Automotive Engineering - August 2022 - 16

R1T EXPOSED!
COVER STORY
With its composite cargo floor removed, the R1T's rear
gearbox, air-suspension components and mixed-materials
construction are visible.
And in some locations on the structure, the Normal
body shop is applying both spot welds and MIG welds.
" Considerable redundancy, " Munro commented.
" Overall, they need to get their body welding and sealing
processes sorted out to eliminate this. They also
need to get those processes up to speed in terms of
ensuring water tightness. "
Subtle innovations
In an all-new vehicle that is clearly loaded with smart, customer-delight
features, the Munro experts noted many
subtle design and engineering elements that impressed.
The R1T's non-exotic materials mix features a plastic composite
cargo bed, and cleverly employs double leaf springs
to hold up the tambour door over the cargo space.
Smith is impressed by the cross-car beam supplied
by Germany-based ElringKlinger, as well as the adjacent
HVAC ducting that uses various plastic materials
to address different loads and conditions. The crosscar
beam is produced using hydroformed hybrid technology
(HFH). The polymer-metal hybrid involves a
mold tool combining two processes - hydroforming
and plastic injection molding - in a single step.
According to ElringKlinger, a robot places an extruded,
thin-walled metal tube into the mold. After the two
halves of the mold are closed, the interior of the tube
is filled with cold water at 600 bar (8700 psi), which
causes it to expand and assume the desired shape.
The injection-molding process then begins in the same
mold cavity.
Molten plastic is injected into the mold at 300 deg. C
16 August 2022
The robust Bosch e-drive units feature hairpin-type motor windings. The motor
does not have a heat exchanger/oil pump - it is directly cooled via coolant
circulating through channels in the stator housing.
and then solidifies in the cavity between the mold and the reshaped
tube, again at 600 bar. Internal counterpressure ensures the aluminum
tube does not collapse during the injection process, the company
maintains. Once the part has cooled and is dimensionally stable, the
hybrid part is removed by a robot and transferred to downstream processing
where various vehicle-specific plastic elements are added.
At the time of our visit, the teardown team was just beginning its
scrutiny of the R1T's battery pack, making that an article for another
time. Initially, Munro is impressed with the pack design's " bottom-up "
cooling strategy featuring a cooling plate between each pair of cylindrical
2170 lithium cells. The traction motor design is " robust, " he said,
with the Bosch electric machine using hairpin-type wiring.
Director of electrification Tom Prucha previously was with in-wheelmotor
specialists Protean Electric, where he developed an acute assessment
of EV driveline dynamics. He said he appreciates the Rivian's
propulsion system architecture with its four separate drive motors. " It's
best-in-class from a performance standpoint and demonstrates how an
electric drive system can and should work, " Prucha noted. " Having said
that, I'm sensitive to driveline backlash. When I tip in and out of the
throttle in the Rivian, I can feel four separate backlashes, one from
each motor. I think it's inherent with four motors and four gearboxes.
" Could they tighten that up? Probably, " he said. " Would it affect vehicle
efficiency? Possibly. "
" For an all-new EV, the Rivian is an outstanding first effort, " Sandy
Munro affirmed. " But overall, it needs to be 'scrubbed' " - his term for
a comprehensive culling of all extraneous parts and a rethink of key
design areas that cause manufacturability issues.
" From what we've seen to date, I think Rivian could take a lot of
money and many kilos of weight out of this truck - and make it a lot
easier to build. "
AUTOMOTIVE ENGINEERING
FROM LEFT: LINDSAY BROOKE; MUNRO & ASSOC.

Automotive Engineering - August 2022

Table of Contents for the Digital Edition of Automotive Engineering - August 2022

Automotive Engineering - August 2022 - Intro
Automotive Engineering - August 2022 - Sponsor1
Automotive Engineering - August 2022 - CVRA
Automotive Engineering - August 2022 - CVRB
Automotive Engineering - August 2022 - CVR1
Automotive Engineering - August 2022 - CVR2
Automotive Engineering - August 2022 - 1
Automotive Engineering - August 2022 - 2
Automotive Engineering - August 2022 - 3
Automotive Engineering - August 2022 - 4
Automotive Engineering - August 2022 - 5
Automotive Engineering - August 2022 - 6
Automotive Engineering - August 2022 - 7
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Automotive Engineering - August 2022 - CVR3
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