Turnbuckle

Small turnbuckle (80 mm)

A turnbuckle, stretching screw or bottlescrew is a device for adjusting the tension or length of ropes, cables, tie rods, and other tensioning systems. It normally consists of two threaded eye bolts, one screwed into each end of a small metal frame, one with a left-hand thread and the other with a right-hand thread. The tension can be adjusted by rotating the frame, which causes both eye bolts to be screwed in or out simultaneously, without twisting the eye bolts or attached cables.

Turnbuckle is also a term used in computer science to refer to the user interface element also known as an Expansion Triangle.

Uses

The corner structure of a wrestling ring showing the attachment of the ring ropes to the ring post via the padded turnbuckles

Turnbuckles are most commonly used in applications which require a great deal of tension; they can range in mass from about ten grams for thin cable used in a garden fence, to thousands of kilograms for structural elements in buildings and suspension bridges.

Construction

Turnbuckles with various size are popularly used in construction. They combine strength and durability, yet are simple to set up and adjust. Very small turnbuckles (as light as 10 grams) might be used to support a fence in a garden. On the other hand, extremely large turnbuckles (as heavy as several thousand kilograms) are widely used as support high-rise buildings or in structures such as bridges.

Aircraft

Turnbuckles have been used in aircraft construction. Historically, biplanes might use turnbuckles to adjust the tension on structural wires bracing their wings. Turnbuckles are also widely used on flexible cables in flight control systems. In both cases they are secured with lockwire or specifically designed wire clips to prevent them from turning and losing tension due to vibration.

Shipping

Turnbuckles are used for tensioning a ship's rigging and lashings. This device is also known as a bottlescrew in this context.

James Craig, main topmast fore stay bottlescrew

Sports

Turnbuckles find common use to tension the ropes in professional wrestling rings and boxing rings, where they serve as the attachment between the ring ropes and ring posts. Rather than the usual bare metal, here the turnbuckles are covered with padding in order to protect participants and staff. Turnbuckles even play a part in professional wrestling where they are often dramatically used by participants as part of their offensive repertoire.

Entertainment industry

Turnbuckles are used in nearly all rigging performed in the entertainment industry, including theatre, film, and live concert performances. In entertainment rigging, turnbuckles are more commonly used to make small adjustments in line lengths. This is generally to make a flown unit sit parallel to the stage. Another way a turnbuckle could prove helpful is with making very minor height or angle adjustments.

Pipe systems

Turnbuckles are used in piping systems as a way to provide minor adjustments for field inconsistencies. This also allows for a minimum amount of resistance when transferring the load to the support components.

See also

• Buffers and chain coupler
• Guy-wire
• Mechanical joint