Dear Sy, (I'll try again!)
No you are not stupid. Those who don't know and won't ask are the
stupid ones.
The butterfly spring is reputed to be faster than the schwander
type of spring. I haven't seen the actual comparison test but believe it
to be so.
Others will probably give you a more detailed answer but I know that
part of the explanation given has to do with far end of butterfly spring,
where it acts as the jack spring. By serving both moviung parts at the same
time it is designed to maintain a working spring relationship between the
jack and the repetition lever. When all parts are properly cleaned,
lubricated, and adjusted, it creates the optimal spring pressures on the
two parts throughout the movement of the parts.
The part you are referring to as possibly being a Shimmel whippen
is now being used by a number of European manufacturers ( and hopefully will
soon be used by many others) is actually made by Renner. A good idea!
Hopefully others can enlighten us further.
Ed Hilbert
VT Chapt
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