Re: (TGR) L and M class Garratts

[The Oracle <ianadunn@yahoo.co.uk>]

> John Dennis wrote:
>
> > Bad form to follow-up your own posting, I know, but a little
> > research has discovered that the M class were 4-4-2+2-4-4
> > 8-cylinder compounds.  I would suggest that the complexity of
> > articulation combined with the complexity of compounding might
> > have had some bearing on the successs or otherwise of these
> > locos.

Correction here: the M class were 8-cylinder simples (2 x 4-cyl engine
units). The mechanism was not complicated, since the inside valves were
actuated by simple rocker mechanisms from the outside
Walschaerts-operated valves. Inside big-ends might have been a source of
difficulty, but there is no record. I would suggest that the simple
reason is that they were too powerful for requirements: the R class was
considerably less powerful, and still able to handle all requirments.
Also, Garratt-purchasing was a quasi-religious matter for CMEs. William
Rufus Deeble was obviously adventurous; his successor was just as
obviously not. Same thing happened in Sth Africa in the late 20s:
Collins was an articulated enthusiast, his successor Day was adamantly
anti kinked engines. Further point: the L and M classes were very early
Garratts, and at this stage of their development the pivots and steam
pipes were not self-adjusting, which caused additional maintenance.
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