Speed machines.....

Discussion in 'OFF-Topic / Misc.' started by Lucky13, Jan 14, 2011.

  1. Lucky13

    Lucky13 Forum Mascot

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    Milwaukee Road class A

    Power type: Steam
    Builder: American Locomotive Company
    Serial number: 68684, 68685, 68729, 68828
    Builder Date: May 1935 (2), May 1936, April 1937
    Total production: 4
    Configuration: 4-4-2
    UIC classification: 2′B1′ h2
    Gauge: 4 ft 8 1⁄2 in (1,435 mm)
    Driver diameter: 84 in (2,134 mm)
    Length: 88 ft 8 in (27.03 m)
    Weight on drivers: 144,500 lb (65.5 tonnes)
    Locomotive and tender combined weight: 537,000 lb (243.6 tonnes)
    Fuel type: Oil
    Fuel capacity: 4,000 US gal (15,000 l; 3,300 imp gal)
    Water capacity: 13,000 US gal (49,000 l; 11,000 imp gal)
    Boiler pressure: 300 lbf/in² (2.07 MPa)
    Heating surface: Firebox 69 sq ft (6.4 m2)
    Heating surface: Total 3,245 sq ft (301.5 m2)
    Superheater area: 1,029 sq ft (95.6 m2)
    Cylinders: Two
    Cylinder size: 19 × 28 in (483 × 711 mm)
    Tractive effort: 30,685 lbf (136.49 kN)


    LNER Class A4 (4468 Mallard)

    Power type: Steam
    Designer: Sir Nigel Gresley
    Builder: LNER Doncaster Works
    Serial number: 1870
    Build date: 3 March 1938
    Configuration: 4-6-2
    UIC classification: 2'C1'h3
    Gauge: 4 ft 8 1⁄2 in (1,435 mm)
    Leading: wheel diameter 3 ft 2 in (0.965 m)
    Driver diameter: 6 ft 8 in (2.032 m)
    Trailing wheel diameter: 3 ft 8 in (1.118 m)
    Length: 70 ft (21.34 m)
    Locomotive weight: 102.95 long tons (104.6 t)
    Locomotive and tender combined weight: 165 long tons (167.6 t)
    Boiler pressure: 250 psi (1.72 MPa)
    Cylinders: Three
    Cylinder size: 18.5 × 26 in (470 × 660 mm)
    Top speed: 126 mph (203 km/h) (529.4 rpm)
    Tractive effort: 35,455 lbf (157.7 kN)
    Locomotive brakes: Steam
    Train brakes: Vacuum





    Now, what I'm wondering is......could Milwaukee Road's Hiawatha's have beaten LNER's A-4's and their 126 mph (203 km/h) record, seeing that they regurlarly ran at 100 mph+ in service?
     
  2. mikewint

    mikewint Well-Known Member

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    I'm also not a Loco-guy and these behemoths pre-date even me but for what it is worth...
    The Class A were designed to average 80mph during any total run. As such they were designed to cruse at 100mph and be able to achieve 120mph. Anecdotal reports of higher speeds cannot be verified.
    In 1937 the Class A was replaced by the more powerful F7s (4-6-4) which were required to average 81mph on a regular basis. A French RR expert recorded a top speed of 125mph and a sustained run (4.5 miles) of 120mph
    The top recorded LNER speed is 125.88mph
    So my best guess is that the LNER would beat the Class A but it would be close between the LNER and the F4
     
  3. cocky pilot

    cocky pilot Member

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    The speed of pre war locomotives was just a vanguard for what came after. The german behemoth with powder injection and all the bobs and whistles set a record, the British in the build up to WW2 set another record but actually all they proved was the maximum speed of a dirct coupled locomotive. Like the speed of a straight winged propellor driven plane a dirct coupled steam locomotive has a natural limit to its speed.

    Having been on a train pulled by a train with the Sir Nigel Gresley (same design as the Mallard) doing the pullin its a bit like saying a Canberra is better than a Lancaster...well maybe it is but it doesnt sound or look the same and it was too late anyway.
     
  4. mikewint

    mikewint Well-Known Member

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    cocky, As I recall the track and bedding also play a major role is what speed can safely be achieved and maintained by any locomotive. The US versions were generally coupled to 9 passenger cars and only run over major commuter runs like Chicago to Milwaukee
     
  5. Lucky13

    Lucky13 Forum Mascot

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    If I remember correctly, think that it says in one of the Miwaukee Road books that I have, that their tracks between Chicago and the Twin Cities, were one of the best maintained tracks in the US at that time....
     
  6. mikewint

    mikewint Well-Known Member

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    They had to be. The posted schedule required the train to average 80mph (Class A) or 81mph (F4) thus the train had to run 100+mph whenever possible
     
  7. Lucky13

    Lucky13 Forum Mascot

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    What an experience that would have been, seen those pas by....! :shock:
     
  8. cocky pilot

    cocky pilot Member

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    The biggest factor in a trains max speed is a side wind which turns every wheel into a disc brake. A direct coupled steam train produces maximum torque at a standstill, the actual horsepower tails off at about 125MPH which is about the speed superheated steam expands.

    heres a steam beast

    Fastest Steam Locomotive
     
  9. mikewint

    mikewint Well-Known Member

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    CockyPilot, I'm not sure about your sidewind and disk brake statement. As to torque the same can be said for any engine. As speed increases more and more energy goes into pushing the air aside which increases with both the speed and the objects cross-sectional area. As to steam expansion the only limit is the speed of sound. the greater the temperature and pressure the greater the rate of expansion. So the trains max speed is determined by the beds ability to withstand the forces exerted on it by the train and the structural ability of the trains components to handle the forces generated by the superheated steam. I have used steam heated to 600+ degrees to set paper on fire
     
  10. cocky pilot

    cocky pilot Member

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    An internal combustion engine produces no power or torque at zero RPM a steam engine does because the combustion is in the boiler not in the cylinders. An internal combustion engine produces maximum torque at a given RPM and maximum power at another given RPM. A steam engines torque starts at its maximum and steadily tails off, the power produced, increases steadily with RPM and then tails off as the torque tails off.

    The reciprocating masses in a steam engine are huge and the forces to accelerate/ decelerate them increase by the square of velocity. It may be theoretically possible to make a faster, that is slightly faster direct coupled steam locomotive but it would be useless in practice. A direct coupled steam locomotive exerts very little force (MEP) at speeds above 125MPH it is a matter of physics, at or around 125MPH the laws of physics conspire against an increase.

    If you dont believe the wheels of a train act as brakes listen to a train on a curve, all modern high speed lines are practically devoid of curves and gradients.
     
  11. mikewint

    mikewint Well-Known Member

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    CockyPilot, Back to the braking effect first. any and all braking is through friction so unless this crosswind is producing friction? how could it have a braking effect. on a curve the inner and outer wheels need to turn at different rpms. since the ditect coupled drive wheels turn at the same rpm the inner wheel has to slip but braking effect?
    In 1906 the Stanley steamer set a land speed record of 127.7mph burning paraffin oil recently a British steamer averaged 137mph and a one way run of 151mph however for our purposes here that does not count because they used a steam turbine.
    My statement is/was that steam per se has no expansion limit save the speed of sound and the power is limited by the temperature of the steam and its pressure. wood burns at a lower temp than coal so the wood steamer could produce less power to begin with due to the lower inherent steam temperature. So we are back to my original statement "limited to the beds ability to handle the stresses placed on it and the physical ability of the engine components to handle the pressures and temperatures of the generated steam." In the real world making these components more robust increases weight and the increasing weight eats up the increased power. So the power to weight ratio decreases after a certain point is reached
    top fuel dragsters burning nitomethane develop 5000+ HP but the engine survival time is measured in seconds due to the monstrous stresses involved
     
  12. cocky pilot

    cocky pilot Member

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    Yes Mike back to the braking effect unless the cross wind is producing friction? (you said).......................
    Its called the flange effect If you read enough then you will find references to the effect of side winds I have managed it and so why cant you?

    If you think that steam has no expansion limit then please re write the laws adiabatic expansion, then calculate the maximum piston speed of a direct coupled train at 125MPH, calculate the energy required to accelerate and decelerate the various connecting rods involved and if you conclude that a direct coupled steam engine could exceed 125MPH then declare that Nigel Gresley was an ill informed idiot. Gresley did not even accept 126 MPH as a measure of Mallards speed because it was impossible even between 125 and 126 MPH the difference in forces is notable, calculable and in practice impossible.

    A steam locomotive is very big and makes a lot of noise but actually isnt very powerful Mallard produced about 1800 to 2000BHP the forces acting against it are calculable and more important they are exponential.

    continue if you want but really you havnt a clue, you sound like Flyboy and and his mate discussing pitot tubes and open bomb doors on Mosquitos......sounds clever but no connection to the real world now or in WW2.
     
  13. drgondog

    drgondog Well-Known Member

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    #13 drgondog, Jan 18, 2011
    Last edited: Jan 18, 2011
    Cocky - just out of curiosity is it possible to disagree without being 'disagreeable'? I personally understand the challenge but even I struggle through from time to time.

    I have zero clue about the fine art of locomotives other than the observation that drag is in fact a 'square of the velocity' issue and those beasts DEFINED flat plate drag ----> ergo the limits have to be defined by the thermal efficiency of the engine, the efficiency of the conversion of energy to the drive/wheels, the track condition, the mass of the system and the flat plate drag of the locomotive.
     
  14. mikewint

    mikewint Well-Known Member

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    #14 mikewint, Jan 19, 2011
    Last edited: Jan 19, 2011
    drgondog, thanks, you said it better than I. My Momma always said "Open the poke and make sure that there really is a pig inside."
    Obviously, there is a Theoretical and practical limit to all engineering. DaVinci's flying machines could not be built at that time because materials tech had not caught up with his ideas.
    How about a plane with 400ft wings. Is there a limit? Imposed by what? How about a plane that flies by flapping its wings? possible but worth the time, energy, and effort to produce?
    A locomotives power weight ratio is determined by material tech. Nigel was an excellent engineer, AT THE TIME. How about steam at 1000 degrees, 1500 degrees? the energy is there, confining it and getting usable work is the question and that is again materials tech.
    However on the practical side is it worth the time, energy, and effort to develop a locomotive with a power to weight ratio that will allow speeds over 125mph. The British steam cars (turbines) are approaching 200mph even now so why bother trying to produce the same effect with a reciprocating engine
    Adiabatic expansion also applies to internal combustion engines but since the fuel burns over time it replaces the energy lost as the piston is pushed downward
    I easily accept 125mph as the PRACTICAL speed limit of a steam powered locomotive until material tech produces a metal stronger and lighter than steel
     
  15. cocky pilot

    cocky pilot Member

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    if producing steam is the criteria then an oxygen plus hydrogen rocket trumps most conteders the subject of discussion is or was a direct coupled steam engine.

    BTW 5000 Horse power is quite a big number but not really in the case of locomotives and loads, do the math.
     
  16. mikewint

    mikewint Well-Known Member

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    true, which makes my point. raise the temp until you have the required energy content. 1000 degrees, 1500 degrees whatever is necessary to provide the needed energy. the problem is then to contain and utilize that energy in a controlled fashion. in a reciprocating piston system the problem is in finding a substance to withstand the stresses and keep mass in a tolerable range so as not to tip the power to weight ratio. If you are confined to plate iron/steel you will indeed reach a point of diminishing returns. That is a materials tech problem solved when someone discovers unobtainium with 20 times the tensile strength of steel and 1/20 its density
     
  17. cocky pilot

    cocky pilot Member

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    #17 cocky pilot, Jan 19, 2011
    Last edited: Jan 19, 2011
    You have changed the discussion from the practicalities of technology to using materials called unobtanium at 1000 degrees C ....I propose using superman to solve all future dicussions. Mike why not admit you were wrong for a change, you flyboy and dragondog may have a pint together which could be cathartic.

    PS MIke ......the mechanical properties of steel start to change above 130C they definitely change above the curie point ( if you know what that is) Above 700C you are into the normalization range and at 900C you are performing Austinization. Show me a ferrous alloy at 1500C and I will show you a ladle full of semi liquid metal...You do not have a clue what you are blathering about but are proposing ever more stupid fantasies about what metallurgy can achieve.
     
  18. mikewint

    mikewint Well-Known Member

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    Acutally I do not care whether the material is diamagnetic or paramagnetic and I was also not considering a solid solution of iron and carbon if you meant to write AusTENizing.
    Nor was I confining myself to ferrous metals or even metals for that matter.
    like that crazy dreamer Da Vinci I speculate on the possible because I realize that the impossible today becomes the everyday once the initial breakthrough is made
    so unobtanium, a dream today, tomorrow people will wonder how we did without it.
    may I remind you:

    1.When a distinguished but elderly scientist states that something is possible, he is almost certainly right; when he states that something is impossible, he is probably wrong.
    2.The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
    3.Any sufficiently advanced technology is indistinguishable from magic.
     
  19. cocky pilot

    cocky pilot Member

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    Dragondog the streamlining of locomotives was not for top speed but to improve mid range acceleration and reduce fuel consuption at high cruising speeds. That is a simple matter of physics which needs very little explanation. At uniform speed the energy expended is equal to the energy consumed (no pitot tubes involved). The only way a steam engine can increase speed is to accelerate. From 125 to 126 MPH it must acceletate the weight of the locomotive and its towed load, overcome the resistance of the bearings on all the wheels and overcome the energy required to increase speed. The pistons are at rest 2 tme in the power cycle and so the enegy required increases exponentially as speed increases.

    However look at the horizontal connecting rod on a steam locomotive. At very low speed this is balanced since acceleating upwards is approximately the same as its weight downwards. At high speed it is scribing an irregular arc. With respect to gravity it is scribing a half elipse and accending/descending rapidly. Once the rate of decent exceeds gravity then the pistons must provide contsant acceleration though the whole cycle BUT OF COURSE YOU KNEW THAT, in the same way you knew that at 400mph a pitot tube was in a wierd unnacountable area where 400mph can read as 600.

    commonly known as the dragondog/flyboy bollox effect to win a facile argument.
     
  20. mikewint

    mikewint Well-Known Member

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    In actual point of fact in any vertical circle gravity will always provide 9.8 m/s2 of that acceleration in the downward direction so to keep acceleration (centripetal) constant the downward force must be less than the upward force which must counteract the gravitational acceleration downward.
    your entire first paragraph is simply Newton's 2nd Law: mathematically F(net) = m a where F(net) = F(applied) - F(friction)
     
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