diff --git a/model/fourbar.scad b/model/fourbar.scad index 40d146a..77966db 100644 --- a/model/fourbar.scad +++ b/model/fourbar.scad @@ -7,10 +7,19 @@ include include include -module fourbar_leg(length=1000, chord=100, long_skew=30, lat_skew=30) { +$fn=64; + +// Wherever you see unexplained numbers in this file, they are +// fudge because I don't yet properly understand the coordinate +// transforms and can't remember enough of the trigonometry I +// learned 60 years ago. There REALLY should not be any unexplained +// numbers. + +module fourbar_leg(length=1000, chord=100, lat_skew=35, long_skew=30) { h = length * cos(lat_skew) * cos( long_skew); w = length * sin( lat_skew); d = length * sin( long_skew); + pivot_radius = 12; translate([0, 0-w, 0]) { // upper pivot needs a complex trig transformation! @@ -23,7 +32,12 @@ module fourbar_leg(length=1000, chord=100, long_skew=30, lat_skew=30) { translate([0 - chord, 0, (chord/2 * sin(long_skew))]) rotate([0, 90+long_skew, 0]) color("black") - cylinder(h=chord, r=12); + difference() { + cylinder(h=chord, r=12); + // through hole for pivot axle + translate([0, -1, 0]) + cylinder(h=chord+2, r=pivot_radius/3); + } // aerofoil section sskew([0, long_skew, 0, 0, 0, 0]) @@ -34,7 +48,7 @@ module fourbar_leg(length=1000, chord=100, long_skew=30, lat_skew=30) { } -module loawer_bar_end_knuckle(chord=100, pivot_radius=12, rise=8) { +module lower_bar_end_knuckle(chord=100, pivot_radius=12, rise=8,lat_skew=30) { l_body=chord * 1.5; w_body=pivot_radius * 2.5; h_axis=pivot_radius * 2.75; @@ -44,17 +58,19 @@ module loawer_bar_end_knuckle(chord=100, pivot_radius=12, rise=8) { translate([l_body/2, w_body/2, h_axis]) rotate([0, 90, 0]) cyl(h=l_body, r=w_body/2, rounding=5); - translate([l_body/2, w_body/2, h_axis/2]) - cuboid([l_body, w_body, h_axis], rounding=5, except=TOP); + + // 'except=TOP' in phrase introduces the spurious hulls + translate([l_body/2, w_body/2, h_axis*.75]) + cuboid([l_body, w_body, h_axis * .75], rounding=5); // bulge for wheel axle; the fork insertion end of // a lefty axle is 25mm diameter - translate([chord * 1.25, w_body/2, 0]) - rotate([90, 0, 0]) + translate([chord * 0.25, w_body/2, 0]) + rotate([90, 0, 0]) cyl(h=w_body, r=25, rounding=5); // fairing for this - translate([chord * 1.25, w_body/2, -7.5]) - rotate([80, 0, 270]) - prismoid([w_body, 35], [w_body, 10], rounding=5, h=l_body/2); + translate([chord * 0.25, w_body/2, -3]) + rotate([80, 0, 90]) + prismoid([w_body, 45], [w_body, 10], rounding=5, h=l_body * .75); } translate([ chord*0.25, -1, pivot_radius * 3]) @@ -68,93 +84,76 @@ module loawer_bar_end_knuckle(chord=100, pivot_radius=12, rise=8) { rotate([0, 90, 0]) cylinder(h=l_body+2, r=pivot_radius/3); // through hole for wheel axle - translate([chord * 1.25, w_body +1, 0]) + translate([ chord * 0.25, w_body +1, 0]) rotate([90, 0, 0]) cylinder(h=w_body-5, r=12.5); } // airfoil stub to be epoxied into the lower bar of // the linkage - translate([(chord * 1.25) - 1, 5 - chord, 0]) - rotate([90-rise, 0, 180]) - airfoil(h=chord, L=chord-2); - // root reinforcement for the above - translate([chord * 1.25, 5 - chord/3, 9]) - rotate([90, 0, 180]) - airfoil(h=chord/3, L=chord); - translate([(chord * .75), 0, 10]) - rotate([90, 0, 0]) - prismoid([chord -1, 6], [chord -2, 0], h=(chord/3)); + translate([chord*1.25, 1, 30]) + rotate([90 + rise, 360 - lat_skew, 0]) + airfoil(h=chord, L=2 - chord); + +// // brake disk +// translate([(0 - (chord*1.25)), (l_hlb * cos(rise)), 1]) +// rotate([90, 0, 0]) +// color("silver") +// cylinder( h=1.5, r=75); +// // wheel (obviously) +// translate([(0 - (chord*1.25)), (l_hlb * cos(rise)), -10]) +// wheel(); } -module fourbar_axle_half( length, chord, long_skew) { - shoulder=650; - lat_skew=30; +module fourbar_axle_half( length=1000, chord=100, lat_skew=35, long_skew=30, shoulder=650) { rise=8; // I've got something wrong in computing the half-lower-bar - // length, and I don't know what. + // length, and I don't know what. It scales with lat_skew, but + // (unsurprisingly) not liniarly. Fudge of 23 works for lat_skew of 30; 34 works for lat_skew of 35 fudge=0; - w = ((length * sin(lat_skew) ) + ( shoulder / 2)); + w = ((length * cos(lat_skew) )); l_hlb= w * (1/cos(rise)) + fudge; - v_offset=l_hlb * sin(rise); - - echo("long_skew", long_skew); + v_offset=(l_hlb * sin(rise)) + 38; - translate([0, 0, 0 - v_offset]) + translate([-15, 0, 0 - v_offset]) rotate([90-rise, 0, 180]) - color("black") - airfoil(h=l_hlb, L=chord); + color("black") + airfoil(h=l_hlb, L=chord); // lower knuckle - translate([(0 - (chord*1.25)), l_hlb * cos(rise), 30]) - rotate([0, long_skew, 0]) - color("black") - loawer_bar_end_knuckle(chord, 12, rise); - - // wheel - translate([-50, l_hlb + 72, -40]) - rotate([270, 0, 0]) - wheel(iso=451); - - // brake disk - translate([-50, l_hlb + 35, -40]) - color("silver") - rotate([90, 0, 0]) - cylinder(h=1.5, r=75); - // brake caliper + rotate([0, long_skew, 0]) + translate([(0 - (chord*1.25)), (l_hlb * cos(rise) + 72), -62]) + lower_bar_end_knuckle(chord, 12, rise, lat_skew); } -module fourbar(length=1000, chord=100, long_skew=30, lat_skew=30, shoulder=650) { - w = (length * sin( lat_skew)) + ( shoulder / 2); - - +module fourbar(length=1000, chord=100, lat_skew=30, long_skew=30, shoulder=650) { translate([0, 0-(shoulder/2), 0]) - fourbar_leg( length, chord, long_skew, lat_skew); + fourbar_leg( length, chord, lat_skew, long_skew); translate([0, (shoulder/2), 0]) mirror([0, 1, 0]) - fourbar_leg(length, chord, long_skew, lat_skew); + fourbar_leg(length, chord, lat_skew, long_skew); - fourbar_axle_half(w, chord, long_skew); + fourbar_axle_half(length, chord, lat_skew, long_skew, shoulder); mirror([0, 1, 0]) - fourbar_axle_half(w, chord, long_skew); + fourbar_axle_half(length, chord, lat_skew, long_skew, shoulder); } translate([-125, 0, 0]) color("blue") - loawer_bar_end_knuckle(); -translate([0, 77, 0]) + lower_bar_end_knuckle(); +translate([-100, 74, 0]) wheel(); -translate([0, 40, 0]) +translate([-100, 34, 0]) color("silver") rotate([90, 0, 0]) cylinder(h=1.5, r=75); -// fourbar(); +// fourbar(length=1000, chord=100, long_skew=30, lat_skew=35, shoulder=650); // fourbar_axle_half(1000,100, 30); \ No newline at end of file diff --git a/model/subframe.scad b/model/subframe.scad index 705c543..a61f099 100644 --- a/model/subframe.scad +++ b/model/subframe.scad @@ -11,7 +11,7 @@ include module subframe_cycleparts(rim=451, chainring_teeth=82, crank=140) { // wheel translate([0, 382, 93]) - rotate([0, 90, 0]) + rotate([0, 0, 90]) wheel(iso=rim); translate([-42, 382, 93]) diff --git a/model/tricycle.scad b/model/tricycle.scad index b05b4f7..6548999 100644 --- a/model/tricycle.scad +++ b/model/tricycle.scad @@ -12,7 +12,7 @@ rotate([0, 0, 270]) translate([0, 1300, 180]) subframe(structure="carbon"); translate([0, 0, 320]) -fourbar(700, 100, 30, 35, 650); +fourbar(length=1000, chord=100, long_skew=30, lat_skew=35, shoulder=650); translate([800, 0, 120]) rotate([0, 4, 0])