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Electrical connection to rotating, submerged (oil) shaft

Electrical connection to rotating, submerged (oil) shaft

Electrical connection to rotating, submerged (oil) shaft

Hi all,

For my theseis I have to modify an existing gearbox in order to be able to measure the film thickness in between the gear teeth during loaded rotation of the gears. In order to do so I have to make an electrical connection to a certain shaft withtin the gearbox. This shaft does not exit the gearbox and is fully submerged in lubricant. First I thought about a copper ring around the shaft + use of carbon brushes. But carbon brushes are not supposed to be used in lubricated conditions from what I read. In attachement I put a paper discussing the measureming method that needs to be used for context. Does anybody know a certain component or method that I can use to make this electrical connection?

Kind regards

RE: Electrical connection to rotating, submerged (oil) shaft

Seems to me that this is a purely laboratory measurement; the dielectric constant of an oil film in working machinery presumably changes as a function of contamination, density, general oil condition, temperature, parasitic capacitances, etc.

You can possibly use a slip ring, which is comparable to a brush, but sealed. Note that parasitic capacitances are probably even higher with this, as well as high electrical noise due to the nature of the contact.

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RE: Electrical connection to rotating, submerged (oil) shaft

Depending on how many intermediate gear/pinion arrangements there are between input an output shafts you might consider instrumenting the gearbox EXACTLY how it was done in the paper - shaft brushes exterior to the housing. Measure the result - you now have the TOTAL capacitance through the gear train, which is really what you're looking for.

If you absolutely have to measure in internal capacitance (i.e. intermediate pinion to output pinion), modify the gear housing exterior (and the intermediate shaft) to allow the interior pinion shaft to exit "out to the real world". Then use the paper's approach, monitoring the two shafts that are on either side of the capacitance you'd like to measure.

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