What’s a happy hand?

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A glad hand is a device used to connect air lines on railway carriages and semi tractor trailers. It is made of cast aluminum with a rubber gasket for a leak-proof seal. It is important to keep the device clean and free of debris to prevent damage to the braking system.

A glad hand is a device found at the end of an air line that connects to another air line. It is found on railway carriages and somewhat resembles a pair of hands involved in a handshake. The two hands are connected by placing them together at right angles and then turning them to form a straight line. To remove the air line, the two content hand assemblies are simply twisted at a 90 degree angle.

While a cheerful hand is found on many train cars, perhaps the most common location for this assembly is on a semi tractor and trailer. The lines used to supply air to the trailer to operate its braking system flow from the trailer’s air tanks through a joystick and into the trailer’s tanks. Although they are much smaller, they are exactly like those used on a train. Assembly and disassembly is the same too.

Typically made from cast aluminum, a merry hand has a small rubber gasket located centrally and surrounding the air hole. When brought together, the two rubber gaskets sit against each other, providing a leak-proof seal for the air system. A small dowel cast into the device locks into a clip on the opposite content hand and snaps them into place when connected.

On semi tractors, the rigs often get packed with dirt and debris riddled with driving miles without a trailer attached to the tractor. It is imperative that water, dirt and debris be removed from attachments before hitching to a trailer. Water is an especially dangerous enemy as the air pressure will force it deep into the air lines of the trailer and it could freeze and cause serious problems during inclement weather. The covers must be placed over unused accessories or connected to the dummy connection at the rear of the tractor cab.

Maintaining accessories is an easy task. Keep dirt, water and debris out of the fittings and apply a little grease to the rubber gasket to keep it flexible. Replacement gaskets are readily available at most truck stops and simply pop out and push in. The air line that runs to the accessory should also be checked for cracks and abrasions and repaired before they rupture and cost the vehicle its braking system.




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