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How to assemble a low voltage, variable speed electric motor in a school laboratory, and how to measure its efficiency? Answered

For a high school physics project, I am doing an investigation on how does the density of the transmission fluid affect the efficiency of a fluid coupling. I am planning to use honey based transmission fluid with varying amounts of water to dilute it, and alter and manipulate its density. For the turbines (blades of the fluid coupling) I need to construct a low voltage electric motor with variable speeds using materials easily available in a school laboratory (though I can use some other source for my materials as well). 
I need to measure its efficiency. and by that I mean to actually compare the input and output energies (perhaps their voltages) using a low inertia dynamo as my output generator.


You could try a Tesla disc pump and turbine setup. The pump drives the turbine. II used a 12-volt Subaru blower motor for a Tesla pump drive system in my giant vortex.https://www.instructables.com/id/Tesla-Tornado-Christmas-Tree/

I used a bladeless Tesla disc Pump as the fluid mover creating the vortex. I used a magnetic coupling from the blower motor to make the discs turn.

One concept is to make a Tesla Pump similar to above. (note; There would have to be a housing around the discs and an output pipe.)
Measure the motor input amps and volts. Then, measure the output energy, by recording the pressure and volume of fluid expelled. (instead of using an output dynamo which may be hard to seal against honey!)

Thanks for your reply, mrfixitrick, but I was thinking something similar to the image below. I planned to use a conventional electric motor with variable speed, and a plexiglass tube filled with honey and water solutions at different concentrations to keep track of the density.
any help with this one?

fluid coupling.jpg

Good luck with sealing the Fan and Turbine shafts, and motors, from sticky gooey honey! ;)

As a solution, I would use magnets mounted on the Fan blades and Turbine blades, to drive two fans located inside the plexi tube. The fans inside the tube would have magnets on their blades to magnetically couple, one with the Fan and one with the Turbine.

However, I realize that four sets of 6 magnets could get expensive, as they have to be fairly strong for the coupling effect.