Angular Acceleration: Understanding the differences between Gyroscopes and Accelerometers
A gyro measures angular velocity, and is relatively insensitive to other movement.  You would need to differentiate to get angular acceleration.  An accelerometer measures acceleration. Period.  It will respond to reorientation with respect to gravity (as gravity is an acceleration).  It will respond to linear acceleration.  If offset from the axis of rotation, it will respond to centripetal acceleration, which will be related to angular velocity (though if motion is sinusoidal, you will need to keep track of tangential accelerations).  

If you can orient the accelerometer to be right on the axis of rotation, you can easily track the orientation with respect to gravity (that is, Z), but not so easily in the xy plane (if that is the earth plane in your system)

Your situation may be easier to use some sort of absolute or relative encoder, which will give you angular position without worrying about drifts and offsets associated with integration.

With your improved description, you might want to die toy measure torque!
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