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 (0.0039, 0.1158, 0.3474). 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:
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