Building New Chrysalis II

October 2013–March 2015

 

© 2013–2024 Cris Forster
All rights reserved.

 

Chrysalis I

 

Chrysalis II

 

 

 

 

 

 

 

 

Butt jointing seven quarter-sawn Sitka spruce boards to make one of two soundboards.

 

Routing eight rib channels and the circumference of the right soundboard.

 

Undercutting the right soundboard and gluing the first birch plywood support ring.

 

Machining and dry-fitting the ribs of the right soundboard.

 

Drilling and tapping four multi-screw rib clamps.

 

Gluing the first set of four ribs to the right soundboard.

 

Setting up and cutting the octagonal Delrin hub.

 

Drilling eight spoke holes in the hub.

 

Machining the soundboard spacers.

 

Comparing the spider assembly dimensions to a to-scale drawing.

 

Drilling, routing, and dry-fitting the second birch plywood support rings.

 

Dry-fitting the spider assembly between the second birch plywood support rings.

 

Machining and installing the buttress support screws.

 

Machining and installing two axle clamps.

 

Dry-fitting and centering the right soundboard with a Delrin axle sleeve.

 

Gluing the second birch plywood support ring to the right soundboard.

 

Turning and installing Honduras rosewood spokes that are much stiffer
and more resistant to bending than the original Delrin spokes.

 

Testing radial runout, which measures the surface parallel to the axis of rotation; and
axial runout, which measures the surface perpendicular to the axis of rotation.

(See also Instrument Construction Archive > Glassdance Components Manual – #1, pp. 2325.)

 

Marking and drilling a template designed for locating and drilling 82 identically spaced tuning gear
post holes and 82 identically spaced nut pin holes of the left and right soundboards.

 

Using the drilling template and two transfer punches to mark the centers
of 82 post holes and 82 nut pin holes of the right soundboard.

 

Counterboring the tuning gear post holes for press-fitting the tuning gear ferrules
of the left and right soundboard/support-ring assemblies.

 

Drilling eight soundboard and two bridge support screw holes in the hub.

 

Epoxying the base of the bridge support screw flange to the right soundboard.

 

Installing the bridge and soundboard support screws of the right soundboard.

 

Drilling six bridge screw holes and installing the bridge of the right soundboard.

 

Turning the axle to length, then drilling/reaming two holes and milling four slots to
accommodate the three longest strings of the left and right soundboards.

 

Installing the machined axle and the three longest strings of the right soundboard.

 

Machining the ash molding.

 

Soaking the ash molding in boiling water and clamping it around a form.

 

Gluing a semicircular ash molding to the right soundboard.
Phase I

 

Phase II

 

Machining full-length cylindrical tuning gear ferrules to replace standard partial-length conical ferrules.

(See also Instrument Construction Archive > Chrysalises Machining Ferrules Manual – #2.)

 

Spray finishing the soundboards.

 

Modification: 2020
Machining the aluminum buttons that cover the machine screw holes
in the soundboards of Chrysalis I and Chrysalis II.

(See also Instrument Construction Archive > Chrysalises Machining Buttons and Color-coding Manual – #3.)

 

Color-coding the buttons of Chrysalis I and Chrysalis II.
Mounting the aluminum buttons on spraying sticks with standoff hex nuts and double-sided tape.

 

Machining the Delrin nuts or the downbearing supports of the strings at the tuning gears.

 

Machining the Lexan soundboard shields.

 

Modification: 2020
Remachining and screw assembling the Delrin nuts and Lexan shields.

 

Geometry of the nut and shield assembly of the right soundboard.

 

Geometry of the nut and shield assembly of the left soundboard.

 


Sawing slots into the Delrin nuts

An earlier sequence of photos shows that the circumferences of two Sitka spruce soundboards are encircled by two birch plywood support rings. This construction provides maximum anchorage for the tuning gears and gives maximum structural resistance against bending the soundboards under the tension of the strings.

Since the two circular aluminum bridges are attached directly to the soundboards, they function as true bridges by transmitting mechanical energy from the vibrating strings directly to the soundboards. However, because this stringing design requires that 164 individual Delrin nuts sit on top of the soundboard/plywood assemblies, numerous tests indicate that these nuts have bridge-like functions; they also transmit energy from the strings to the soundboards. Consequently, the nuts significantly affect the quality of sound, or the amplitude, ring-time, and timbre of the vibrating strings.

Instead of the strings passing across the nuts and touching them over an area of contact, I discovered that the strings sound best if they pass through the nuts and only touch them at a point of contact. To achieve a bridge-like contact point, I sawed slots into the nuts with a circular saw blade. The following sequence of drawings and photos shows that by clamping the nuts in the milling machine vice at an angle of 53.5° and passing them into a revolving saw, the saw cuts a tangent line or a straight channel into the nuts. So, although the nuts have a wide base to counteract the downbearing force of the strings at the tuning gears, they also have a point at the top to maximize the transmission of mechanical energy from the vibrating strings to the soundboards.

 


 

 

Assembling the wheel of Chrysalis II: two Sitka spruce soundboards,
two sets of 82 tuning gears, and two circular aluminum bridges.

 

Based on the dimensions of the original Chrysalis I stand, designing a proportionately
larger stand for Chrysalis II without changing the critical distance
between the floor and the bottom of the new wheel.

 

Two sides of the new birch plywood stand clamped together.

 

Drilling eighteen dowel holes into two sides of the stand clamped together.

 

Drilling three holes for the Delrin ball bearing pillow block supports.

 

Drilling four flat bottom holes for the load bearing maple dowels
on the inner stand surfaces covered with beech veneer.

 

Drilling off-center lock screw holes that prevent the dowels, which hold the sides
of the stand together, from turning on their center screws.

Two dowels, like the kind shown below, each have two Honduras rosewood
blocks for mounting the instrument’s four casters.

 

Assembling the stand with eighteen maple dowels and two Delrin ball bearing pillow block supports.

 

Gluing the beech veneer to the outer stand surface.

 

The 82 strings of the right soundboard and a newly powder coated
bridge with a 14° string relief angle on the rim of Ring B.

 

Installed 16 powder coated brass brackets designed to counteract movement
of the soundboards at the tuning gears due to the tension of the strings.

And attached 16 felt-covered Delrin brake pads designed to stop the wheel
against the top of the left knee while playing with both hands.

 

Machining left string performance markers.

(See also Instrument Construction Archive > Chrysalises Machining Left String Performance Markers Manual – #4.)

 

Stringing.

(See also Instrument Construction Archive > Chrysalises Stringing Manual – #1.)

 

Chrysalis II

(See also Instrument Construction Archive > Chrysalises Tools and Parts.)

The Chrysalis Foundation