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A Marman clamp is a type of heavy-duty band clamp; it allows two cylindrical objects to be clamped together end-to-end with a ring clamp. It is sometimes also known as a "Marman ring". It consists of a circular strap with an interior V-shaped groove. Tension is applied to the strap with a threaded bolt and nuts connecting to the ends of the strap. As the tension increases, the V-groove wedges over flanges on the circular parts to be assembled, providing the force that holds the ends of the two cylinders together. The Marman clamp is an alternative to a bolted flange connection which would be heavier and require more labor to connect. Another variety uses a flat strap, used where systems carry low pressure or to hold a cylindrical object in position.[1]
A common use for Marman clamps is as quick-disconnect connectors in flexible aircraft fuel lines.[2]
Marman clamps are used extensively in spaceflight systems and are common mechanical load-transfer and clamping mechanisms for connecting the upper stage and the satellite payload of space vehicles,[3][4] for example, on the Cassini Plasma Spectrometer on the Cassini orbiter. They may also be used to join stages of a booster rocket.[3]
Early separation systems using Marman clamps used explosive bolts for release. These have problems of unpredictability, the need to contain debris and difficulties in testing them.[5] A more recent approach uses a screw thread. The tension of the clamp band itself is used to power the unscrewing of a central bolt, when released by a pyrotechnic pin puller triggered by a set of redundant NASA Standard Initiators (NSIs).[6]
The Marman clamp was first produced by Herbert Marx, better known by his stage name Zeppo Marx;[2][7] it was manufactured by his company, Marman Products from the 1930s.[8]
At the time it was designed to secure cargo during transport. The U.S. Military used Marman clamps to transport the atomic bombs used at the end of the Second World War.[9]
Marman clamps are found in many modern moving vehicles, though the screw band type clamp is becoming more popular.[citation needed]