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Tornado

Discussion in 'Steam Traction' started by Leander's Shovel, Oct 20, 2007.

  1. Eightpot

    Eightpot Resident of Nat Pres Friend

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    Having seen the video and photos, if the piston valve had seized this is what I would have expected to happen, possibly damage to the expansion link and its bearings, too.
     
  2. Lplus

    Lplus Well-Known Member

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    However the radius rod is in direct compression, whilst the combination lever is in bending. Both loads reversing at high speed. Bear in mind the siezure doesn't have to be complete, so this is no immovable object vs irresistable force scenario, just much greater loads than usual. Given that situation I wouldn't put any bets on the combination lever surviving longer.

    Interesting blobs and runs of material on the end of the radius rod. Could be grease, but I can see why it might have been identified as white metal.
     
  3. fergusmacg

    fergusmacg Resident of Nat Pres

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    Although its always useful to hear of other failures of locomotives when a valve seized, although what happened on one loco will be totally different to another.

    It appears from what has been said that the valve seized and what followed was the combination lever broke before much/any damage occurred to the radius rod. If that was the case the expansion link could carry on and do what it does without (further?) damage to those parts - hence it looks ok in that video - although with just a brief view on a video its difficult to be sure. Meanwhile bottom part of the combination lever and the union link can flail about until the inevitable break below the crosshead. Meanwhile the top of the combination lever is swinging in motion driven from the expansion link. Well that's my take on it from just 220 miles away!
     
  4. W.Williams

    W.Williams Well-Known Member

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    Off an running in speculation mode now. If it wasn't a seized valve that caused this, then the A1 Trust must have jumped on the fake news bandwagon!

    Thing is tho, it was. The failure has occurred below the valve centreline axis, you are unlikely to see the other half of the failure, (the bit still on Tornado) from the platform.

    The good news is, she has liners! Maybe that cylinder wont have to come out! Although I fear an oxy-acc torch might.
     
  5. W.Williams

    W.Williams Well-Known Member

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    Indeed, the loose components doing their best to smash of the nearest shiny thing and generate a fair bit of metal shavings, which we see all over the assembly. Not to mention that this would have occurred as she came down from 90+ to a dead stop.

    How long does that take by the way? A mile?
     
  6. 30854

    30854 Resident of Nat Pres

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    In truth it's only exceptions (i.e. alerts) anyone's interested in when things go belly-up and which need to grab your attention. Just as with endless road signage, TV adverts or the promises of politicians, it's all too easy to become blasé when senses are continually bombarded by umpteen irrelevant - or worse - confusing messages.

    Watching YouTube clips of Class I US steam operation, I've been struck by quite how much modern IT kit festoons the cab. Leaving aside, for the moment, the aesthetic concerns of yer actual traditionalists, there's an awful lot for the footplate crew to keep an eye/ear on. Even with a traction inspector increasing the number of eyes and ears available by 50%, smooth operations in critical conditions are all too dependent on 'the human factor'. If you've worked on a footplate, ask yourself how many incidents you've heard of - anywhere - when you'd thought, on learning the full details, "is that what I would have done under those circumstances"? A fair percentage of the time, the answer will depend on what class of locos you're considering, as much as what's gone wrong.

    I wonder whether all the available gizmos and their associated "human interfaces" (screens, speakers, keyboards, handsets etc. etc.) are optimised to give crew, at need, the best shot at a least worst option? Looking at footage I've seen, my gut reaction is that they're not, with such kit as is employed seeming more 'tacked on' than integrated, although this is hardly surprising given commercial steam locomotive development pretty much hit the buffers long before the IT revolution was ever conceived of.
     
  7. NSWGR 3827

    NSWGR 3827 New Member

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    Another question worth asking would be if it is a valve seizure why has all the apparent visible damage occurred well below said valve? And as stated the combination lever has broken but there is also a sizable piece of crosshead attached to the union link. What broke First?

    Feel free to ask via PM of details of similar failure I referred to earlier.
     
  8. W.Williams

    W.Williams Well-Known Member

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    The weakest link breaks first, probably the combi lever, due to the stuck valve.

    The union link is then feee to jam into whatever takes its fancy.

    The cross head encounters one stubbourn union link and says “stuff this, I’m out”

    That’s my reading of probable events.

    Failures flow down the chain of weakest to strongest, so I suspect the last thing to let go was the crosshead, explaining why the union link is so badly twisted up. Id suggest it tried to resist the entire motion somewhere and lost out.
     
  9. fergusmacg

    fergusmacg Resident of Nat Pres

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    Why not post details of that failure you mention - always willing to learn from others.

    As for Tornado from what has come out so far and assuming its correct and trying to keep the description as simple as possible:

    1. the valve seized and the connection to the combination lever is stationary but can pivot at the end of the valve spindle (is it also guided on a A1?).

    2. the combination lever receives forward and backward motion from the reach rod at the top and the union link at the bottom - something had to give.

    3. With the pivot stationary there are two possibilities it looks like the break in the combination lever lost the battle - not surprising especially if one considers how much more support is usually given to the valve spindle.
     
    Last edited: Apr 17, 2018
  10. Enterprise

    Enterprise Part of the furniture

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    Not exactly comparable but some major air crashes have been attributed to over reliance on automation, digital instrumentation and consequent failure by the crew to understand what is happening.
     
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  11. talyllyn1

    talyllyn1 Member

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    If the piston valve had seized (or partially seized) the combination lever most likely fractured at or below the pivot point for the valve spindle, under stress from the moving crosshead. The loose end would then be thrashing about, along with the union link, under momentum from the crosshead. It's not surprising that the drop link would then fracture, dumping the union link and broken parts of the combination lever and drop link in the four foot as a "sub assembly". If the combination lever fractured below the valve spindle pivot, the radius rod would still be free to reciprocate above the pivot.
    I can't avoid thinking that it was fortunate that the shed "bits" stayed in the four foot and didn't fall between wheel tread and rail - the consequences of that just don't bear thinking about!

    The A1SLT will no doubt publish a thoroughly professional report in due course.
     
  12. Lplus

    Lplus Well-Known Member

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    I hate to think just what collateral damage has been caused by the flailing part.
    The detail of the broken part is interesting. If the crosshead is like the outer crossheads, the drop bracket is welded to the face of the crosshead in a rebate and the gudgeon pin goes through it. If I'm seeing it right (the union link is pointing backwards?) the break appears to have been across the hole for the gudgeon pin.
     
  13. fergusmacg

    fergusmacg Resident of Nat Pres

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    I think the public nature of the event will be the driving force for any report, lets hope the A1SLT learned from the initial problems they had with the boiler when it took some time for anything to be revealed.
     
  14. fergusmacg

    fergusmacg Resident of Nat Pres

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    I too did wonder if that partial part of the crosshead assy. was the hole for the gudgeon pin, the consequences of a failure of the crosshead/little end does not bear thinking about.
     
  15. W.Williams

    W.Williams Well-Known Member

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    Indeed, the remaining motion will have taken some abuse in the fallout. Hence my theory on the shavings being all over the motion.

    The crosshead does look like it broke across the hole, being a sharp change in geometry and the thinnest section, this is where the stress will have finally found a way out.

    The union link is a serious lump and is also in double shear, where as the cross head is in single shear, the cross head attachment was always going to lose out in that fight.
     
  16. MellishR

    MellishR Resident of Nat Pres Friend

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    And such incidents go back a long time, at least to the Lady Be Good: https://en.wikipedia.org/wiki/Lady_Be_Good_(aircraft)
    They had flown past their base but thought they couldn't have got so far so quickly so they continued to fly south -- into the desert, where they died.
    Apologies for increasing the thread drift.
     
  17. GWR4707

    GWR4707 Nat Pres stalwart

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    I assume that it was possible to take down certain pieces of the inside motion before she was moved as the videos suggest that she was noisy when being towed, but not that bad!

    From the log of the run published earlier it did seem to suggest that the brake application was not that hard but not a great time to be on the footplate with all that flailing around under the boiler?
     
  18. Lplus

    Lplus Well-Known Member

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    Indeed - fortunate that the upper part of the drop bracket remained to keep the gudgeon pin nut tight for long enough.

    I think the drop bracket is a separate piece of metal which is welded to the crosshead from top to bottom. The upper piece of the bracket seems to have remained in place to keep the gudgeon pin nut from getting loose. So the inner rod didn't need to be removed for the loco to be towed slowly as the crosshead itself would still be in one piece. The only bit likely to still move a lot would be the remains of the combination lever, but even that would be still if the loco was in mid gear. That said there may have been other damage due to the bits flailing about before they fell off.
     
  19. fergusmacg

    fergusmacg Resident of Nat Pres

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    This photo just found on the internet may help or confuse? (not my photo) Is shows to me that the combination lever did get a tad warm before it "let go" tuther end was a bit more sudden?

    u4ipy4ce copy.jpg
     
    Last edited: Apr 17, 2018
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  20. class8mikado

    class8mikado Part of the furniture

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    Don't get me wrong, I am enjoying this nuts and bolts discussion, its just my kind of thing; but having met some of the A1SLT, and even cleaned some of the motion parts being described I am also very, very sad indeed.:Depressed:
    Sad that it happened at all, and especially sad that the Halo of certainty and confidence that seemingly hovered over the Mighty 60163's smokebox has also clattered to the ground...
     
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