Truck & Off-Highway Engineering - August 2024 - 24

GEARING UP A NEW
ELECTRIFIED TRUCK
ELECTRIFICATION FEATURE
As noted by Hopkins, the transmission
really does not shift much on level surfaces
and below freeway speeds.
However, we were able to verify his claim
that above 62 mph (100 km/h), the
transmission did indeed grab fourth and
operate as a direct drive unit would mechanically
even with a load in the back.
We also tackled various grades in the
truck, which provided an opportunity to
show off a few of the truck's party
tricks. The powertrain has a hill hold
function that works much like an ICE
vehicle would. Even on grades as steep
as 25%, one could lift their foot off the
accelerator and the truck would hold
itself on the grade for a short period
before freerolling again.
The steeper grades also provided an
opportunity to demonstrate the shift logic
of the transmission when more torque is
required to make a hill. Like an ICE vehicle,
the truck will usually not give a downshift
command under full acceleration.
BAE has focused on simplifying the underhood packaging of BEV trucks to make it
easier to assemble and repair.
However, if the driver feels the truck slowing
while on a steep grade, a lift off the
accelerator at a low enough speed would
signal the transmission to engage first so
   
that the truck could continue climbing.
The off-road grades also demonstrated
the truck's capability to not turn the
manicured dirt roads of Eaton's proving
grounds into the starting line of a WRC
stage. Naturally, because full torque is
available from a dead stop, full power in
first gear would likely spin tires in low
mu situations. However, the throttle calibration
is refined enough even in this
prototype that its rear tires won't suddenly
turn into gravel machine guns.
  
    
       
     
   
    
    
       
     
 
   
24 August 2024
Final thoughts
What Eaton and BAE have collaborated
to create is quite impressive. By reintroducing
a transmission to a BEV powertrain,
they have demonstrated that an
electrified powertrain can be even more
flexible for truck applications while also
reducing the overall weight of the motor
and battery packs, which is still a major
sticking point for pure electric vehicles.
Eaton and BAE are not the first to put
a gearbox in a battery-powered truck.
Volvo, for example, uses a two-speed
gearbox in its VNR Electric. But the
companies' approach demonstrates
that not only can electrified powertrains
become more flexible in operation, they
also can be far more simplified in terms
of installation and overall architecture
while still providing the necessary performance
that fleet owners demand.
TRUCK & OFF-HIGHWAY ENGINEERING
SAE/MATT WOLFE
http://nasatech.hotims.com/86282-705
Truck & Off-Highway Engineering - August 2024

Table of Contents for the Digital Edition of Truck & Off-Highway Engineering - August 2024
