Bicycle Torque Coupling
An S and S Coupling also known as a Bicycle Torque Coupling or BTC is a coupling which enables bicycle frames to be separated into smaller pieces, usually to facilitate packing and transporting. They can be built into the frame by the frame manufacturer when the frame is originally assembled or they can be added to a frame after it is finished. A special spanner is available for tightening and loosening the couplers.
The couplers are usually installed in the top tube and down tube of a single-rider diamond frame. This enables the bicycle to be boxed small enough to avoid the extra fee most airlines charge to check a bicycle as luggage. They can also be installed in tandem and recumbent frames. Santana manufactures a "triplet (or quad) that can be transformed into a tandem by simply removing the center section of the frame."
The couplers are available in stainless steel, cromoly steel, and titanium. The couplers come in different sizes, from 5/8 inch (15.8 mm) to 2 inches (50.8 mm) to match the frame tubing in which they are installed. They are light, about 8 oz. (227 grams) per pair, and as strong as uncoupled tubing. The couplers use a Hirth joint to resist torsion.
It takes only a few minutes to separate the couplings.
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