(posted by RR, 5 July 2017)
"Here's a question for anyone with experience with shimming leslies; Say I want to produce spacers for a 31 and 37 bell to mock up 277 and 330 bells, could I just subtract the distance recorded on S3J diagrams for those bell lengths and make spacers of those lengths for the 31 and 37? or is there a more 'dialed in' spacer length for those two bells to match the appropriate frequencies?"
(comments)
MF: "It's a trial and error process, the spacers are unique to each bell. The external length isn't the important measurement, it's the shape of the internal throat flare. I don't know of any published specs for that."
BM: "Size of the resonating air column is what determines pitch. With a Leslie, sand cast parts produce many flaws so it's impossible to cut and weld or make spacers to predetermined specs."
RR: "I've read about and experimented with external length only and produced different pitches that way, the man RES himself even related the length and diameter of the column to pitch as a two-part equation, so it isn't just the internal measurement that matters. That said, thanks for the input, I'll just play around with some spacer numbers."