[PSUBS-MAILIST] Motor modification

Wed Dec 7 18:51:13 EST 2016

Rick, found some of Carsten's comments.Nothing like experience.....Alan and the other gentlemens,

our expierence with oil filled motors, batterys or even propeller shafts is that the oil expand if the motor is runing longer
time.
Simple because its warm up. We had that problem on Eurosub on the first dives.
And on Euronaut we filled the bladder complet up and the get pretty hard in the hot summer just by sun heating the sub.
A full filled bladder with over pressure creates a lot of interal
pressure in the wrong direct - a lot of force for the bladder itself and hose work.

Therefore our bladder are only half expand during the filling. But still free of any air.
An other point is that the bladder has to be not to small.

To create a slightly overpressure on the motorseal you just install the bladder below the motorcasing.
But we found out that on trolling motor (electric outboards) this is not nessesary. There seals are good for some
douzend feets at least - so you can install the bladder else were.
Filling is simpler if the bladder is slightly over the motor - you can vent the system direct on the filling point.

Another point is that we install now one bladder per motor  - in the earlier sub (Sgt.Peppers) we install a central
one for all motors. Hard to find a leak after a dive with all the T-crossing piepings and motorseals..

vbr Carsten

      From: Alan James via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Thursday, December 8, 2016 12:42 PM
 Subject: Re: [PSUBS-MAILIST] Motor modification

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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