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use <wheel.scad>;
use <suspension_fork.scad>;
// total outer dimension of the lasttretrad
ltr_length = 3000;
ltr_width = 1000;
ltr_height = 160;
bed_height = 18;
// the universal standard board used during prototype construction
board_width=25;
board_height=120;
module frame() {
bessel=sqrt(3/2) -1;
// translate([-l/2, -w/2, 0])
// cube([l, w, h]);
translate([0, 0, -board_height - bed_height]) {
// front/back boards
for (pos = [-0.9, -0.4, 0, 0.4, 0.9])
translate([pos * (ltr_length - board_width)/2 - board_width + board_width/2, -ltr_width/2, 0])
cube([board_width, ltr_width, board_height]);
// left/right boards
// Positioned at the bessel points (yields minimal mean bend
// assuming equal load on the cargo bed); see
// https://de.wikipedia.org/wiki/Bessel-Punkt
for (pos = [-1,1])
translate([-ltr_length/2, pos * (1 - 2*bessel) * (ltr_width - board_width)/2 - board_width/2, 0])
cube([ltr_length, board_width, board_height]);
}
}
// use a large plywood board
module cargo_bed() {
translate([0, 0, -bed_height/2])
cube([ltr_length, ltr_width, bed_height], center=true);
}
// specify (f)ront/(c)enter/(b)ack as -1/0/1 and (l)eft/(r)ight as -1/1
module wheel_position(fcb, lr) {
translate([1250 * fcb,
(fcb == 0) ? (340 * lr) : (370 * lr),
0])
children();
}
// specify (f)ront/(b)ack and (l)eft/(r)ight as -1/1
module steered_wheel(fb=-1, lr=-1, rot=0, suspension_depth=0) {
rotate([ 0, 0, fb*rot]) suspension_fork(suspension_depth);
translate([0, 0, wheel_offset(suspension_depth)])
rotate([90, 0, fb*rot]) wheel();
}
// specify (l)eft/(r)ight as -1/1
module powered_wheel(lr=-1, suspension_depth=0) {
axis_distance = 500;
board_length = axis_distance + board_height;
default_suspension_depth = 0; // used to calculate anchor point
axis_offset = board_height/2 + bed_height; // distance from upper axis to cargo floor
rot = asin((250 - suspension_depth ) / axis_distance);
default_rot = asin((250 - default_suspension_depth - axis_offset) / axis_distance);
translate([-axis_distance * cos(default_rot), 0, -axis_offset])
rotate([0, rot, 0]) {
translate([axis_distance, 0, 0])
rotate([90])
wheel();
for (i = [-1,1])
translate([0, i*40 - lr*5, 0])
// board with rounded edges
hull()
for (i = [0, 1])
translate([i * axis_distance, 0, 0])
rotate([90, 0, 0])
cylinder(r=board_height/2, h=board_width, center=true);
}
}
module lasttretrad(rot=0, suspension_depth=0) {
color("SaddleBrown") frame();
color("Cornsilk") cargo_bed();
for (lr = [-1,1])
for (fb = [-1,1])
wheel_position(fb, lr)
steered_wheel(fb, lr, rot=rot, suspension_depth=suspension_depth);
for (lr = [-1,1])
wheel_position(0, lr)
powered_wheel(lr, suspension_depth=suspension_depth);
}
lasttretrad(30, 50);
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