[PSUBS-MAILIST] Motor modification

Sun Dec 11 16:46:48 EST 2016

Rick & all,I have my thruster running in a swimming pool at the moment.I have it oil filled with the oil continuing up the wiring tube.I made a note of the oil level in the tube before running, then notedthe level had risen by a few inches while the motor was running.Obviously the centrifugal force of the motor is pushing the oil out.   This is probably not a problem at depth  where the water pressureacting on the bladder would  stop that happening. But while running on thesurface it would keep oil away from bearings & the rotary shaft seal.   Although I am using lip seals at the moment, I will be using mechanicalseals in the next version,  & it will be important to keep oil on the sealfaces. This makes a good case for a compensator with over-pressure,to counteract this.Cheers Alan

      From: Rick Patton via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Monday, December 12, 2016 7:12 AM
 Subject: Re: [PSUBS-MAILIST] Motor modification

Alan,
OK, then it sounds like a semi filled flexible oil bladder is the best way to go. It is more unsightly and needs to be secured somehow so it doesn't flop around while under-weigh compared to the coiled tube idea but bottom line is what works the best. I didn't realize that there were two 0 rings in the Minn-Kota motors until just recently when this thread started and I agree that that void should be filled with liquid so will look into the feasibility of that. We have two mountains here on the big Island that top out just under 14,000 feet and they usually get snow on the tops every year. There is one on Maui as well but usually doesn't get as much. It's funny to see some people drive up there and fill their pick ups with it and drive back down to their house at sea level and shovel it into there yard for the day!
Rick
On Sat, Dec 10, 2016 at 5:45 PM, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Rick,
I think the problem with the tube is not so much that it won't allow for expansion,
but that it won't collapse under pressure before water can leak past your seal.
   Karl Stanley told me he air compensated his thrusters on Idabel (that goes to 2000ft)
with a first stage regulator with spring removed to give ambient pressure. When I asked 
him how the expanding air escaped on ascent he told me it just blew out past the seal.
   I wouldn't do that as it could destroy the seal, but it demonstrates what you can
get away with. Vance pulled Karl's motors apart & said there was a bit of water in them,
but that it could have been from condensation of water from the several atmospheres of air
that would be compressed in there.
   Alec used the tube wrap system on Snoopy as did other Psubbers. I believe he
did get water in, in the latter stages.
   There is a gap between the two seals in the Minn kota 101 & one of them will fail
if you take it deep enough. So you will end up with either oil or water in the gap.
If you regard the outer seal as sacrificial & just there to stop sand & crud damaging
the inner seal, then I guess it's not a big deal. Vance has said he regards the 101
as a disposable unit. I think the cheapest purpose built thrusters start around $4000-
   Best as Sean says, to have an expansion / compensation bag. Better to add some 
pressure to it so that oil is more likely to flow out than water flow in. Microscopic
spiral lines on the shaft from machining can pump water in or oil out.
   I have built an oil filled brushless thruster that I am pool testing at the moment. 
A bit of work to go on it yet, but it's looking promising.
   Snow in Hawaii??? 
Alan

      From: Rick Patton via Personal_Submersibles <personal_submersibles at psubs. org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs. org> 
 Sent: Sunday, December 11, 2016 7:42 AM
 Subject: Re: [PSUBS-MAILIST] Motor modification

Hey Alan,
Been tied up for a couple days since this post but thanks for the heat/expansion/volume data as it makes it much easier to comprehend. Based on what I see here, is it safe to assume that due to the amount of expansion of oil, just wrapping the motor several times with the clear PVC hose and connecting the other end to the second barbed fitting on the motor would not work due to the fact that the hose would not expand enough to allow for the volume of expanded oil where as a bladder half filled would work better? Also would like to hear from the others out there who have used only the clear hose to see if they have had any issues with leakage? 
Thanks allRick
On Wed, Dec 7, 2016 at 1:42 PM, Alan James via Personal_Submersibles <personal_submersibles at psubs. org> wrote:

Rick,Sean's beat me to it, but I'll add that you can usually look upyour compensating oil's coefficient of thermal expansion, &calculate how much it will be. Engine oil is about .0007. Thatwould mean that if you had a liter of oil (1000cc) & the temperaturewent up by 50 degrees C, then the oil would expand another 35cc.Not a lot given  that you would not require a lot of oil in the thruster.Getting the air out could be a bigger problem & it would expand more.In a declassified military document on compensating I read , it talksabout & demonstrates how to pull a vacuum on a thruster to get allthe air out.Another issue that I mentioned earlier is that all seals leak oil tolubricate themselves, so having a reservoir makes sense.What I am doing is enclosing my motor wiring in a hose & fillingthe motor & hose with oil. In to this I will have a T to a relieving regulator(PR 364) that will pressurize the system with air at 4psi above ambient.Carsten & Emile had all sorts of problems about oil expanding & leakingthen contracting & sucking in water. Will re post their emails if Ican find them.Regards Alan

      From: Rick Patton via Personal_Submersibles <personal_submersibles at psubs. org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs. org> 
 Sent: Thursday, December 8, 2016 10:38 AM
 Subject: Re: [PSUBS-MAILIST] Motor modification

Alan,
I am embarrassed to say that I am still not getting this concept. You mentioned in your email about the clear hose that people wrap around there Minn-Kota motors and mention about collapse pressure and also mention about lighting systems. Maybe we are talking about two separate things? My question was based on wondering about that same clear tubing that wraps around the motor pods to allow for when the oil gets hot from use and expands.Taking any air out of the equation, I got the impression that you could completely fill a motor with dielectric oil (or any liquid for that matter) and then take it to any depth and since you basically can't compress a liquid, there would be no water ingress to the motor (except for the small space between the two prop shaft 0 rings.) So now when you add a slight internal increase in pressure from the oil being heated from use, people use the clear tubing that wraps around the outside of the motor (which is also 100% filled with the same oil) as a place for the oil to go to expand rather that spitting out the prop shaft 0 rings. Am I correct so far?So my question was, the clear hose wall must be flexible enough to allow for expansion before placing enough pressure on the prop shaft 0 ring to dislodge? And then if you don't get all the air out of the motor or clear hose or bladder, don't you have the water pressure trying to compress that bubble from not only the bladder or tube but past the shaft 0 ring as well? 
Rick

On Mon, Dec 5, 2016 at 11:03 AM, Alan James via Personal_Submersibles <personal_submersibles at psubs. org> wrote:

Some compensating thoughts.
On James Cameron's sub they used IV drip bags. I am not sure what they were compensating.
These come with various means of hose attachment.
   With regard to the wrap around hose method; I did some calculations on a standard pvc hose, & surprisingly
the colapse pressure was around 100psi. I am sure one of Nuytco's technicians told me they crimped the hose 
that was compensating their lights, to initiate the collapse of the hose for compensation.
   The industry standard for thrusters seems to be around 4psi internal overpressure,
but the compensators they use for this are relatively expensive. Hugh came up with
the novel idea of using a releiving regulator set at 4psi (Parker PR364). Cliff is using this.
This could be used for air or oil compensation.
   The seals need oil for lubrication, & I have read that they can use about a teaspoon a day. Based
on that I would have some sort of reservoir.
   Depending on the motor it may be tricky to get all the air out. If you have a bearing in a bore
followed by a seal, the air / oil would have to move through the bearing which may be a sealed type
or packed with grease. The Minn kotta diagrams I have seen show 2 seals; so how do you get oil or
ambient pressure between those? One will fail when you exceed it's pressure limit.
Alan

      From: James Frankland via Personal_Submersibles <personal_submersibles at psubs. org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs. org> 
 Sent: Tuesday, December 6, 2016 4:44 AM
 Subject: Re: [PSUBS-MAILIST] Motor modification

Hi Antoine\Hank.
Thanks guys.  drinking bladder looks good.  I was thinking of a furniture lift bag, which is very similar.  I use a hot water bottle for the aft motor. Hank, what do you use for a bladder? ThanksJames  
On 5 December 2016 at 13:18, hank pronk via Personal_Submersibles <personal_submersibles at psubs. org> wrote:

James,I put my fill plug under the prop, in the flat end cap,  and it works like a dream. Hank 

    On Monday, December 5, 2016 5:37 AM, Antoine Delafargue via Personal_Submersibles <personal_submersibles at psubs. org> wrote:

 Hi frankI have done something like that for my prop shaft seal oil filled compartment.  But first i removed the hose and filled with a serynge with long steel needle. Then put the tube and filled it with the serynge. The tube is flexible and transparent, from endurance sport platypus drinking bladder
Works wellRegards Antoine 
On Monday, December 5, 2016, James Frankland via Personal_Submersibles <personal_submersibles at psubs. org> wrote:

Hi All I have been talking to Rick about motor compensation which has got me thinking. I originally did my motors like other psubbers have done with the rubber tubes around the sides, but have found them a real pain to fill.  Problem is the location of the tube, plus the tiny bit of protruding pipe nipple on the inside. So, I modified the motors by drilling a hole in the top part of the aluminium endcap and use that now as the vent\final fill.  Its better, but still awkward. I have suggested to Rick this idea, which I am tempted to adopt myself.  Blocking off the existing side mounted pipe nipples and filling\venting\compensating all from the one top hole.  There would be a rubber bulb of some sort on the end of the pipe.  2x pictures show filling and operation.  Appologies for rubbish drawings, im at work. What does everyone think? 

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