Truck & Off-Highway Engineering - August 2024 - 23

ELECTRIFICATION FEATURE
Justin Hopkins,
product director,
E-Powertrain, Eaton.
" By introducing a
transmission, you're
reducing overall
weight and reducing
overall motor costs. "
" Copper is expensive, and you also have various motor
types that use rare earth metals. Scaling these motors
up also adds weight. By introducing a transmission,
you're reducing overall weight and reducing overall motor
costs, " he said.
The transmission that Eaton has integrated into the
test truck has only four speeds, which is a fraction of
what has become customary not only in trucks, but also
light vehicles. " Because the motor has a much larger
range of operation, you don't need as many speeds, "
Hopkins explained. " We really landed on where we think
the market sweet spot is. "
" You don't always use all four speeds. Even with
fully loaded 33,000-lb Class 7 trucks, it's perfectly fine
to launch in second gear and skip over first. But if you
get on a 20% grade, the vehicle recognizes that now I
need a deeper ratio to go up that grade, so it will then
select first gear, " Hopkins explained. " In this application,
it doesn't shift into fourth which is direct drive
until 62-64 mph. So, most of the time, it's really operating
as a two-speed transmission. "
Cutting complexity
The test bed for Eaton's EV transmission is a reworked
2018 Freightliner M2 crew cab equipped with a Meritor
TRUCK & OFF-HIGHWAY ENGINEERING
A peek under the hood of Eaton and BAE's test truck.
rear axle geared at 3.9:1. While this is still a test mule that began its life
running on liquid gold rather than electrons, the overall installation and
integration of its adopted powertrain is noticeably simple. It's what you
don't notice under the hood that catches your eye.
" There's a lot of current generation-one EV trucks that you see at
various tradeshows that have a lot of 'stuff' in them. A lot of these
generation-one EVs have a very distributed architecture [and] when
you remove petroleum, you have to power all your accessories with
electrons, " BAE's Webb said. " So, what we've done is build a six-inone
architecture where we've integrated a lot of different functions. "
Indeed, the simplicity of the installation makes the test truck in
question look much closer to a production-ready product rather than
a rolling laboratory. " Our system isn't just highly integrated, it's also
modular, " Webb said. " So, each of these functions are like slices that
can come together or be removed so we can expand and contract
them. We wanted to have the ability to support different platforms
and duty cycles so that we didn't constantly have to go back and
start from scratch. "
" This allows us to service multiple markets with a core building
block, " Webb continued. " That drives commonality between all the
core functions, but also benefits the OEM and end user in terms of
reducing NRE [non-recurring engineering]. It's expensive to electrify
each platform, so if there's commonality that carries over, that helps
the industry. "
Take a ride
Truck & Off-Highway Engineering was permitted to take Eaton/BAE's
test mule for an extended test drive around Eaton's proving grounds
in Marshall, Michigan. The facility features an oval test track, an offroad
course and several paved and unpaved grades ranging from 5to
25-percent.
August 2024 23
BOTH IMAGES: SAE/MATT WOLFE
Truck & Off-Highway Engineering - August 2024

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