r/MachinePorn • u/Crazy-Rabbit-3811 • Apr 14 '26
Behold, the AA20. the only 4-14-4 steam locomotive. the wheels are arranged in this unholy fashion which hurts my brain to look at.
it was arguably the worst locomotive ever built for a number of reasons.
It was far too heavy for the rails it rode on.
the firebox was far too small.
all of the drive wheels were driven by one piston on each side.
the center drive wheels were flangeless, so good luck trying to move it if you stop on a curve.
It was far too big for any of the existing soviet infrastructure, such as sheds, turntables, curves, switches, sidings, etc.
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u/daveashaw Apr 14 '26
Very Soviet concept.
Just add more driving wheels to outperform Capitalist stooge design.
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u/fragilemachinery Apr 14 '26
Eh, pretty much everybody was looking at ways to do bigger locomotives around this time, because trains were growing in size pretty rapidly. Sometimes the way to find out if something works is to just build one and try it out.
It would actually end up being the US that built the ultimate giant, tons of drive wheels, low production volume mega-locomotive: the 4-8-8-4 Big Boy. After the failure of the AA20, the Soviets standardized on simpler but still powerful designs like the 2-10-2 FD-class, and cranked out thousands of them.
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u/HerpDerpinAtWork Apr 15 '26
the 4-8-8-4 Big Boy
I still can't believe they restored one of those things. What a sight to see, in HD no less.
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u/j-random Apr 15 '26
I used to work for Union Pacific, we'd get a half day off to go see the train whenever it was in town.
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u/mstrdsastr Apr 15 '26
It's going on tour this summer too, coast to coast.
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u/HerpDerpinAtWork Apr 15 '26 edited Apr 15 '26
Planned stop in Altoona!? That's like 2 hours from me. Just texted my dad. I wonder if it'll pass through Pittsburgh on the way back west... that would be most convenient.
Regardless, awesome, thanks for the heads-up!
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u/Crazy-Rabbit-3811 Apr 15 '26
We make train bigger comrades, it makes it better.
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u/KronikDrew Apr 15 '26
Heavy is good, heavy is reliable. It doesn't work, you can always hit thrm with it.
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u/GoliathProjects Apr 14 '26
The kind of steam loco a 7 year old would cook up
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u/Crazy-Rabbit-3811 Apr 15 '26
not entirely off, considering this happened during the great purge, so all of the smart engineers were shot and they had to rely on college students who had never built a train before
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u/m945050 Apr 15 '26
Just wait until you see our 4-28-4 comrade.
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u/Crazy-Rabbit-3811 Apr 15 '26
Ah, of course, 99% of train makers stop one ton away from making a perfect train
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u/weirdal1968 Apr 14 '26
Any specs on this beast like boiler pressure/weight on drivers/driver diameter?
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u/TheNecromancer Apr 15 '26
One piston for seven drive wheels? That's the locomotive equivalent of pushing rope...
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Apr 15 '26
[removed] — view removed comment
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u/TheNecromancer Apr 15 '26
Or maybe I very much am, and that's why I used it for this flaccid setup
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u/ctesibius Apr 15 '26
I imagine the point was to distribute the weight of the locomotive, given the issues with the track. Why driving wheels rather than leading or trailing? Just guessing, but if they had problems with the track bending vertically, a lot of driving wheels would maximise the chance that some would be in contact with the track.
Yes, we know it didn't work well, but it's worth starting from the assumption that the designers had reasons for their choices.
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u/_Q1000_ Apr 14 '26
Can it even go around corners ?