Infinite holding pivot mechanisms for dual screen systems

An encasement for a mobile computer, comprising:

• an external casing in a clamshell form factor, the external casing comprising a base, a secondary display chassis hingedly connected to the base at a secondary hinge, and a primary display chassis hingedly connected to the secondary display chassis at a primary hinge;
• a current driver circuit to selectively apply an electrical current;
• and
• a one-way roller clutch disposed on the secondary hinge, the a one-way roller clutch comprising a shape memory alloy (SMA) spring in opposition to a compression spring of the one-way roller clutch, wherein the SMA spring is electrically connected to the current driver circuit and receives therefrom the electrical current, wherein the one-way roller clutch and SMA spring together freely permit upward rotation, bias against downward rotation when the electrical current is absent, and permit downward rotation when the electrical current is present.