CAD

The bodies of the superchargers are sand-cast in aluminium and then machined. The sand-casting process is inherently very inaccurate so it is unrealistic to measure to a precision of greater than 1mm on them but the machined surfaces such as the casings of the rotors, the mating surfaces and the bearing housings are done to much higher precision. For these reasons all measurements were taken with respect to machined surfaces when constructing the models. For example, rather than measuring the position of each point on the base with respect to its neighbors, the position of each point and edge was defined with respect to the supercharger outlet. This greatly reduced the accumulation of errors that could have otherwise occurred. Another advantage of choosing this reference was that the Vernier calipers we used for all our measurements could not measure any dimension larger than 150mm. Due to the outlet's location near the center of the supercharger's base nearly all the perimeter points were in reach of the Verniers.
After constructing the bases as simple extrusions (of not quite so simple sections, see right) the rotor housings were placed on top, again by simple extrusion, with cut-outs the diameter of the rotors. The cooling fins on top of the housing were made by a short extrusion of a section above the housing which was then patterned along the whole length of the housing.


(Base of Eaton M62)

The throttle bodies required the use of a height gage to produce an accurate section which was then extruded. From there we constructed the duct between the throttle body and the rotors. For the sake of simplicity we idealized the duct as circular at the throttle body and elliptical at the rotor inlet and lofted the duct. The internal geometry of the duct, such as the duct for the boost by-pass valve and the housings for the bearings of the rotor shafts, were then cut out and extruded as necessary.
The superchargers are of a standard helix roots design; meaning they have two rotors with three lobes each, and a constant cross-section that is twisted 60 degrees along the length of the rotor. A Teflon coating is used to seal the small gap between the rotors. We modeled a single lobe, patterned it to create a cross-section, which was than extruded and twisted to generate a complete rotor. The complimentary rotor is identical to the first, merely twisted in the opposite direction. The M62 is the smaller cousin of the M90, with decreased rotor length and cross-section dimensions. See right for the rotor subassembly.

(Eaton M62 Rotor subassembly)
Various parts of the superchargers had been shared between four people. To guarantee that everything fit together in the end we needed a system of standardization. This was most apparent with the rotor mounts. These parts were spacers between the bodies of the blowers and the snouts and held the shafts of the rotors. On one side the parts are flat plates with the outer shape of the mating surface of the blower housing. This was made by selecting as a section the end of the rotor housing, complete with its bolt holes but without the internal cut-out for the rotors, and extruding as a new part for the thickness of the spacer. The other side, which had to mate with the snout, was hollowed out thus having the same outer cross-section and bolt-hole position as both the blower body and the snout but a different internal cross-section to match the snout. The snout was then started from this section just as the spacer was from the body. Similar methods were parts made by different people were to be assembled.
Eaton M62 Components  

Housing

The housing contains the rotors, rotor shafts, bearings, the bypass valve, and various cooling passages. The housing receives air from the throttle body adapter, and forces air through the outlet into the engine's intake manifold.

Rotor mount / Spacer

The spacer secures the other end of the rotors shafts, and allows the rotors to be removed as a single assembly.

Bypass plate

When actuated by a vacuum powered solenoid, the bypass valve allows pressurized air to recirculate instead of entering the engine's intake manifold.

Drive coupler

Connects the first drive gear to the snout shaft. Made of plastic that can shatter if the rotors jam.

Drive gears

First drive gear is driven by the coupler and shaft, while the second transfers power to the counter rotating second rotor.

Rotors

Constant cross section is twisted through 60 degrees into a helical shape. The second rotor is identical, with the exception that it is twisted through the opposite angle. The two rotors turn in opposite directions. The rotors are coated in Teflon to reduce noise and friction.

Rotor shafts

The two rotor shafts are identical. The rotors and gears are pressed on.

Drive shaft

The drive shaft has a key on one end for the drive pulley.

Snout

The snout covers the drive shaft, drive gears, and coupler. It is half filled with oil during operation.

Assembly

We explored the ability of CAD programs to assemble virtual parts, check clearance and proper movement, and animate an entire assembly. All parts were constrained in small subassemblies and animated to ensure the proper degrees of freedom. The subassemblies were then assembled to create complete superchargers, which are shown below. Other aspects of Assembly we explored include exploded views, shown at bottom, and animation which we were unable to export from I-DEAS.


(Eaton M62 - Cad model)

(Eaton M90 - Cad model)

(Eaton M90 - Exploded view)


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Eaton Supercharger Group is a student group not affiliated with Eaton Corp. All materials contained on this webpage are for educational purposes only.

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