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Re: [PSUBS-MAILIST] Air compensating motors
Hi Jon,
I bought 20 liters of Shelsol D60 as it was a lot kinder over time on various
plastics than WD40 , also it was a similar viscosity. I think from memory the flash point was higher than
WD40. I ran a motor OK on it but not for long.
I read a couple of posts from Carstens on oil compensating wich I'll post below. It seems as lot more complex
than air compensating as you ideally have an expandable oil bladder for each motor. Also will be testing this
sub in a few swimming pools & don't want to leave an oil slick behind.
regards Alan
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
9. Run the motor a half hour with the boat in the water and see may how the hot oil gets out of the weakest point by internal
overpressure..
10. Switch of the motor and let the boat still in the water for two hours or so.
Open the engine the next weekend in you shop and found partly water in it because of the underpressure creates as the oil cool
down..
The best for the seal is if it see no pressure differtial doesnt matter from which side. So logical the bladder has the same high as
the motor.
A deeper installed bladder indicates a leak by oil getting out in the water, A higher install may not.
A higher installed bladder indicates maybe allready a leak onshore - and thats maybe the better solution.
The best solution is that the hose work between using device and bladder is from clear material and has a loop higher than the user
and the bladder. So air in the system can be easy spotted.
See here: http://www.euronaut.org/content/upload/notes/IMG_3321a.jpg
Euronaut has seven bladders on:
- Stern Thruster (oil)
- Bow Thruster (oil)
- Anchor winch motor (oil)
- Propeller shaft (oil)
- Void space frame cave between fwd.ballast tank and pressure hull (coolant water)
- Void space frame cave between aft.ballast tank and pressure hull (coolant water)
- One bag for all three fix rudder skegs (coolant water)
- Side Rudder and Stern deeprudder are also filled with c.water but without bags.
See also the other mail I just send.
----- Original Message -----
From: "Jon Wallace" <jonw@psubs.org>
To: <personal_submersibles@psubs.org>
Sent: Friday, January 27, 2012 1:35 PM
Subject: Re: [PSUBS-MAILIST] Air compensating motors
Alan,
What were the results of your testing with various oils? A couple years ago you were looking at WD-40, Marvel Mystery Oil, DOT5
Brake fluid, and a few others. I know you said wd-40 caused some problems with plastic, did you finalize your decision on what
you were going to use for oil-compensation?
Jon
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