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                For my project, I reverse engineered an old oilfield viscometer. The goal of this machine is to measure the viscosity of an oil sample for processing processes. The viscometer used a gear train to rotate the oil sample at a constant angular velocity. A cylinder of known size was inserted into the sample and the viscosity of the sample caused the cylinder to rotate. The shear force that caused this motion was counteracted by a torsional spring in the display dial. By knowing the angular output of the sample and the angular displacement of the dial, we can calculate the viscosity of the fluid.

                                Some interesting findings of this mechanism was the adjustability of the mechanism. By changing out the dial spring, one would be able to change the torsional spring factor and measure a different range of viscosities for the device. For the measurement of crude oil samples, only one torsional spring is needed to measure the full range of viscosities. The mechanism had two input motor speeds of 900 and 1800 rpm and three different gearing ratios (0.03760039, 0.11941158, 0.35813474). These three different settings were needed in order to cover the range of viscosities that could be seen in the oilfield. According to Petrowiki¹, the range of crude oil viscosity is between 0.001N-m/s² and 1 0.001N-m/s². With a torsional spring constant of 0.002 N-m/rad and the three gear settings, the whole range of oilfield sample viscosities may be tested. The angular velocities of the sample with the varied motor input and gear setting are as follows:

As we can see, the different gear trains and motor speeds can allow for a wide range of angular velocities of the sample. Therefore, the sample can be subjected to a variety of shear rates and a variety of shear forces. These shear forces are converted into an angular displacement in the dial, which is measured.

The range of viscosities that can be tested accurately (0.5°<θ<300°) at are as follows:

In the appendix, I wrote a MatLab file in which one can input the angular displacement of the dial and the output of the program would be the viscosity of the fluid. Furthermore, the program suggests when you should increase or decrease the gear ratio or motor speed to be able to measure the viscosity of the fluid accurately. Furthermore, the program will create a digital dial in which the graph rotates with the change in viscosity of the fluid. The program works in reverse as well. If one knows the fluid's viscosity, the angular displacement of the dial can be calculated and graphed. The following is an example with the input of the program was a viscosity of 1 N-s/m^2, high motor speed, and the lowest gear ratio.

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Find viscosity [1] or angular displacement [0] : 0
Fluid dynamic viscosity in N-s/m^2 : 1
Motor speed high [1] or low [0] : 1
Gear high [2], medium [1], or low [0] : 0
Angular displacement of cylinder is 124.9622 degrees.

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The following is an example with the input of the program was a viscosity of .001 N-s/m^2, high motor speed, and the highest gear ratio.

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Find viscosity [1] or angular displacement [0] : 0
Fluid dynamic viscosity in N-s/m^2 : 0.001
Motor speed high [1] or low [0] : 1
Gear high [2], medium [1], or low [0] : 2
Angular displacement of cylinder is 1.1908 degrees.

>>This table shows that the viscometer can accurately measure the expected range of crude oil samples with just one machine and one torsional spring. There is no need to switch out springs to adjust for an extreme viscous sample. This fact is one of the wonders of this mechanism.