Re: [PSUBS-MAILIST] Air compensating motors

["Alan James" <alanjames@xtra.co.nz>]

Hi Carsten,
No I don't want hot water bottles all over my submarine. It doesn't look cool.
Couldn't open the second image, but the bellows in the third link looks like
something this company manufactures.
http://sigmanetics.com/pdfs/bellows.pdf
Phil mentioned this company as a supplier for bellows for his "bellows add system".
Thanks for all that experience, it's invaluable.
I was thinking of air compensating my motors with a slight over pressure, & maybe fitting
a pressure gauge or some alarm system that indicates that the pressure is low.
Regards Alan

----- Original Message ----- 
From: <MerlinSub@t-online.de>
To: <personal_submersibles@psubs.org>
Sent: Friday, January 27, 2012 9:55 PM
Subject: Re: [PSUBS-MAILIST] Air compensating motors


Hi Jon and all.
We work on various sub with both systems air compensate and oil compensate.

Both have pro and contras. Air compensate is in general nice. No additional resistance in the engines.

My first air system compensate both together:
Engines and batterys. But we found acid  gases from the batteries in the engines and mainfolds and corrosion by this.
So we divided it in pressure air compensate engines and oil bladder compensate batterys.

But with a little leak and just a little (salt) water in the air system and engines it will destroy them by corrosion.
But normaly during dive check up on the harbour you will notice a leak.

One day on Sgt.Peppers the small air pressure bottle was not right connect (bad o-ring) and we lost all air
during the dive. All motor were flooded and I notice that during the dive because the boats get heavier and the engine slow down.
It was happend in freshwater and we were able to rescue the engines.
We quit with air compensating for that reason.

Later we run the engines on various oil compensating system.

We work with mineraloil but they are all to thick and the motors gets start problems and slow down a lot. Rpm loss of 20% and more.

Than we go with very light oils like WD40 or equal.
But this oils gases a lot if the motor runs longer and create a lot of overpressure. The bladder goes hard like somebodies eggs.
And oil get out of the seals. Vissible on the lake surface, but vapour a away on the surface in just a minute.
Also the WD40 types damage various plastics. Make them hard or soft.

The good one on the oil compensating is that a small leak dosent matter.
The oil works as corrosion protection system in the engines.

Since some month we run the engines on a special oil.. all looks good but the oil cost about 90 USD per galleon.
The engine still lost 10% of the max.rpm but the oil not gas much and the bladder seems allways in operable condition range.

One practial problem with the oil-bladder system is the bladder conection to the hose or pipe system.
We use as bladder what we can grap - something like a soft bag and they all are not made for a conection to something.

http://www.spreepharma.de/dokumente/artikel/FotoGross/3841183.jpg
http://www.firmba.de/images/product_images/info_images/219_0.jpg

So it is difficult to build a real tight connection to hose or pipe system which can take some pressure from one or the other side.

The best will be a compensator from plastic or rubber witzh a hard endcap from metal like this schematic: (But it is a hard find..)
http://www.schweizer-fn.de/rohr/kompensator/icon_kompensator.jpg

Another problem with the oil system are with bushes engines. The bushes lost material over the time,
and that makes the oil dirty and conductive.

At the moment our last developments are a special silicon oil in combination with bushless engines.
But we have no result at this stage. Nordicsub will may use this combination in a couple of months.

vbr Carsten




"Jon Wallace" <jonw@psubs.org> schrieb:
> 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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