[PSUBS-MAILIST] MK 2 Brushless Thruster

Thu Mar 24 19:24:02 EDT 2016

Hi Steve,sorry, I left a bit of detail out of that drawing.Firstly the motor is an outrunner; so the back section with wires coming out is stationaryas are the coils inside, but the rest of the can, with magnets, rotates.The motor has a thrust bearing in it, and that takes the forward load from the propeller.There will be a circlip on the propeller shaft that will run against the bearing shown,when in reverse. The motor comes with 4 threaded holes in the back for mounting.I am putting 4 pins in these that will locate in 4 holes in the rear section of the thrusterhousing. The pins will only centralize the motor & stop the back section of the motor rotating. The whole motor could move laterally on the pins when going from forward to reversebut with a tight tolerance this shouldn't be a problem.   I am replacing the propeller shaft with 316 SS as I did in the last version. The factory thatsupplied the motor kindly sent it disassembled to facilitate this. They normally Loctite everything.   The wiring tube takes the 3 phase wires + 6 hall sensor & 2 heat sensor wires. I may adda water sensor in the bottom tube. The wires in the last version came out through a hoseconnector fitting that was press fitted in with Loctite and had a clear plastic hose clamped to it. I like this, as the oil for compensation also runs in it & the clear hose is a level indicator. I will send the wiring through a penetrator at the hull.Cheers Alan

      From: Stephen Fordyce via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Friday, March 25, 2016 11:06 AM
 Subject: Re: [PSUBS-MAILIST] MK 2 Brushless Thruster

Hi Alan,That looks great!  Very small for the power.  A couple of comments/queries:- There's no second bearing or thrust bearing - perhaps these are not shown?- Just wondering how the wiring tube is connected?  Ie. tapped hole for a cable gland or compression fitting?- How is the motor held in place within the housing?- I'm guessing the motor has a carbon steel shaft and the external propeller shaft should be SS316 - are you going to weld them together or connect mechanically?
Cheers,Steve
On Fri, Mar 25, 2016 at 8:13 AM, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

OK Hank I will bolt the front section on.I had problems machining the bearing seat on the first thruster as the front section was one piece & I needed a long boring tool. I will have the same trouble if I have to machine these after welding. I will probablyloc-tite everything in on the front section as it doesn't need to come apart.The whole thruster housing (2000W) is only 80mm x 174mm (3&1/4" X 7")& there is very little to it.Are you planning any other submarine events in Europe apart from visiting Emile?I went up to Cherbourg & had a look at the submarine museum. You could spenda day there, I am sure your wife would love it.Cheers Alan

      From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Friday, March 25, 2016 9:05 AM
 Subject: Re: [PSUBS-MAILIST] MK 2 Brushless Thruster

Alan,I like the two seals also and now that you mention you are putting in a fill plug to vent air-I am with you.  I would get it welded before you machine the bearing seats etc, if possible.I would still make both ends bolt together-there is nothing like having it come apart to work on it.  My Perry thrusters break down into a million pieces and it is real nice to work on.Hank 

    On Thursday, March 24, 2016 1:55 PM, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 Hank,I left out some details on that drawing. The back end fits the sameas the front & has a radial o-ring seal on the end housing & 6 cap screws thatbolt in to the central housing. Alan

      From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Friday, March 25, 2016 1:31 AM
 Subject: Re: [PSUBS-MAILIST] MK 2 Brushless Thruster

Hi Alan,It wouldn't hurt to clamp the end cap tight but you do have a nice shoulder for the end cap to sit on.  Any time I make a part that can and usually does warp, I make it oversize and machine it true after welding.  I am curious why you want to weld it-that big shoulder has room for an o-ring.   I would also ditch the second seal-it is an air trap.    Great project!Hank 

    On Thursday, March 24, 2016 12:27 AM, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

  This is my latest brushless thruster design for scrutiny.The last thruster I made was 2 piece with one seal.I machined the last version out of aluminum rod, which was expensive & difficult.The end pieces in this design are from solid rod but the mid section is from a stock tubethat I intend to have welded to the propeller end. The back end is bolted on.Am I likely to get distortion when welding the two sections together? There is a sleevepress fitting to help give it some rigidity for welding. Should I make a jig to clamp it infor welding?The thruster is for 500ft depth & is oil filled with a slight over pressure above ambient. Oil filled mainly for cooling purposes, but also as a secondary defense against any leaks,& for lubrication of bearings & seals. I am using low pressure lip seals & have a double seal redundant arrangement. The outboard seal is orientated to keep the oil in & with theinternal overpressure should keep the water out. The outboard seal should fail first as it is exposed to abrasives, especially in sea water. The inboard seal is oriented so that it keepsany water out that may get past the outboard seal. The tube coming out of the seal cavity is for pressurizing it & for collecting any water thatmay get through & come out of suspension. I am thinking of putting a water sensor in there.Any comments welcome.Alanp.s. if image isn't big enough keep hitting ctrl & + TO ENLARGE.

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