Momentum - November 2017 - 13

STUDENT
GENERATION

Photo credit: Michael Jarrett

The team finished first in the Design event at Formula SAE Lincoln.
could eliminate that packaging issue. The narrower
engine allowed for the oil tank and exhaust to be
mounted inside the chassis along with a custom titanium
exhaust routed out the back of the vehicle while still
reducing weight.
The decreased mass from the engine helped meet
the vehicle weight requirement but posed a problem for
the vehicle's weight distribution. To solve the problem,
the team started by creating a MPS (Mass Properties
Spreadsheet) to analyze mass placement in the car prior
to starting CAD modeling. The MPS allowed the team to
determine the location of every component to ensure
vehicle requirements could be meet. During the design
cycle, the MPS was updated to make sure the vehicle
stayed on target. One final check was completed during
the build cycle as components were weighed while the
car was being reassembled in preparation for unveiling.
By taking this approach the vehicle was measured to be
within less than 1% of the weight-distribution goal.
One of the keys to success in the Formula SAE series
is reliability and being able to finish endurance. With the
switch to a new motor, the team prioritized acquiring
an engine dyno for developing and testing the new 675.
After scouring the internet for an affordable one, the
team decided to take a scrappy approach and convert
an old motorcycle wheel dyno to work as an engine
dyno. The engine dyno allowed for individual system
testing and engine tuning long before the car was built.
Every engine system was tested and tuned on the dyno,
with the results fed back into the Ricardo Wave engine
simulation.
Rapid prototyping was a key advantage to having an
engine dyno, allowing the powertrain team to iterate
through different system parameters over a short period
of time. The intake was just one of the systems that
benefitted from this testing method. An initial testing
intake was constructed to allow for runner lengths to be
changed between dyno runs. Runner lengths between 7"
and 17" were simulated in Ricardo Wave and then tested
on the engine dyno.

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One of the biggest challenges the team faced with the 675 was
designing the dry sump oil system. In the past, the team took
advantage of off-the-shelf components for the F4i. While many of
these components could be made to work with the 675, they would
be detrimental to the improved weight reduction and packaging
capabilities of the new engine. To solve the problem, powertrain team
lead Moy Barajas chose to design a custom oil pump.
The student-designed pump consists of four spur-gear stages: three
for scavenging, and one for high pressure supply to the engine with a
scavenge ratio of 3:1. The oil pump was packaged completely inside the
engine cases, with inlet and outlet lines passing through the cases via
the ports originally used for the OEM mechanical water pump. Initial
testing was performed on a single stage of the pump to determine
pump characteristics. The stage was fitted with a clear cover to check
for cavitation and allow for flow visualization. It was then connected to
the engine on the dyno and tested for flow through the engine. The oil
pump design allowed for a flat plate to replace the stock oil pan, in turn
allowing the engine to be mounted lower in the chassis than the F4i.
Spartan Racing's 2017 season got off to a strong start at Michigan
International Speedway, with the team passing both static and dynamic
technical inspection without issue. The team kept up the intensity in
the static events, and for the first time in the team's history, they made
Design Finals at the Michigan competition. Despite some ups and downs
during the dynamic events, the team would end up finishing eighth in
Endurance. The team's hard work would pay off with an overall finish of
sixth place, with a third in Powertrain Development.
After a strong performance in Michigan, the team looked to carry
momentum into the Lincoln competition. The team once again had a
strong performance, placing second in Acceleration, second in Skidpad and third in Autocross. Heading into the final event, Endurance, the
team was sitting in first place overall. Unfortunately, it wasn't meant
to be, as an engine sensor failure just before the driver change would
mean a DNF for Spartan Racing. Despite this failure, the team would go
on to win the Design event, another first in the team's history.
Sam Osman, the chief engineer and chassis team lead for San Jose
State University's Spartan Racing team who graduated in May
2017 with a bachelor's degree in mechanical engineering, wrote
this article for MOMENTUM. He is now an engineer at SpaceX.

November 2017 13

Momentum - November 2017

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