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Longevity of raiway carriages

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9 hours ago, Nearholmer said:

As Mr Ingram has made clear, some carriages only last five minutes before having condemnation heaped upon them.

 

How long coaches last before being condemned in the other sense depends upon many things;

 

- changing traffic demands, which have seen-off or seen-demoted many vehicles with "life left in 'em"; 

 

- decay, of either wood or steel body structures, for example some post-WW2 all-steel coaches actually didn't last very well at alll, because welding and corrosion-proofing knowledge had yet to be accumulated;

 

- bogies becoming beyond economic repair and taking the rest of the vehicle with them;

 

- need for extensive and uneconomic re-wiring (a problem with some quite modern stock as demand for infotainment, mood-lighting etc has grown);

 

- etc.

 

Book lives of c30 years seem to have been common, and survival in service of c40 years equally so.

 

Hefty old traditional steel under-frames are bordering on indestructible, so have been re-used in many cases, notably by SR and BR(S).

 

Many late C19th wooden six-wheelers were doubled-up onto steel bogie chassis in the Edwardian period, and survived for a further fifty years.

 

The D stock of London Underground has survived super-well, due to aluminium structures, new bogies, and internal refits, and now new traction packages as they become diesel-electric or battery.

 

Have you been to the Isle of Man? 

 

How long is a piece of string?

 

Kevin

 

 

Another reason is that modern vehicles have a much higher usage, meaning they accumulate the miles much quicker.

 

I remember reading that in 1927 when the LMS built new stock for the Royal Scot, they built 3 sets. Two ran 6 days a week on a single journey and the 3rd was a maintenance spare.

Later formations (after 1974 electrification to Glasgow) were expected to do a return trip each day AND a fill in turn to places like Ayr. So roughly 2 1/2 times the daily mileage, plus no dedicated spare.

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Interesting point about mileage, because it only seems to affect the life of the wheel-sets, bogies, draw-gear, corridor connections etc.
 

Bodies, or on older stock under-frames, must experience stresses and strains in operation, but are presumably made so strong in order to provide rigidity for comfort reasons that their fatigue-life is effectively infinite.
 

Not like aircraft, where the fatigue-life of the fuselage is an important factor in life expectancy.


Be interesting to know for certain.

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Materials can have a huge effect on frame life. Speaking purely from an Australian experience, when the Southern Aurora was introduced in 1962 it had high carbon steel frames and mild steel brake blocks to reduce noise during braking when all the passengers were asleep. Some bean counter in the 80s decided that composite brake blocks were cheaper, but they were much noisier due to vibration. As a result many cars had metal fatigue around the bogie pivot when they were retired in the early 90s.

 

In comparison, the Indian Pacific was built in 1969 and enterered service in 1970. They had corrugated stainless steel frames of a Budd design and composite brakes from day 1. They are still in service today.

 

Cheers

David

 

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Island Line (Isle of Wight) is shortly to withdraw it's ex LU 1938 stock - 82 years?

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The original Glasgow Underground stock was long-lived 1896–1977

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Queen of Scots observation car 41, entered service in July 1891.. its still in service today on the network..

 

 

6484EA25-D03D-4AC8-BA4E-3EFE50D35AD7.jpeg.7a196c8f864deb6745645a0ae557763d.jpeg

 

The first 5 vehicles on this train have combined,  more than 500 years service between them..

 

81C52339-6C1C-4550-AA45-6BA4C36AE98A.jpeg.531341387b1600341eba129784ff761d.jpeg

 

Edited by adb968008
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11 hours ago, DavidB-AU said:

Materials can have a huge effect on frame life. Speaking purely from an Australian experience, when the Southern Aurora was introduced in 1962 it had high carbon steel frames and mild steel brake blocks to reduce noise during braking when all the passengers were asleep. Some bean counter in the 80s decided that composite brake blocks were cheaper, but they were much noisier due to vibration. As a result many cars had metal fatigue around the bogie pivot when they were retired in the early 90s.

 

In comparison, the Indian Pacific was built in 1969 and enterered service in 1970. They had corrugated stainless steel frames of a Budd design and composite brakes from day 1. They are still in service today.

 

Cheers

David

 

David,

 

Having been involved with railway rolling stock for a considerable part of my career, I would be inclined to suspect that any linkage between fatigue failures around the bogie pivots and the adoption of composition brake blocks is likely to be coincidental. The alternating stresses and strains that cause fatigue failure are more likely to have come from poor dynamic performance of the bogie and/or poor track quality. A classic example of that on UK stock was the persistent loosening of the bogie pivot pins on the LU C69/77 stock, which were bolted to the underframe.

 

Underframe and body fatigue are unusual but not unknown in the UK. London Underground's 1972 tube stock, which is now approaching 50 years of service, is reported to be suffering from cracking in the swan neck sections of the main underframe longitudes. There are also some telltale patches on the body panels, which are structural, by the inner door openings, which are known high stress areas in monocoque bodyshells.

 

Jim 

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18 hours ago, PatB said:

Wasn't some of the stock in the Charfield crash of 1880s vintage? So that would have been ~40 or more years old. 

 

Yes but those were rather specialised vehicles - a pair of 6-wheel TPO vans dating from 1885. They were at the rear of the train and suffered only minor damage. The vehicles that were destroyed were mostly ex-Midland or ex-M&SW Joint Stock clerestory carriages from around the turn of the century and still gas lit. Full details in Col. Pringle's report. A principal recommendation that the LMS acted on reasonably quickly was the marshalling of all-steel passenger brake vans at the head of express trains.

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19 hours ago, kevinlms said:

How long is a piece of string?

All the way to the end, from the other end.  The real question is how long is a loop of string...

 

19 hours ago, Nearholmer said:

 

Not like aircraft, where the fatigue-life of the fuselage is an important factor in life expectancy.

Aircraft that do not have the ceiling to need pressurised cabins can last a very long time, the classic example being the DC3; many are still flying with replacement turboprop engines having seen off the original radials years ago.

 

10 hours ago, adb968008 said:

Queen of Scots observation car 41, entered service in July 1891.. its still in service today on the network..

 

it's replacement Gresley style bogies are more modern than 1891, though.  Not that they aren't worthy of mention in themselves, as they must date from no later than the early 60s, nearly 60 years ago now, when the last Gresley bogies were put under Manchester/Liverpool area 25kv suburban emus (and probably from much earlier).  1891 or not, it looks remarkably like a 1st generation dmu vehicle!

 

 

Edited by The Johnster
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In Fraser, Geen and Scott's The GWR in the 1930s, vol 1 there is a picture (18) which includes  a C3 and in vol 2 there is a picture (214) which also includes a C3.  Both pictures apparently post date 1933.  According to Harris, C3's were built 1891/2 and some were built as BG/NG convertibles, so must have been over 40 years old when photographed.  Whether the particular coaches photographed were converted from BG or were NG from the start, I don't know, but to go back to the question posed by BorderCollie at the start, regarding whether GWR broad gauge convertible carriages could have been seen in 1929, the answer is coaches of the same type certainly could, but not on crack services.

PS Identification of the coaches is what is stated in the books, it is well beyond my expertise.

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17 minutes ago, eastglosmog said:

PS Identification of the coaches is what is stated in the books, it is well beyond my expertise.

 

@Penrhos1920's wonderful website is your friend. Using this, even a tyro Midland enthusiast can pass himself off as an expert on Great Western carriages.

Edited by Compound2632
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On 15/02/2020 at 08:18, Nearholmer said:

Interesting point about mileage, because it only seems to affect the life of the wheel-sets, bogies, draw-gear, corridor connections etc.
 

Bodies, or on older stock under-frames, must experience stresses and strains in operation, but are presumably made so strong in order to provide rigidity for comfort reasons that their fatigue-life is effectively infinite.
 

Not like aircraft, where the fatigue-life of the fuselage is an important factor in life expectancy.


Be interesting to know for certain.

I recall from somewhere that steel can have an infinite fatigue life if the variation in stress is below a certain limit.  But aluminium will suffer from fatigue eventually whatever the stress regime.  

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On ‎14‎/‎02‎/‎2020 at 22:10, royaloak said:

Yet some were withdrawn after just 10 years service due to different travelling habits making them surplus to requirements.

 

...including Mk1 long-fame suburban (non-gangway) stock, some of which became Carflats.

 

Bill

 

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3 hours ago, Edwin_m said:

I recall from somewhere that steel can have an infinite fatigue life if the variation in stress is below a certain limit.  But aluminium will suffer from fatigue eventually whatever the stress regime.  

Could someone remind the remaining DC3s?

 

 I will not claim to be an expert in this, but my recollection is that for the fatigue life to be less than infinite two factors are required. One is the level of stress in the material (and localised stress raisers such as corners, changes in section and holes are important in this), the other is that the stress is repeatedly reversed.

 

Jim

 

 

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2 hours ago, jim.snowdon said:

Could someone remind the remaining DC3s?

 

 I will not claim to be an expert in this, but my recollection is that for the fatigue life to be less than infinite two factors are required. One is the level of stress in the material (and localised stress raisers such as corners, changes in section and holes are important in this), the other is that the stress is repeatedly reversed.

 

Indeed.  But my dim recollection from university lectures (in a topic I wasn't much interested in) was that there was a level of reversing stress that steel could withstand indefinitely, but not so for aluminium.  That's entirely consistent with the possibility that the stresses experienced in DC3s are such that the fatigue life is in the hundreds of years.  

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Corrosion aside, steel will theoretically last forever below a certain level of stress. There is no minimum level of stress below which aluminium will not eventually fail. A empty 15g aluminum drink can will eventually fail under its own weight.

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An interesting concept. Perhaps I had better stop using aluminium alloy rails for our 7.25" gauge railway? Or should I suspect that my successors, and probably their successors will have long since turned to dust before the rails give up? :scratchhead:

 

Jim

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I remember getting onto one of Sydneys single decker 'red rattler' carriages sometime in the late eighties or very ealy nineties and noticing the inscription on the bogie - 'Clyde engineering 1927'.

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59 minutes ago, monkeysarefun said:

I remember getting onto one of Sydneys single decker 'red rattler' carriages sometime in the late eighties or very ealy nineties and noticing the inscription on the bogie - 'Clyde engineering 1927'.

 

The last of the 1927-29 Standard stock was retired in 1992. They were still doing full overhauls on them until 1988.

 

Cheers

David

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One of the basic principles of fatigue is the S-N curve, where the level of stress (S) is plotted on the vertical axis of a graph, and the number of cycles to failure (N) is plotted along the horizontal. Every material has its own curve. In general, ferrous metals have a curve that slopes down steeply initially, and then levels off and never falls all the way to zero, continuing horizontal at some positive value of S. As long as the level of cyclic stress is kept below this value, a steel component will last forever or, at least, won't fail as a result of fatigue. Aluminium alloys, AFAIK, all have curves which, at some point, cross the horizontal axis. IOW, any level of cyclic stress will eventually induce failure after a finite number of cycles. This number may be very large, but is, theoretically, reachable. 

How critical this is depends heavily on how quickly stress cycles are accumulated. For example, relevant to the DC3 aircraft, an aircraft wing spar's most dominant stress cycle is probably the transition from flying to not flying, and so N accumulates roughly as the number of flights. On the other hand, the stress cycles of a con-rod in one of its engines accumulate as one per engine revolution, or thousands per hour, and so it scoots along the N-axis at a much greater rate. 

For railway rolling stock, I would expect the N for the running gear to be partly related to the number of rail joints and crossings that the wheels cross, and partly to the various vibrations and resonances that become more and more significant as speed rises.

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On 15/02/2020 at 05:41, PatB said:

Assuming the Newcastle Metro is still using its original stock, they'll be ~40 years old now. Its a bit worrying to think I rode on them when they were almost new. 

VERY worrying that I photographed a couple of them when they were almost new*  -  but I STILL haven't travelled on them ! ( Must hurry up ! )

 

* interestingly, the next couple of photos show "the new “Ark Royal” being fitted out .... Amid the cranes of Swan Hunter’s shipyard" : maybe someone's got a 'Longevity of warships' and/or 'Longevity of shipyards' thread ? 

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On 16/02/2020 at 04:01, The Johnster said:

.......  1891 or not, it looks remarkably like a 1st generation dmu vehicle!

I believe the end IS contemporary with 1st generation DMUs.

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On 15/02/2020 at 11:01, Curlew said:

The original Glasgow Underground stock was long-lived 1896–1977

........ but wouldn't have lasted much longer - you could see and HEAR - the body moving every time it stopped or started !

Edited by Wickham Green
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On 14/02/2020 at 11:43, Fat Controller said:

The L&SWR, later the SR, were pretty 'careful'. When they started an electrification scheme, prior to WW1, the stock used bodies salvaged from 19th century stock. The underframes were not wasted, but used under 'new' bogie Passenger Luggage Vans; one of which carried Churchill's coffin from London to Oxfordshire in January 1965.

Yes, the Southern 'kit-bashed' bodies from all three principal constituents onto new chassis for their 1920's suburban electrification schemes ......... and when the bodies were eventually deemed life expired they stuck new Bulleid-style bodies on and, as EPB units, many of the chassis ran on into the eighties.

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6 hours ago, PatB said:

For example, relevant to the DC3 aircraft, an aircraft wing spar's most dominant stress cycle is probably the transition from flying to not flying, and so N accumulates roughly as the number of flights.

I understand that in practice it's cyclic loading due to turbulence (there's always some turbulence) that drives fatigue life, which is largely a function of flying time. Except that some flying hours are more equal than other flying hours. Aircraft (and ships, for that matter) can be fitted with gadgets that measure the stress cycles in the main spar and convert it to equivalent cycles at a certain standard stress level.

 

Rather highlighting the point about aluminium failing under any cyclic stress at all, the Vickers Valiant is of interest. After several fell apart in flight, the main spars were examined and found to have severe fatigue cracking. Vickers had built a number of spare wing spars which had never been flown - and they, too, had appreciable fatigue cracking. The properties of the particular aluminium alloy used on the Valiant were so poor that thermal and handling loads for the spares were enough to cause them problems.

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