RMweb Premium Compound2632 Posted February 17, 2020 RMweb Premium Share Posted February 17, 2020 Turning the clock back a little: in 1896, T.G. Clayton, carriage & wagon superintendent of the Midland Railway, considered that 20 years was about the working life of a carriage and that in any case fashions changed so much over that time span that a 20 year old carriage was outmoded. In designing new carriages, he took the view that one should be trying to anticipate what the carriages of ten years' time were likely to be. Indeed, at that date, the Midland had only 20 carriages aged 21 years or more, all thirds. He noted that ten years previously (1886) Midland carriage design had been well ahead of that of other lines but several had since more than caught up. The outcome of this cogitation was, of course, the famous Midland clerestory [R.E. Lacy and G. Dow, Midland Railway Carriages (Wild Swan, 1986) p. 123]. Link to post Share on other sites More sharing options...
RMweb Premium kevinlms Posted February 17, 2020 RMweb Premium Share Posted February 17, 2020 3 hours ago, RLBH said: 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. I voted for 'Informative/Useful', but I mean Informative only, because I don't it will be Useful, next time I design aircraft spars! I don't have a clue and don't believe I'm going to contribute anything worthwhile! Link to post Share on other sites More sharing options...
RMweb Gold The Johnster Posted February 17, 2020 RMweb Gold Share Posted February 17, 2020 Never held me back, kevin... 4 Link to post Share on other sites More sharing options...
Edwin_m Posted February 17, 2020 Share Posted February 17, 2020 5 hours ago, RLBH said: 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. One where the number of takeoff/landing cycles does determine the fatigue life is the parts of the fuselage that withstand the pressurization, as the aircraft is almost always pressurized after takeoff and only depressurized before landing. There was the 747 in Japan that was inadequately repaired after a tail strike and ultimately (and close to the number of cycles later calculated) failed and blew the tail off. There was also the Siemens Combino tram, of which several hundred had to be modified when it turned out the stresses were under-estimated and there was a risk of the aluminium roof cracking and the heavy equipment mounted on it coming down onto the passengers below. The successor design was steel. Credit though to Siemens for describing the problem on their own website! https://assets.new.siemens.com/siemens/assets/public.1492593473.c92813ee7bbb340ac1677f1ecdb2934ab8989177.avenio-m-technical-article-en.pdf Link to post Share on other sites More sharing options...
PatB Posted February 17, 2020 Share Posted February 17, 2020 12 hours ago, RLBH said: 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. Whilst I'm not familiar with the Vickers case, I can think of other examples of components that will fail, even if unused. I have it on good authority, for example, that the magnesium alloy uses for the crankcase of the VW Type 1 (Beetle) engine will eventually develop cracks as it ages, even if it's spent all its life in storage and never been part of a running engine. Something that's not widely appreciated, even amongst VW enthusiasts and specialists and which contributes to the VW's reputation as an incurable leaker. Link to post Share on other sites More sharing options...
royaloak Posted February 18, 2020 Share Posted February 18, 2020 2 hours ago, PatB said: Whilst I'm not familiar with the Vickers case, I can think of other examples of components that will fail, even if unused. I have it on good authority, for example, that the magnesium alloy uses for the crankcase of the VW Type 1 (Beetle) engine will eventually develop cracks as it ages, even if it's spent all its life in storage and never been part of a running engine. Something that's not widely appreciated, even amongst VW enthusiasts and specialists and which contributes to the VW's reputation as an incurable leaker. Which is why a lot of classic racing or rally cars have had their original magnesium wheels replaced with alloy ones, magnesium simply ages. 1 Link to post Share on other sites More sharing options...
Wickham Green Posted February 18, 2020 Share Posted February 18, 2020 CAUTION : PEDANT MODE - "An alloy is a combination of a metal with at least one other metal or nonmetal." ........ which may well include magnesium ! Link to post Share on other sites More sharing options...
RMweb Premium Compound2632 Posted February 18, 2020 RMweb Premium Share Posted February 18, 2020 12 minutes ago, Wickham Green said: CAUTION : PEDANT MODE - "An alloy is a combination of a metal with at least one other metal or nonmetal." ........ which may well include magnesium ! @royaloak is distinguishing between magnesium alloy and aluminium alloy wheels. I believe that the corrosion problems with the former have been overcome in more recent alloys, though that doesn't help the classic car owners. Link to post Share on other sites More sharing options...
jim.snowdon Posted February 18, 2020 Share Posted February 18, 2020 Are you sure that, at this point, we aren't getting confused between plain simple fatigue failure and the effects of intergranular corrosion (the effects of which could easily precipitate fatigue failure)? Jim Link to post Share on other sites More sharing options...
Wickham Green Posted February 18, 2020 Share Posted February 18, 2020 If we're not careful somebody will bring this thread back to a model railway topic by mentioning Mazak rot ! 1 Link to post Share on other sites More sharing options...
jim.snowdon Posted February 18, 2020 Share Posted February 18, 2020 8 minutes ago, Wickham Green said: If we're not careful somebody will bring this thread back to a model railway topic by mentioning Mazak rot ! An excellent example of intergranular corrosion, exacerbated by impurities (lead, I believe) in the alloy, and, it would appear, still prevalent in some of the 4mm stuff being imported from China. Jim 1 Link to post Share on other sites More sharing options...
Administrators Phil Parker Posted February 19, 2020 Administrators Share Posted February 19, 2020 Can I remind you to play nice. If you get abusive then the post gets hidden and you end up on the naughty step. Thank you. 1 Link to post Share on other sites More sharing options...
DavidB-AU Posted February 19, 2020 Share Posted February 19, 2020 (edited) Obviously there is some very old stock in preservation still operating. Queensland Railways had a composite lavatory brake van built in 1882, rebuilt in 1920 as a brake second. It was used on the Cairns - Kuranda service, run for tourists but still a daily revenue service (in fact the only QR service that runs at a profit!) until 2004. Can anyone beat that? Cheers David Edited February 19, 2020 by DavidB-AU Link to post Share on other sites More sharing options...
Curlew Posted February 19, 2020 Share Posted February 19, 2020 15 minutes ago, DavidB-AU said: Obviously there is some very old stock in preservation still operating. Queensland Railways had a composite lavatory brake van built in 1882, rebuilt in 1920 as a brake second. It was used on the Cairns - Kuranda service, run for tourists but still a daily revenue service (in fact the only QR service that runs at a profit!) until 2004. Can anyone beat that? Cheers David I am guessing that Ffestiniog and Talyllyn stock is at least partly original, in which case it has been running for a very long time - though maybe not quite continuously? Link to post Share on other sites More sharing options...
RMweb Premium Compound2632 Posted February 19, 2020 RMweb Premium Share Posted February 19, 2020 2 minutes ago, Curlew said: I am guessing that Ffestiniog and Talyllyn stock is at least partly original, in which case it has been running for a very long time - though maybe not quite continuously? The Brown, Marshalls carriages of 1866/7 are described on the Talyllyn Railway's website as having been in continuous service and are pretty much original, more so than the Lancaster carriage. The Ffestinog Railway's Brown, Marshalls carriages, which are two or three years older, seem to have been largely restored in the 50s and "rebuilt" more recently, which suggests to me that they retain less original material. 1 Link to post Share on other sites More sharing options...
RMweb Gold The Johnster Posted February 19, 2020 RMweb Gold Share Posted February 19, 2020 Back to Trigger's broom. A wooden carriage can easily have replacement parts put in when components rot, which begs the question of how much is original in any case. Some of the IoM stock must be getting on a bit as well. We've had a similar discussion with locomotives, many of our most historic preserved examples containing very little material from their original construction. The LNWR in particular never threw anything away that it could find a further use for and it is reckoned that some Claughtons still had wheel centres from Grand Junction locos when they were rebuilt to Patriots. One might argue that the only original part of Flying Scotsman is the nameplate, and there are others... 2 Link to post Share on other sites More sharing options...
RMweb Premium Compound2632 Posted February 19, 2020 RMweb Premium Share Posted February 19, 2020 1 minute ago, The Johnster said: Back to Trigger's broom. A wooden carriage can easily have replacement parts put in when components rot, which begs the question of how much is original in any case. Rot will only occur through neglect; a well-maintained carriage built from sound materials ought to survive pretty well. The TR's Lancaster carriage is recorded as receiving new frames in 1958, the implication being that such major reconstruction has not been necessary for the Brown, Marshalls carriages. They're certainly "original" in contrast to the ex-Penrhyn carriages that were reconstructed out of all resemblance to their original form. 8 minutes ago, The Johnster said: it is reckoned that some Claughtons still had wheel centres from Grand Junction locos when they were rebuilt to Patriots. A flight of fancy. Quite apart from significant difference in design - those large bosses on the Claughton wheels - the GJR had no 6'6" engines, the Allan type being 6'0". Also, one would have needed three Allan singles for every Claughton, so the supply of GJR wheel centres wouldn't have lasted very long! 1 Link to post Share on other sites More sharing options...
Wickham Green Posted February 19, 2020 Share Posted February 19, 2020 1 hour ago, Compound2632 said: A flight of fancy. Quite apart from significant difference in design - those large bosses on the Claughton wheels - the GJR had no 6'6" engines, the Allan type being 6'0". Also, one would have needed three Allan singles for every Claughton, so the supply of GJR wheel centres wouldn't have lasted very long! Not necessarily the driving wheels ! .............. but it's rather unlikely anyway. 1 Link to post Share on other sites More sharing options...
RMweb Gold TheSignalEngineer Posted February 19, 2020 RMweb Gold Share Posted February 19, 2020 1 hour ago, The Johnster said: The LNWR in particular never threw anything away that it could find a further use for and it is reckoned that some Claughtons still had wheel centres from Grand Junction locos when they were rebuilt to Patriots. Unlikely, although they were pioneers of recycling via their steelworks at Crewe. Much of the raw material for casting came from dismantled stock. 2 Link to post Share on other sites More sharing options...
RMweb Gold Bucoops Posted February 19, 2020 RMweb Gold Share Posted February 19, 2020 3 hours ago, The Johnster said: Back to Trigger's broom. A wooden carriage can easily have replacement parts put in when components rot, which begs the question of how much is original in any case. Some of the IoM stock must be getting on a bit as well. We've had a similar discussion with locomotives, many of our most historic preserved examples containing very little material from their original construction. The LNWR in particular never threw anything away that it could find a further use for and it is reckoned that some Claughtons still had wheel centres from Grand Junction locos when they were rebuilt to Patriots. One might argue that the only original part of Flying Scotsman is the nameplate, and there are others... Flying Scotsman's nameplates are replicas the originals were removed in the 90s. One was sold in 2018. 1 Link to post Share on other sites More sharing options...
RMweb Gold adb968008 Posted February 19, 2020 RMweb Gold Share Posted February 19, 2020 6 hours ago, The Johnster said: The LNWR in particular never threw anything away that it could find a further use for and it is reckoned that some Claughtons still had wheel centres from Grand Junction locos when they were rebuilt to Patriots. One might argue that the only original part of Flying Scotsman is the nameplate, and there are others... 5 hours ago, TheSignalEngineer said: Unlikely, although they were pioneers of recycling via their steelworks at Crewe. Much of the raw material for casting came from dismantled stock. Anyone looked at 45596’s Bahamas’s front pony wheel to check ? Link to post Share on other sites More sharing options...
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