Bob and shaft designs for portable rheometry units

A viscometer in a portable rheology unit, comprising:

• a motor;
• a switch operatively connected to the motor, wherein the switch is configured to connect the motor to an electrical source;
• a cup with an interior configured to hold a drilling fluid;
• a bob defining an open volume and configured to be at least partially submerged in the fluid;
• a driving mechanism connected to the bob and the motor, wherein the driving mechanism conveys rotational movement from the motor to the bob to rotate the bob;
• a strain gauge configured to measure a torsion resistance of fluid interacting on an exterior portion of the bob;
• and
• a platform configured to support the cup, wherein the platform is configured to move from a first position wherein the bob is outside of an interior of the cup to a second position wherein at least a portion of the bob is located within the interior of the cup.

A method of performing a viscosity test, comprising:

• pouring a drilling fluid into a cup of a viscometer;
• immersing a hollow bob with an attached hollow sleeve into the drilling fluid within the cup;
• rotating the hollow bob in the drilling fluid with a motor;
• and
• reading a viscous drag of the drilling fluid on the hollow bob by a torsion measuring apparatus.