[Harp-L] David Pearce's CAD/CAM design software

Robert Coble robertpcoble@xxxxx
Wed Aug 2 16:33:17 EDT 2017

Thanks, David, for sharing the info.

You win, no contest!

I'm not trying to build something to sell; it is for my own usage. I dislike slide chromatic harmonicas with valves,

for the obvious reasons: leaking and sticking. I've tried the Tombo slideless chromatics (SS-50; 1157) but the note

layout tries to "mirror" the standard chromatic (with the stupid double C notes and switch in blow/draw pattern

on scale degree 7), which is counter-intuitive to ME. I looked at converting one of them (1157) but the amount of

work is about what it would take to just start from scratch.  I've known players who are content to learn the Tombo

patterns; all the Asian players can't all be wrong!

I arrived at a note layout via the spiral (circular; Zirkular) tuning used on Seydel diatonics. It's the same idea of

spiraling the chromatic scale (blow/draw) up the harp. Winslow Yerxa was so nice to point out that it is actually

a whole-tone tuning in each breath direction (blow/draw) with a half-tone difference between the blow and draw

notes in each hole. That allows a slight amount of bending between the blow and draw notes, ala the diatonic

scheme. There is nothing "magical" or proprietary about that aspect of it. This results in having to learn just two

note patterns (one for blow keys and one for draw keys) for the whole harmonica. The initial design had 27 holes

(54 notes), simply because that represents the full range of currently available Seydel stainless steel reeds. If I use

brass reeds, I can extend the lower end to cover the bass range as well with more holes. That obviously has an

impact on size of chambers (thickness) and covers. I spent a lot of time figuring out an alternative design for Tate

ramps that do NOT duplicate current designs. I'm sure there are many people who would say "Why bother?" but

it's something I want to experiment with. As previously stated, my goal is to have a harmonica designed the way

-I- want it. Whether it appeals to anyone else is of no concern. I know how easy it was for me to transition from

standard diatonics to spiral tuning, and I wouldn't go back for anything.

At Brendan Power's suggestion some time ago, I had a prototype made by Seydel on their 12-hole Solist model

diatonic. It works GREAT - FOR ME! Unfortunately, it's not possible to get a chassis with more holes in it from


I've tried finding someone locally  who is willing to input the design into CAD/CAM for pay, but no luck so far.

The search continues in fits and starts as I get spare time and save my shekels.

The Creo CAD package looks impressive! I watched an introductory video today. It's considerably more intuitive

than SketchUp.

So many wonderful opportunities for experimentation these days, especially with quality 3D printing available!

Good luck!

Crazy Bob

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