Talk:Cylinder (locomotive)

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Timing[edit]

One fascinating thing about steam locomotives is that every child (and every adult too) I have ever seen "playing trains" by chuffing along with their hands mimicking the "motion" of two outside cylinders (a very common and natural activity, even now the age of steam is long gone, thanks in part to Thomas the Tank Engine I suspect) gets it subtly wrong... the left hand goes forwards while the right hands goes back, giving two chuffs per wheel revolution.

Of course, this mimicks an action with the cranks 180 degrees out of phase, while nearly all two cylinder locomotives have the cranks 90 degrees out of phase, as the cylinders are double acting. This gives four evenly spaced puffs per revolution, and one side of the motion is at mid-stroke whenever the other side is at the end of the stroke. (The exceptions are two-cylinder compound engines, with one high pressure and one low... common on traction engines but very rare on railway locomotives.)

It's such a ubiquitous error that even Thomas & Friends seems to have it wrong. There's a shot of the underside of his inside cranks in the introductory sequence of Season 16 (and probably appears in other intros as well) that appears to have two cylinders, 180 degrees out of phase - the crank assembly that is driven by the pistons and drives the valve gear is flat. (Thomas is based on the LB&SCR E2 class... two inside cylinders, Stephenson valve gear with slide valves.) Tut tut tut.

If we could source this somehow it would be a valuable factoid to have somewhere. Surely I am not the only one to have noticed. Or am I missing something? Andrewa (talk) 12:29, 9 November 2016 (UTC)[reply]