[PSUBS-MAILIST] Thruster Reliability

Wed Jul 26 11:43:13 EDT 2023

 Thanks Carsten. This low viscosity silicon oil looks good.  I like the fact that it is inert to metal and plastics.  I don't think that it's preventing of gluing would impact anything I do on the Minn Kota 101s.
Cliff
    On Wednesday, July 26, 2023 at 10:01:32 AM CDT, MerlinSub at t-online.de via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

The glue of the permanent magnets can be affected. 

I use silicone oil with a low ct around 1 after bad expierence wir air compensation. 

But oil compensation needs also an compensator.bag. 

Siliconeoil is inherend to metal and plastic. (But prevent re-glueing) 

ELBESIL SILIKONÖL B 1 (1 cSt) - 500 g - SILIKON-PROFIS

vbr Carsten

. 

-----Original-Nachricht-----

Betreff: Re: [PSUBS-MAILIST] Thruster Reliability

Datum: 2023-07-26T14:36:40+0200

Von: "Cliff Redus via Personal_Submersibles" <personal_submersibles at psubs.org>

An: "River Dolfi via Personal_Submersibles" <personal_submersibles at psubs.org>

 These reports look good.  I am in the process of digesting them.  Is this the Univolt transformer oil you use?  Kinematic viscosity is low at 2.3 cSt. https://www.mobil.com/en-us/industrial/pds/gl-xx-univolt-n-61-b Good point compatibly issues and need for testing.  The good news on the MK 101's is there are only a few parts to evaluate, lips seals, brushes, wire insulation and for my case, a Subconn connector.  The other parts are metal.  I don't think the permanent magnet would be affected. Cliff  On Tuesday, July 25, 2023 at 07:07:54 PM CDT, River Dolfi via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  Cliff,Those sound like signs of an incompatible fluid to me. Especially considering the length of time that the thrusters were filled with WD40 compared to the hours they have run in the field. The US Navy created a bunch of technical reports on various aspects of deep submergence systems design, and distributed them among defense companies and researchers as part of the "Deep Submergence Systems Project" in the 60's and 70's. All of the documents are now approved for public release and readily available online. This one is particularly interesting and relevant to this conversation. I consult it often enough that I have a physical hard-copy on my office shelf."Handbook of Fluid-Filled, Depth/Pressure-Compensating Systems for Deep Ocean Applications"https://apps.dtic.mil/sti/citations/AD0894795There is also:Handbook of Fluids and Lubricants for Deep Ocean Applicationshttps://apps.dtic.mil/sti/citations/AD0866350 I suspect that the bushing wear is caused by the low viscosity of the WD40 making it a poor choice for lubrication. I've always been told WD40 is a penetrating oil, not a lubricating oil. I maintain and operate a small fleet of ROV's and AUV's that routinely work at a depth of 6000m. All of them use motors that are compensated with either univolt transformer oil where high voltages are involved, or a silicone oil. The caveat being that all of these are brushless electric motors, so don't have the complications of carbon fouling of the fluid. We have been evaluating fluids that can serve as both a hydraulic system oil and an electrical system compensation oil, as we currently run two separate oils for each function. The problems we are running into are material compatibility with existing components. Things like wiring, heat shrink, seals, adhesives, etc. We know what not to do with Silicone and Univis, but the only way to determine the compatibility of a particular oil with a particular off the shelf or proprietary component, like a Minn Kota or any other motor, is testing. Thanks, -River J. Dolfi
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