FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)


TITLE OF THE INVENTION Test set up and procedure for testing automobile rear suspension -twist beam
APPLICANTS
TATA MOTORS LIMITED, an Indian company
Having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
INVENTORS
Mr. Suyog Panse, Mr. G Ragvendra, Mr. Sameer Ghodekar, Mr. D. P. Salunkhe,
Mr. Atul Kajalkar, Mr. Santosh S Gosavi, Mr. Amol Apte, Mr. Kanad Karandikar,
Mr. Gautam Pingle, Mr. Santosh Singh, Mr. Girish Chavan and Mr. Mithun
Chaskar
All Indian Nationals
of TATA MOTORS LIMITED,
An Indian company having its registered office
at Bombay House, 24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
Preamble to the description
The following specification particularly describes the invention and the manner in
which it is to be performed.


FIELD OF INVENTION:
The present invention deals with the method of accelerated testing of twist beams on specially designed rig and developing test setup for validation of the same. More particularly this invention deals with the test setup and testing of twist beam on rig which will simulate the field condition.
BACKGROUND OF INVENTION:
Conventional method of testing includes making of a welded fixture either in vertical position or in horizontal position. Two actuators were used in displacement control mode or in force mode to simulate vehicle condition for achieving required displacement/Load at wheel centers. Limitations of conventional method of testing:
a. It is time consuming as all displacement/force data events considered based on
Road load data. As number of cycles was more it will take more time for fatigue
life test
b. Different displacements controls needed to be monitored for each actuator.
c. High infrastructural cost due to use of servo hydraulic actuators.
d. High operating costs of the rig.
SUMMARY OF INVENTION:
The main object of this invention is to develop a low cost reliable test setup and accelerated method of testing the twist beams by simulating the field condition. Yet another object of this invention is to provide a test method which will utilize one actuator for testing the twist beam by achieving relative displacement at both wheel centers.
Yet another object of this invention is to reduce the number of testing cycles without reducing the fatigue damage which in turn reduces the testing time. The present invention describes novel test setup and method of testing twist beam which is cost effective and takes less time for testing. This novel test setup makes use of one actuator and one fulcrum to produce desired relative displacements at the wheel centers. While testing only cross events of displacement were used and

twist beam is tested in displacement control mode. As cycle contains only cross events of relative displacement both the wheels are out of phase with each other, one actuator can be safely eliminated by using one fulcrum and one actuator. Load cell is provided to notice failure of the component is decided based on load drops during testing.
According to the present invention a test setup for testing twist beam for a vehicle comprising; a lower platform for fixedly mounting the vehicle; said vehicle having a twist beam connected through coil springs; said twist beam end points attached with wheel rim; a fulcrum mounted on the floor and engaged with said wheel rims through a ball joint assembly; an actuator connected to a vertical frame for actuating said fulcrum.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows the test setup for testing twist beam of a vehicle Figure 2 shows the ball joint assembly for transferring the displacement.
DETAILED DESCRIPTION OF INVENTION:
Referring now to the drawings wherein the showings are for the purpose of illustrating preferred embodiments of the invention only, and not for the purpose of limiting the same.
Figure 1 depicts the embodiment of body in white (BIW) (1), Twist Beam (2), wheel rim fixtures (3), ball joint asembly (4), fulcrum (5), specifically designed studs (6) for reproducing vehicle condition on the rig, actuator (7), frame for mounting the actuators (8), Ball joints (9) to connect the actuator to the fulcrum, coil spring (10) connecting twist beam to BIW, load cells (11) located between actuator and ball joint (9), surface plate (12) for supporting BIW through the mounting blocks (13) and ball joint (14) to connect actuator mounting frame to the actuators. Placement of these ball joints is very important as they act as

nodal points to transfer the forces and rigidity of any nodal point may result in
uneven transfer of loads.
BIW is fixed to metal blocks (13) made of steel plates, blocks are fitted on surface
plate (12). Twist beam (2) is fitted on BIW (1) along with brake assembly and
suspension coil spring (10). In this arrangement is spring reactive loads are
balanced by using actual springs. To this twist beam, wheel rim fixtures are
attached (3).
The wheel rim fixtures will now work as a member that will transmit the load to
the wheel centre depending on testing condition i.e. testing in X, Z direction and
in roll fatigue tests, these fixtures can be rotated.
The test setup is easy to manufacture and low cost. It can be used at any angle to transmit displacement of actuator to wheel centre. Further setup have wheel hub and hand break assembly on which wheel rims are fitted. Hand break levers on actuation will press break pads against hub. This will intern the wheel rim and act as a locking arrangement for wheel rims. The conventional hand break system mounted on twist beams is used for locking arrangement.
As shown in figure (2) Ball joint assembly (4) connected to wheel rims and fulcrum on LH as well as RH side. It may happen that angular displacement of a ball joint may not be sufficient to completely transfer the displacement to the wheel centre and in extreme conditions side loads may come on the wheel center. Two ball joints which are at angle to each other (figure 2), are used to avoid this. This prevents side loads on the wheel centre of twist beam caused by bottoming of the ball joint. Ball joint assembly (4) is bolted to fulcrum. The distance between two ball joint assemblies is equal to the vehicle wheel track. The twist beam is tested in displacement control mode. Two trailing arms of twist beam are out of phase with same displacement while testing. In this test setup use of fulcrum has three advantages over conventional method:
i. It eliminates one actuator.
ii. Lowers infrastructure cost incurred due to equipments used in test set up.

iii. Lowers the operating cost of the test. The actuator (7) is mounted on the vertical column and connected to the fulcrum (5) through load cell (11) and ball joint (9). Load cell (11) attached to the fulcrum, used to monitor the load drop which indicated the failure of twist beam. The fulcrum (5) is asymmetrical having an extended portion at one end. The ball joint assembly (4) is placed at symmetrical with swinging point of the fulcrum and engaged with the wheel fixtures. The ball joint (9) for transferring displacement form actuator is located at extended portion of the fulcrum (5). For fitment of twist beam a stud (6) is used to mount the twist beam on B1W for required height of coil spring. This will limit the twist beam physically if twist beam fails during testing and reduce operator fatigue while fitment and removal of twist beam.
Twist beam rear suspension has higher stiffness characteristics, slightest of crack can considerably reduce the loads on twist beams and can be used as a criterion for failure detection.
Customized software is used to sense the load through load cell and control the positions of actuator. Linear Variable Displacement Transducer used for sensing the position which has interface with controller. Following are the steps for preparation of test setup.
1. Fulcrum assembly kept on the ground and clamped properly.
2. Specially arranged ball joints are connected to fulcrum assembly.
3. Metal blocks made from 12mm thick metal plate was kept on surface plate.
4. Blocks clamped properly with the help of clamps.
5. Body shell kept on mounting blocks and clamped with blocks through
mounting holes.
6. After fitment of shell, pivot arm bracket is fitted to rear portion of shell (under body).
7. Twist beam is fitted to pivot arm bracket.
8. Coil spring is placed between twist beam and mounting on shell.
9. Height of coil spring is adjusted with specially designed studs.
10. Brake drum and wheel rim fixture assembled with twist beam.

11. Fulcrum and actuator assembled together.
12. Torques given to the setup.
The test derivation is based on road load data collection on torture track. Data is captured as per torture track recipe and data is used to extrapolate for vehicle life. There are various conventional tools like rain flow analysis; joint probability distribution; peak valley counts method are used to derive test specifications. The road load data of wheel force transducers and wheel to body for rear wheels are collected and the relative displacement of wheels are calculated.
In the first approach, rain flow analysis method is used to prepare test derivations; the number of cycles crossing particular relative displacement is identified and half of the relative displacements are given inputs to the actuator. Approach 2: To reduce the test cycle and to get the same damage, a potential damage method is decided to implement. This method is derived from S-N slope wherein strain or force data is required. A data measured for displacement & shear strain which generates damage to twist beam is measured on the torture track.
The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.

We claim
1. A test setup for testing twist beam for a vehicle comprising; a lower platform for fixedly mounting the vehicle; said vehicle having a twist beam connected through coil springs; said twist beam end points attached with wheel rim; a fulcrum mounted on the floor and engaged with said wheel rims through a ball joint assembly; an actuator connected to a vertical frame for actuating said fulcrum.
2. A test setup for testing twist beam for a vehicle as claimed in claim 1 wherein said fulcrum is asymmetrical having an extended portion at one end.
3. A test setup for testing twist beam for a vehicle as claimed in any one of the preceding claims wherein said ball joints engaged with wheel rims are located symmetrically about the rotational hinge of said fulcrum and said actuator is connected through a ball joint at extended portion of the fulcrum.
4. A test setup for testing twist beam for a vehicle as claimed claim 1 wherein said ball joint assembly having two ball joints placed at an angle to each other.
5. A test setup for testing twist beam for a vehicle as claimed in claim 1 wherein the vehicle mounted to lower platform through a block.
6. A test setup for testing twist beam for a vehicle as claimed in claim 1 wherein said actuator connected to said vertical frame through a ball joint.

2 9 SEP 2009
7. A test setup for testing twist beam for a vehicle as claimed in any one of the preceding claim wherein said actuator connected to said fulcrum through a ball joint.
8. A test setup for testing twist beam for a vehicle as claimed in claim 7 wherein a load cell is located between said actuator and said ball joint.
9. A test setup for testing twist beam for a vehicle substantially as herein described with reference to accompanying drawings.