Why are equilateral triangles so difficult?

CodeCogsEqn6.gif

CodeCogsEqn.gif

CodeCogsEqn2.gif

CodeCogsEqn3.gif

CodeCogsEqn4.gif

the radius of a circle r that touches the walls of a triangle
inscribed in a circle with a radius of R is simply

    r = R/2

where;

    r = the radius of the hole
    R = the radius of the circle that contains the points of the triangle

d = 20;     //Diameter of circle in which Triangle is inscribed
tH = 20;    //Height of the Triangle
wT = 2;     //Wall Thickness

difference()
{
	cylinder(r=d/2, h=tH, center=true, $fn=3);
	cylinder(r=d/4-wT, h=tH+1, center=true, $fn=100);
}

TriHole.jpg

hD = 10; // Diameter of Hole
tH = 20; // Height of the Triangle
wT = 2;  // Wall Thickness

difference()
{
	cylinder(r=hD+2*wT, h=tH, center=true, $fn=3);
	cylinder(r=hD/2, h=tH+1, center=true, $fn=100);
}

TriHole2.jpg

Quote
o_lampe
I wish, there would be a global openSCAD repository and a sticky-post in this subforum with the link.

Two beer granted, when you are near Kassel next time
-Olaf

Quote
o_lampe
I hope, I don´t stumble across more serious things....

Danke
-Olaf

Quote
o_lampe
That´s what happens, when I get the right tips from the right People

A parametric freewheel assembly that needs only 4 parameters to render.
1. shaft diameter
2. wall thickness
3. height
4. number of notches in the outer rim

It´s not finally tweaked. Some values cause nonfunctional results, but I´m working on it.

Thanks again
-Olaf

Quote
o_lampe
For me, the freewheel is just a stepstone in a much greater project.
Ofcourse, I could buy a freewheel. But for demonstration only, I think, I can use a selfmade ratchet. ( The noise even helps people understand what´s going on in my project)
-Olaf

/*
isogonal.scad

        +
       /|\
      /o| \
   r /  |y \
    /   |   \
   +----+----+
   |  x      |
   |<-- l -->|
*/

module isogonal(length, number)
{
    angle = 360 / number;
    theta = angle / 2;
    x = length / 2;
    r = x / sin(theta);
    y = r * cos(theta);

    // hull() is better than for() and scale() method.
    hull()
    {
        for (i = [0 : number-1])
        {
                rotate([0, 0, angle*i]) translate([0, -y, 0])
                square([length, 1], center=true);
        }
    }
}

module demo()
{
    linear_extrude(height = 40, twist = -180, scale = 1/2, center = true, slices = 200)
            isogonal(20, 3);

    translate([0, 30, 0])
    linear_extrude(height = 40, twist = -180, scale = 2/3, center = true, slices = 200)
                isogonal(20, 4);

    translate([30, 30, 0])
    linear_extrude(height = 40, twist = 270, scale = 1/2, center = true, slices = 200)
                hollow_hexagon();
}

module hollow_hexagon()
{
    difference()
    {
        isogonal(20, 3);
        isogonal(17, 3);
    }
}