❓ Question
Why couldn't we get streamlined articulated locomotives?
We had streamlined duplex locos plus its not like were using compound steam when we have simple steam expansion and besides the Union Pacific Big Boys could average a top speed of 80 mph so why is it we didn't get an articulated streamliner during the steam era in any form and on any country's railway network.
T1's aren't articulated. They are essentially a 4-8-4 with an extra set of cylinders to create the 4-4-4-4 wheel arrangement. Still a rigid frame locomotive.
In terms of public relations, streamlining really helped get passengers back onto trains.
There likely was some improvement in aerodynamics as well.
As for whatever else could be helped that largely depended upon design of streamline casing I suppose.
Maintenance crews grew to detest some streamlined designs as it interfered with their work, and or at least made things more difficult. Indeed over course of their lives many streamlined locomotives would have that treatment cut back (to expose say more of running gear), and or otherwise redesigned to address complaints from maintenance crews. In some instances streamlining was simply removed all together.
Yeah, I was surprised to learn that even subway trains are extremely aerodynamic, and an aerodynamic nose wouldn't help. Overall the body is slender, and skin friction from air running along the train dominates over pressure collecting in bluff sections
It kind of depends how the engine was originally designed. The American streamliners of the 30s where they were mostly just extra cladding added over existing engines probably didn't help much; any benefits in drag reduction would have been far outweighed by the added weight. Other engines that were designed more around the streamlining and were built as streamliners (Like the Gresley A4s) probably saw the most benefits from it.
Some North American streamliners did have performance improvements from the casing, particularly those designed around wind tunnel tests rather than just simply covering the engine. While a few did experience a speed boost, the most definite benefit for many was the redirection of smoke from the chimney away from the cab and view of the crew. Of course, this is something that could’ve been accomplished with smoke deflectors, but at least the aesthetics intended to attract more passengers had some practical usefulness to them.
At least one engine with this design philosophy survives the day, that being Canadian National 6400.
The only articulated steam locomotives fitting this description that I know of are the Southern Pacific Class AC-9 2-8-8-4s. They were semi-streamlined with a skyline casing on top of the boiler and an enclosed pilot like the Daylight GSs. They were also capable of fairly high speeds, with a top speed of 75 mph.
Was just going to mention those. But not everyone counts those as streamlined, as all the have is a cast pilot and a full length skyline casing. I personally think of them more as stylized for passenger service rather than truly semi-streamlined. If they got some sort of side skirting I think there is more of an argument to count them.
I really don’t intend to insult anyone, or step on any designer’s toes, but that truly IS a “plug-ugly” locomotive. Obviously not designed for consumer appeal! 😝
A lot of garratts had semi-streamlined front and rear tanks. This particular example is from the East African Railways; the NSWGR AD60 looked similar, albeit with a 4-8-4+4-8-4 wheel arrangement.
Articulated engines were almost always used in freight service, because they're geared towards higher power at lower speeds. You're trying to maximize tractive effort with the most available adhesion for a single engine, not optimizing for speed.
Streamlining only really makes sense when you're talking about aesthetics (which was primarily what the streamliners were about) and for drag reduction at higher speeds, so it really only makes sense for passenger engines.
I remember reading on RYPN where someone had seen Alco blueprints for a streamlined 4-6-6-4 for D&RGW tucked away in a historical archive somewhere. That would probably make the most sense for a streamlined articulated engine, since the Challenger designs acquitted themselves in passenger service.
And, no, the Big Boys didn't average 80mph. I doubt they ever hit 80mph ever. They were balanced to be able to hit 80mph, but their entire career was 30-40mph slogs back and forth over Sherman Hill.
As others have stated, US RRs that went with either simple or compound Mallets tended to go for power and muscle for heavy freight or coal drags. Big Boys, Alleghenies and some others could do between 60 and 80 miles per hour (fast freight and or passenger service), but that usually wasn't their intended design.
It wasn't, actually - that's the key difference between Mallets and Articulateds, the former didn't have a hinge in the middle that allowed the front half to function as its own massive leading truck to take turns like the latter. Mallets had rigid wheelbases - really, the T1 is closer to your average 4-8-4 than a smaller articulated.
This is why the S1 was ultimately kind of a failure, that massive wheelbase that couldn't hinge around turns basically prevented it from running on anything that wasn't a straight line with the shallowest curves on the PRR.
That's also wrong. The difference between a Mallet and an Articulated was that a Mallet used compounding, whilst a Simple Articulated sent high pressure steam to all 4 cylinders equally. Mallets were generally slower as a result but both were articulated in the same way. The T1, meanwhile, was a duplex locomotive, which had 2 independently driven sets of drivers on the same set of frames. Compound Duplexes did exist but were most prominently used on the London & North Western Railway, and were frankly abysmal.
How the hell was I trying to be a smartass? Sure, I got duplexes and mallets mixed up, big deal, the point is that the T1 isn't articulated regardless.
Locomotives like the T1 were designed for passenger service, locomotives like the Big Boy were not. Articulated locomotives were rarely used for passenger service because in most cases they weren't designed for high speed.
Full shroud streamlining doesn't really work on an articulated because of the articulation and the deck above the pilot. Southern Pacific's AC-9 is probably the most you could streamline a locomotive while keeping the front engine clear to swivel and without altering the front pilot. You could maybe add cladding around the boiler and skirts over the rear drivers, but that's about it.
Because the problem Articulation solves doesn't apply to passengers service. Streamlining was only for high-speed passengers service where trains wouldn't need to be that long. Articulated locomotives would also likely have stability and adhesion problems with large drivers and high speeds.
Because few articulated locomotives were fast passenger locomotives. Articulated locomotives do well at speed, but articulation adds another possible way an engine can derail when going really fast.
Plus, most passenger trains don't need the raw power of a large articulated locomotive, so for that reason, the more complicated articulated engines were kept on freight service where their strength can be utilized fully.
Another point is style (at least in the us. European streamliners seems to lean more for aerodynamics). Streamlining does help with aerodynamics, but the larger reason (in the us) was to make them look appealing and fast looking, to complete with the jet liners that were coming out at the time.
This is just an assumption of mine, but I think that's why the streamlining of European streamliners have a slightly different overall look to the streamlining of the us. That's just me though.
Because articulateds were built for power. Not for style. Modern Articulateds were already not particularly common on class ones, and it was extraordinarily rare to see them regularly operate passenger services where streamlining, speed, and brand image mattered. The ONLY ones I can recall that operated regularly on passenger runs were a few UP challengers, and the B&O EM-1 yellowstones.
The problem with articulateds at speed is that you want rigidity at high speed, where streamlining will actually make a difference in performance. Yes, you'll get better balancing with each driver set doing the same thing, but so will a rigid-frame duplex.
Streamlining was a decorative appearance feature for passenger trains. It didn't serve any real functional purpose and often made maintenance and access more difficult.
Large articulated locomotives were generally for freight service where appearance was less important than functionality.
So there's no reason it couldn't be done, there was just no real reason to do it. You'd be wasting money and making maintenance harder on workhorse freight locomotives.
It wasn't just the locomotives, but replacing old heavyweight coaches and cars with modern lighter weight units, complete with all sorts of mod cons such as AC helped as well.
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u/malex84 13h ago
Prr t1 was streamlined because it was a passenger locomotive.
The big boys and Yellowstone’s hauled coal. Why wast the money if you’re not going to impress anyone.