Hi,

How about the first steam engine (not locomotive)?

c500 BC the Greeks had a brass sphere on a rod that could be set on two forked stands. Perpendicular to this were two angled spouts pointing in opposite directions. The sphere was filled with water and placed on the forked stands over a fire. As the water heated, steam escaped from the two "jets". This was the first steam turbine. It was not until metalurgy got much better that if could be anything more than a parlor trick.

Doug vV

I'd go with;

Stephenson Link motion
3 Point Suspension
Superheating
Cast steel frame/cylinders
Roller bearings

Steve

Brother Peartree's response reminds me of the time a magazine asked a group of academic technology historians what the greatest "invention" of the AD 1001-2000 millennium was, specifically "the development that had the greatest impact on human life and civilization".

This is the kind of question where the "average Joe" responds with stuff like light bulbs, telephone, printing, radio/TV, computers, etc.

The historians' most common, and correct, response?

Civil sanitation engineering.

Similarly, one could add something like directing exhaust blast up the stack to increase draft--an idea often attributed to George Stephenson.

I'm not sure if that would qualify as one of the most important design advances or not? I realize that may sound odd, since the railroad I work with prides itself on having one of the largest geared locomotive collections around. However, it is a bit of a technological dead end. The vast majority of steam locomotives don't use his design, as ground breaking as it was. Yes, for their intended use there's nothing better, but it's definitely a niche.

If we were talking "innovative designs", then, by all means yes. But most important technological advances? I'm thinking stuff like superheaters, roller bearings and even air compressors/air brakes. Oh, and simple and obvious (these days) things like routing the exhaust steam up the stack to use as draft for the fire. Remember, that stuff all had to be invented at some point.

I would add the stoker and combustion chamber.

Important based on what criteria? As Bob says, Shays are damn important if you run a mountain logging line, useless if you are the water level route.

Based on "most important" we can only speak of the broadest common denominator elements of design.

How about the injector? Can you imagine larger locomotives being fed from just a crosshead pump?

This is true in and of itself (and the injector, even if designed for aircraft, is important both for its principle and its usefulness on locomotives).

But on any 'larger locomotive' of any particular sophistication, the feed would most definitely have been from pumps, albeit not crosshead pumps. Feedwater heaters of any efficiency make the water too hot for injectors.

We could compare Ross Rowland's opinion, that on one of the largest and most sophisticated 4-8-4, a pair of Nathan 4000s did the job just as well as a much fancier FWH, with the recent retrofit of a FWH on power for the revived NS steam program...

The exhaust steam injector ranks up there with rotary-cam poppet valve gear as an innovation that OUGHT to have achieved far more importance than it actually did. I am fond of the idea behind the Elesco ES ... but I don't think I'd want to have to pay to make one, or even maintain the parts to keep it running. I also have my suspicions that its 'automatic' maintaining action worked about as well as the 'automatic' slip control on Q2s, but since I do not have firsthand experience I will say little.


Frankly, I think we ought to give careful thought to 'five great innovations' for each stage of the evolution of locomotive technology. For example, one of the defining technologies of the 4-4-0 era was the design of the frame to be separable into two pieces; it was considerably more difficult to work on many parts of the locomotive if the frame were in one piece, and it was easier to put a given locomotive back in service. The cast engine bed is just about the antithesis of the 4-4-0 evolutionary design, but just as essential ... for its time.

Dave has already mentioned another distinction that needs to be made: functional. What is optimal for a logging railroad (and quite a bit of experience with geared power up to the Shay was QUITE different from gears that worked in mud with minimal maintenance or careful tribology!) won't be at all optimal for high-speed passenger service on comparatively light track. And both will be different from the design features that matter for freight ... either at the turn of the century, with both coupler and brake evolution still in progress, or a quarter-century later with the various features of Super-Power and then simple articulateds becoming valuable.

If I am not mistaken, Trevithick invented induced draft on steam vehicles, in fact doing it much better (with separate pipes curving up into the stack) than any early Stephenson expedient. IIRC Seguin had a better multitubular boiler, years earlier. The big principle that Stephenson developed, which I haven't seen mentioned yet even though it counts as one of the 'big five of all time', is the idea of 'automatic action' -- the idea that the degree of draft on the fire and hence the degree of steam generation would automatically match steam demand without having to tinker with the analogue of spark advance, or varying the speed of a fan or clutching its drive in and out. For all the 'innovations' of jumper caps and superheater dampers and emphasis on multinozzle free-breathing Lempors that augment full-throttle power ... even in the '50s an important design principle on practical motive power was the most efficient automatic action.

Oh, and let's not forget the principle of steel-on-steel adhesion with smooth tires. (Or its chilled-iron-on-iron early equivalent.) Upon this simple innovation rests a considerable amount -- pro and con -- of development right to the end of steam, and continuing with if anything even more importance through the DC and then AC diesel age, right to the limiting speed of the TGV tests.

While several suggestions are interesting and refer to some very nice locomotives, I would suggest that a rather mundane device changed the landscape of locomotives more drastically than any mentioned already. How about the powered stoker? A human could only shovel so many btu's of solid fuel into a boiler's furnace. This seriously limited the power that a locomotive was able to use and therefore the size of the beast. A stoker allowed the locomotive to grow to the dimensional limits of the track system with corresponding growth in horsepower. Of course, the addition of the the various efficiency devices others have mentioned made the ultimate power delivery possible. But the power stoker set the fuel, (energy), input higher than humanly possible.

I would love to agree with metallurgical suggestions but mostly they are evolutionary, the exception is probably cheap steel via the Bessemer process.

Fred the retired metallurgist

Interesting question, Here are my initial thoughts:

1) Stephensons exhaust induced draught.
2) Henri Giffards injector.
3) Egide Walchearts valve gear (most widely used throughout the world on modern steam)
4) Superheat and Piston Valves combined (pioneered by Brooks locomotive works I think?)
5) Francis Fairlies "Fairlie Patent" articulated locomotive (arguably the first successful articulated locomotive, precursor of Mallets, Garratts etc.. It also made an argument for the economic value of narrow gauge construction, and also set the pattern for B-B and C-C diesel and electrics.)

A few others that jump to mind are the pop safety valve, and the Westinghouse automatic brake system.

Pat

Stoker history is interesting. Note that the early history of the stoker is not entirely positive, with a couple of decided dead ends (the Crawford underfeed stoker on what was then considered large power being interesting) and some locomotives that clearly needed them for best 'effect' did not get them originally (the PRR K5 being a particularly notorious example). A considerable part of the 'rationale' for the D&H high-pressure experiments was to allow them to be hand-fired (!)

It could also be argued that many of the manufactured stoker designs were wasteful for the advantage they provided. Porta apparently resuscitated the Elvin stoker (why he didn't use the Detroit as an example instead, I don't know) as not crushing the fines and giving a theoretically better distribution.

I don't think there is much argument that stokers were essential to the Super-Power revolution, and certainly to allowing simple articulated power to reach the sizes it did. But in most cases where the sheer capacity of the stoker wasn't needed, skilled hand firing remained both better and more economical...

I note pointedly that no one seems to be mentioning that logical follow-on to stoking, GPCS, as one of the great technological advances.

Out here on the West Coast, we would place the development of fuel oil firing as major advance. It made use of local resources (at least in California), it eliminated the difficulties of dealing with solid fuel, either with the fireman's scoop or the mechanical stoker, and it made possible the Cab-forward design for the Southern Pacific.

Regarding Mr. Trevethick--his locomotive might be called a "proof of concept", but after his experiments, the idea lay dormant for over a decade, presumably while other aspects of technology caught up. One might consider that Edison didn't "invent" the electric light, but he made the first one that worked and made economic sense. Likewise, Stephenson is creditied with building the first steam locomotive that could really do the job.

One thing about 'Rocket' is how quickly many features of that locomotive became obsolescent. Stephensons themselves were making far more use of the Patentee type (2-2-2) in less than a decade. And there were blind alleys in Rocket's design, too. So yes, Rocket's important as 'the first time many significant details came together in a design' -- but that's not 'technological advances' in the sense of a list of the five greatest 'advances' would be concerned.

Unless we want the question to be illustrated by five specific LOCOMOTIVE designs. In which case I would mention the 'canonical' American 4-4-0 (already cited), the modern American-style Mallet (or simple articulated), the USRA attempt to 'standardize on "best" designs' (as practiced by Dilworth et al. so successfully later),the Super-Power Berkshire (either Woodard's or AMC's), and 242 A1 as four major influences that could be considered stable 'quantum leaps' in the state of the art.

If we are looking at design principles, another one that hasn't been mentioned yet (although hinted at) is the use of practical equalization (something deprecated, sometimes with comical effect, in British steam design right to the end). One classical form of this (seen on Mikados and the 'redesigned' production PRR T1s, for example) is what might be called a double-three-point suspension: the equalization is separated into two groups at the effective center of the driver wheelbase, and is carried via levers to the engine and trailing truck.

I would also consider the practical application of thermodynamics to steam-locomotive design (replacing generations of 'practical man' designs with weird at best performance) as one of the major influences.

Flexible staybolts anyone?

From the point of view of the engine crew....I would suggest the "cab!"
It is no fun standing out in the open in inclement weather.
(The fireman on center cab locomotives excepted...they got cold and wet)

Keith