EVs are the latest trend for transportation, everything from cars to buses todays are turning electric. Small vehicles like golf carts are no different, many golf courses are turning their golf carts electric. This brings us to our topic i.e., Nylon composite wheel hub.
In Golf karts, the wheel hub plays a vital role in the power
transmission system. Battery life directly depends on the rate of power being
consumed. The dominant and direct factor affecting wheel hub design is stress
created through operating loads on wheels.
First, let’s address some obvious questions about wheel hub
What does
a wheel hub do?
Wheel hubs are essential because they connect each wheel to
the vehicle. While you cannot see them without removing the wheel, the vehicle
could not operate without these hubs. The wheel hubs enable the driver of a
vehicle to move the wheels and steer.
If they are not working correctly, this is when a driver can
have issues with their steering wheel alignment. The wheels can become wobbly
if the wheel hubs are not correct, and too much friction is placed on the wheel
itself.
What does
the wheel hub connect to?
The wheel hub is responsible for connecting a wheel to a
vehicle. As a result, it connects to both the wheel and the vehicle itself. The
wheel hub connects to the vehicle’s wheel axle, which is located on the brake
disc side of the chassis.
The tyres are then connected to the wheel hub assembly with
studs. Given the wheel hub assembly location behind the wheel, you can only see
it when the wheel of a vehicle has been removed.
Now let’s get started with the technical details
Design
Procedure
In the wheel alignment system, the hub is the main part
where the rim is attached to the hub. This hub’s Pitch Circle Diameter (PCD)
depends on the number of bolts used. The hub may have a minimum of 4 studs and
generally, the PCD used for designing the hub is 100 mm or 114.3 mm. In this
study, 100 mm PCD with 4 bolts has been used. The hub assembly consists of the
wheel bearing and hub to mount the wheel to the vehicle. It is located between
the brake rotors and the axle. The bolt pattern is determined by the number of
bolts on the wheel hub. The material used in this assembly should be strong
enough to take the weight of the car. The wheel bearing for the hub is selected
based on the inner and outer diameter of the spindle coming out.
Parameters
used to design the wheel hub
• Design of Sleeve: Selection of material and calculation of
Outer diameter (OD), Inner diameter (ID) and
Length.
• Design of Flange: Selection of material and calculation of
hole diameter for bolts, PCD and thickness.
• Design of Bolts: Defining bolt diameter and selecting a
standard size along with a selection of nuts.
• Design of Key: Defining width, length and height.
• Design of Splines: Defining width, length and height.
In this study AISI 1040 is selected for the design of the shaft,
i.e., according to ASME, twisting as well as bending of the shaft is considered
while designing.
Furthermore, the shaft is subjected to braking torque and
bending moment. Braking torque is the force applied at the brake wheel to stop
the motion of the moving equipment. The operating conditions for the equipment
are constant; a brake having a retarding torque equal to the full load torque
of the motor to which it is applied is usually satisfactory. The braking torque
is calculated as follows.
The shaft is also subjected to bending moment along with
braking torque due to lateral forces. The bending moment is maximum at the
point where the Shear Force is zero and it is zero at the fixed support.
Design of
sunk key
Now let’s start with the star of our discussion
THE WHEEL HUB DESIGN
Here two trials are performed
Trial 1
The procedure used in trial 1
• Model is opened in Mechanical application. The “Geometry”
object in the Tree is expanded to make the
body objects visible.
• The body that is desired to be rigid is selected and in
the “Details” menu, under the “Definition” view for the
body, the value of stiffness behaviour control is changed to
Rigid. The mesh method is controlled by right-clicking on the “Mesh” object in
the Tree and by inserting a “Method” using the “Insert” command.
• In the “Details” view, the mesh method is scoped to the
rigid body.
• The value of “Element Mid-side Nodes control” is also
changed if required.
Results of trial 1
Trial 2
Using the same type of meshing and boundary conditions as
the 1st trial, stress analysis of this new model was carried out. The software
used for modelling is Fusion 360 and the analysis is ANSYS 17.
it can be observed that the analyzed stress for that design
is much higher than the maximum allowable stress whereas, in the other trials
the analyzed stress is either less than or slightly above the maximum allowable
stress.
From Table 5 it can be observed that substituting MS with
Nylon 6 GF in the wheel hub can result in a weight reduction of the electric
kart by almost 80%. This can help improve the efficiency of the kart. In
addition to it, the battery life of the vehicle can also increase. Hence, the
usage of Nylon 6 GF instead of MS can prove to be much beneficial for the
electric kart’s life.
CONCLUSION
In this study, the wheel hub is successfully redesigned and a new optimized design is presented along with changing the material to plastic/nylon. In an attempt to reduce the overall weight of the wheel assembly, application of the Polypropylene as an alternative material has been investigated well. In the stress analysis, two trials were carried out. The first trial did not use an optimized design; it can be observed that the analyzed stress for that design is much higher than the maximum allowable stress whereas, in the other trials the analyzed stress is either less than or slightly above the maximum allowable stress. By substituting MS with Nylon 6 GF in the wheel hub can result in a weight reduction of the electric kart by almost 80%. This can help improve the efficiency of the kart. In addition to it, the battery life of the vehicle can also increase. Hence, the usage of Nylon 6 GF instead of MS can prove to be much beneficial for the electric kart’s life.
Reference
Credit :
Pratik
Nagre
(Team
R&D)
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