There are two types of static drains. The drains will be referred to as "non-load cell" and "load cell".
The "non-load cell" type of static drain consists of a plate which fits into the cavity of a lower bearing. The "non-load cell" static drain attaches with four 6x32 socket cap bolts. The static drain has a stand that is mounted to a plate which holds a copper-beryllium strip.
The "load cell" type of static drain is mounted with a Phillips screw and a washer. The static drain is mounted to the top of the "load cell" device.
Both types of static drains remove static electricity from the rotor by having the copper-beryllium strip on the surface of the polished bottom retainer bolt.
There are two procedures that make sure that the proper amount of tension is applied to the polished bolt and the static strip.
The Non-Load Cell Static Drain can be upgraded to the Load Cell Static Drain. Refer to Systems Operation, Testing and Adjusting, "Attachments" for information in upgrade kits.
- Measure the distance from the mating surface of the plate on the static drain on the bearing to the polished bolt head. The measurement will be referred to as (A).
- Adjust the angle of the copper-beryllium strip so that the height from the surface of the plate to the tip of the brush is
1.0160 mm (0.040 inch) greater than measurement (A).
- Verify that the replacement charge drain measures
8.6360 ± 0.5080 mm (−.34 ± .02 inch) from the tip to the middle of the bend with calipers.Show/hide table
Illustration 1 g01269970 Check of the Length for the Charge Drain - Add one drop of thread compound into the threaded hole next to the charge drain slot in the load plate.
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Illustration 2 g01269975 Initial Installation of the Charge Drain Strip - Thread the screw through the washer. Install the screw and the washer onto the load plate.
Do not tighten the screw completely. Allow enough clearance so that the washer can slide freely underneath the screw head. Refer to Illustration 2 (B).
- Slide the folded, short end of the drain (charge) into the slot of the load plate and underneath the washer. Refer to Illustration 2 (C).
The drain (charge) should seat all the way to the back of the slot. The washer is oversized. The washer should be positioned so that the washer does not overlap the bend in the drain (charge). Refer to Illustration 2 (D).
- Verify that the tip for the drain (charge) is at the correct angle. Use the gauge block for the drain (discharge).
Slide the gauge block so that the tip of the drain (charge) is resting on the block. Refer to Illustration 3. This should be no more than
(1/8 inch) .If the tip is at the correct angle, then the tip for the drain (charge) will rest flat on the angled surface. Make sure that the tip does not deflect downward when the block is removed.
Do not use the gauge block as a means of bending the charge drain into position. By using the gauge block to bend the drain (charge), the tip will bow.
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Illustration 3 g01269999 Gauge Block - With the tip of a small flat head screwdriver, adjust the bend in the drain (charge). Adjust the bend so that the tip is at the correct height. Make adjustments by applying pressure near the base of the drain (charge).
Do not apply force at the tip of the drain (charge). Force on the tip will cause the tip to bow.
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Illustration 4 g01270035 Adjustment of the Drain (Charge) - Check the height of the tip after each adjustment.
- After the drain (charge) is installed, check for continuity. using the following procedure.
- The commutation sensor should still be disassembled from the flywheel. If the commutation sensor is not removed, remove the commutation sensor.
- With a standard ohmmeter, check continuity between the retaining bolt of the upper rotor and any unpainted, bare metal surface on the flywheel housing.
If there is no continuity, the charge drain has not been installed and adjusted properly.
- If there is no continuity:
- Remove the "load cell" assembly from the lower bearing cartridge.
- Check the installation of the charge drain and the height adjustment.
- Verify that the contact surfaces are clean.
- Check continuity between the upper and lower rotor retaining bolts.
- Reinstall the "load cell" assembly.
- Repeat the check for continuity.
- Once continuity is verified, reinstall the commutation sensor onto the upper bearing cartridge.
- Apply a light coat of vacuum grease to the commutation sensor O-ring. Reinstall the commutation sensor onto the assembly in the O-ring groove.
- Reinstall the commutation sensor with the three mounting screws.
- Remove rotor support shims.
If the rotor support shims are still bound between the rotor and pole ring surface, remove the "load cell" and add a "2 mil" shim to the "load cell" shim package. Reinstall the "load cell".
Note: If the bearing cartridge shim package is measured correctly, then no more than a one shim should be required in this adjustment. If the gap between the Retainer and Bearing is less than "6 mils", the cartridge must be removed and an additional "2 mil" shim must be added to the brass shim package:
- If the gap is "7 mils", one "2 mil" shim may be added to the "Load Cell" shim package.
- If the gap is "9 mils", two "2 mil" shims may be added to the "Load Cell" shim package.
If the load plate should become stuck, try to wiggle it loose by hand. Do not use a screwdriver or any other tool because of the risk of damaging the charge drain.
- Apply Dow-Corning High Vacuum Grease to the O-rings that are located on four plugs.
- Install four plugs.
- Connect the "load cell" cable, 19 pin instrument connector and vacuum hose on the bottom of the flywheel.
- Connect the thermistor and 19 pin instrument connectors at the top of the flywheel.
Note: Refer to Systems Operation, Testing and Adjusting, RENR9988, "Flywheel Load Cell - Calibrate" for the Load Cell Calibration procedure.
- Complete the following:
- Remove the "load cell" assembly from the lower bearing cartridge.
- Check the installation of the charge drain and the height adjustment.
- Verify that the contact surfaces are clean.
- Check continuity between the upper and lower rotor retaining bolts.
- Reinstall the "load cell" assembly.
- Repeat the continuity check.
- Once continuity is verified, reinstall the commutation sensor onto the upper bearing cartridge.
- Apply a light coating of vacuum grease to the commutation sensor O-ring. Reinstall the O-ring onto the commutation sensor assembly in the O-ring groove.
- Reinstall the commutation sensor with three mounting screws.
- Remove rotor support shims.
If the rotor support shims are still bound between the rotor and pole ring surface, remove the "load cell" and add a "2 mil" shim to the "load cell" shim package. Reinstall the "load cell".
Note: If the bearing cartridge shim package is measured correctly, then no more than a one shim should be required in this adjustment. If the gap between the Retainer and Bearing is less than "6 mils", the cartridge must be removed and an additional "2 mil" shim must be added to the brass shim package:
- If the gap is "7 mils", one "2 mil" shim may be added to the "Load Cell" shim package.
- If the gap is "9 mils", two "2 mil" shims may be added to the "Load Cell" shim package.
If the load plate becomes stuck, try to wiggle it loose by hand. Do not use a screwdriver or any other tool because of the risk of damaging the charge drain.
- Apply Dow-Corning High Vacuum Grease to the O-rings that are located on four plugs.
- Install four plugs.
- Connect the "load cell" cable, 19 pin instrument connector and vacuum hose on the bottom of the flywheel.
- Connect the thermistor and 19 pin instrument connectors at the top of the flywheel.
Note: Refer to Systems Operation, Testing and Adjusting, RENR9988, "Flywheel Load Cell - Calibrate" for the Load Cell Calibration procedure.