2) Field of invention ;
It is a-mechanical engineering design which comes into operation during the ground testing of helicopter tail rotor Spider, which is used during strain gauge calibration for flight load . measurement.
3) Use of invention
This invention finds application in the ground testing of helicopter tail rotor Spider. '
. 4). Prior art
In the previous design, spider is fixed on mounting bracket by using dummy ^control tube. To accommodate spider has internal taper bore, dummy control.tube will have external taper shaft. Down ward calibration of spider can be done easily by pan and wire rope. Whereas upward calibration - . requires loading frame with friction-less pulleys and it is tedious setup. During'unloading of dead ^weights,~due to friction / misalignment strain values will not come back-to original values. There is a need to lift up the dead weights. This will lead to erroneous results in strain gauge calibration of spider.

5) Draw backs of prior art
' There are few shortcomings in the earlier design which is mentioned below:
. .• Dead weight is touching to the mounting bracket during downward loading
• Requires moresetup time for upward loading {there is no quick changeover) .
• Friction/misalignment in the mechanical set up leads wrong results
• This set up has more number of parts
• Inspection process istedious.
6) Comparison between prior art and present invention
The spider.is fixed to the Z-bracket in the current configuration whereas in earlier design the spider is attached to vertical mounting bracket. Avoidance touching of dead weight to mounting bracket can be assured with present design by using Z-bracket. In present scheme, the provision to mount spider i reverse direction to apply upward load. Present design simplifies the downward and upward calibration of spider.
7) Aim of the invention
The prime objective of the invention is to ensure accuracy of strain gauge calibration so that accurate flight load measurement are possible during flight of Helicopter. The present invention also aims to improve the productivity by reducing the enormous human effort / time which was spent during setup.
8) Summary of the present invention
In the present design, two dummy control tubes are assembled on Z-bracket, to facilitate downward and upward strain gauge calibration of tail rotor spider. One of dummy control tube is assembled on top of Z-bracket and another one assembled on bottom surface of Z-surface. This setup will allow' specimen to subject to direct loading and unloading and gives accurate results.
9) Brief description of drawings
The Figurel explains the basics of prior design and the attachment details of the set-up for calibration of spider. The Figure 2 illustrates downward calibration setup for tail rotor spider by using Z-bracket. The Figure 3 depicts the reversal specimen and upward calibration setup for tail rotor spider.

10) Statement of invention
The present invention of Spider calibration setup improves the .accuracy of strain gauge reading " , during flight: Mechanical set up is easy in present, design improves the productivity and hence reliability ' of the set up is enhanced when compared to the previous design.
11) Detailed description of invention
To measure flight critical loads on helicopter dynamic components, strain gauging and calibration is
mandatory during development stage. The spider calibration setup consist of UTM with T-base z-bracker, dummy control tubes, pan and dead weights. Dummy control tubes with z-bracket has assembled.on T-base of UTM to get clearance between pan and test rig. The spider has internal
taper bore,'it requires two dummy control tubes for calibration. The spider is mounted on top
dummy control tube for downward calibration. After completion of 4 arms one after another strain gauge calibration in downward direction, the spider is reversed and will be mounted on bottom dummy control tube. • •
in present method, spider is subjected to direct loading / unloading during the upward / downward strain gauge calibration.than earlier method. Quick change over of arm is possible by loosening, dummy control.tube nut.

Claims
We claim that,
1. The spider calibration setup consist of UTM withT-base z- bracket, dummy control tubes, pan and dead weights. Dummy control tubes with z-bracket has assembled on T-base of UTM to get clearance between pan and test rig. The spider has internal taper bore , it requires two dummy control tubes for calibration. The spider is mounted on top dummy control tube for downward calibration. After completion of 4 arms one after another strain gauge calibration in downward direction, the spider is reversed and will be mounted on bottom dummy control tube. Spider calibration setup is simple in design and easy to install spider on Z-bracket.
2. In present method, spider is subjected to direct loading / unloading during the upward / downward strain gauge calibration than earlier method. Quick change over of arm is possible by loosening dummy control tube nut. Spider calibration setup design caters for high accuracy of strain gauge reading in upward and downward loading.
3. It requires minimum number of parts and less effort to calibrate the spider.
4. Misalignments can be avoided during loading and unloading of dead weights.
5. Improves quality of flight data of the Helicopter during flight/landing.