The Drive Shafting

 

         
Boeing CH-47D Chinook Drive Train.

 

             The CH-47D helicopter drive system includes: five transmissions (forward, aft, combining, number one and two engine nosebox), and aft vertical shaft, nine synchronizing shafts (drive shafts), and two engine drive shafts (cross shafts). Each transmission has an independent oil lubrication system that is air cooled through a heat exchanger. Each transmission's oil pressure and temperature is monitored in the cockpit. Each transmissions status is also monitored on a maintenance panel located in the aft right rear of the helicopter on the ramp. The maintenance panel has indicators for chip detectors and debris screens that latch when metal particles are detected in the oil system. A tripped latched would indicate possible transmission failure.

 

         
Boeing CH-47D Chinook drive shaft rotational velocities.

 

             The drive system provides power to turn the rotors. Engine output is connected to the engine transmission, then to the combining transmission. From the combining transmission the power is directed, through the synchronizing shafts, to the forward and aft transmissions.

 

             The reduction in gear ratio between the engine and the rotary wing blades is 66.96:1. All synchronizing shafts are free floating at their inputs and secured to the transmissions at their outputs.

 

 

         
A drawing showing the placement and operation of the drive shafts connecting the transmissions and the gears inside the various CH-47D transmissions.

 

             Above: A drawing showing the placement and operation of the drive shafts connecting the transmissions and the gears inside the various CH-47D transmissions. Upon close examination, one can see that there is not a rigid connection between the input and output of either the forward or aft transmission. The sun/planetary gear sections (upper portion of the transmissions) rotate around each other. From input to output in each component of the drive train there is large reduction in speed. This translates in to a tremendous increase in torque that is used to drive the rotor system. Numbers associated with a "T" indicate the number of teeth on a particular gear. Numbers associated with a rotational symbol is the speed that component rotates per second. The rotor system rotates at 225 revolutions per minute (RPM). 3.75 blades will pass the same point in space every second. Click-N-Go Here to view a larger image.

 

 

          Related Sites

 

          Power Train Student Handout

 

 

          The CH-47 - 40 years old and still circling the world.

         

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