[PSUBS-MAILIST] Brushless Thruster

Mon Oct 3 18:44:10 EDT 2016

Alan,You are right, the mechanical seal is the easiest way to go.  My Perry thrusters had simple spring loaded seals with a sealed cavity behind the mechanical seal.   You will be oil filled, so the seal will have the back up oil.Hank 

    On Monday, October 3, 2016 1:27 PM, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 Hank,yes I like the idea of going straight to the penetrator with the clear tube attachingon to a barbed fitting. I want to put a 4psi overpressure in the system & areintending to do this with compressed air; so need to tee in an air line. I alsoneed an oil filling point, however the air connection point could double for this.I like the clear tube as it is a visual indication of the oil level.I have 2 lip seals at the moment. Hugh wasn't too impressed with that idea& thought I should go with a mechanical seal. From what I have read, the shaftthe lip seal runs on needs to be plunge ground to a certain finish, & a mechanicalseal would eliminate that precision process.Also I look at what other large manufacturers have done & figure they havedone the research on seals & have the experience.Cheers Alan
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On 4/10/2016, at 12:37 am, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Alan,You can make up a pretty simple penetrator for the wires, or why not leave the wires the way they are in the clear tube and run the tube to a penetrator on the sub that is made from a barbed fitting.  The clear tube can be oil filled and act as your compensator.  I know you already though of this.  I think the DW's work like that.If you are oil filled, why the mechanical seal.  Just go with a higher pressure rated lip seal.Hank 

    On Monday, October 3, 2016 3:40 AM, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 Hi Hank, thanks.yes am intending on getting that type of seal, but I will try & get some adviceon an appropriate seal for the viscosity & type of oil I am using (Morlina S2 Bl 10).Must be a bit barmy because I was getting quite excited about the new compensating oil I bought. I haven't quite decided how I am going to terminate the wires coming out of the motor. At present I have the wires running through a clear hose up to a manifold.I say manifold but it is a modified brass T plumbing fitting. The hose is hose clampedto one end & the wires are silicone sealed coming out the other end. On the T I havea plug that I can remove to fill the tube & thruster with oil. This is okay for experimentalpurposes but will need to add pressure to the system & a through hull fittingwhen I mount it on the sub.Alan

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On 3/10/2016, at 9:28 pm, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Alan,That is great! well done..  What type of mechanical seal will you use?  Are you planning a spring loaded pump seal?  Hank  

    On Monday, October 3, 2016 2:07 AM, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 Just did a pool test of my latest brushless thruster.
This thruster uses a 60kv (revs per Volt) 6374 (dimensions in mm) brushless
sensored outrunner motor. The propeller was a 3 bladed 7&1/4" x 4" with no kort nozzle.
I was getting 30kg (66lb) thrust from 30 amps off 52 volts (1560W) with the thruster
oil filled. This seems comparable to what Cliff was getting from his Minnkota 101.
The difference is this is a much smaller unit. I have been keeping a file on
performance statistics of commercial thrusters & trolling motors & this is slightly 
above average.
The manufacturer told me not to run the motor more than 40 amps continuosly,
so I am being conservative with the 30 amp draw. I could bump it up by putting
on a bigger prop.
Next step is to use it as a boat motor & notch up 100 or so hours, then build
another housing with a mechanical seal.
Added a couple of photos to the project page, but they loaded upside down for
some reason. Couldn't change them. 
 http://www.psubs.org/projects/1235435392/brushlessthruster/
Alan

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