SpHEAR/TinySpHEAR_mount_pcb.scad

//
// Spherical Harmonics Ear Project (*SpHEAR)
//
// TinySpHEAR, First Order (B-format) Ambisonics Microphone
// Mount for four Zapnspark phantom power printed circuit boards
// 
// Copyright 2015-2016, Fernando Lopez-Lezcano, All Rights Reserved
// nando@ccrma.stanford.edu
//
//  This program is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program.  If not, see <http://www.gnu.org/licenses/>.
//
// 3d Models released under the Creative Commons license as follows:
//   Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)
// http://creativecommons.org/licenses/by-nc-sa/4.0/

include <TinySpHEAR_common.scad>;
include <CCRMA_logo.scad>;

////
//// default model parameters
////

// size of Zapnspark printed circuit board
// kicad length = 79.375
// measured length = 79.20 (2016.08.25)
pcb_length = 79.20;
// kicad width = 19.050
// measured width = 18.82 (2016.08.25)
pcb_width = 18.85;
// ultimaker spec thickness = 1.61
// measured thickness = 1.56 (w/ copper)
pcb_thickness = 1.58;

// tolerance to add to length and width of pcb
//
// measured 3d print width = 18.70 (with pcb_fit = 0.3)
// actual printed = 18.70 - 0.3 = 16.97
// total correction = 18.85 - 16.97 = 1.88
//
pcb_fit = 0.4;

// tolerance add to thickness of pcb
//
// printed with pcb_tfit = 0.15 -> 1.58 + 0.15 = 1.73 (ideal printed)
// measured print channel = 1.63 : 0.1 thinner (ultimaker 2 plus, 2016.08.24)
// measured pcb thickness = 1.58 (othermill)
//
pcb_tfit = 0.15;

// we leave part of the pcb exposed on the bottom of the body so that we
// can solder the wires that connect the microphone with the
// preamplifier, same at the top of the pcb to solder the wires
// to the capsules
pcb_low_exp = 12.0;
pcb_hi_exp = 8.0;

// clearance from the bottom and top of pcb's to the start of the flare,
// this adds space for the protuding molex pins on which we solder
pcb_low_clear = 15.0;
pcb_hi_clear = 15.0;

// back and front clearance of pcb (components and leads)
pcb_front = 13.25;
pcb_back = 3.0;

// depth of slot into which the printed circuit board fits
pcb_slot_depth = 1.0;

// diameter of four conductor cable (Mogami W2931)
cable_diam = 9.5;

// diameter of microphone capsule cable (Mogami 2490)
capsule_cable_diam = 1.7;

// lip that mounts flares into main body box
mount_lip = 10.0;

// lip fit for flares
lip_fit = 0.05;

// capsule array mount, height of flare and stalk
flare_height = 50;
stalk_height = 40;

// adjust mic array to mount relative height
mic_to_mount_fit = 0.0;

// wall thickness
wall = 1.0;

// calculated minimum "radius" of microphone box
box_radius = pcb_front + (pcb_thickness + pcb_tfit) + pcb_back + 2 * wall;

// calculated main body corner radius
mount_corner = box_radius - pcb_width / 2 + pcb_slot_depth + 4.0;

//// snap joints to join the body to the two flares
//
// render snap joints to join all three main assemblies
render_snap_joints = false;

// body to flares snap joint arm slot width
snap_joint_slot_w = 0.75;

// width and radius of snap joint hook that locks upper and lower flanges to body
snap_joint_hook_w = 5.0;
snap_joint_hook_r = 1.4;

//// screw holes to join the body to the two flares
//
render_screw_holes = true;

// dimensions of 12 pin male bottom connector
//
// Amphenol T 3635 002
// 12 pin DIN male to cable, gold plated contacts
//
// inner diameter of connector core
conn_core_diam = 13.00 + 0.2;
// outer diameter of connector core sleeve
conn_core_o_diam = 17.00;
// inner diameter of connector core sleeve
conn_core_s_diam = 15.00;

// from top of connector to sleeve
conn_core_sleeve = 13.00;
// from top of connector to holes
conn_core_holes_h = 6.00;
// between holes
conn_core_holes_w = 9.20;
// hole diameter
conn_core_holes_d = 1.95 + 0.2;
// screw head diameter
conn_core_screw_d = 2.75 + 0.5;
// sleeve overlap
conn_core_overlap = 3.00;

// shock mount parameters
//

ring_sep = 30.0;
ring_height = 10.0;
rubber_band_angle = 40;
main_radius_inc = (ring_sep / 2) / tan(rubber_band_angle);

// gap between internal ring and microphone body
internal_ring_gap = 1.0;

// connector that joins the two internal rings
connector_w = 10.0;
connector_d = 2.0;

// wall thickness and height of shock mount rings
ring_wall = 4 * wall;
ring_ext_height = 6;

// gap between external ring and support arm
ring_arm_gap = 20;


// all four printed circuit boards

module tetra_pcb_clear(length, width, thick, slot_depth, front, back) {
    for (rot = [0, 90, 180, 270]) {
        rotate([0, 0, rot]) {
            pcb_clear(pcb_length + pcb_fit, pcb_width + pcb_fit, pcb_thickness + pcb_tfit, slot_depth, front, back);
        }
    }
}

// the main body of the microphone mount

module tetra_mount_body(height, radius, corner, lower_lip, upper_lip, clear) {
    difference() {
        rounded_block(height, radius, radius, corner);
        union() {
            // hollow out the inside with slots for pcbs
            tetra_pcb_clear(pcb_length, pcb_width, pcb_thickness, pcb_slot_depth, pcb_front, pcb_back);
            // trim square angles
            cylinder(r = pcb_front, h = height, $fn = facets);
            // remove slots from inside body
            slot_len = 30;
            translate([0, 0, slot_len]) {
                difference() {
                    rounded_block_relative(height, radius, radius, corner, - (2 * wall));
                    if (render_screw_holes) {
                        // add columns for upper screw holes
                        col_w = 3.5;
                        for (r = [45, 135, 225, 315]) rotate([0, 0, r])
                        translate([radius - col_w*2/3, -col_w/2, 0]) {
                            cube([col_w, col_w, height]);
                        }
                    }
                }
            }
            // upper lip for flare to microphone
            translate([0, 0, height - upper_lip]) {
                difference() {
                    rounded_block(upper_lip, radius, radius, corner);
                    rounded_block_relative(upper_lip, radius, radius, corner, -(wall + lip_fit));
                }
            }
            // lower lip for flare to cable
            translate([0, 0, 0]) {
                difference() {
                    rounded_block(lower_lip, radius, radius, corner);
                    rounded_block_relative(lower_lip, radius, radius, corner, -(wall + lip_fit));
                }
            }
            if (render_screw_holes) {
            // make eight holes in the the body for screws that hold both flares
            // (number 0 size, 1/4" long = thread diameter: 1.6mm, head diameter: 2.75)
                for (z = [lower_lip/2, height - upper_lip/2])
                for (r = [45, 135, 225, 315]) {
                    rotate([0, 0, r])
                    translate([-(radius + 2 * wall), 0, z]) {
                        rotate([0, 90, 0]) {
                            cylinder(r = 0.7, h = radius + wall, $fn = facets);
                        }
                    }
                }
            }
            if (render_snap_joints) {
                // slots for snap joint hooks
                // lower
                for (m=[-1, 1]) rotate([0, 90, 0]) {
                    translate([-lower_lip * 3/4, (radius - wall/2)*m, -(snap_joint_hook_w/2 + 0.25)]) {
                        cylinder(r = snap_joint_hook_r, h = snap_joint_hook_w + 0.5, $fn = facets);
                    }
                }
                // upper
                for (m=[-1, 1]) rotate([0, 90, 0]) {
                    translate([- height + upper_lip * 3/4, (radius - wall/2)*m, -(snap_joint_hook_w/2 + 0.25)]) {
                        cylinder(r = snap_joint_hook_r, h = snap_joint_hook_w + 0.5, $fn = facets);
                    }
                }
            }
        }
    }
    if (render_snap_joints) {
        // upper lip is too thin, reinforce the back of the snap joint hook holes
        for (r = [0, 180]) rotate([0, 90, r]) {
            translate([- height + upper_lip * 3/4, (radius - wall), -(snap_joint_hook_w/2 + 0.25)]) {
                difference() {
                    cylinder(r = snap_joint_hook_r * 1.25, h = snap_joint_hook_w + 0.5, $fn = facets);
                    translate([- snap_joint_hook_r * 1.25, - wall, 0]) {
                        cube([snap_joint_hook_r * 3, snap_joint_hook_r * 3, snap_joint_hook_w * 1.5]);
                    }
                }
            }
        }
    }
    // add parts for clearance check
    if (clear == 1) {
        // electrolytic capacitors
        cap_diam = 10.2;
        for (rot = [0, 180, 270]) {
            rotate([0, 0, rot]) {
                translate([-pcb_front + cap_diam/2, 0, 0]) {
                    *cylinder(r = (cap_diam/2), h = 20, $fn = facets);
                }
            }
        }
        // PCBs
        for (rot = [0, 180, 270]) {
            rotate([0, 0, rot]) {
                translate([-(pcb_front + pcb_thickness), -pcb_width/2, -pcb_low_exp]) {
                    cube([pcb_thickness, pcb_width, pcb_length]);
                }
            }
        }
        // connectors
        cap_h = 12.3;
        cap_w = 10.53/2;
        for (rot = [0, 180, 270]) {
            rotate([0, 0, rot]) {
                translate([-pcb_front, -cap_w/2 - 2.5, 0]) {
                    *cube([cap_h, cap_w, 20]);
                }
            }
        }
    }
}

// flares from the body to the microphone stalk and cable

module tetra_mount_flare(height, lip, transition, bot_radius, bot_corner, top_radius) {
    // bottom rounded box
    difference() {
        union() {
            rounded_block(height, bot_radius, bot_radius, bot_corner);
            if (render_screw_holes) {
                // small supports for the screws that attach the flare to the body
                // (number 0 size, 1/4" long = thread diameter: 1.6mm, head diameter: 2.75)
                for (r = [45, 135, 225, 315]) rotate([0, 0, r]) {
                    translate([bot_radius + wall/3, 0, lip/2]) {
                        rotate([0, 90, 0]) {
                            cylinder(r = 1.5, h = 2 * wall, $fn = facets);
                        }
                    }
                }
            }
            if (render_snap_joints) {
                // make snap joint arm thicker
                for (r = [0, 180]) rotate([0, 0, r]) {
                    translate([- snap_joint_hook_w - snap_joint_slot_w / 2, bot_radius, 0]) {
                        cube([snap_joint_hook_w * 2 + snap_joint_slot_w, wall / 2, lip * 1.25]);
                    }
                }
            }
        }
        rounded_block_relative(height, bot_radius, bot_radius, bot_corner, -(2 * wall));
        // cut flange to mount on body
        rounded_block_relative(lip + 1.00, bot_radius, bot_radius, bot_corner, - (wall));
        if (render_screw_holes) {
            // holes for screws that attach the flare to the body
            // Number 0 Size, 1/4" Long = thread diameter: 1.6mm, head diameter: 2.75
            for (r = [45, 135, 225, 315]) rotate([0, 0, r]) {
                translate([bot_radius + wall, 0, lip/2]) {
                    rotate([0, 90, 0]) {
                        cylinder(r = (1.6 + 0.1)/2, h = bot_radius, $fn = facets);
                    }
                }
            }
        }
        if (render_snap_joints) {
            // cut slots for snap joint hooks
            for (r = [0, 180]) rotate([0, 0, r]) {
                for (m = [-1, 1]) {
                    translate([m * (snap_joint_hook_w + snap_joint_slot_w) - snap_joint_slot_w / 2, bot_radius - 1.5 * wall, 0]) {
                        cube([snap_joint_slot_w, 2 * wall, lip - 1.0]);
                    }
                }
            }
        }
        // and make a smooth transition to avoid overhangs
        translate([0, 0, lip + 1.00]) {
            hull() {
                rounded_block_relative(thin_mint, bot_radius, bot_radius, bot_corner, - wall);
                translate([0, 0, 1.0]) {
                    rounded_block_relative(thin_mint, bot_radius, bot_radius, bot_corner, - 2 * wall);
                }
            }
        }
    }
    if (render_snap_joints) {
        // add snap joint hook to arm
        for (r = [0, 180]) rotate([0, 0, r]) {
            translate([- snap_joint_hook_w / 2, bot_radius - wall/2, 1/4 * lip]) {
                rotate([90, 0, 90]) {
                    difference() {
                        cylinder(r = snap_joint_hook_r - 0.2, h = snap_joint_hook_w, $fn = facets);
                        translate([0, -snap_joint_hook_r, 0]) {
                            cube([snap_joint_hook_r, snap_joint_hook_w, snap_joint_hook_w]);
                        }
                    }
                }
            }
        }
    }
    // flare to round section
    translate([0, 0, height]) {
        difference() {
            hull() {
                rounded_block(thin_mint, bot_radius, bot_radius, bot_corner);
                translate([0, 0, transition]) {
                    cylinder(r = top_radius, h = thin_mint, $fn = facets);
                }
            }
            hull() {
                rounded_block_relative(thin_mint, bot_radius, bot_radius, bot_corner, - wall);
                translate([0, 0, transition]) {
                    cylinder(r = top_radius - wall, h = thin_mint, $fn = facets);
                }
            }
        }
    }
}

// stalk that connects upper flare to capsule array mount

module tetra_mount_array_stalk(height, radius) {
    difference() {
        cylinder(r = radius, h = height, $fn = facets);
        cylinder(r = radius - wall, h = height, $fn = facets);
    }
    // add marker for "back of microphone" orientation
    rotate([0, 0, 90]) {
        translate([0, radius - wall * 2 / 3, height - radius]) {
            difference() {
                sphere(r = radius / 3, $fn = 32);
                translate([0, -radius + radius / 2, 0]) {
                    cube([radius, radius, radius], center = true);
                }
            }
        }
    }
}

// bottom cable holder

module tetra_mount_cable_holder(height, radius) {
    difference() {
        cylinder(r = radius, h = height, $fn = facets);
        cylinder(r = radius - wall, h = height, $fn = facets);
    }
}

// bottom connector holder

module tetra_mount_connector_holder(height, radius, inside_radius, sleeve_height, sleeve_radius) {
    difference() {
        union() {
            cylinder(r = radius, h = height, $fn = facets);
            // add seats for screw heads
            for (m = [-1, 1]) translate([m * conn_core_holes_w / 2, radius / 2, conn_core_holes_h]) {
                rotate([90, 0, 0]) {
                    scale([1, 1, 1]) cylinder(r = conn_core_screw_d / 2, h = radius * 1.43, $fn = facets);
                }
            }
        }
        cylinder(r = inside_radius, h = height, $fn = facets);
        // transition from thin wall to thick wall at the bottom of connector
        cylinder(r1 = radius - wall, r2 = inside_radius, h = 2.0, $fn = facets);
        // holes for connector core screws
        for (m = [-1, 1]) translate([m * conn_core_holes_w / 2, - radius / 3, conn_core_holes_h]) {
            rotate([90, 0, 0]) {
                cylinder(r = conn_core_holes_d / 2, h = radius, $fn = facets);
            }
        }
        // substract cutout for screw heads
        for (m = [-1, 1]) translate([m * conn_core_holes_w / 2, - radius + 1.5, conn_core_holes_h]) {
            rotate([90, 0, 0]) {
                cylinder(r = conn_core_screw_d / 2, h = 2.0, $fn = facets);
            }
        }
    }
    // thinner cylinder sits inside connector sleeve
    translate([0, 0, height]) {
        difference() {
            cylinder(r = sleeve_radius, h = sleeve_height, $fn = facets);
            cylinder(r = inside_radius, h = sleeve_height, $fn = facets);
        }
    }
}

// top conical section that plugs into capsule array

module tilted_cylinder(radius, height, offset) {
    hull() {
        cylinder(r = radius, h = thin_mint, $fn = facets);
        translate([offset, 0, height]) {
            cylinder(r = radius, h = thin_mint, $fn = facets);
        }
    }
}

module tilted_cube(width, depth, height, offset) {
    hull() {
        cube([width, depth, thin_mint]);
        translate([offset, 0, height]) {
            cube([width, depth, thin_mint]);
        }
    }
}

module tetra_capsule_array_mount(angles, mount_radius, mount_wall) {
    difference() {
        union() {
            rotate([0, 0, 45]) {
                wire_offset = wall;
                wire_diam = mic_wire_diam + mic_wire_fit;
                // FIXME: this 1.75 is the former leg_thick value, it should be calculated
                // based on the capsule diameter so that the cable fits in between the capsules
                sleeve_width = 1.75 + wire_offset + wire_diam * 2 + wall / 2;
                sleeve_width_max = capsule_radius + wall;
                sleeve_w = (sleeve_width > sleeve_width_max) ? sleeve_width : sleeve_width_max;
                difference() {
                    hull() {
                        cylinder(r = mount_radius + mount_wall, h = thin_mint, $fn = facets);
                        translate([0, 0, mount_top_height]) {
                            rounded_block(thin_mint, sleeve_w, mount_radius_capsule - wall/2, mount_radius*4/5);
                        }
                    }
                    // cavity for printing without support
                    scale([1.0, 1.0, 3.0]) {
                        sphere(r = mount_radius, $fn = facets);
                    }
                    // holes for cables
                    // offset for outer hole
                    hole_offset_l = mount_radius - wire_diam / 2;
                    hole_offset_h = (sleeve_w - wall - wire_diam / 2) - hole_offset_l;
                    for (m = [0, 1]) mirror([m, 0, 0]) {
                        translate([hole_offset_l - wire_diam, 0, 0]) {
                            tilted_cylinder(wire_diam / 2, mount_top_height, hole_offset_h);
                        }
                        translate([hole_offset_l, 0, 0]) {
                            tilted_cylinder(wire_diam / 2, mount_top_height, hole_offset_h);
                        }
                        // shave the inside of the double tube
                        translate([hole_offset_l - wire_diam, - wire_diam / 4, 0]) {
                            tilted_cube(wire_diam, wire_diam/2, mount_top_height, hole_offset_h);
                        }
                    }
                }
            }
        }
        // indentations that match the two lower capsule holders
        // add ridge height adjustment
        translate([0, 0, mount_top_height + (mic_radius - capsule_height) + capsule_height * cos(elev_angle) - mic_to_mount_fit]) {
            rotate([0, (90 + elev_angle), angles[0]]) {
                translate([0, 0, mic_radius - capsule_height]) {
                    capsule([], 0, 1, 0.02, 0.02, 1);
                }
            }
            rotate([0, (90 + elev_angle), angles[1]]) {
                translate([0, 0, mic_radius - capsule_height]) {
                    capsule([], 0, 1, 0.02, 0.02, 1);
                }
            }
        }
        // slice top sides of mount
        for (rot = [45, 45 + 180]) {
            translate([0, 0, 0]) {
                rotate([0, 30, rot]) {
                    translate([-mount_radius_capsule, -(mount_radius_capsule), mount_top_height])
                        cube([mount_radius_capsule*2, mount_radius_capsule*2, 10]);
                }
            }
        }
    }
}

////
//// render all the different parts
////

// microphone body: flare to capsule array (slips into PCB holder body)
//

module render_tetra_capsule_flare(z_offset) {
    translate([0, 0, z_offset]) {
        tetra_mount_flare(pcb_hi_clear + pcb_hi_exp, 
                    mount_lip, flare_height, box_radius + wall,  mount_corner, mount_radius + wall, stalk_height);
        translate([0, 0, pcb_hi_clear + pcb_hi_exp + flare_height]) {
            tetra_mount_array_stalk(stalk_height, mount_radius + wall);
        }
        translate([0, 0, pcb_hi_clear + pcb_hi_exp + flare_height + stalk_height]) {
            tetra_capsule_array_mount([-45, 135], mount_radius, wall);
        }
    }
}

// microphone body: main body, holds printed circuit boards
//
tetra_pcb_mount_height = pcb_length - pcb_low_exp - pcb_hi_exp;

module render_tetra_pcb_mount(z_offset, showint) {
    translate([0, 0, z_offset]) {
        tetra_mount_body(tetra_pcb_mount_height, box_radius + wall, mount_corner, mount_lip, mount_lip, showint);
    }
    // add ccrma logo
    rotate([0, 0, -90]) {
        translate([0, -(box_radius - 0.5), tetra_pcb_mount_height / 2]) {
            rotate([90, 270, 0]) {
                logo_scale = 1 / 2.4;
                scale([logo_scale, logo_scale, 1.0]) {
                    ccrma_logo(1.65);
                }
            }
        }
    }
}

// microphone body: flare to microphone cable (slips into PCB holder body)
//

module render_tetra_cable_flare(z_offset, flip) {
    translate([0, 0, z_offset]) {
        tetra_mount_flare(pcb_low_clear + pcb_low_exp, mount_lip, 20, box_radius + wall, mount_corner, cable_diam / 2 + wall, 10);
        translate([0, 0, pcb_low_clear + pcb_low_exp + 20]) {
            tetra_mount_cable_holder(10, cable_diam / 2 + wall);
        }
    }
}

// microphone body: flare to 12 pin connector (slips into PCB holder body)
//

module render_tetra_connector_flare(z_offset, flip) {
    translate([0, 0, z_offset]) {
        tetra_mount_flare(pcb_low_clear + pcb_low_exp, mount_lip, 20, box_radius + wall, mount_corner, conn_core_o_diam / 2, 10);
        rotate([0, 0, -90]) translate([0, 0, pcb_low_clear + pcb_low_exp + 20]) {
            tetra_mount_connector_holder(conn_core_sleeve, conn_core_o_diam / 2, conn_core_diam / 2, conn_core_overlap, conn_core_s_diam / 2);
        }
    }
}

// microphone body: render all parts with a vertical separation
//

module render_tetra_body(z_offset, spread, showint) {
    rotate([0, 180, 0]) {
        render_tetra_connector_flare(0);
    }
    lippy = spread - mount_lip;
    render_tetra_pcb_mount(lippy, showint);
    render_tetra_capsule_flare(tetra_pcb_mount_height + 2 * lippy);
}

// microphone: render the full assembly with a vertical separation
//

module render_tetra_microphone(z_offset, spread) {
    render_tetra_body(z_offset, spread);
    lippy = spread - mount_lip;
    render_tetra_capsule_array(z_offset + tetra_pcb_mount_height + mount_top_height +
            flare_height + stalk_height + pcb_hi_clear + pcb_hi_exp + 2 * lippy + spread + mic_radius);
}

// microphone: render the full assembly with a vertical separation
//             cut out halt of the assembly so that we can see the inside
//

module render_tetra_microphone_cutout(z_offset, spread) {
    difference() {
        render_tetra_microphone(z_offset, spread);
        // a cube that blots out 1/4 of the microphone
        rotate([0, 0, 90]) {
            translate([0, 0, -50]) {
                cube([50, 100, 650]);
            }
        }
    }
}

// shock mount: microphone clip on stand mount
//

module render_tetra_shock_mount_stand(z_offset) {
    translate([z_offset]) {
        shock_mount_stand(mic_mount_height, mount_wall, mic_mount_wall);
    }
}

// shock mount: external ring
//

module render_tetra_shock_mount_external_ring(z_offset) {
    translate([0, 0, z_offset]) {
        shock_mount_external_ring(ring_height, box_radius + wall, box_radius + wall, mount_corner, main_radius_inc, 0);
    }
}

// shock mount: bottom internal ring
//

module render_tetra_shock_mount_internal_ring_bot(z_offset) {
    translate([0, 0, z_offset]) {
        shock_mount_internal_ring(ring_height, box_radius + wall, box_radius + wall, mount_corner, internal_ring_gap, 1);
    }
}

// shock mount: all four internal ring connectors
//

module render_tetra_shock_mount_ring_connectors(offset) {
    for (o = [0, 1, 2, 3]) {
        translate([-18, (10 + offset) * o, 0]) {
            shock_mount_connector(ring_sep, 4, connector_w, connector_d, 0.1);
        }
    }
}

// shock mount: top internal ring
//

module render_tetra_shock_mount_internal_ring_top(z_offset) {
    translate([0, 0, z_offset]) {
        shock_mount_internal_ring(ring_height, box_radius + wall, box_radius + wall, mount_corner, internal_ring_gap, 0);
    }
}

// shock mount: render all parts
//

module render_tetra_shock_mount(z_offset) {
    // internal rings
    translate([0, 0, z_offset + ring_sep / 2]) {
        render_tetra_shock_mount_internal_ring_top(0);
        rotate([0, 180, 0]) {
            render_tetra_shock_mount_internal_ring_bot(ring_sep + 2);
        }
        // insert the connecting rods
        for (r = [0, 90, 180, 270]) {
            rotate([0, 0, r]) {
                translate([box_radius + 3 * wall + internal_ring_gap, 0, -1]) {
                    rotate([0, 90, 0]) {
                        translate([-4, -5, 1]) {
                            shock_mount_connector(ring_sep, 4, connector_w, connector_d, 0.1);
                        }
                    }
                }
            }
        }
    }
    // external ring
    translate([0, 0, z_offset - ring_height / 4]) {
        render_tetra_shock_mount_external_ring(0);
    }
    // mount to stand
    translate([box_radius + mount_corner + ring_wall + ring_arm_gap + 8 + ring_wall / 2 + 1, 0, -(mic_mount_height + mic_mount_radius + ring_height / 4 + 2.2)]) {
        render_tetra_shock_mount_stand(0);
    }
}