| 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)
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| 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 |
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|
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.
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Rotor mount
/ Spacer
The spacer secures
the other end of the rotors shafts, and allows the rotors
to be removed as a single assembly.
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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.
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Drive coupler
Connects the first
drive gear to the snout shaft. Made of plastic that can shatter
if the rotors jam.
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Drive gears
First drive gear
is driven by the coupler and shaft, while the second transfers
power to the counter rotating second rotor.
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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.
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Rotor shafts
The two rotor shafts
are identical. The rotors and gears are pressed on.
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Drive shaft
The drive shaft
has a key on one end for the drive pulley.
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Snout
The snout covers
the drive shaft, drive gears, and coupler. It is half filled
with oil during operation.
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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) |
