Figure 3-29.--Safetying a V-band coupling.
the snap ring firmly seated in a groove. The external
6. Tighten the coupling firmly with a ratchet
types are designed to fit in a groove around the outside
wrench. Tap the outer periphery of the coupling with a
of a shaft or cylinder. The internal types fit in a groove
plastic mallet to assure proper alignment of the flanges
inside a cylinder. Special pliers are designed to install
in the coupling. This will seat the sealing edges of the
each type of snap ring.
flanges in the gasket. Tighten again, making sure the
recommended torque is not exceeded.
Snap rings can be reused as long as they retain their
shape and springlike action. External snap rings may be
7. Check the torque of the coupling with a torque
safety wired, but internal types are never safetied.
wrench and tighten until the specified torque is
obtained.
STUDS.--There are four types of studs used in
8. Safety wire the V-band coupling, as shown in
aircraft structural applications. They are the coarse
figure 3-29, as an extra measure of security in the event
thread, fine thread, stepped and lockring studs. Studs
of T-bolt failure. The safety wire will be installed
through the band loops that retain the T-bolt and the
trunnion or quick coupler. A minimum of two turns of
the wire is required. Most V-band connectors will use a
T-bolt with some type of self-locking nut.
TAPER PINS.--Taper pins are used in joints that
carry shear loads and where the absence of clearance is
essential. See figure 3-30. The threaded taper pin is
used with a taper pin washer and a shear nut if the taper
pin is drilled, or with a self-locking nut if undrilled.
When a shear nut is used with the threaded taper pin and
washer, the nut is secured with a cotter pin.
FLAT-HEAD PINS.--The flat-head pin is used
with tie rod terminals or secondary controls that do not
operate continuously. The flat-head pin should be
secured with a cotter pin. The pin is normally installed
with the head up. See figure 3-30. This precaution is
taken to maintain the flat-head pin in the installed
position in case of cotter pin failure.
SNAP RINGS.--A snap ring is a ring of metal,
either round or flat in cross section, that is tempered to
have springlike action. This springlike action will hold
Figure 3-30.--Types of aircraft pins.
3-17
