Design of a Weight-Optimized Gearbox for a Formula Student Car
Typ
Examensarbete på kandidatnivå
Program
Publicerad
2021
Författare
Alexsson, Emil
Henrikson, Erik
Lund, Carl
Tsobanoglou, Christian
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Chalmers Formula Student is a team consisting of student engineers that design and
build race cars to compete against other universities’ teams. Since 2019, Chalmers
Formula Student has been designing electric powered four-wheel drive cars. In 2020,
Chalmers Formula Student began utilizing electric machines and gearboxes powering
all wheels at the wheel hub. This design has many advantages in terms of mechanical
packaging and lowering the center of gravity, but the design also means higher mass
for the shock absorbers to handle, also called unsprung mass. Higher unsprung mass
has a negative effect on the vehicle dynamics. The project purpose is therefore to
design a lighter gearbox than the most recently manufactured Chalmers Formula
Student gearbox to reduce the unsprung mass.
This report covers the process of developing a gearbox for the Formula Student
car with the purpose previously mentioned. The project starts with investigating
different gearbox configurations via a concept generation, resulting in that a single
stage planetary gearbox is the most suitable concept. Then a method for deriving
the dimensioning load cases for the gears, bearings and gearbox housing is developed
by translating sensor data from competition to resulting forces.
The load cases are then used for dimensioning the gears with the gear dimensioning
software KISSsoft and for stress and deformation analysis on the gearbox
housing and bearings with the FEM software ANSYS and 3D-modelling software
CATIA V5.
The result is a single stage planetary gearbox with a gear ratio of 11.5:1 that is
2.4% lighter than the most recent manufactured Chalmers Formula Student gearbox.
However, if only the shared components are compared the final design is 12.3%
heavier. The high gear ratio resulted in problematic gear design resulting in heavy
gears in order to achieve acceptable safety factors.
The conclusion is that even though the developed gearbox became marginally
lighter, a single stage planetary gearbox is not a suitable gearbox layout for the
application. However, the methods for developing the dimensioning load cases are
considered accurate and suitable for dimensioning future gearboxes.
Beskrivning
Ämne/nyckelord
Gearbox , Formula Student , Gears , Planetary gearbox , Unsprung mass , Design , Dynamics