nuts & bolts

building basics

Techniques for Safetying Turnbuckles Ron Sterkenberg

T

urnbuckles are used to adjust cable tension in a cable system or to rig aircraft parts. After rigging the cable system, no more than three turnbuckle threads should be exposed on either side of the turnbuckle barrel. When all adjusting and rigging on the cables is completed, safety the turnbuckles with a locking clip or use safety wire. In most cases the use of the locking clip is easier and preferred, but in areas of high vibration and exposure to the environment, safety wire might be the better choice. Note that locking clips cannot be reused because they are damaged during removal. Always install new locking clips.

Locking Clip Installation Q Make sure there are slots in the barrel and threaded terminals before you attempt to install locking clips. Install safety wire if there are no slots. Q Align the slot in the barrel with the slot in the terminal. There are typically two slots in the barrel 102

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and one slot in the terminal end. Q Insert the straight end of the clip into the opening formed by the aligned slots. Q Insert the hook end of the clip over the hole in the barrel and seat the hook into the hole. Q Apply pressure to the hook shoulder to engage the hook lip in the turnbuckle barrel. A pair of pliers could be helpful. Q Repeat the above steps to safety lock the other side of the turnbuckle. Q Both clips may be installed in the same hole in the barrel, or they may be installed opposite from each other (as pictured).

A locking clip.

Insert straight end into slot.

Safety Wire Techniques The double-wrap methods are the preferred safety wire methods, but in some cases they are not possible or practical and an alternative single-wire method could be used. Single-wire methods are acceptable, but not the equal of the doublewrap methods. All lockwire used in the safetying of turnbuckles should be

Two locking clips.

carbon steel, corrosion-resistant steel, Monel, or aluminum alloy. The smallest wire size that can be used per AC 43-13-1B is .040 inch. This is rather thick, and there are instances in which this wire size won’t fit through the hole in the swaged terminal or eye. In these cases, use the thickest wire that will go through the hole.

Q Bend the sharp end of the safety wire toward the shank with a pair of pliers. Q Repeat the above procedure for the other terminal end.

Wrap four turns.

Single Wire Technique Q Cut a piece of wire about 18 inches long and straighten the wire. Q Insert the wire through the hole in the barrel and bend the ends of the wire toward the ends of the turnbuckle. Q Insert the end of the wire through the hole in the terminal end. Q Wrap the wire around the shank, and wrap it a minimum of four turns around the shank.

Run the wire through the barrel.

Wire runs through terminal end.

Bend sharp end toward shank.

Single Wire Spiral Technique Q Insert a piece of 18-inch safety wire through the hole in the

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building basics terminal. QSpiral the two ends of the wire in opposite directions around the barrel so they will cross each other twice before both wires will be inserted through the center hole in the barrel. Q Spiral the ends of the wires again in opposite directions around the barrel so that they will cross each other twice before both wires will be inserted through the hole in the terminal. Q Lay one wire end along the barrel and wrap the other end at least four times around the shank and cut off the wire end. Q Bend the sharp end of the safety wire toward the shank with a pair of pliers. Q Wrap the remaining wire end at least four turns around the shank

Spiral each end so they cross twice.

Bend the wire in opposite directions.

Continue spiral to terminal hole. 104

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Lay one end straight and wrap the other.

Lay the wire along the barrel.

and cut it off. Q Bend the sharp end of the safety wire toward the shank with a pair of pliers.

Double Wrap Safety Wire Technique Q Insert a wire through the hole of the barrel and bend the ends toward the terminal ends. Q Insert a second wire through the hole and bend the ends toward the terminal ends. Q Pass the two wire ends in opposite directions through the hole in the terminal. Q Lay one wire end along the barrel and wrap the other end at least four times around the shank and cut off the wire end. Q Bend the sharp end of the safety wire toward the shank with a pair of pliers. Q Wrap the remaining wire end at least four turns around the shank and cut it off. Q Bend the sharp end of the safety wire toward the shank with a pair of pliers. Q Repeat the above steps for the other terminal.

Q Insert two wires through the hole in the barrel like in the double wrap method, but spiral the two ends of the wire in opposite directions around the barrel so they will cross each other twice between the center hole and the terminal hole. Q Pass both wires in opposite

Pass the two ends in opposite directions.

Spiral the two wires in opposite directions.

Wrap one around the other.

Bend sharp end toward shank.

Double Spiral Wrap

times around the shank, and cut off the wire and bend the remaining part. Q Wrap the remaining wire at least four times around the shank, and cut off the wire and bend the remaining part flush.

over the free end of the other wire. Q Wrap both ends at least four times around the shank.

Alternative Double Wrap Method Wrap one with the other. directions through the hole in the terminal. Q Lay one wire along the barrel and wrap the other wire at least four

Q If the hole in the terminal is too small to insert two wires, you can use an alternative method. Q One wire is passed through the hole in the terminal and is looped

Bend the remaining wire.

If the hole is too small for two wires.

Loop the free ends of both wires, then wrap them around the shank.

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