[PSUBS-MAILIST] Hydraulic idea

Sat Nov 26 22:03:20 EST 2016

Hi Hank,
Wouldn't you have to exhaust the air as in a pneumatic system?
Also air would have to displace the volume of oil in the cylinder
as the piston moves in & out, so there would be marginal benefits
over a pneumatic system. It would also be spongy like a pneumatic 
cylinder because any bouncing force on the cylinder would compress the air
that is the source for the movement.
You were talking about saving space with this idea, but if compressed
air was a good form of power we would have pneumatic thrusters 
instead of batteries & electric motors..
I once did the maths on how much energy was stored in a dive tank;
can't remember the result, but there was at least 3 x more energy in
a battery of an equivalent size.
WD40 as hydraulic oil? It is flammable with a reasonably low flash point.
Also at that viscosity you would be more prone to leaks wouldn't you?
https://www.wd40company.com/files/pdf/wd_40tec16952473.pdf
Cheers Alan

      From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Sunday, November 27, 2016 4:59 AM
 Subject: Re: [PSUBS-MAILIST] Hydraulic idea

Sean,The receiving tank will take the full depth pressure and be large enough  to take all the oil without building up excess air pressure, no need to vent off, since it is only receiving oil and displacing air.  I need a balance with two tanks to maintain neutral buoyancy.I am not worried about oxidation of the oil because the oil is not going through a pump and the flow rate is so small.   I ordered air cylinders for the manipulator with a 5\8 rod to reduce the back pressure.  Gamma's manipulator operated at 1,100 psi when the sub was at 1,000 feed of depth.  The arm will loose power, but I don't expect that to be an issue, because the oil tank will be powered from a separate bottle of air.  I have to work with what I have to keep the cost in check, so I can modify an open centre valve by blocking the final pressure port drain.  I also have some HP tanks.  If it does not work out easily, I have a few electric pumps I can use.  
If I go electric, I intend to submerge the motor pump unit in the oil reservoir with a bladder top to compensate.  That means I will use WD40 as hydraulic fluid. 

    On Saturday, November 26, 2016 6:25 AM, Sean T. Stevenson via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 How do you intend to control the pressure on the receive tank? Just vent it through a check valve to the water? You need to design carefully to prevent contamination in either direction.I wouldn't use air as the drive gas under high pressures, in order to prevent oxidation of the oil. Charge with nitrogen if you intend to do this.To generate the same drive capability as a hydraulic pump, you are talking about very high precharge pressure - approaching the pressure at which HP bottled gas is supplied, unless you can source e.g. 6000 psi nitrogen and regulate it down to 2500-5000 depending on your manipulator requirements. In any case, if your cylinders are single acting, or even dual acting with a single rod, you have to contend with the force from the ambient water pressure, so your receive tank pressure needs to be this at minimum, and with a pressure reservoir source instead of a pump, that available delta-P is further reduced the moment you demand any fluid from the system (i.e. HP bottle pressure will drop), so your manipulator becomes weaker over time.Just a few things to think about.Sean

On November 25, 2016 5:25:47 AM MST, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
Hi All,I have an idea to replace the hydraulic pump for my new manipulator with a air over hydraulic system.  It is quite simple, the hydraulic oil reservoir is a hp tank that can be pressurized from a designated HP supply.  The oil return goes to another HP tank  to receive the oil.  This eliminates the pump completely and that is a dream.  The manipulator can go through 54 complete extensions and retractions, that is 54 complete movements of all functions.  After the oil is used up, the oil can be returned to the pressure tank by reversing the air flow.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/20161127/099cf8da/attachment-0001.html>