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Does anyone know when clocksprings were first used on rotary valves? I'm having no luck with Web searches.

I believe clockworks antedate the rotary valve... they were used on some of the earliest Vienna twin piston valves, along with leaf springs. By 1840, certainly, they were as common as any other spring mechanism. However, they were never common in the U.S.

J.c.S.

Here's an interesting read on early valve design development (related to the Horn in F):
http://www.public.asu.edu/~jqerics/earlval.htm" target="_blank

There's not much mention of spring methods on rotary valve systems in this article, but you may be able to use it as a starting point for additional research since it describe the origins of the rotary valve.

From the same set of articles, here's one about the development of the 'double horn':
http://www.public.asu.edu/~jqerics/double.htm" target="_blank

Thank you, gentlemen.