Paul
I had got the joke about the soccer game results ./. loco class ## alright - only , somehow in this forum we tend to get overly correct - some more some less - usually I'm the more easy going type , yet sometimes I get an itching , too .
I guess you point to the never-ending , never quite serious ribbing of Austrians and Bavarians . Seen from Munich , people in Vienna allegedly are still in nostalgia about the loss of the k&k Austrian-Hungarian Empire ( and true : while I was in Vienna , *I* tended to feel it , strangely ) - seen from Vienna the Munichians are forever trying to compete with fashionable places like Paris , London , New York , in delusion of grandeur wishing to adopt the Frank Sinatra slogan 'if you can make it here - you can make it everywhere' in his song about NewYork - the city that never sleeps .. oops ? never sleeps ? b-but wait a minute , that's going too far for little Munich where the lights still go out pretty much after 1 o'clock in the night .. *gee*
Nice to learn about your Great-Grandfather - and yes Hungarian language *is* very special indeed !
Regards
Juniatha
Juniatha Hello Paul , ( uhm , it's spelled class 50 or 71 really - fifty / seventy-one ) the 71 was a 2-4-2 light tender engine , however given a full treatment of the 20 bar ( 290 psi ) b.p. then in fashion with DR standard design .
Hello Paul ,
( uhm , it's spelled class 50 or 71 really - fifty / seventy-one )
the 71 was a 2-4-2 light tender engine , however given a full treatment of the 20 bar ( 290 psi ) b.p. then in fashion with DR standard design .
You were experiencing Austro-Hungarian-Croatian railroad humor.
My great grandfather was a civil engineer in the employ of the State Railway, which in Croatia was the Hungarian half to the Austro-Hungarian Empire. Great Grandfather had to take an exam demonstrating knowledge of Hungarian, which to many Europeans is as difficult as learning Korean. The family story is that he had to study for the possibility of writing an autobiography or a "letter to a friend."
Great Grandfather Viktor had limited time to prepare, so he guessed the test would be the autobiography. He guessed wrong, it was a letter to a friend. So his essay read, "Dear Friend. It has been so long that we are apart. Let me tell you all that has happened to me . . ."
On the topic of hand, someone posted (off topic) to offer congratulations to Germany for a stunning 7-1 victory in a crucial World Cup match. I joked about knowing about the 5-0 steam locomotive (I meant the 0-5, the 1930's 160 km/hr passenger locomotive), and wondered about the 7-1 locomotive.
So it is true that there is a 71-class locomotive? Is it also true that persons from the provinces of Germany are very serious whereas those of us whose heritage is from the Osterreich, the poly-ethnic, polyglot Eastern Empire tend to tell silly jokes?
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
see :
Drawing
http://www.alfons-schuerhaus.de/images/d71.jpg
http://dlok.dgeg.de/104.htm
Model
http://www.modellbahnshop-lippe.com/produkt/Liliput/6-4-003001-63846-0-0-0-3-3-2-0-gatt-de-p-0/ein_produkt.html
It's success was compromised by cracks developing from the rivet holes in the special steel boiler shells - a story all of the DR 20 bar designs built with St47K steel boilers were bound to share , giving birth to a number of post WW-II reboilered engines while other 20 bar locos never returned to post war service and just got scrapped instead , such as the (in-)famous disproportioned design 4-8-4 which unintentionally provided evidence the Wagner concept of standard design was not be extended to American standard size of wheel arrangements without creating some weird effects which proved not exactly promoting performance nor reliability nor aesthetics of design – which is why in my inevitable irony I enjoyed to call the 06 class the ‘no-sex’ class , for your own ideas on it , see description at
http://schneider-mayenfisch.com/drg_lokomotiven_06.htm
As you will easily see the design is pretty cramped around the firebox due to limitation of overall wheel base by 23 meters turn table , really , it is only *just* worth a 4-8-2 w/a . With firebox much the same size as in the 01 class Pacific and *still* without combustion chamber as to the doctrine of Wagner's boiler design was headed towards aberrant proportions . For an interesting imagination of the 06 as ‘would be’ reboilered & oilfired by DB , imagined along the usual procedures by DB in other cases of reboilering ( except for the 12 wheel double bogie tender ; in fact , these engines had the 10 wheel tender common to 01-10 , 05 , 06 and 45 classes ) , see line 17 of images at
http://www.lokomotive.de/bildergalerie/dampfloks.html
( there is at least one fully imaginative DR loco class ‘running’ as you scroll down – there have been concepts put up and much thought spent , yet it all came to nothing – do you see which one I mean ? there are some more engines probably of interest to you further down ..)
Firelock76 NorthWest Just to get over that starting resistance, indeed! I've learned a lot about roller bearing equipped locomotives in the last couple weeks. (PS. Well, the Brazilians lost this time...) Yes, and blown away by the Germans 7-1! I understand there's a revolution in the works down in Brazil... Well, my dad once said if East and West Germany ever got together again they'd turn into a major sports powerhouse. Looks like Dad was right, and he said it 40 years ago.
NorthWest Just to get over that starting resistance, indeed! I've learned a lot about roller bearing equipped locomotives in the last couple weeks. (PS. Well, the Brazilians lost this time...)
Just to get over that starting resistance, indeed! I've learned a lot about roller bearing equipped locomotives in the last couple weeks.
(PS. Well, the Brazilians lost this time...)
Yes, and blown away by the Germans 7-1! I understand there's a revolution in the works down in Brazil...
Well, my dad once said if East and West Germany ever got together again they'd turn into a major sports powerhouse. Looks like Dad was right, and he said it 40 years ago.
I know about the German 5-0 class locomotive, but what was the 7-1?
selector Firelock76 NorthWest Just to get over that starting resistance, indeed! I've learned a lot about roller bearing equipped locomotives in the last couple weeks. (PS. Well, the Brazilians lost this time...) ... Well, my dad once said if East and West Germany ever got together again they'd turn into a major sports powerhouse. Looks like Dad was right, and he said it 40 years ago. [Emphasis in bold font mine...] I seem to recall rampant abuse of athletes by their coaches in DDR, notably the heavy forced use of anabolic steroids. Today, I think your dad would probably not be so keen with his prediction. -Crandell
Firelock76 NorthWest Just to get over that starting resistance, indeed! I've learned a lot about roller bearing equipped locomotives in the last couple weeks. (PS. Well, the Brazilians lost this time...) ... Well, my dad once said if East and West Germany ever got together again they'd turn into a major sports powerhouse. Looks like Dad was right, and he said it 40 years ago.
...
[Emphasis in bold font mine...]
I seem to recall rampant abuse of athletes by their coaches in DDR, notably the heavy forced use of anabolic steroids. Today, I think your dad would probably not be so keen with his prediction.
-Crandell
Well Crandell, if I remember correctly Dad made his prediction during the 1968 Olympics in Mexico City. long before the DDR coaches discovered the wonders of modern bio-chemistry. The DDR swim team wasn't so hot, but they were pretty respectable in the other events, as was the BRD team.
It was during the 1972 Olympics that American swimmer Shirley Babashoff sounded off about the DDR swimmers using SOMETHING, "No one gets that good that fast!" she said, commenting on the marked, if not incredible improvement in the DDR's swim team's performance in four years. She was called "Surly Shirley" and a sore loser for her trouble. Turns out she was right after all.
I mean, who heard of steroids 40-plus years ago?
Before we get too far off-topic let's just say those East German swimmers were going at it like they were steam-powered and call it a day.
Actually, I believe it was four showgirls who pulled the "Four Aces" in that timken roller bearing stunt.
Is it true? Does it matter?
Ya , but , NorthWest
you don't believe *that* advertising trick , don't cha ?
Why , I can pull a Malley if you crack the throttle open ..
enough ..
= J =
.. or if the piece of track is on a downward incline juuust right to start the loco rolling slowly
(After watching the US lose...)
Thanks for explaining that. I had forgotten about the low speed factor, I should have remembered the famous one-person pulling of the Timken Four Aces.
Thanks.
@ Locobasede
Since in a sound design of a steam locomotive , cylinder t e was in command of t e at adhesion limit , there was no direct gain in actual drawbar tractive effort – yet , roller bearings on axle bearings because of their lower rolling resistance and especially lower starting resistance enabled to reach same adhesion limit tractive effort on a somewhat lower cylinder tractive effort . At speed the difference was not that large – it is difficult to tell a percentage because of the widely varying rolling resistance with plain bearings – not only due to their design and materials combination but also due to the kind of lubrication used . As a rule of thumb roller bearings on axles should have reduced rolling resistance of a steam locomotive – engine without tender – by some 40 – 50 % ; if fully equipped roller bearings on rods and axles reduction of rolling resistance could reach 60 – 80 % , depending among other things on design and dimensioning of wheels , bearings , piston thrust and more ; this does not account for other sources of rolling resistance independent from bearing design such as coasting devices which gave widely differing degrees of resistance to pistons floating in cylinders .
High steaming rate demanded large grate and that caused fireboxes to increase ; it was Woodard’s idea to increase firebox significantly to increase sustained on-the-line speed and thus first applied four wheel truck under firebox . . I don’t think anyone questioned this here . The idea was to get the same trainload over the line faster – however the RRs , as usual , soon bent this towards hauling heavier trains at little improved speed
@ NorthWest
Oh , they did improve a couple of things in steam loco design and maintenance , for instance :
@ timz
What I meant was : a new valve gear of new design with progressive valve events , providing basically larger free steam port cross sections , faster port opening and larger lead especially in the short cut-off range if locomotive is to run at high rpm , free exhaust , properly tuned clearance and compression ; now if you should ask “ which valve event concretely “ then I’d have to actually design that valve gear – which I must say I’d take a dim view of as an exercise without meaning .
Juniathanew progressive layout of Walschaerts valve gear
My understanding is that roller bearings actually have little advantage over friction bearings, if well lubricated. It is the maintenance advantage that is the big part.
(Juniatha, I take time off from the forum to watch the World Cup games. They are far too important!)
Well , well .. I should not post hastily sewed up texts straight away , especially when written while having side glimpses on the soccer game Brazil – Chile where I hoped the big ego machos would get stopped by the Chilenians , which in the end wasn’t to be ..
So here's my posting revised passim , wording more to the point and one important straightening out my performance outlook for revised , uhm , let's say , Pennsy Pacifics -
If you should have read the former version , please take your time to re-read , thanx .
That's a complex matter – several influences weigh in here and do so to varying extend at various speeds and loads and combinations of these .
Keeping in mind the usually published power output curve is just a two-dimensional graph like a cross section taken from the real thing which would be a three dimensional spherical figure where in addition to the abscissa y for power and the ordinate x for speed , steaming rate , applikate z , is taken into account ; to allow for proper evaluation of power available with a steam loco in question the usual two dimensional curve should correctly be based on constant – generally nominal – steaming rate . This alone has not always been observed with some RRs , having lead to aberrant ideas of steaming capacity of boiler varying with speed – which logically it can’t if you come to think of steaming being a result of combustion heat production by factor of boiler efficiency and thus calorific fuel consumption which again is dependant on draught which in it’s own turn again relies on amount of steam passed through draughting – and thus if the latter is constant , so is steaming rate .. *if* , I should add , draughting is correctly designed and does not drowse away when valve gear is being brought in ( shortening cut-off ) .
As so often , errant design has been explained by aberrant theories .
Why do steam locomotive fare less well in lower speed range ? There are many aspects influencing this , you mentioned some . Short answers to your points :
1 >> efficiency dropping off -- a lot -- as you slow down, even when reducing the steam rate to maintain constant cutoff. This appears to be a pure cylinder efficiency effect not having to do with boiler efficiency <<
Correct
2 >> The drop off at the "top end" is understandable in terms of "breathing limits" <<
Uhm – not really ; in a well proportioned engine which has both ample cylinder displacement volume in relation to adhesion mass *and* accordingly high boiler steaming capacity combined with a really good Walschaerts ( Baker ) valve gear functioning properly with appropriate valve events offering ample cross sections in cylinder steam passages, indicated cylinder output should continue to climb while surpassing regular service top speed . It was just because of a wide range of possible valve gear malfunctions or imperfections that indicated power output started to drop more or less severely before that speed , in some cases it could also have told of insufficient boiler steaming capacity which would then have asked for shortening cut-off beyond what valve gear could handle because of insufficiencies in its own turn .
As in many of the late American Super Power , boiler capacity was high in relation to engine service mass while cylinder displacement volume was on the small side in relation to adhesion mass , there should have been enough steam to support an ever-climbing indicated power output curve beyond top service speed – if generally this wasn't so it told of more or less severe deficiencies in steam distribution to and from cylinders .
There is another consequence of inadequate valve gear functioning : steam distribution holds no reserve over boiler capacity making short bursts of super-elevated outputs impossible ; so , with superior boiler capacity sustained nominal output has fallen in line with maximum cylinder output . Effects of valve gear deficiencies in the presence of a very good boiler was clearly shown in the PRR K4s when equipped with stoker firing . Pressing all that steam through cylinders was only done by accepting horrible specific steam consumption , making but some 3300 ihp of 70,000 lbs/h steam or more ; had the class had an adequately functioning , free valve gear with concordantly designed free steam passages through cylinders , indicated output could have been rising to pass 4200 – 4400 ihp (*) at 80 mph and climbing . Alco should wisely have had a scrutinizing going over J-3a engine drawings , although they would just have saved the day by a couple of hundred hp .
3 >> challenged the assumption that high-drivered locomotives are no good for drag service, which is a widely held assumption <<
This question is not to the point since there are various reasons why a large drivered locomotive can be unsuited for low speed high tractive effort jobs . First of all , generally large drive wheel diameters were typical of wheel arrangement with smaller number of powered wheels made up by more carrying wheels than in a small drivered wheel arrangement of the same total number of axles – for example : a Mountain type as compared to a Santa Fé .
Clearly , on the same track , a Mountain type could never be made competitive to a Santa Fé in starting and slow speed drawbar power output because it lacked adhesion . The matter was more complex if , say , a second series of a given design was to be equipped with larger wheels , assuming here cylinder dimensions were kept proportional so that both series offered the same indicated cylinder tractive effort at same percentage of boiler pressure .
There could be mechanical reasons responsible for the smaller drivered series to be more sure-footed in actual service . Yet again within the limits of adhesion one or the other could produce a somewhat better power output in slow speed range or do so on a somewhat lower steaming rate depending on valve events , clearance volume , losses by steam leaks past valve and piston rings , glands and losses by cylinder wall effects which all may have differed in the two series , depending on improvements having been introduced . However , with mechanically and thermally sound design and same level of cylinder tribology there should have been no practically noticeable difference in engine behavior with drive wheels of , say , 63 or 70 ins to name but typical figures .
4 >> Some railroads thought of Northerns in this way. <<
Yes – however , if I wanted to be cynical about it , I could add : “.. only because they didn’t think all through it !”
Since a Northern could not have a larger adhesion mass than could have been designed into a contemporary Mika , the 4-8-4 only provided 2-8-2 heavy haulage capacity – and since *there* you have a much larger difference in respective wheel diameters , say , 80 “ against , again say , 65 “ and this was *not* fully made up by adapting cylinder volume , *there* you could have a train haulage situation the Mika could live with – if not without much strain – while the Northern was pressed to its limits cylinder-wise , doing the job but on a significantly higher coal and water consumption because of having to run at , say , 65 .. 70 % cut-off while the Mika could do on comparatively ‘easier’ 50 % because of cylinder volume better exploiting adhesion – or in other words : more ample cylinder volume in relation to wheel diameter and adhesion .
5 >> Also, with high drivers you are going to have a longer rigid wheelbase and preclude going to 5-axle (2-10-2, 2-10-4) types. <<
Now we get into comparing strawberries with pineapples – they both taste good and are healthy , yet you should make a sensible choice when baking a cake .
If the loco design dept of a RR wanted to increase drive wheel diameter that much as to run into trouble with powered wheel base and concluded they’d have to drop an axle , then something had really become mixed up . On basis of a given maximum mass per axle . of course a locomotive having a larger number of powered wheels was always bound to perform clearly better within the range of adhesion limit ( range where maximum drawbar tractive effort is governed by adhesion not piston thrust ) . With 20 wheels each , that’s what the 2-8-8-2 slow plough was for in contrast to the 4-6-6-4.
6 >> the monster firebox <<
.. the need for which IMHO was an expression of torturing engines at the – extended – outer fringe of their very limit of haulage capacity .
7 >> But at the same cutoff, can you really get the same power just running a high-drivered engine at low wheel RPMs as you can with a low-drivered engine at a more efficient RPM level? <<
Interesting phrasing : the latter part of your sentence offers the answer to your question in the former part . While in principle the steam engine can start from stand-still , this was only done with a rather low cylinder thermo-dynamic efficiency because all the adjacent losses – leaks , wall effects , truncation of expansion and other – were up while power output rate was down as clearly evident by the principal power , speed , tractive effort equation . See 4th point .
There would be more to mention , yet I hope this will give an idea of the general situation .
* note:
Having gone over my text I had to revise my originally given power at speed note put up under a mental switch-over , which I forgot to mention , to the heftier *K5* with longer 30 “ stroke instead of 28 “ and 250 psi instead of but 200 .
So : 5000 ihp at 90 mph might have been attainable had the *K5* been rebuilt with new 27 “x 30 “ cylinders and new , progressive layout of Walschaerts valve gear , increased superheating and effective low backpressure draughting .
In view of the *K4s* low b p , the power output range now given for 80 mph , which I consider a more reasonable service top speed for this class , is more realistic by technology available – if unfortunately not always applied – about the final years of the pre-WW-II steam era , demanding but a milder increase of superheating , yet again new progressive layout of Walschaerts valve gear , new 27 “ x 28 “ cylinder blocks plus effective low backpressure draughting .
A quick note: Reciprocating internal combustion engines typically have a minimum operating that is usually a factor of five to ten less than the maximum operating speed. Efficiency of most IC engines drop off at the low speed range, in part due to cooling of gases during the power stroke.
My guess is you are on the right path in suspecting heat loss to the cylinder walls.
- Erik
A characteristic of the traditional "rod-driven" steam engine is that, apart from the variable valve gear, it is direct drive with just one "gear ratio" down to zero speed. Diesel-electrics famously have that complicated and expensive electric drive to better match a reciprocating prime mover (the Diesel engine in this case) to the wheels with an "infinitely variable gear ratio."
One of the traditional arguments for Diesel over steam is that steam locomotives favor a particular operating speed, so you need one class of steam engine for drag freight, another for manifest freight, yet another for passenger service, maybe yet another collection of designs for mountain districts. This is fantastic for train watchers but imposes restrictions on the railroad companies. Because of the electric drive, Diesel, with some exceptions because you can get them with different traction motor gearing, is pretty much universal service.
Feeding into this is a question that I feel I didn't get a satisfactory answer. David Wardale's "Red Devil" book shows steam locomotive efficiency dropping off -- a lot -- as you slow down, even when reducing the steam rate to maintain constant cutoff. This appears to be a pure cylinder efficiency effect not having to do with boiler efficiency as you see this with respect to steam supplied to the cylinders and "indicated" power.
The answer offered was "all (reciprocating) engines" show curves like that, of an "island of peak efficiency", but the answer doesn't go to causes. The drop off at the "top end" is understandable in terms of "breathing limits" (i.e. flow choked by pressure drops at high rates). The drop at the lower end of speed is attributable by Harry Ricardo and others to heat losses through the cylinder walls, but the high temperature peaks in combustion engines require a cooling system that could be robbing a lot of heat yet a steam engine doesn't have such a thing.
This feeds into another question. On another thread, was it Overmod who challenged the assumption that high-drivered locomotives are no good for drag service, which is a widely held assumption in writings about historic steam, such as "the Super Power Allegheny type was misused in drag service" and so on.
The though-provoking counter argument is that if you have a high-drivered locomotive, which benefits wheel balance and allows higher speed before reaching the track-pounding dynamic augment problem, you provide it with enough cylinder size that it has a starting tractive effort at the 25% of weight-on-drivers anyway. If you give it enough boiler to keep up with those big cylinders connected to high drivers, this machine provides tractive effort up to its adhesion limit at low speed, and it keeps giving tractive effort up to high speed, so you have a universal service locomotive. Some railroads thought of Northerns in this way.
The only difficulties are fitting that big boiler within the loading gauge or perhaps the extra carrying wheels (6 wheels on 3 axles on the H8 Allegheny) for the monster firebox. Also, with high drivers you are going to have a longer rigid wheelbase and preclude going to 5-axle (2-10-2, 2-10-4) types.
But at the same cutoff, can you really get the same power just running a high-drivered engine at low wheel RPMs as you can with a low-drivered engine at a more efficient RPM level? What is behind the drop in efficiency running a high-drivered engine at low piston speeds? Could this be countered by better cylinder and steam pipe insulation?
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