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I'm looking for some guidance on converting an old, Large, 3v front action Piston, to a rotor system, I am having lingering issues with my right hand, post motorcycle accident.
So..., my thoughts went to a convertion of a piston to a rotor system because of the apparent shorter throw.. I quess the question is, are their significant issue relating to the tube lengths of the valve system/cluster when laying it out, or does the length of each slide remain the same based on the key of each instrument, once the open bugle has been established? AND would you put a fifth rotor on a BBb or leave it as a 4vR? Thanks in advance. Looking for answers from the guys who have done addition and subtraction of valves. Or those who can respond from the accoustical theory element.

Not a repairman and too bland to be considered seasoned. Yet:

Theoretically the valve loop lengths are the same independent of valve type. Included in the loop length is the length of the additional valve passage (which may vary from valve type to valve type and even within each type). The changed geometry of the valve passages may have some influence on pitch and response, but that will be hard to pre-calculate.

In general rotor blocks take up a larger portion of the main bugle than a piston block with the same number of valves. That may introduce a need for the rotor block to have a progressive (and increasing) bore to match the leadpipe and the tubing going to the main tuning slide respectively.If there is some cylindrical tubing to be cut, you may not need a valve block with a progressive bore. Such rotor blocks do exist. The probably best know sample is the 5 rotor block for the old B&S F tuba, where all 5 rotors were of a different bore.

Klaus

Thanks Klaus, your input is always accepted and much appreciated, A progressive rotor system would be nice, The question than is; stay with four rotors and omit the fifth , or 4 rotors connected and a fifth independant or five fixed in a row. Lot's of options.

A fifth valve improves accuracy of the lower range, but there might be a price to be paid in form of a less alive response. I am not into dependent valves with mostly conical instruments, as the differences in bore profile between the open bugle and the 4th + 5th valves combined will be huge. And you loose some fingering permutations like 235.

If you can get a spare original tuning slide and a rotor of an adequate size, it may be worthwhile placing the 5th rotor in the tuning slide, so that this second slide can be mounted when the repertory has special needs in the low range.

Klaus