[PSUBS-MAILIST] thruster compensation

[Alan via Personal_Submersibles]

Hank,
in hindsight there is a problem in that when the external water pressure
pushes on the rod & tries to make the piston move down the cylinder
there is a vacuum created behind the cylinder that needs filling with oil.
Not sure if that's the right terminology.
If water can move in to that void through one of the ports, it would work. 
Or the rod & piston were the same diameter. You may have already thought 
through this. I encountered this when trying to compensate linear actuators.
Alan

Sent from my iPad

> On 16/02/2017, at 11:25 AM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Brian,
> 
> The piston is mid way.
> Alan,
> I was going to install an internal spring to create internal pressure but I only have one seal oriented to keep oil in.  I will try this first and see where it leads.
> I have tried this in the past on Gamma's prop shaft and it did not work- I am sure it is because of the seal orientation.
> Hank
> 
> 
> On Wednesday, February 15, 2017 3:21 PM, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> 
> Hank,  where is the piston situated in the cylinder upon start up of operation ?   Half way ?
>  
> Brian
> 
> --- personal_submersibles at psubs.org wrote:
> 
> From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
> To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
> Subject: [PSUBS-MAILIST] thruster compensation
> Date: Wed, 15 Feb 2017 21:32:47 +0000 (UTC)
> 
> I have just installed my two additional motors on Gamma that are mounted to the manipulator assembly borrowed from Elementary 3,000.  To compensate them I used a single air cylinder 1.5 in bore with 4 in stroke as the compensation bladder.  The cylinder is filled with light hydraulic oil and the motors are filled with WD40.  There are hydraulic hoses connecting the cylinder to the two motors.  I reversed one seal in each motor so the one seal keeps water out and one seal keeps oil in.  There is a tiny bit of air in the system but that makes no difference because the cylinder piston has enough travel to compress the air.  I think oil enters compensated motors because the oil spinning creates pressure from centrifugal force and the seals are oriented to keep water out.  The oil can then escape, that is why I have turned one seal around.  I will be testing in a month or so, and we will see, I guess.
> Hank
> _______________________________________________ Personal_Submersibles mailing list Personal_Submersibles at psubs.org http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
> 
> _______________________________________________
> Personal_Submersibles mailing list
> Personal_Submersibles at psubs.org
> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
> 
> 
> _______________________________________________
> Personal_Submersibles mailing list
> Personal_Submersibles at psubs.org
> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.whoweb.com/pipermail/personal_submersibles/attachments/20170216/1055a260/attachment-0001.html>