Drawing a Snow Blade in OpenSCAD
Over the holidays my friend Greg was talking about making some snow blades but he said he didn't know how to draw a 3D model of one. I figured I'd make some instructions for drawing a simple snow blade core in OpenSCAD. These instructions don't include any camber or rocker. I don't really know anything about ski design, so this example probably won't lead to a usable model, but it's a start.
Step 1: The Body of the Ski
We'll draw the tips and tails of the ski separately from the rest of the ski, which I'm going to call the body. We'll draw the body first. The body will start as a simple rectangle.
edgeLength = 100;
maxWidth = 15;
maxThickness = 2;
cube([edgeLength, maxWidth, maxThickness]);
Step 2: Centring the Ski
We'll centre the ski in the X and Y axes. This will make things a little easier later on.
edgeLength = 100;
maxWidth = 15;
maxThickness = 2;
translate([-edgeLength/2, -maxWidth/2, 0])
cube([edgeLength, maxWidth, maxThickness]);
Step 3: Make the Body Into a Module
To keep thing neat we'll make a module that contains the ski body and call that module.
edgeLength = 100;
maxWidth = 15;
maxThickness = 2;
module body(length, maxWidth, maxThickness)
{
translate([-length/2, -maxWidth/2, 0])
cube([length, maxWidth, maxThickness]);
}
body(edgeLength, maxWidth, maxThickness);
Step 4: Make the Tip
Make the tip. Keep it simple and just make it a semicircle. We'll draw a full circle because it's simpler.
edgeLength = 100;
maxWidth = 15;
maxThickness = 2;
module body(length, maxWidth, maxThickness)
{
translate([-length/2, -maxWidth/2, 0])
cube([length, maxWidth, maxThickness]);
}
module tip(edgeLength, maxWidth, maxThickness)
{
translate([edgeLength/2, 0, 0])
cylinder(h=maxThickness, r=maxWidth/2);
}
body(edgeLength, maxWidth, maxThickness);
tip(edgeLength, maxWidth, maxThickness);
Step 5: Make the Tail
The tail is just like the tip.
edgeLength = 100;
maxWidth = 15;
maxThickness = 2;
module body(length, maxWidth, maxThickness)
{
translate([-length/2, -maxWidth/2, 0])
cube([length, maxWidth, maxThickness]);
}
module tip(edgeLength, maxWidth, maxThickness)
{
translate([edgeLength/2, 0, 0])
cylinder(h=maxThickness, r=maxWidth/2);
}
module tail(edgeLength, maxWidth, maxThickness)
{
translate([-edgeLength/2, 0, 0])
cylinder(h=maxThickness, r=maxWidth/2);
}
body(edgeLength, maxWidth, maxThickness);
tip(edgeLength, maxWidth, maxThickness);
tail(edgeLength, maxWidth, maxThickness);
Step 6: Make the Sidecut
This is where things get fun. We'll make the sidecuts circular for simplicity. They could be parabolic with a little change to this function. To make them we'll draw two cylinders and subtract them from the ski's shape. We need to find the part of the circle that is the width of the edge length. That will take a little trigonometry. When defining the cylinders we need to set the $fa parameter to 1 to make each segment of the cylinder one degree or less.
edgeLength = 100;
maxWidth = 15;
maxThickness = 2;
sidecutRadius = 600;
module body(length, maxWidth, maxThickness)
{
translate([-length/2, -maxWidth/2, 0])
cube([length, maxWidth, maxThickness]);
}
module tip(edgeLength, maxWidth, maxThickness)
{
translate([edgeLength/2, 0, 0])
cylinder(h=maxThickness, r=maxWidth/2);
}
module tail(edgeLength, maxWidth, maxThickness)
{
translate([-edgeLength/2, 0, 0])
cylinder(h=maxThickness, r=maxWidth/2);
}
module sidecut(radius, edgeLength, thickness, maxWidth)
{
hypotenuse = radius;
opposite = edgeLength/2;
offset = sqrt(hypotenuse*hypotenuse - opposite*opposite) + maxWidth/2;
translate([0, offset, 0])
cylinder(h = thickness, r = radius, $fa = 1);
translate([0, -offset, 0])
cylinder(h = thickness, r = radius, $fa = 1);
}
difference()
{
union()
{
body(edgeLength, maxWidth, maxThickness);
tip(edgeLength, maxWidth, maxThickness);
tail(edgeLength, maxWidth, maxThickness);
}
sidecut(sidecutRadius, edgeLength, maxThickness, maxWidth);
}
Step 7: Make the Thickness Profile
To make the thickness profile we'll make a series of cubes that vary in height. Polyhedrons would probably work better here, but let's keep things simple. I chose a cosine function for the width. I don't know if that makes sense, but we can use any function here. We'll use the intersection function to keep only the spaces where the profile intersects with the ski.
edgeLength = 100;
maxWidth = 15;
minThickness = 1;
maxThickness = 2;
sidecutRadius = 600;
tipLength = maxWidth/2;
tailLength = maxWidth/2;
totalLength = edgeLength + tipLength + tailLength;
module body(length, maxWidth, maxThickness)
{
translate([-length/2, -maxWidth/2, 0])
cube([length, maxWidth, maxThickness]);
}
module tip(edgeLength, maxWidth, maxThickness)
{
translate([edgeLength/2, 0, 0])
cylinder(h=maxThickness, r=maxWidth/2);
}
module tail(edgeLength, maxWidth, maxThickness)
{
translate([-edgeLength/2, 0, 0])
cylinder(h=maxThickness, r=maxWidth/2);
}
module sidecut(radius, edgeLength, thickness, maxWidth)
{
hypotenuse = radius;
opposite = edgeLength/2;
offset = sqrt(hypotenuse*hypotenuse - opposite*opposite) + maxWidth/2;
translate([0, offset, 0])
cylinder(h = thickness, r = radius, $fa = 1);
translate([0, -offset, 0])
cylinder(h = thickness, r = radius, $fa = 1);
}
module zProfile(length, minThickness, maxThickness, width)
{
segments = 100;
increment = length/segments;
for(x = [0 : segments])
{
thickness = minThickness + (maxThickness - minThickness)*cos(90*(x / segments));
echo(90*x/segments, thickness);
translate([x*((length/2)/segments), -(width/2), 0])
cube([increment, width, thickness]);
translate([-x*((length/2)/segments), -(width/2), 0])
cube([increment, width, thickness]);
}
}
intersection()
{
difference()
{
union()
{
body(edgeLength, maxWidth, maxThickness);
tip(edgeLength, maxWidth, maxThickness);
tail(edgeLength, maxWidth, maxThickness);
}
sidecut(sidecutRadius, edgeLength, maxThickness, maxWidth);
}
zProfile(totalLength, minThickness, maxThickness, maxWidth);
}