Mechanical Design

The components that make up the mechanical design include a motor, slip rings, an encoder, a dipole magnet, measuring coil, and bearings.  A motor must be used to rotate the shaft at varying speeds up to 600rpms.  In order to accurately simulate the magnetic field in the LHC, a dipole magnet is used.  The measuring coil rotates within the field created by the dipole magnet and generates a voltage that is then read by the slip rings.  The encoder processes data by measuring the shaft speed, shaft angles, and the number of rotations, which is sent to the data acquisition system along with the slip ring data.

Mechanical test bed assembly composed of 2 bearings, 3 slip rings, dipole magnet, encoder, motor, and rotating coil 

When designing a test bed that can simulate the wear over time of the chosen slip rings, it is in the interest of time that the design incorporates the testing of all three slip rings at once. This fact, coupled with the necessity to have the measurement coil, encoder and support bearings all included in the design, creates the need to have a rotating shaft with varying diameters.

The three slip rings have different inner bore diameters of 38.1 mm (AC4598), 31.75 (CAY-731-2), and 30mm (SM 050) and an encoder with an inner bore of 25 mm. This automatically suggests that the rotating shaft used in the test bed must have four different diameters, 38.1 mm, 31.75mm 30 mm and 25 mm, the support bearings can then be chosen on this basis to fit the shaft. Of further importance are the dimensions of the rotating coil. It has a length of 116 mm and has to be mounted by hand inside the rotating shaft. This immediately suggests that it must be placed close to an open end of the shaft for ease of mounting and accessibility, as shown to the left: 

Coil mounting into shaft

Furthermore the wires from the coil must be connected to the slip rings, creating the necessity for a partly hollow shaft to provide space for the wiring, as well as holes in the shaft to run the wires to their respective slip rings. These holes must be drilled in front of slip rings, to ensure a proper connection is made, as shown to the right.

Detailed drawings of each component can be found here