Momentum - March 2018 - 7

STUDENT
GENERATION

The team-built "overkill" silent air box (at left, with insulation) compared to the OEM air box (at right, in
black). The extra volume in the team-built box reduces the velocity of air entering it, resulting in lower
noise generation.
sound meter. Additionally, the team instrumented the
snowmobile with an EVO4 data acquisition system.
The EVO4 allowed the team to record engine speed,
snowmobile ground speed, air intake temperature, and
exhaust temperatures. For each testing occasion, an
unmodified control snowmobile was utilized both at start
and end of testing events to monitor changes in ambient
environmental noise.
To characterize the sound profile of the stock
snowmobile, the team built and used hardware to
minimize noise from certain critical snowmobile systems.
The team attached the term "overkill" to these over-built
system components for clarity.
The single largest generator of noise on any power
equipment is most often the engine, which is no
exception on a snowmobile. With the engine, the primary
causes of noise are related to the air intake, mechanical
noise of engine rotation, and exhaust noise. The next
major contributor to noise is the chassis, as the power
transmission from the engine to the ground occurs
across this platform. The skid (semi-rigid structure under
the chassis that maintains track geometry) also transfers
energy from encountered terrain features back into
the chassis.

The "overkill" muffler with rear cover off.

holes drilled into it-three in the side for the engine throttle body hoses
and three in the top for initial air draw. The inside of the lower tote and
underside of lid were lined with R-11 fiberglass insulation to damp any
ambient noise and vibration experienced by the box.
Exhaust attenuation was accomplished using the same methodology
as the intake attenuation. By increasing the static volume of the exhaust
system via an oversized secondary muffler, the velocity of exhaust gases
exiting the snowmobile were greatly reduced.
The team used a steel 55-gal drum packed with R-11 fiberglass
insulation as a sound damper. The drum has twin inlet hoses of 1.5-inch
diameter to mate with the stock muffler outlets on the snowmobile.
The drum outlet is a hole of 2-inch diameter. Additionally, the inside of
the drum was lined with R11 fiberglass insulation to mitigate vibrationgenerated noise within the muffler and to quiet the exhaust stream by
providing increased surface area within the gas flow area.

THE SOLUTION
To accomplish intake attenuation, the team built a custom
air box that exceeded the stock air box static volume.
By increasing the static volume, the required velocity of
air being pulled into the box was reduced, decreasing
the audible noise generation of the box. The air box was
built utilizing an 18-gal storage tote, which had six 2-in

MOMENTUM

The competition snowmobile outfitted with "overkill" air intake + muffler and
experimental track skirt.

March 2018 7



Momentum - March 2018

Table of Contents for the Digital Edition of Momentum - March 2018

Momentum - March 2018
Contents
Companies mine talent at CDS competitions
All quiet on the snowmobile front
Monash University a double winner at Formula SAE-Australia
A return to glory days?
Setting the record straight on Baja SAE technical inspection
Paccar reveals new and future tech at CES 2018
OA-X contender moonlights as AFRL testbed
Chevy unveils larger, lighter 2019 Silverado
Students get the spotlight at SAE Carolina Section meeting
SAE 101: WCX World Congress Experience
More U.S.-born faculty: a university responsibility
Dossier: Lauren Goulet of John Deere
Help yourself by helping others
Just announced: new student scholarships—apply by March 15
Momentum - March 2018 - Momentum - March 2018
Momentum - March 2018 - Cover2
Momentum - March 2018 - Contents
Momentum - March 2018 - Companies mine talent at CDS competitions
Momentum - March 2018 - 3
Momentum - March 2018 - 4
Momentum - March 2018 - 5
Momentum - March 2018 - All quiet on the snowmobile front
Momentum - March 2018 - 7
Momentum - March 2018 - 8
Momentum - March 2018 - 9
Momentum - March 2018 - Monash University a double winner at Formula SAE-Australia
Momentum - March 2018 - 11
Momentum - March 2018 - A return to glory days?
Momentum - March 2018 - 13
Momentum - March 2018 - Setting the record straight on Baja SAE technical inspection
Momentum - March 2018 - 15
Momentum - March 2018 - Paccar reveals new and future tech at CES 2018
Momentum - March 2018 - OA-X contender moonlights as AFRL testbed
Momentum - March 2018 - Chevy unveils larger, lighter 2019 Silverado
Momentum - March 2018 - Students get the spotlight at SAE Carolina Section meeting
Momentum - March 2018 - SAE 101: WCX World Congress Experience
Momentum - March 2018 - More U.S.-born faculty: a university responsibility
Momentum - March 2018 - Dossier: Lauren Goulet of John Deere
Momentum - March 2018 - 23
Momentum - March 2018 - Just announced: new student scholarships—apply by March 15
Momentum - March 2018 - Cover3
Momentum - March 2018 - Cover4
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