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U.S.Patent 115218.00001
All Rights Reserved
© Copyright 2009 WALIN TOOLS LLC

 R.A.B. Radial, Axial, Bearing Measuring Tool
NSN: 5180-01-572-1858
Part # RAB6977

Operation Instructions

A. Purpose:

The R.A.B. (Radial Axial Bearing) Tool is designed to measure the RADIAL and AXIAL allowable variation and tolerance of the AH-64 Apache Helicopter Main Rotor (M/R) and Tail Rotor (T/R) Pitch Change Link Spherical Bearings. The R.A.B. also includes a “Trammel” Tool for replacement of Main Rotor (M/R) Pitch Link Rod Ends.

B. Content Paragraph
Calibration
V-Block Set UP
Measurement Procedure
Axial Check
Radial Check
Final Determination
Trammel Bar Function

 WARNING: Prior to measuring the variation and tolerance of any bearing the RAB must be calibrated. Any residual play is measured, recorded and later subtracted from the final bearing reading.

 

C. Calibration

1. A Master Gauge is stored on the front of the RAB on the adjustable Trammel. (click here to see Figure 1) Place the master gage in both V-Blocks of the RAB. Secure the forward end between the adjustable Axial Assembly (A) andthen secure the link with both top forward and aft Radial Assembly Clamps (M) . Do not over tighten the clamps.

2. Adjust all gauge indicators to Zero.

3. Move the Axial Handle (B) back and forth. Observe the Axial Gauge (C) (each gauge measurers in thousandths .001). Record the reading of on the worksheet.

4. Move the Radial Assembly Handle (D). Observe Radial Gauge (E) and record reading. The calibration is complete and remove Master Gauge andset aside.

5. Locate and remove the bearing marking tool (O) .

6. Calibrate bearing by marking 120°

 D. V-Block Set-Up

1. The R.A.B may be set-up to accommodate either the Main Rotor (M/R) Pitch Link Rod or Tail Rotor (T/R) Pitch Link Rod. In order to accept either link, the aft removable clamp and V-Block must be positioned correctly. The aft removable clamp and V-Block assembly (F) is reversible. Loosening the aft clamp at the base and sliding the assembly completely off the stainless support and reinstalled as needed.

a. Long Main Rotor Link (M/R) Pitch Link – The V-Block facing outboard.
b. Short Tail Rotor (T/R) Pitch link – The V-Block facing inboard.

 E. Measurement Procedure:
To check the bearing displacement measured in thousands of an inch.

 A. Position the link and the bearing to be inspected between the Axial Assembly (A). The pins are used to secure the bearing and prevent slippage or motion. While supporting the link in one hand, engage the pins by finger-tightening the Axial Assembly Knob (G) to secure the bearing. The knob will “click” when secure and break free if continued to be turned. 

B. Assure the two upper clamps are open and the brass V Blocks (H) are visible. Lay the link in the V-Blocks on Radial Assembly (I), lightly secure both clamps.

 C. Once secure, you are ready to check the Radial or Axial bearing readings.

 D. To check the bearing reading move the handle in one direction, hold it in that position. Then rotate the face of the gauge until “Zero” is aligned with the needle. Release and move the handle in the opposite direction and record the distance traveled. (Axial or Radial).

 1. AXIAL Check – Checking bearing variation of the axial range.

a. Ensure that both Locks on the Axial Assembly and Radial Assembly are backed off and loose.

 b. Actuate the Axial Assembly Handle (B) 2 to 3 times. This will center the bearing in the bearing housing thus ensuring the maximum measurement of Axial movement.

 c. Move the Axial Assembly Handle (B) in one direction and stop. Zero the gauge, release the handle and move to the opposite direction. Record the total Axial reading on the gauge. 

d. After recording the reading, release the bearing within the Axial Assembly (A) and rotate the bearing approximately 120 degrees and retighten. Recheck the Axial reading and record. Release and rotate the bearing one last time, recheck and record, to ensure the bearing is checked in at least three locations. Three checks in various positions are required because no two bearings will wear evenly. The largest measurement of the three will be the final measurement recorded and utilized to determine the actual amount of axial reading.

 e. Compare the recorded Axial reading with the allowable limits from the aircraft technical manual to determine bearing serviceability. 

2. RADIAL Check – Checking bearing variation of radial range. There are two directions to check the Radial reading, Longitudinal and Lateral. Both methods are required and described below in detail. 

A. Lateral – The Lateral direction is along the axis of the link lengthwise (end to end). 

1.) Ensure both the Radial Lock and Axial Lock are backed off and loose. 

2.) Actuate the Radial Assembly Handle (D) back and forth 2 to 3 times. This will center the bearing in the bearing housing thus ensuring the maximum measurement of Radial movement. 

3.) Move the Radial Assembly Handle (D) in one direction. While applying pressure in one direction, grasp the linkage between the on the Radial Assembly Clamps and lightly move up and down vertically. By doing this it allows the bearing to travel the maximum distance in the bearing housing.

 4.) Move the Radial Assembly Handle (D) in one direction. Zero the gauge, release the handle and move to the opposite direction. Record the total Radial reading on the gauge.

 5.) After recording the reading, release the bearing within the Axial Assembly (A) and rotated the bearing approximately 120 degrees and retighten.

 6.) After recording the reading release the bearing between the dowels and rotate the spherical bearing approximately 120 degrees. Recheck the Radial reading and record the Radial measurement again. Release and rotate the bearing again, recheck, and record to ensure the bearing is checked in at least three locations. Use the largest of the three measurements to determine bearing serviceability against the Technical manual.

 B. Longitudinal – Second check is in the Longitudinal direction, or at right angle to the Lateral check, (checking the bearing side to side reading). This last check does not use either handle and is designed to identify that rare bearing that might wear laterally to normal bearing loads. 

Note: The Radial Assemble Gauge (N) mounted on the side of the RAB facing the trammel. This is the gauge that will be utilized for this check. 

7.) Grasp the linkage between the on the Radial Assembly Clamps and lightly move up and down vertically (vertically) while monitoring the additional Radial Assembly Gauge. Record the radial measurement and repeat the process three times while loosing and rotating the bearing in the rod end approximately 120 degrees each time. The largest of the three measurements will be used to determine serviceability against the Technical manual.. 

8.) Use the largest Radial measurement from either “A” or “B” Radial checks, (Lateral or Longitudinal) and compare that number to the Technical Manuals maximum allowable Radial limits in order to determine bearing serviceability. 

2. Final Determination – In order to make the final determination if a bearing has exceeded the applicable aircraft technical manuals maximum allowable range for both the Radial and Axial limits, the readings taken during the initial set-up will now be used to subtract from the maximum readings recorded during the Axial and Radial checks.

A) Axial determination – Using the largest of the three readings taken during  the Axial check, subtract the RAB Tool residual Axial readings recorded during the initial set-up with the fixed link. The resulting reading is the maximum Axial readings of the bearing being checked. 

B) Radial determination – Using the largest of the three readings taken during the Radial check, subtract the RAB Tool residual Radial reading recorded during the initial set-up with the fixed link. The resulting reading is the maximum Radial reading of the bearing being checked. 

D. Trammel Bar Function
The Trammel Bar on the base of the R.A.B. is for the AH-64 Apache Main Rotor Pitch Link only. Because the M/R Link has two replaceable “lollypop” rod ends, it may be necessary at some point to replace an entire rod end, not just the bearing. The Trammel provides the Operator the capability to remove an unserviceable rod end, and reinstall a new rod end to the same settings while taking into consideration the bearing tolerances from both rod ends.

a) Loosen the left hand sliding dowel pin (J) assembly by rotating the thumb (K) wheel. 

b) Position the Main Rotor Link over both Trammel dowels and slide both rod end bearings over each dowel pin. 

c) Adjust the Trammel Gauge to make contact with the dowel arm (L). If not, adjust the gauge position as necessary. 

d) Move the adjustable (Left hand) dowel left and right while observing the Trammel Gauge. Center the dowel between the maximum amounts of travel and lock down. For example if the Trammel gauge reads .030 total play, then center the needle directly in the middle with .015 on either side and lock down the sliding dowel. 

NOTE: By centering the gauge in the middle of the total travel, this sets the link at a nominal setting taking into consideration the Radial play of both Rod End Bearings. A Rod End replaced with a new Rod End containing a new bearing without consideration to the previous bearing play or Rod End positioning could result in several additional track and balance movements during Test Flight.

e) Remove the link from the Trammel Assembly; replace the affected rod end in accordance with the Aircrafts technical manual leaving the jam nut loose.

f) Reposition the newly replaced rod end (thread in or out) until both bearings comfortably fall back in to place on each dowel pin. Retorque the jam-nut in accordance with technical manual procedures. The link is now ready for reinstallation on the aircraft per the T.M.