Experimental Locomotives of the Past from outside North America

[Overmod]

You've got some acknowledged whoppers in there.  Leader is perhaps the best example of a wrong answer to a question nobody asked that exists -- and I speak as someone who appreciates much of the tech in the design that actually functioned ("worked" is really semantically wrong in context).  Gresley's 'hush-hush' even had problems with airflow under the shrouding; while you're on the topic of high-pressure designs with a curl in the middle of their forehead, be sure to mention the aptly-in-retrospect-named Fury.

The GT-1 is cuter than a bug's ear to a steam fan ... but as innovative motive power for actually pulling trains (let alone doing so in a cost-effective manner) not so good.  When I read about it I am somehow reminded of an old sailplane article discussing research in yaw strings (it mentioned the special alloy version for hypersonic gliders...)  At least the North American Alco A-100 had a legitimate reason for retaining the side-rod drive.  (My fingers, in a kind of Freudian slip, kept trying to type 'drivel' for that last word!)

As you probably know, I'm fond of immensely-overcomplicated motor locomotives, and the Sentinel probably qualifies in the top tier.  If you thought a McKeen car was interesting to keep running, try six of them in parallel, built in the best English shop-steward tradition, and then add all the fun of steam as a working fluid.  This for locomotives running at relatively slow speed on indifferent track, not mainline service.  Think "all the costs of a diesel locomotive, and few of the advantages".

I'm surprised you did not mention the Fell locomotive.  Perhaps because not steam?

One very good reference everyone interested in the topic of this thread should read is Fryer's book on experimental steam.  There is more stuff in there that will curl your hair if you are interested in innovation that did not always pass the conventional-wisdom test -- rightly or wrongly.

 

[Miningman]

Is there any one making these bold and radical locomotives any longer. Of course we tinker with the insides and software but is anyone making some real eye popping total shifts in thinking and engineering as we did in the Classic past?