1) Title of invention
Design concept of Hinged Fork assembly for holding the blade during bird hit test.
2) Field of invention
It is a mechanical engineering design incorporated in bird hit test set up of Main Rotor Blades. During this test the specimen has to malntain different angles with different specimens in vertical and horizontal planes.
3) Use of invention
With this concept the required Bird hit angle on the blade aerofoil can be set to the gun axis and maintained during bird hit.
4) Prior art.
In the previous design, to set the bird hit angle to gun axis a simple fork ends are attached to the ends of the blades. Once the required angle is reached the forks used to be welded to the Main support.
5) Draw backs of prior art
There are few shortcomings in the earlier design which is mentioned below:
• It is used to take' more time to set one angle on different specimens and Holding or maintaining to particular position was difflcult while welding. During welding There are chances of set angles changed and damage to the composite.blade
• Additional stöppers and gussets are required to strengthen the test set up.
• Test set up time from one specimen to other specimen is more.

Prior art Present invention
It is a simple fork without any Provision for This is basically a cup and socket hinge "
swiveling. It is very difficult to set and mechanism. Thls concept not only gives good
maintain different angles on different test swiveling Provision to set and maintain different
specimens in vertical arid horizontal planes, angles in vertical and horizontal planes but also
there Is Provision for arresting radial
movement.
Test set up time is more Test set up time is less : r"
Consumes more man hours Requires less man hours
In this concept there is chances of specimen There is no welding on the test rig during
damage at the time of alignment and during alignment and then safety of specimen is
welding on the test rig during alignment ensured.
7) Aim of the invention
The specimens will be subjected to bird hit test with a bird velocity of ranging from 173 to 248 m/s and bird hit angles varies from specimen to specimen. To achieve this, the concept of ball and cup hinge mechanism implemented. Through this concept the test . specimens can be swiveled of in both vertical and horizontal planes to achieve the reqüired bird hit angles with respect to gun axis for various test specimens, and to withstand the loads experienced düe to bird hit at varies velocities. This concept has Provision to prevent rotational movement duö to bird hit impact and also eliminates misalignnient of the test specimen with respect to the vertical.
8) Summaryof the present invention
The bird hit test specimen of main rotor blade is an aerofoil with a pre twist incorpprated at layup stage itself. The hinged fork assembly is reqüired for holding the test specimen in place, to set the bird hit angle with respect to gun axis and to align the bird hit point with the gun axis.
The bottom half of hinged fork assembly is attached to the T-slotted base using tee bölts and clamps. The top half of the hinged fork assembly is with the test specimen and top end of the test specimen is attached to the rig through another hinged fork assembly
The cup and socket concept of the hinged fork assembly will allow rotation of upper half along with test specimen for fixing bird hit angle. It also allows

Claims
We claim that,
1. The design concept of Virtual hinged fork assembly which allows rotation of the specimen, accommodate inclination of the specimen with respect to vertical and holds the specimen at the set angular position.
2. Methodology adopted in using the concept of hinged fork assembly.
CV