Blueprints

ISTR Holcroft sketched a conjugating gear that would do 8 beats from 4 cylinders with two sets of valve gear. Whether that's it I couldn't say.

 

Here you go - the Holcroft 4-cyl conjugated gear as applied to Tugboat Annie, 8 beats to the bar and all. I'm not particularly surprised it didn't catch on...


From "LBSC" His Life and Locomotives by Brian Hollingsworth.

 

You're correct, that's a layout of A.G. Watson's proposed Class 22 2-10-4. The class 21 2-10-4, of which there was a single example, was basically a 15F on a 2-10-4 chassis; this would have been a considerably more powerful machine, even more so than the later Class 25. A 2-10-4 would have been much better suited to SAR traffic patterns than either the 4-8-2 or 4-8-4, but this one was a bit too much of a monster to ever be sanctioned. I think it had the same 21 ton axle load as the 16E Pacifics, so maybe the SAR took fright at the route availability and behaviour on tight curves. Interestingly, North British later proposed a small-wheeled 4-10-4 when the Class 25 was under development, but the larger-wheeled (all of 5'0") 4-8-4 won out.

 

Good Grief!

 

It just goes to show, there just aren't any big chuffers in Britain at all...

 

Tugboat Annie certainly has the Holcroft conjugated gear to give 8 beats per revolution. At one time she was owned by George Barlow and ran regularly on the track of the Romney Marsh MES; the first picture in post 18 shows George driving her there. I know of one other loco fitted with this conjugated valve gear, Lord Howe on the Torry Hill railway, shown in the picture. below. Interestingly enough this picture also shows George Barlow filling the tender with water. This loco, and the other 2 currently at Torry Hill, were built by Joe Liversage; he is the man in the woolly hat.

 

I've just read, admittedly on Wiki, that the first application of Holcrofts conjugated valve gear was actually on 'Tugboat Annie' before being made in full size.

 

I think what the article should have said was that it was the first application of Holcroft's *4 cylinder* gear to provide 8 beat events. I'm not sure that has ever been implemented in "full size".

 

The information that I picked up came from Live Steam, presumably a magazine from July/August 1951

 

I have just found a picture of Tugboat Annie's valve gear. The total width of the conjugated assembly is about 4" - an impressive achievement.