//small drive wheel for light weight rotator
//D shaft
//21st June 2021
// smaller shaft hole to fit motor
//print time 25 min

module gear (
	mm_per_tooth    = 3,    //this is the "circular pitch", the circumference of the pitch circle divided by the number of teeth
	number_of_teeth = 11,   //total number of teeth around the entire perimeter
	thickness       = 6,    //thickness of gear in mm
	hole_diameter   = 3,    //diameter of the hole in the center, in mm
	twist           = 0,    //teeth rotate this many degrees from bottom of gear to top.  360 makes the gear a screw with each thread going around once
	teeth_to_hide   = 0,    //number of teeth to delete to make this only a fraction of a circle
	pressure_angle  = 28,   //Controls how straight or bulged the tooth sides are. In degrees.
	clearance       = 0.0,  //gap between top of a tooth on one gear and bottom of valley on a meshing gear (in millimeters)
	backlash        = 0.0   //gap between two meshing teeth, in the direction along the circumference of the pitch circle
) {
	assign(pi = 3.1415926)
	assign(p  = mm_per_tooth * number_of_teeth / pi / 2)  //radius of pitch circle
	assign(c  = p + mm_per_tooth / pi - clearance)        //radius of outer circle
	assign(b  = p*cos(pressure_angle))                    //radius of base circle
	assign(r  = p-(c-p)-clearance)                        //radius of root circle
	assign(t  = mm_per_tooth/2-backlash/2)                //tooth thickness at pitch circle
	assign(k  = -iang(b, p) - t/2/p/pi*180) {             //angle to where involute meets base circle on each side of tooth
		difference() {
			for (i = [0:number_of_teeth-teeth_to_hide-1] )
				rotate([0,0,i*360/number_of_teeth])
					linear_extrude(height = thickness, center = true, convexity = 10, twist = twist)
						polygon(
							points=[
								[0, -hole_diameter/10],
								polar(r, -181/number_of_teeth),
								polar(r, r<b ? k : -180/number_of_teeth),
								q7(0/5,r,b,c,k, 1),q7(1/5,r,b,c,k, 1),q7(2/5,r,b,c,k, 1),q7(3/5,r,b,c,k, 1),q7(4/5,r,b,c,k, 1),q7(5/5,r,b,c,k, 1),
								q7(5/5,r,b,c,k,-1),q7(4/5,r,b,c,k,-1),q7(3/5,r,b,c,k,-1),q7(2/5,r,b,c,k,-1),q7(1/5,r,b,c,k,-1),q7(0/5,r,b,c,k,-1),
								polar(r, r<b ? -k : 180/number_of_teeth),
								polar(r, 181/number_of_teeth)
							],
 							paths=[[0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16]]
						);
			cylinder(h=2*thickness+1, r=3.2, center=true, $fn=90);
		
          
            
		}
	}
};	


//make shaft hole into D shape
difference () {
translate ([-5,2.7,-5])
cube([10,4,16]); 

//shaft screw
translate ([0,10,8])
rotate ([90,0,0])
cylinder (h=20, r=1, $fn=90, center = true);
}

//make shaft hole into D shape
difference () {
translate ([0,0,8])
cylinder (h=6, r=8, $fn=90, center = true);
  
cylinder(h=25, r=3.2, center=true, $fn=90);
    
//shaft screw
translate ([0,10,8])
rotate ([90,0,0])
cylinder (h=20, r=1, $fn=90, center = true);
}



//these 4 functions are used by gear
function polar(r,theta)   = r*[sin(theta), cos(theta)];                            //convert polar to cartesian coordinates
function iang(r1,r2)      = sqrt((r2/r1)*(r2/r1) - 1)/3.1415926*180 - acos(r1/r2); //unwind a string this many degrees to go from radius r1 to radius r2
function q7(f,r,b,r2,t,s) = q6(b,s,t,(1-f)*max(b,r)+f*r2);                         //radius a fraction f up the curved side of the tooth 
function q6(b,s,t,d)      = polar(d,s*(iang(b,d)+t));                              //point at radius d on the involute curve

//a rack, which is a straight line with teeth (the same as a segment from a giant gear with a huge number of teeth).
//The "pitch circle" is a line along the X axis.
module rack (
	mm_per_tooth    = 3,    //this is the "circular pitch", the circumference of the pitch circle divided by the number of teeth
	number_of_teeth = 11,   //total number of teeth along the rack
	thickness       = 6,    //thickness of rack in mm (affects each tooth)
	height          = 120,   //height of rack in mm, from tooth top to far side of rack.
	pressure_angle  = 28,   //Controls how straight or bulged the tooth sides are. In degrees.
	backlash        = 0.0   //gap between two meshing teeth, in the direction along the circumference of the pitch circle
) {
	assign(pi = 3.1415926)
	assign(a = mm_per_tooth / pi) //addendum
	assign(t = a*cos(pressure_angle)-1)         //tooth side is tilted so top/bottom corners move this amount
		for (i = [0:number_of_teeth-1] )
			translate([i*mm_per_tooth,0,0])
				linear_extrude(height = thickness, center = true, convexity = 10)
					polygon(
						points=[
							[-mm_per_tooth * 3/4,                 a-height],
							[-mm_per_tooth * 3/4 - backlash,     -a],
							[-mm_per_tooth * 1/4 + backlash - t, -a],
							[-mm_per_tooth * 1/4 + backlash + t,  a],
							[ mm_per_tooth * 1/4 - backlash - t,  a],
							[ mm_per_tooth * 1/4 - backlash + t, -a],
							[ mm_per_tooth * 3/4 + backlash,     -a],
							[ mm_per_tooth * 3/4,                 a-height],
						],
						paths=[[0,1,2,3,4,5,6,7]]
					);
};	

//These 5 functions let the user find the derived dimensions of the gear.
//A gear fits within a circle of radius outer_radius, and two gears should have
//their centers separated by the sum of their pictch_radius.
function circular_pitch  (mm_per_tooth=3) = mm_per_tooth;                     //tooth density expressed as "circular pitch" in millimeters
function diametral_pitch (mm_per_tooth=3) = 3.1415926 / mm_per_tooth;         //tooth density expressed as "diametral pitch" in teeth per millimeter
function module_value    (mm_per_tooth=3) = mm_per_tooth / pi;                //tooth density expressed as "module" or "modulus" in millimeters
function pitch_radius    (mm_per_tooth=3,number_of_teeth=11) = mm_per_tooth * number_of_teeth / 3.1415926 / 2;
function outer_radius    (mm_per_tooth=3,number_of_teeth=11,clearance=0.1)    //The gear fits entirely within a cylinder of this radius.
	= mm_per_tooth*(1+number_of_teeth/2)/3.1415926  - clearance;              

//////////////////////////////////////////////////////////////////////////////////////////////
//example gear train.  
//Try it with OpenSCAD View/Animate command with 20 steps and 24 FPS.
//The gears will continue to be rotated to mesh correctly if you change the number of teeth.
pi=3.1415927;
dia= 20;
nt=12;

gear (
	mm_per_tooth    = pi*dia/nt,    //this is the "circular pitch", the circumference of the pitch circle divided by the number of teeth
	number_of_teeth = nt,   //total number of teeth around the entire perimeter
	thickness       = 10,    //thickness of gear in mm
//3.9 last time



	hole_diameter   = 4.2*2    //diameter of the hole in the center, in mm
);