Alignment Of New Brushes; Slip Rings; Machining Of Slip Rings; Replacement Of Slip Rings - Piper Navajo Chieftain PA-31-350 Service Manual

NAVAJO CHIEFTAIN SERVICE MANUAL
NOTE
If concentricity is not obtained or if residual solder is allowed to
flow on the exterior of the barrel, the barrel may catch on the
brush block causing the brush to "hang-up" and consequently,
the system will malfunction.
j. Place tubing over the brush lead. (Refer to Figure 14-14.) Soft solder the brush leads to the appropriate
pin in the connector plug. Wicking on the leads should be held to .125 maximum.
k. Wipe flux from leads and connector pins.
1. Pull tubing up over connector pins to insure that no electrical shorts exist and, if necessary, bend the
leads away from each other.
m. Reinstall the connector plug to the brush block, utilizing the hardware removed in step 14-37, d.
n. Carefully remove the rubber bands from the brushes.
o. Assemble the brush block per paragraph 14-36, b.
p. Check for free movement of brushes by pushing the brushes back into the block and allowing the
spring pressure to return them. DO NOT SNAP. If free movement is impaired, correct the restriction and
recheck. In particular, check the concentricity requirement in paragraph 14-37, i.
q. Reinstall the brush block to the mounting bracket utilizing the hardware removed in paragraph 14-35, a.
14-38. ALIGNMENT OF NEW BRUSHES. Anytime the brush block assembly is dismounted, the alignment
at reinstallation must be checked as described in paragraph 14-33, fand Figure 14-12.
NOTE
A brush alignment tool is available (Piper P/N 762 109) for
checking and adjusting brush alignment. (Refer to Figure 14-15b.)
14-39. SLIP RINGS.
14-40. MACHINING OF SLIP RINGS. Slip rings with roughened or damaged surfaces can be machined to
restore to serviceability. Remove the starter ring gear assembly from the aircraft to mount it in a lathe, located
concentrically in the lathe and with not over 0.002 inch wobble or run-out over 360
°
rotation with respect to
mounting surface of starter gear/slip ring assembly. Take light cut for smooth finish and cut no deeper than
required to remove surface damage. Contact surfaces of the three slip rings must be parallel within 0.005 inch
and flat within 0.005 inch overall- deviation from flat not to exceed 0.002 inch over a 4 inch arc. If necessary,
undercut insulation between slip rings to a depth of 0.030 inch below the contact surface of the slip rings. In
this operation, width of slip ring must not be reduced more than .005 inch. Contact surface of slip rings must
have a finish of 29-35 micro inches. Deburr slip ring edges and install on airplane.
NOTE
If in machining, the solder or braze connection on the underside of the slip ring is exposed, replacement of the
ring gear assembly will be necessary.
1441. REPLACEMENT OF SLIP RINGS. Starter ring assemblies that are open or shorted electrically,
cracked or damaged structurally, or which have damaged surfaces beyond the scope of minor repair to clean
up, should be replaced with a new starter ring assembly.
Revised: 3/31/94
ACCESSORIES AND UTILITIES
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