"Christopher Tidy" wrote in message
...
Am Freitag, 18. August 2017 05:43:55 UTC+2 schrieb Cla

A Loco doesn't use a clutch.

I know. It was hypothetical. I was trying to work out why not.

The history of locomotive engineering is interesting in that the
demands of being such a heavy and powerful moving vehicle made the
simplest-seeming things like following a curve or wheel balance very
difficult.
https://en.wikipedia.org/wiki/Hammer_blow

One consequence was the gradual weakening of cast-iron bridge
components:
https://en.wikipedia.org/wiki/Tay_Bridge_disaster
"A joiner who had worked on the bridge from May to October 1879 also
spoke of a lateral shaking, which was more alarming than the
up-and-down motion, and greatest at the southern junction between the
high girders and the low girders. He was unwilling to quantify the
amplitude of motion, but when pressed he offered 2 to 3 inches (50 to
75 mm). When pressed further he would only say that it was distinct,
large, and visible."

In addition to hammer blow the necessary 90 degree piston offset
between the two sides to avoid being stuck on top-dead-center makes
the loco wiggle (yaw) sideways.
-jsw