Connecting Rods

Cyclic animation with sine and cosine function.

Connecting Rods:
By this motion the given values are the angle of rotation of the wheel "Wheel_angle", the radius of the point, where the connection rod is fixed at the wheel "C_radius" and the length of the connection rod "C_Rod_Len".
With this values we can calculate (see also the image below) the x and y values of the point where the connection rod is fixed at the wheel and the rotation angle of the connection rod
(Note: Sine and cosine in POV-Ray need the angle in radians: if the "Wheel_angle" is given in degrees we have to use "radians(Wheel_angle)"!).

scene description
for POV-Ray:
"con_rod1.ini" and
"con_rod1.pov"

#declare C_x =  C_radius * cos(radians(Wheel_angle));
#declare C_y =  C_radius * sin(radians(Wheel_angle));
#declare C_Rod_y = C_y;
#declare C_Rod_x = sqrt(C_Rod_Len*C_Rod_Len-C_Rod_y*C_Rod_y);
#declare C_Rod_Angle = degrees(atan2(C_Rod_y,C_Rod_x));

Attention : For guarantee of the mechanically correct flow of this motion, it is necessary that the piston rod is in the same line as the axis of the wheel. So it's a good idea, to construct the complete combination with the wheel centred at <0,0,0> and then to move altogether upwards by the radius of the wheel.
 
Some examples for animations of this kind
you can find here: 3D-Animations - Railroad (steam engines)
and here: 3D-Animations - Engineering (4- u. 6-cylinder engines).