Attach a mounting plate to a back side of the peripheral hub by welding. In this way, you are able to fix the variable pitch fan directly on a rotating part of an engine such as a piece of heavy machinery. Except for a rotary union, which transfers the liquids while rotating from one connection to the other, the entire variable pitch fan will manage to rotate together.
Secure a front plate to the front side of the peripheral hub to set up a pitch change piston within the cylinder. Close the pitch change piston at one end and on its other end that the annular cylinder portion receives within. An annular piston portion will form between an outer piston wall and an inner piston wall on which you can drive the piston change using different drive settings.
Protect the rotary union within the inner cylindrical wall to provide a hydraulic supply to the driven side of the pitch change piston. Hold the rotary union in place using a spiral spring and connect a hydraulic line to the rotary union. The rotary union will have conventional internal parts allowing the hydraulic line to remain fixed, while the variable pitch fan rotates.
Connect the pitch change piston with the fan blades to control pitch of the fan blades using a pin. The pin will extend from the fan blade connector piece into a receiving socket in a shifter block that forms part of the pitch change piston. Attach the shifter block to the other parts of the pitch change piston with the aid of cap screws and spacing devices.
Feed hydraulic fluid through the rotary union if you need to change the pitch in an integral control scheme. A variable pitch fan cools best when its fan blades are in full normal pitch and it is in normal operating position. This will lead to a full reverse thrust causing a change in the pitch as you add fluid in a series of pulses between the front plate and closed end of the pitch change piston.
Use a pitch sensor if you want to return the blades to their original position before you changed it. Attach the pitch sensor on the hydraulic supply line to detect any changes in the hydraulic gear. The pitch sensor is capable of sensing motion corresponding with the movement of the pitch change piston.
Attach a fluid bypass port to arrest leakages from the sensor piston in case it collapses due to intense pressure from hydraulic fluid pulses. The sensor piston may stop working before the blades manage to reverse the pitch of the fan completely. You may also bypass function by letting the ports extend through the sensor piston or by applying pressure from a spring.