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GMN 1729TP_2001

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GMN 1729TP_2001

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     North American ENGINEERING STANDARDS Retractor ?C VSR Tilt Angle and Sensitivity

     Test Procedure

     (Book)

     GMN 1729TP

     1 Introduction

     Note: Nothing in the specification, however, supersedes applicable laws and regulations unless a specific exemption has been obtained. Note: In the event of a conflict between the English and the domestic language, the English language shall take precedence. 1.1 Purpose. To determine the minimum angle of retractor rotation and the level of accelerations required to lock-up a vehicle/webbing sensitive retractor. 1.2 Foreword. The purpose of this procedure is to accurately measure the static tilt angle, the sensitivity to webbing acceleration, and sensitivity characteristics of a retractor to acceleration, in the fore, aft and lateral directions. 1.3 Applicability. To all emergency locking seat belt retractors. 1.4 Definitions. 1.4.1 Excitation Direction. A retractor is said to be excited in the direction that corresponds to the initial movement of the sensor mechanism (i.e. pendulum, standing man, ball, etc.) relative to body installation. For example, a retractor is excited in the inboard direction if the initial movement of the sensor mechanism is towards the center of the vehicle. The four excitation directions are: forward, rearward, inboard and outboard. 1.4.2 Lock Tooth Scanning

     orientation of the spool relative to the locking mechanism. These positions are ??scanned?? by indexing the sled every 2 mm (therefore changing the relative position of the spool to the locking mechanism) prior to each test. 1.4.3 Check Position.

     The acceleration sled position that corresponds to 25.4 mm (1 inch) of webbing payout. For example, if the initial position of the sled is 6 mm then the check position is 31.4 mm (6 + 25.4 mm).

     2 References

     Note: Only the latest approved standards are applicable unless otherwise specified. 2.1 Normative. 2.2 GM. 2.3 Additional.

     3 Resources

     3.1 Facilities. GM certified test lab. 3.2 Equipment. The following required. 3.2.1 equipment or equivalent is

     Retractors to be tested.

     3.2.2 Acceleration test device capable of reaching the desired acceleration level in less than 50 milliseconds. Over shoot must not

    exceed 10% of the test value. Acceleration must remain constant within +/- 5%. 3.2.2 Acceleration data recorder.

     This refers to the sampling procedure used to check if a specific acceleration level will consistently lock-up a retractor regardless of the

     Copyright Date General Motors Corporation All Rights Reserved

     Originated Date: October, 1989 Revised Date: March, 2001 Approval Date: March, 2001

     GMN 1729TP Page 1 of 4

     GM ENGINEERING STANDARD

     3.2.3 3.2.4 Fixture to mount retractor in body position. Static tilt angle fixture.

     GMN 1729TP

     4.3.1.2 With the specified amount of webbing remaining on the spool, attach the webbing end to the fixture clip or hook. 4.3.1.3 Set the sled start position to 0 mm and set the check position to 25.4. 4.3.1.4 Accelerate the retractor once at the specified ??Must Lock?? acceleration to pack the retractor (do not record the test result). 4.3.1.5 Accelerate the retractor at the specified ??No Lock?? acceleration, at a rate of less than 38 g??s per second, and record the amount of webbing payout if lock-up occurs. The choosen onset rate is to be used for the remainder of the test process (i.e. at all subsequent acceleration levels). (It is permissible to start sampling at a higher rate of acceleration, if the minimum sensitivity is identified). 4.3.1.6 If the retractor did not lock-up within the maximum specified payout limit, increase the acceleration level by .05 g and repeat the test. Continue to increase the acceleration level by .05 g and retest the retractor each time the retractor does not lock-up within the specified payout limit. 4.3.1.7 Once the retractor has locked-up within the specified payout limit, move the starting position of the sled or fixed end of webbing 2 mm. Adjust the check position if required. Retest the retractor. 4.3.1.8 Each time the retractor locks-up within the specified payout limit, index the retractor??s start and check positions (per step 4.3.1.7) and test for lock-up. Continue this test sequence until the retractor is tested at ten consecutive positions or the retractor does not lock-up as specified. If the retractor did not lock-up as specified, move the sled back to the starting position, reset the check position to 25.4 mm, increase the acceleration level by .05 g and retest as outlined. After ten consecutive lockups, record the amount of webbing payout and acceleration level. 4.3.1.9 Repeat steps 4.3.1.1 ?C 4.3.1.9 for the rearward, inboard and outboard excitation directions. 4.3.2 Webbing Acceleration Sensitivity.

     NOTE: All equipment must be calibrated in accordance with American

    National Standard for Calibration, Calibration Laboratories and Measuring and Test Equipment ?C General Requirements. 3.3 Test Vehicle / Test Piece. 3.4 Test Time. Calendar time: days (range) Test hours: hours (range) Coordination hours: hours (range) 3.5 Test Required Information. 3.6 Personnel / Skills.

     4 Procedure

     4.1 Preparation. See Seat Belt Subsystem Specifications. 4.2 Conditions. See Seat Belt Subsystem Specifications. 4.2.1 Environmental Conditions. 4.2.2 Test Conditions. Deviations from the requirements of this test procedure shall have been agreed upon. Such requirements shall be specified on component drawings, test certificates, reports etc. 4.3 Instructions. 4.3.1 Retractor Acceleration Sensitivity.

     NOTE: For retractors with dual spools and a common sensor mechanism, the sensitivity of each spool must be checked simultaneously with each webbing displacement individually measured. 4.3.1.1 Mount the appropriate mounting fixture with the retractor to the sled such that the retractor is in body position and will be excited in the ??forward direction, to simulate a frontal impact??.

     Originated Date: October, 1989 Revised Date: March, 2001 Approval Date: March, 2001

     GMN 1729TP Page 2 of 4

     GM ENGINEERING STANDARD

     4.3.2.1 Mount the retractor to the fixed portion of the sled. 4.3.2.2 With the specified amount of webbing remaining on the spool, attach the webbing end to the sled. 4.3.2.3 Set the sled start position to 0 mm and set the check position to 50 mm. 4.3.2.4 Holding the retractor fixed, accelerate the webbing out of the retractor once at the specified ??Must Lock?? acceleration to pack the retractor (do not record the test result). 4.3.2.5 Accelerate the webbing out of the retractor at an acceleration below the specified ??No Lock?? acceleration, at a rate of less than 100 g??s per second, and record the amount of webbing payout if lock-up occurs. 4.3.2.6 If the retractor did not lock-up increase the webbing acceleration level by .1 g and repeat the test. Continue to increase the acceleration level by .1 g and retest the retractor each time the retractor does not lock-up. Maintain the specified amount of webbing stowed on the retractor spool. 4.3.2.7 After ten consecutive lock-ups, record the amount of webbing payout and acceleration level. 4.3.3 Web Sensing Mechanism Strength 4.3.3.1 Mount the retractor to the cycle machine. Set-up such that the webbing is extended and retracted with minimum interference between webbing and the retractor opening. 4.3.3.2 Extract the specified amount of webbing from the spool. 4.3.3.3 Preset the machine counter to the number of cycles specified. 4.3.3.4 Holding the retractor fixed, accelerate the webbing (at a rate lower

    than that needed to trip the web sense lock mechanism) to a velocity of at least 1016 mm per second. Increase the acceleration to a value high enough to lock the web sense lock mechanism. The velocity of the webbing, when the web sense mechanism locks, must be at least 1524 mm per second. The force generated on the retractor, from the webbing, after the spool has Originated Date: October, 1989 Revised Date: March, 2001 Approval Date: March, 2001

     GMN 1729TP

     locked should be that stated in the technical specification. Repeat for specified number of cycles or until failure occurs. 4.3.3.5 Offset lockup cycles such that the loading is evenly distributed over 40 mm of webbing extraction in 10 mm increments. 4.3.3.6 Record number of cycles completed and any other pertinent data. 4.3.4 Static Tilt Angle. 4.3.4.1 Rotate the tilt angle table to the level position and verify this with a bubble level. 4.3.4.2 Install the mounting fixture to the static tilt angle table such that the retractor can be excited (tilted) in the forward direction. 4.3.4.3 Secure the retractor to the mounting fixture. An appropriate mounting fixture should hold the retractor in body position while the static tilt table is level. 4.3.4.4 Rotate the tilt angle table slowly such that the retractor lock-up mechanism is activated in the forward direction (do not exceed 2 degree per second, a slower speed may be used during the critical area). Extract webbing from the retractor until the lock bar engages a sprocket tooth. Stop the rotation of the table and check if the lock bar engages on the previous five consecutive sprocket teeth. 4.3.4.5 Record the tilt angle if the lock-bar engaged on six (6) consecutive teeth; otherwise, continue to rotate the table and test as directed in step 4.3.4.4. 4.3.4.6 Rotate the retractor about the tilt angle table as required to determine the sensitivity for the rearward, inboard and outboard directions. For each new orientation, repeat steps 4.3.4.4 ?C 4.3.4.5 to determine the static tilt angle sensitivity. 4.3.5 Webbing Payback to Unlock. 4.3.5.1 Install the retractor to the static tilt angle table such that the retractor can be excited (tilted) in the forward direction. An appropriate mounting fixture should hold the retractor in body position while the static tilt table is level. 4.3.5.2 Rotate the tilt angle table slowly such that the retractor lock-up mechanism is GMN 1729TP Page 3 of 4

     GM ENGINEERING STANDARD

     activated in the forward direction. Extract webbing from the retractor until the lock bar engages a sprocket tooth. Stop the rotation of the table when the lock bar engages a sprocket tooth. 4.3.5.3 While preventing the webbing from retracting into the retractor, rotate the tilt angle table back to the starting position. Allow 7 mm of webbing to retract back into the retractor. Check for retractor lock / unlock

    by trying to extract webbing from the retractor. If unlock occurs, repeat steps 4.3.5.2 ?C 4.3.5.3 for five consecutive unlocks. 4.3.5.4 If retractor remains locked, allow webbing to retract back into the retractor in 2 mm intervals until unlock occurs. When unlock occurs, repeat steps 4.3.5.2 ?C 4.3.5.3 for five consecutive unlocks. Record the amount of webbing payback needed to unlock.

     GMN 1729TP

     user of this method to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

     7 Coding System

     This test procedure shall be called up in other documents, drawings, VTS, CTS etc. as follows: "Test to GMN 1729TP". This test procedure is categorized as: Lab, Interior Ctr, Restraints.

     8 Release and Revisions

     8.1 Release. The specification was first approved and released in 10/1989. Initially referred to as GMUTS L1-1A2R-2 / MTL 1729. GMN number assigned to identify document within GMNA. 8.2 Revisions. Rev. Date Description / Reason Originating Organization / Committee Interior Ctr.

     5 Data

     5.1 Calculations. 5.2 Interpretation of Results. 5.3 Test Documentation. Record pertinent test results.

     1

     03/01

     Reformatted and Reviewed

     6 Safety

     This method may involve hazardous materials, operations and equipment. This method does not propose to address all the safety problems associated with its use. It is the responsibility of

     Appendix Deviations

     Originated Date: October, 1989 Revised Date: March, 2001 Approval Date: March, 2001

     GMN 1729TP Page 4 of 4

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