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Design Improvement in “Kingpin Stub Axle Assembly” Using FEA
Yaseen Khan
Asst.Manager - R&D, CAE
International Tractors Ltd.
R&D Center,vill.Chak Gujran
Jalandhar Road, Hoshiarpur
Punjab - 146001, India
yaseen.khan@sonalika.com
Vibhay Kumar
Sr. Manager- R&D, CAE
International Tractors Ltd.
R&D Center,vill.Chak Gujran
Jalandhar Road, Hoshiarpur
Punjab - 146001, India
vibhay.kumar@sonalika.com
Satpal S Saini
Head - R&D, CAE
International Tractors Ltd.
R&D Center,vill.Chak Gujran
Jalandhar Road, Hoshiarpur
Punjab - 146001, India
satpal@sonalika.com
Abbreviations: Itr.-Iteration,FEA-Finite Element Analysis
Keywords: Kingpin,Stub axle,thrust bearing,Off road vehicle,FEA, Static analysis
Abstract
Kingpin stub-axle plays major role in many direction control of the vehicle. It is also linked with other linkages and supports the vertical
weight of the tractor. Therefore, it requires high precision in tolerance, quality and durability. The main objective of the work is to
explore performance opportunities in the design and production of kingpin stub-axle. This can be achieved by performing a detailed
load analysis. In order to resist the bumps and jerks that usually occur in an off-road track, an integrated approach of design is
developed to obtain an optimized geometry which can give the drivers a ‘fun-to-drive’ experience.
This paper deals with kingpin strength improvement, material selection, thrust bearing selection, taper roller bearings, bushing
arrangement of kingpin stub-axle assembly and number of parts by using HyperWorks capability. These objective are achieved by
static analysis in number of iterations.
Introduction
Agricultural tractor is one of the main example for off road vehicles category. Off road condition includes
uneven agricultural field surfaces and bumpy village roads, on which the tractor has to operate. These
ground irregularities leads to unexpected loads coming on the tractor components. In Off-road vehicle the
turning radius is required to be small. This helps in maneuverability. Ackermann geometry is another aspect
which helps in maneuverability at low speed. Thus 100% ackermann was used in the geometry as the
speeds dealt in tractors and other off road vehicles is generally leading to lower unloading of inner tyre and
thus the ackermann geometry plays an important role in the turning radius.
Kingpin stub-axle assembly is the main load carrying member for front wheels and helps in steering of the
vehicle. It is fitted below the front axle . Stub-axle takes the load coming from the front wheels and transfer it
to the support. Front axle is like a simply supported beam member with the partial tractor weight acting on
the center and ends being subject to ground reactions through the front wheel .

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Objective of this paper was to study the behavior of kingpin stub-axle assembly in different load cases,
finding weak area and strength improvement so that testing may be reduced or eliminated assembly
Details:
King pin one end is connected with the stub-axle and another end with the front axle beam via kingpin tube
& bushes. Axle-hub is fixed over the stub-axle with taper roller bearings. Thrust bearing is fixed between
kingpin and kingpin tube
Figure 1: Kingpin Stub-axle assembly
FE Modelling
Considering different test load conditions, like drop test, torture test, 8-shaped track test, one side impact
test etc. Three worst possible loads were calculated for the king pin. Vertical load was applied in the
upwards direction, frontal load was applied in the backward direction (towards the rear) and transverse Load
(Axial load) of was applied in the outward direction. These loads were applied on the hub and the beam
was fully constrained from the area where it joins with the pivot pin tube. For the analysis, parts were joined
with each other according to the actual assembly of the king pin. Refer Fig.2.
Front axle beam, axle-hub,stub-axle, kingpin are modeled using 3D-tetra10 elements while bearings,
bushes are modeled with hex elements. Rigid elements are used to represent bolts and connections.
Taper Roller Bearing
Thrust Bearing
Bush
Kingpin
Axle
Hub Stub-
axle
Kingpin
Tube
Front Axle
Beam

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Figure 2: Loads & Boundary condition
Note:- Since Part is symmetric along Center axis, only half of axle was modeled for analysis.
Iteration Details
In 1st iteration (Fig. 3a), there were only two bushes between kingpin & kingpin tube. Since stresses was
high on kingpin in 1st itr., 2nd iteration (Fig.3b and Fig.3c) was carried out with additional bush . In 3rd
iteration (Fig.3c) thrust bearing assembly was rearranged.
3rd
Bush added
Thrust bearing
fitment modified in
3rd
iteration.

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Thrust Bearing Fitment
In iteration-3 thrust bearing fitment was improved.
according to the reference 1, the smaller bore inner
ring(Shaft Washer) of a thrust bearing should be
fastened on a shaft and the outer (housing washer)
Should be clamped in housing for the assembly to function
properly. Previously in the king pin assembly, this was
not so. Changes was done in the assembly to make
the thrust bearing function properly
Results & Discussions
Linear static analysis of king pin stub-axle assembly was done to check its strength.
Three Load cases were simulated i.e. Vertical load, Frontal load & Transverse load.
In iteration 1st
stresses was quite high at kingpin mid area hence 3rd
bush
inserted to transfer load properly.
In 2nd
iteration thrust bearing was not inserted properly hence local stress was high, its fitment corrected in 3rd
iteration.
It was found to be safe in 3rd
iteration.
Maximum stress is observed at kingpin mid near middle bush area.( Fig 4)
Maximum stress at stub-axle is observed as shown in figure. 6.
Note:- These images (Fig.4,5,6) are of vertical load case, frontal & transverse load case
images are not attached.
Fig. 3c : Iteration- 2 Fig. 3d : Iteration- 3
Fig. 3a : Iteration- 1 Fig. 3b : Iteration- 2

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Figure 4: von-Mises Stress Plot of Kingpin (3rd Itr.)
Figure 5: Global deformation of model (3rd
Itr.) Figure 6: von-Mises Stress Plot of Stub-axle (3rd
Itr.)
Benefits Summary
Kingpin stub-axle failure in testing eliminated and quality improved.
Challenges
Modeling of thrust bearing to freeze load transfer path, taper roller bearing and bushes and their connection was a
challenge.
Conclusions
With the help of HyperWorks we are able to model the complex behavior of bearings, bushes & all parts
effectively in all iteration. After number of iterations, we are able to conclude that in final model, stress level
are within material permissible limits and successfully eliminated its costly testing.

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ACKNOWLEDGMENTS
The authors would like to thank International Tractors Limited - R&D & Altair India for their support.
REFERENCES
[1] Mechanical Power Transmission Components by David W. South.
[2] The Steel Handbook by Alok Nayar.
[3] Industrial Steel Reference Book by S.N. Bagchi & Kuldip Prakash.
[4] SKF Bearing Catalogue.