assemblies have been installed.
(1) Attach brush block assembly, spacers, and shims (thin washers) to the mounting bracket with the two screws and washers provided. Locate the brush block on the mounting bracket using care not to exert any side loads on the brushes which may cause breakage. Secure, but do not tighten the two mounting screws at this time.
C. Brush Block Assembly Alignment Requirements
(1) In order to get smooth, efficient and quiet transfer of electrical current from the brushes to the slip rings, brush alignment must be checked and adjusted, if necessary, to meet two requirements:
(a) Brush Projection. Projection must be such that the distance between the brush holder and the face of the slip rings is 0.064 inch, +0.015 or -0.015 inch, through 360 degrees of slip ring rotation.
(b) Face Alignment. The brushes must be lined up with the slip rings so that the entire face of each brush is in contact with the slip ring throughout the full 360 degrees of slip ring rotation (refer to Figure 403).
D. Brush Block Alignment Methods
(1) Brush Projection. Brush projection can be adjusted by loosening the two screws attaching the brush block assembly to the mounting bracket and holding the brush block in the designated position while retightening the screws. Slotted holes are provided in the mounting bracket for this purpose. Torque screws in accordance with the applicable installation drawing in the McCauley Propeller Systems Application Guide.
(2) Face Alignment. Face alignment of the brushes must be adjusted by removing the two screws that hold the brush block to the mounting bracket. Add or remove the thin washers (shims) under each spacer as required to correct alignment. Reinstall screws and lockwire screw heads.
Torque screws in accordance with the applicable installation drawing in the McCauley Propeller Systems Application Guide.
Brush/Slip Ring Alignment Figure 403 (Sheet 1)
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Page 421© McCauley Propeller Systems Aug 18/2014
(3) Testing Alignment. When a chattering or screeching noise is emitted from the brush/slip ring area, the probable cause is the improper alignment of the brush block and slip ring assemblies.
NOTE: Chattering or screeching may be detected by pulling each propeller through slowly in the direction of rotation and should be corrected immediately.
If this chattering or screeching noise is noticed over idling engine noises, the trouble is severe and should also be corrected immediately.
As a general rule, engines should be run for one hour before energizing the deice system. This will ensure proper seating of the brushes to the slip rings and prevent any arcing which could cause radio noise or rapid wear of the brushes.
5. Wiring Harness Or Lead Strap Installation
A. General. There are basically two methods of transferring electrical current from the slip ring assembly to the deice boots.
(1) With a detachable lead type deice boot a separate wiring harness is used to transfer electrical current from the slip ring to the deice boot.
(2) On installations using integral lead type deice boots the lead strap of the boot is attached directly to the slip ring assembly.
B. Installing Wire Harness (Detachable Lead Type Boot)
(1) First attach wiring harness leads to the deice boot lead mounting bracket with hardware provided as shown in Figure 404.
(a) For wire harnesses that use a mechanical clamp as shown in Figure 404, make certain that harnesses are located in the clamp so that the shoulder of the molded rubber portion of the harness is against the side of the clamp.
(b) For wire harnesses that do not use a mechanical clamp as shown in Figure 406, make certain that the wire harnesses are captured by the tie straps as shown.
NOTE: Proper security of the wire harness at the deice boot lead mounting bracket will help prevent damage to the harness due to centrifugal force.
(2) After the harness is connected to the deice boot leads, route the remainder of the harness to the slip ring assembly.
NOTE: Make sure the deice leads do not chafe the lockwire that secures the propeller blade balance weight holder. If required, install spaghetti tubing over the lockwire between the screws that secure the balance wight holder to the propeller blade.
(a) Some wire harnesses will come with an alignment mark to help locate the wire harness, refer to figure 406.
(b) Most installations will secure and support the harness to the propeller bulkhead with a clamp located on the spinner bulkhead.
(c) Make sure all excess harness length is placed between the clamp/spinner bulkhead and the attachment to the deice boot leads. This will ensure proper harness length when the propeller blade is in its furthest angle away from the bulkhead clamp, whether it be reverse or feather position, depending upon the application.
(d) In addition to securing the deice harness to the clamp provided for attachment to the deice boot lead mounting bracket, some applications will require additional clamping on the blade shank or to the blade counterweight, refer to figure 406. For these installations, make sure all excess harness length occurs between the bulkhead clamp and the last clamp/
attachment located on the blade shank.
(e) On all applications requiring additional clamping to the blade shank a special balance weight holder is supplied as part of the propeller assembly. This special holder has a provision for mounting the clamp refer to Figure 405.
(3) After connecting the harness to the deice boot leads and clamp, bulkhead clamp and any additional blade shank clamps, route the remaining harness length to the slip ring assembly.
Some applications require that the harnesses extend through the spinner bulkhead. On these applications, grommets are required in the bulkhead to prevent breakage of the harnesses.
Some applications, using extended hubs, require that the wiring harnesses be routed along the propeller hub and are held in place with nylon tie wraps. Attach leads to corresponding slip ring studs with nuts and washers provided.
C. Installing Lead Straps (Integral Lead Type Boot)
(1) The lead straps should be clamped to the spinner bulkhead with clamps provided. All excess strap length should fall between this clamp and the deice boot. A rubber grommet is to be used when routing the strap through the spinner bulkhead. Attach leads to the corresponding slip ring studs with nuts and washers provided. Torque nuts in accordance with the applicable installation drawing in the McCauley Propeller Systems Application Guide.
NOTE: Leads for both the wiring harnesses and lead straps are marked for attachment to the slip ring studs and to the deice boot leads when using the wire harness. However, the slip ring studs of the slip ring assembly are not marked. In all cases the smallest diameter slip ring is used as the ground, "G" connection. On a three ring slip ring assembly the largest diameter ring is used for the outboard or "0" connection and the middle ring is used for the inboard or "I" connection.
(2) After installation of the wiring harnesses or lead straps is complete, make sure that the length is sufficient so as not to be placed in tension when the propeller is moved through full pitch range.