The M3 Tripod
http://atiam.train.army.mil/portal/atia/adlsc/view/public/296764-1/fm/23-65/ch1.htm
The M3 tripod is on of many mounting systems used for the M2 .50 cal. The M3 is strictly used when the weapon is ground mounted. The M3 consists of three adjustable legs which support the weight of the weapon as well as transfer the energy of the recoil from the weapon to the ground. The M2 causes incredible forces on the tripod and can actually move the entire weapon system. To keep the the weapon from moving the tripod must be dug into place. Each leg is dug in separately so the recoil does not push the tripod backwards and then each leg of the tripod must be weighted down(usually with sand bags) so to keep the tripod from moving during firing. Even after the weapon has been dug in some settling may occur during the first shots of the weapon.
Free Body Diagram for the M3 tripod when weapon is at rest.
Where
all have an x and y component, g is gravity, M is the mass of the machine gun, and Fn is the normal force.
Free Body Diagram of the M3 tripod During firing.
Fr is the force caused by the recoil of the weapon and has both x and y components.
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