J.B. asks: "Is your harmonica design like the Hohner Polyphonia #7 'recording bass'?"
Yes and no.
It is a Circular design, based on the chromatic (NOT diatonic) scale. I know you are familiar with Circular, because you designed the first ever Circular Chromatic Harmonica based on the Seydel Chromatic Deluxe and were the inspiration for the second one - by me.
The Wholetone Tuning results from applying Circular logic to the CHROMATIC scale. (As noted before, I must thank Winslow Yerxa for pointing out that not-so-obvious-to-me detail; I was only trying to apply Circular logic.) It was after-the-fact that I found Pat Missin's description of Wholetone Tuning on Harp-On!
Each hole has two notes - one blow, one draw. These notes are a half tone apart, with the draw note a half tone higher than the blow note. The blow note in the next hole is a half tone higher than the draw note in the previous hole, but a whole tone higher than the previous blow note. Lather, rinse, repeat. All blow notes are a whole tone apart, and all draw notes are a whole tone apart, but blow to draw notes are only a half tone apart in a given hole.
To determine the feasibility, I had Seydel make me a 2-octave version based on the frame of a Solist Pro 12-hole diatonic. It worked, but the two octave range was just too limiting to be a useful musical instrument when playing.
Before starting the comb, cover and reedplates design, I made sure that Seydel made stainless steel reeds that would cover the desired note range (E2-A6). I found that if I used the Seydel Session Steel diatonic as a basis, and picked 6 reeds from those available for each hole (either blow or draw - the reeds in a given hole, whether blow or draw, have the same geometry), then I could use the diatonic reed slot and chamber geometry. Instead of just one hole with a given geometry, I used 3 holes (6 notes) with the same geometry. As a result, I only had to use 9 different geometries (the first 9 holes of the diatonic) resulting in 27 holes. I considered extending it out to 30 or 33 holes, but decided that having the entire human voice range (54 notes) was more than adequate for anything I would ever want to play musically. I've also considered 3 octave (19 holes), 3.5 octave (22 holes), and 4 octave (25 holes) designs. It's fairly simple to design once you get the idea of tripling the holes with a given geometry. The extra hole gives the octave note for the lowest and highest octaves.
I had a local precision machine shop measure the reedplate geometry using CMS (Coordinate Measuring System). I assumed that there would be a certain amount of tolerance built-in, since the Seydel reedplates are punched. I averaged the slot widths and took the average width as the specified width. The reed slot lengths, on the other hand, I used as-is for each slot. Will informed me that the factory could make things to +/- 0.05 mm tolerance. As a consequence, I had Will relax the specifications to match that tolerance. (I had specified values on my drawings to 4 decimal places in millimeters, knowing that was far too precise.)
The comb uses a 4 mm wide reed chamber for holes 1-21, and 3 mm wide for holes 22-27. This is based on some ideas of resonance gleaned from Brendan Power. (It remains to be seen if that helps or hurts the sound of the smallest reeds.) The mouthpiece holes center-to-center are 9 mm apart. The mouthpiece holes are round, 7.5 mm in diameter on the outside, chamfered and narrowing to either 4 mm or 3 mm as the hole goes into the reed chamber. The mouthpiece extends on either end for an extra 18 mm, providing a "landing zone" for the mouth when playing the last hole, without going off the end. I did that because I U-block, and didn't want half of my mouth hanging off the end.
The cover design curvature is based on two shapes - a parabola and a circle. The outer side of the cover in the first 12 mm (on the mouthpiece side) follows a parabolic curve, derived from the shape of the diatonic covers. The remainder of the outer surface follows a slight outward curve. The inner surface of the cover follows a circle in the first 12 mm, and then simply follows the outer curve for the remainder, giving a 2 mm thickness as the minimum thickness. There are 8 "ribs" in the cover, which help stabilize and support the covers. These ribs also allow for cupping around any group of 3 reeds for muting.
The idea of a 1-piece cover came from Antaki's Turbo Harp design. Instead of having two cover pieces that snap together around the comb, I decided to simply fit the comb through a cutout in the cover, and then fasten the comb to the cover with a retaining plate. Unfortunately, machining of that cover design was very complicated; Will recommended that I switch to the traditional two-cover design. One of his innovations is to use magnets to hold the covers on the comb; I asked him to use that idea.
The cover is 3D printed ABS plastic, the comb is silver-plated brass, and the reedplates are brass. The covers and comb could have been made of stainless steel or brass, but it would have added several hundred more dollars to the cost, which was already very high.
Hope that helps to understand the design.
Crazy Bob