Propeller Thrust & Torque Test Rig

Blackfish was asked to supply a test rig that compared the performance of different propellers. Different coatings were being used on the propellers in order to see how they degrade with time, being left in the seawater for a 6-month campaign.

PML Applications undertake all kinds of research into corrosion and biofouling for offshore sectors. This rig was required in orderr to make detailed assessmetn sof long term anti-fouling paint performance for propellers.

Different identical propellers were painted with different paints and then installed on this rig to monitor how the propeller thrust and torque changed with long term immersion over a 6 month period. Load cells were used to measure thrust and torque individually, whoch were logged and presetned as data files.

Blackfish designed, managed manufacture and installed the rig in plymouth Marina, complete with cover to keep the seagulls away.

The rig was so good that it actually detected a micron level manufacturing fault, resulting in a different profile for one ofthe propellers that was not apparent previously.

Challenge

The test rig needed to monitor thrust, torque, speed very accurately and have a meaningful way to present the result to the client. The unit also needed to be easily deployed and retrieved, as well as having the ability to be stored long-term on the quayside.

Approach

We designed a system whereby the mass of the unit being tested was balanced with a dumb counterweight. This enabled us to use a much more sensitive load-cell to measure the thrust. The torque was measured in-line and also verified by the motor current, and the speed was logged as well. It all came together using custom software that was used to log the data and show the results.

Outcome

The client was able to carry out the testing campaign with no reliability issues from the hardware. The sensitivity of the rig was so good, it enabled the client to detect an unexpected variance in one of the propeller's profile, and subsequently found that it was not the same as the others being used, which happened to be identical to the eye.

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