious business, the design process a severe test of ability and stamina: and then you have to build the thing...
If you have that kind of ability and energy, while building an example of an obsolete form of railway traction would be fun, I cannot help but feel that working on power generation might actually be more useful for society.
Oh yes, something I didn't mention about the rods on US locos, the late designs had roller bearings on the crankpins, which need much larger housings compared to the plain bearings used in UK steam practise; that also pushed up the size of the rod cross sections.
QUOTE (steamrailuk @ 25 Aug 2008, 17:48) <{POST_SNAPBACK}>.. it claims that this loco can produce 5000 horsepower and to my astonishment it can reach 120mph. Can a loco of this size be capable of running almost as fast as Mallard?
I know locos that have small diameter wheels are capable of high speeds as I've heard stories that Evening Star could haul expresses up to 90mph, but is it possible to reach 120 without causing serious damage to either loco or track?
The power output is nothing extraordinary for the final express 'superpower', and should be adequate for the speed claim. For comparison the NY Central's final brute the 4-8-4 'Niagara' was good for 6,000hp. The Chessie laid some of the heaviest rail used in the steam era, capable of accepting the 42 ton axle load of their H8 2-6-6-6 simple mallets (a freight machine with an output over 7,000hp), which may well have enabled the track to stand the pounding of the J3 4-8-4. The 72"wheels are a bit on the small side for the ultimate in speed; the Hiawathas had 84" and quite definitely ran over the 100mph mark in daily service, simply to make schedule. These likely were the fastest ever steam locos in regular service. Somehow it never occurred to anyone to formally time one at full chat...
Quite how well the loco stands up to the battering long term is just one reason why I have my doubts about the 5AT project. The US experience in the final 'superpower' locos weighing around 200 tons was that a cast steel frame with integral cylinders was the way to go. Their experience showed that built up constructions were worked to failure by the piston thrusts of around 80 to 90 tons, alternating each side, bending the frame. Trying to accomodate the necessary 50 ton or thereabouts thrusts within the 90 ton all up 'envelope' of the 5AT is going to be challenging in the extreme. Compare to the UK experience with locos that were called upon regularly to put out approaching 2,000hp: the Princess Coronations suffered from loose cylinders throughout their career, the A4's were noted for deforming their frames: and these were 4 and 3 cylinder designs, not 2 cylinder. The US designs have roller bearings on the axles and the coupling rod pins; more weight, but necessary to stand up to the hammering. The rod cross sections have to be heavier to house the bearings, more weight required for rotational balance...
The final developements in US steam power make fascinating reading, and much of it is now on the web. 'Why didn't the PRR duplexii succeed?' is always a good one!
I know locos that have small diameter wheels are capable of high speeds as I've heard stories that Evening Star could haul expresses up to 90mph, but is it possible to reach 120 without causing serious damage to either loco or track?
The power output is nothing extraordinary for the final express 'superpower', and should be adequate for the speed claim. For comparison the NY Central's final brute the 4-8-4 'Niagara' was good for 6,000hp. The Chessie laid some of the heaviest rail used in the steam era, capable of accepting the 42 ton axle load of their H8 2-6-6-6 simple mallets (a freight machine with an output over 7,000hp), which may well have enabled the track to stand the pounding of the J3 4-8-4. The 72"wheels are a bit on the small side for the ultimate in speed; the Hiawathas had 84" and quite definitely ran over the 100mph mark in daily service, simply to make schedule. These likely were the fastest ever steam locos in regular service. Somehow it never occurred to anyone to formally time one at full chat...
Quite how well the loco stands up to the battering long term is just one reason why I have my doubts about the 5AT project. The US experience in the final 'superpower' locos weighing around 200 tons was that a cast steel frame with integral cylinders was the way to go. Their experience showed that built up constructions were worked to failure by the piston thrusts of around 80 to 90 tons, alternating each side, bending the frame. Trying to accomodate the necessary 50 ton or thereabouts thrusts within the 90 ton all up 'envelope' of the 5AT is going to be challenging in the extreme. Compare to the UK experience with locos that were called upon regularly to put out approaching 2,000hp: the Princess Coronations suffered from loose cylinders throughout their career, the A4's were noted for deforming their frames: and these were 4 and 3 cylinder designs, not 2 cylinder. The US designs have roller bearings on the axles and the coupling rod pins; more weight, but necessary to stand up to the hammering. The rod cross sections have to be heavier to house the bearings, more weight required for rotational balance...
The final developements in US steam power make fascinating reading, and much of it is now on the web. 'Why didn't the PRR duplexii succeed?' is always a good one!
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