Posted by Sauerkraut on January 04, 2002
In Reply to: Off his rocker posted by James Briggs on January 04, 2002
: I can find nothing in the Archives for this phrase. Today I had an email, part of which said:
"....anyway the reason for the e-mail is that I am sure I
: have heard a proposed origin for the phrase 'off his rocker'... if memory
: serves the idea was that it came from early days of steam engine
: development....in particular beam engines....the beam engine rocks back and
: forth and if it comes off the pivot (rocker) it goes mad, flailing about and
: smashing up everything about it...."
: What do others think of this? There's no origin offered in any of my reference books - in fact the phrase is only mentioned in two of them.
A good and very probable explanation. These beam type steam engines were used in ferry boats and other "light" water craft - examples can be seen in San Francisco's maritime museum, and many others of the sort around the country. These engines were also used for stationary power - often to pump oil.
The engines also gave rise to the expression of getting somebody or some project "off dead center."
Ocassionally, when the engine was stopped it would end up with the beam perfectly horizontal, and when it was started again, the rocking motion was frozen, since the force of the steam cylinder was straight up. Wherever one of these engines was used, there was close at hand a long lever bar which the crew would use to lift the beam end just enough to start the normal motion, thus getting the engine off dead center.
Perhaps at this critical jucture, if pressure was wrongly applied, the beam would jump from its rocker - certainly not a desired end, and with all the imaginable consequences.