Listen, I have a question for anyone who can answer it. I've read that British steam locomotives, well some of them, had copper fireboxes. Anyone know the reason why?
Copper is more thermally conductive than steel. It certainly can't rust, but I'm not sure if it's still less susceptible to corrosion than steel. Those would be the good parts. On the downside, it costs more; and it's not as strong. The latter might be negated by using thicker material, but see cost again. I think it would also be easier to form for an equal thickness.
Ed (one of anyone)
I did a Google search for locomotive copper firebox and below is one result. There are other results also.
http://tinyurl.com/664hsmb
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Thanks for the answers, gentlemen! I know there was a British locomotive displayed at the B&O's "Fair of the Iron Horse" in 1927, and that one had a copper firebox, to the amazement of the American railroaders. I was surprised to read of one built that "late" in the steam era still using copper instead of steel. Presumably there were others.
Speaking from experiance with model steam locomotives (11/2" scale). Copper firebox/boiler is the way to go. They are faster to get up to operating pressure, eaiser to control the fire in the firebox. And use much less coal than a steel firebox/boiler. I would think these same benefits would be found in the prototype too.
About forty years ago I was working with a boilermaker who had been in England with one of the U.S.Army Railway outfits during WWII. He mentioned that some British engines had copper fireboxes because of the better heat transfer and that they (the British) had a couple of men that went around to various shops just to do the welding on the copper fireboxes.
Interesting responses from everyone, and I thank you all. As far as corrosion resistance we have "living" proof of that on the Civil War battlefields here around Richmond, Va. On display are 12 pounder bronze "Napoleon" field guns, and aside from a green patina all are perfectly serviceable and capable of being fired at the age of 150. The Yorktown battlefield has bronze guns from the Revolution on exterior display and the same applies. Of course, bronze WAS a pretty expensive matierial to make cannon tubes from, but it was considered worth the expense just for the corrosion resistance, among other things.
Thank You.
Copper foreboxes were the norm in American Railroading for as long as most engines burned wood for fuel. With the changeover to coal it was noted that copper was no longer satisfactory. Wood soot and ash is soft but coal ash and cinders are very abrasive. Copper fireboxes just couldn't stand up to a forced draft coal fire so steel came into use because of its superior resistance to abrasion.
Here's a quick summary of the pro's and cons of copper fireboxes compared to steel fireboxes.
Advantages:
- Copper is a superior conductor of heat (~6 greater than steel)
- Thicker plates give greater thread contact of staybolts
- Scale is less likely to develop due to greater expansion/contraction
- Copper is minimally affected by corrosive water
- Minimal corrosion or wastage
- Scrap value of copper is high
Disadvantages:
- Steel is much cheaper
- Steel plates are thinner, reducing weight
- The seams of the entire firebox can be welded, eliminating rivets and double thickness of plates (which retards heat transfer)
- No galvanic action between dissimilar metals
- Less expansion of steel reduces bending stress on staybolts
- Abrasive wear due to cinders is much higher with copper than steel
Hope that helps!
"If a nation expects to be ignorant and free, it expects what never was and never will be." Thomas Jefferson
Danke shoen, Herr Rittmeister von Burgard!
Hi Firelock
About all said so far . Maybe a note to add : Lower heat transfer of steel caused problems when boilers originally designed for copper boxes were later equipped with steel boxes , still riveted at that time . Steel qualities were inadequate leading to frequent failures by ruptures firebox sheets, cracks usually starting from lower end at foundation ring . Why so ? As firebox sheets got heated by fire , metal could not expand freely because of restricting influence of staybolts and surrounding boiler sheets . In normal locomotive operation fire side of firebox sheets got roughly twice as hot as outer sheet to name a rule of thumb – clearly this meant tension to build up due to unequal thermal expansion . Fatal : sheets got compressed when they were hot and they got re-expanded when cooler – that left a dimensional deficit at the end of a cycle .
In a boiler of the Stepensonian type thermal expansion of firebox sheets was suppressed by cooler outer sheets and staybolts because inner and outer firebox sheets were held firmly in relative position by staybolts . Even at firing up while getting steam pressure to operating level , forces suppressing expansion of firebox sheets rose above elastic limit of material , yield point was reached in normal operation, so firebox sheets suffered plastic deformation . If they could have cooled down from that temperature , shrinking freely , they would have ended up slightly smaller than before the heating / cooling cycle . However , staybolts and out sheets were again hindering , in this case causing reverse of the former plastic deformation – only this reverse action was less than complete because it worked on cooler sheets with higher resistance. In process of heating / cooling , staybolts , too , were being deformed to and fro , submitting them to pulling as much as bending forces , the latter causing the stays to work in their threaded holes which caused copper to yield , thus widening the hole , causing leakage .
Copper plates by themselves were quite enduring to these repeated cycles of plastic deformation and in sheds staybolt heads were repeatedly expanded to re-tighten seating. High heat transfer rate of copper also helped to balance evaporation rates of firebox and tubes part of boiler so that little attention was given to relations between radiation or direct heating surface and indirect surface , generally considered identical with tubes surface (this was not always true as I will mention further down) . In the years around 1900 to WW-I more concern was directed to shape of firebox with narrow or wide grate , adapting boiler form to vehicle chassis in consequence of chosen wheel arrangement . Boiler form and length much followed vehicle chassis form and with 4-4-0 and 4-6-0 or 4-4-2 and 2-8-0 engines this lead to acceptable forms of boilers . Yet, things changed dramatically with the next steps towards Pacifics, Mikados and – to lesser degree – Decapods. Early Pacifics , namely , suffered from boilers derived from Atlantics and given longer tubes . Results showed , this was clearly not the way to engines performing as anticipated . Some early Pacifics were not just shy of showing superiority over Atlantic ancestors but actually fell short of them , as with deGlehn Atlantics of the Nord Railway (France) that had a reputation for very lively performances . It was left for next generation of engineers to find out tubes surface in relation to firebox surface had become disproportional , on top of that tubes dimensions by themselves had in cases attained extreme values that in spite of larger total evaporation surface could cause about nil increase of steaming capacity of these boilers , simply because gas flow rate and thus combustion had become compromised . As long as these boilers had copper fireboxes , small direct heating surface was helped by high heat transfer for acceptable steaming . When such boilers got replacement steel boxes due to shortage of copper , problems started multiplying as the (then too small) firebox surfaces overheated and caused excessive temperatures at firebox tubes wall . All this caused steel sheets to crack prematurely and frequently . Terrible ‘remidies’ were ‘invented’ by some railways , cutting away cracked steel sheets and riveting on copper inserts . Of course this lead to rapid corrosive consumption at the joining areas of the two electrolytic differing materials and generally must be considered tampering rather than repairing . However , in war time any locomotive that could pull a load on the road was called upon , no regards to firebox leaking . In the 1930s higher boiler pressures , larger boilers with larger grates had slowly lead locomotive construction towards steel fireboxes , in the large majority still to much the same construction as copper boxes .
In Germany , between 1920 to ‘25 DRG had established their steam loco design standardization system when boiler construction was still based on copper boxes . RP Wagner , leading head in putting up the vast program of detailed standardization , had established his so-called ‘long boiler’ concept , characterized by fireboxes of simple straight forward design , average size and grate surface with no attempt to maximize radiation heating surface or volume as to Wagner’s theory main evaporation was (supposed to be) by tubes barrel . When these boilers were built with copper boxes , all that caused minor concerns were tendencies to tubes leakage at the firebox tubes plate . It is quite interesting to read in retrospect how detail changes were adopted to repair practice in hope to contain (not solve) the problem , in fact “vershlimm-bessern” (improve-worsening) matters in a vicious circle , such as attempting to improve seating of tubes by thicker tube plates – only to sharpen the problem of tubes plate expansion at the fire side , thus encouraging again tubes shifting with changing heat loads according to engine working rate in traffic . During the 30ies , Wagner type boiler got equipped with steel boxes , then of tolerably suitable quality steel , IZ-I [i-z-one] as by designation then used , meaning the grade of steel was designed to withstand alternating cycles of plastic deformation (to last over a period of running between classified overhauls – which was not reached to acceptable degree , partly due to material , partly to boiler design) .
With steel heat transfer dramatically lower than that of copper , Wagner type boilers acquired a major design problem as their firebox surface now proved clearly on the small side in relation to overall boiler and engine size and output demand . At higher steaming rates (medium high by American contemporary standards) and with short brick arch free gas volume and travel from fire bed to tubes plate was too short to complete combustion before gases entered tubes (in this case some initial length of tubes should have been added to ‘actual’ radiation heating surface, leaving only the rest of tubes length for indirect surface) . Logically , this left tubes plate with excessive heat load and with tubes of large diameter this lead to epidemic tubes leakage as with tubes expanded to the holes surface in the plate , two opposed directions of heat expansion – tubes outwards , plate holes inwards – worked against each other , easily surpassing elastic limits of tubes , i e compressing their ends which lead to leaking as soon as the heat load level came down . Again , it is interesting to read how in test reports attention was drawn to “the curiosity that leakage did not occur during sustained high steaming rate but only afterwards” (off hands quote from 03 class light Pacific Grunewald test reports and translated) the writer of the report explicitly noting that “the earlier point of view boilers would not stand high steaming rates is not supported by our high performance runs ..” continuing to wonder what might cause leaking tubes and staybolts in the aftermath of such a run . Similar phenomenons were experienced in traffic when at the end of a hard run , throttle was eased nearing a stop ; when departing , a crew had to find things meanwhile had changed to the worse . It seemed to have been practice to shut off rather abruptly , which lead to temporary lack of air supply in relation to fire bed temperature and combustion rate and this might have caused solid clinkering , spoiling access of air to grate on the remaining part the run ; combustion problems following an intermediate stop had , it can be read in reports , repeatedly been complained about by engine crews and sheds . It doesn’t take much to imagine troubles an engine crew encountered having to continue with an engine that had tubes leaking and grate partly clinkered .
In due course Grunewald testing department did find out pretty well what went wrong and what was needed to improve things . One of the wanting points obviously was ‘soft draughting’ initiated by Wagner both to improve cylinder efficiency by low back pressure and to improve boiler efficiency by low l factor in combination with introducing “little and frequent firing” (as the method was called) to keep a shallow fire bed . While in theory this way hand firing should have come as near as can be to continuous firing by stoker , I could understand a fireman who would have put on twenty shovels in a row to sit down and have a rest , smoking for the next couple of miles . However it was left for post WW-II DB to put draughting right . Tragically , Wagner himself prevented his initially very creditable work to reach full success with his resisting possible remedies by collective effect of small improvements , invariably pointing to established standardisation , brushing off complaints with quick-witted sarcastic returns that more than once silenced a critical voice . Complementing improved draughting , welding of firebox and staybolts plus tubes in tubes plate would have cured leakage problems . With the advent of Pacific #3566 rebuilt for high performance on the Paris Orleans railway , boiler welding was being introduced in France .
When a few years later Chapelon’s first 4-8-0 , more radically rebuilt former small drivered Pacific , was prepared for road tests , Prof Nordmann of Grunewald testing department was invited and having attended runs was much impressed with the performance of that “rather small engine” as he had initially remarked on #4701 , freely acknowledging Chapelon’s success . In the years following , various proposals were being brought forward in DR HQ to break what was meanwhile recognized as ‘Wagner’s stagnation of progress’ . Borsig locomotive works took a leading position in promoting a substantial change towards ‘high performance locomotives’ but nothing had come to fruition before WW-II . It was of necessity when reserves against welding were largely thrown aside with mass production of the 52 (and 42) class austerity Decapod – yet it was left for F Witte on DB finally to establish a modernized design scheme with the 1950 standardization , including fully welded boiler construction , including quite a number of detail design improvements aimed at increasing longevity of components such as Tross staybolts contoured for uniform bending moment and a number of further due modernizations . Welding boiler components offered superior longevity regarding tightness , thermo-mechanical sturdiness and uniformity of heat transfer as the boiler was virtually fused into one piece . Namely , there were no staggered joints of firebox plates leading to overheating , bending moments could not work staybolts or tubes in holes to become leaky (until staybolts break or tube ends crack, that is) . Since many detail design and maintenance improvements to all components of engines were also applied to Wagner Pacifics as they came due for large overhaul (L4) , Wagner’s ‘long boiler type’ finally lived up to perform as had been high hopes when the first standard Pacifics were being tested – only , that was long after Wagner had resigned in 1941 and meanwhile DB had placed orders for E10 electrics and V200 diesels to replace Pacifics and in the end all steam …
Regards
Juniatha
Thanks for the reponse, Juniatha. It amazes me that something we would think as a relatively simple piece of machinery such as a steam locomotive could have so many complicating factors. It just increases my respect for the designers and builders of the same who had nothing to go on but experience, mathematics and the metalugy of the time. No computer models or computer assisted design, just their own minds and guts. As a student of history a lesson I re-learn constantly is never underestimate the sophistication of the "old-timers", they'll surprise you every time!
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