[PSUBS-MAILIST] Motor Modification

Tue Dec 6 09:28:03 EST 2016

Alan, I am having trouble pulling up the Vulcan seal off the V3
0100.20.N.C. part number.  Can you send a link so I can have a look at this
single mechanical seal?  I have quite a bit of room for the seal so if it
is not to big, it might work.

Cliff

On Tue, Dec 6, 2016 at 1:02 AM, Alan James via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Cliff,
> thanks for wading in.
> Can you fit a mechanical seal in the Minn kotta end housing?
>    I have ended up choosing a mechanical seal for my brushless thruster.
> (V3 0100.20.N.C.)
> I firstly consulted with an N.Z. rep who recommended this bellows type
> seal; then after
> buying it, ended up sending my drawings & description of operation to
> Vulcan the manufacturer,
> who independently recommended the same seal.
>    I have a gap between my bearing & seal that doesn't allow for free flow
> of oil
> & are going to drill a hole at an angle in to this cavity from the middle
> section
> of my thruster housing.
>    Glad to hear there was air coming out of the relieving valve on the
> regulator;
> it must work! I am finalizing a purchase of some similar regulators for my
> thrusters.
> Alan
>
>
> ------------------------------
> *From:* Cliff Redus via Personal_Submersibles <
> personal_submersibles at psubs.org>
> *To:* Personal Submersibles General Discussion <
> personal_submersibles at psubs.org>
> *Sent:* Tuesday, December 6, 2016 5:06 PM
> *Subject:* Re: [PSUBS-MAILIST] Motor Modification
>
> I can give you my experience with the seals on the Minn-Kota 101 I have on
> the R300.  Much of this was covered in my Psub presenation at Watkins Glenn
> earlier this year.
>
> The OTS Minn-Kota lower unit (MK part number 2886289) consist of a center
> section that contains the permanent stator magnets, the plain end housing
> assembly (bow) that contains two radial roller bearing that support the
> shaft and armature assembly, a brush end assembly that holds the brushes, a
> bronze flange bearing and two lip seals with a carboard spacer between them
> each oriented to expect higher external pressure than internal.  There is a
> static o-ring seal between the center magnet section and the plain end
> housing assembly.  On the brush end assembly, the dual lip seals are design
> for approximately 10 feet submergence but have been known to work to a
> depth of about 30 ft.  To modify this MK-101 for the four thrusters on my
> boat, I reverse engineered the brush end assembly so that I could machine a
> replacement  brush end assembly that beefed up the part so that I could
> screw three 316-SS supports to hold a nylon MARLIN Wageningen nozzle 37.
> This modify part was made of 6061-T6 and hard anodized.  This new part uses
> the same two lip seals in the original part design and the same static
> o-ring seal beween the brush end addemlby and the center section.  In the
> nozzle that is welded to the center section that the two 10AWG conductions
> exit from , I inserted a 316-SS adapter that would accept a Subconn BHB2M
> bulkhead connector and a Swagelok 1/4" NPT to 1/4" tube fitting.  I use a
> single pressure reducing/ releaving regulator that Hugh Fulton specified
> for his Q-Sub for air pressure compensation of all four thrusters.  The
> regultor is adjustable and I have mine set to hold a pressure of 4 psi over
> ambient water pressure.
>
> For both the original MK-101 brush end assembly and my modified version,
> there is no barrier fluid other than air beween the two lip seals and their
> is no compensation line.  As Alan mensioned in an earier post, it is likely
> that this arrangement would cause the the outer lip seal to collapse
> againsit the cardboard spacer beween the two lip seals because the initial
> pressure beween the two seal is initially 1 atm.
>
> On Jan 24th this year I took my boat to Lake Amistad and did a manned dive
> to 155 ft. I had no issues with the thrusters either before or after the
> deep dive. They worked great. When I was ascending from the deep dive I did
> note that the pressure regulator was releasing air from the thrusters. When
> I disassembled the thrusters after the dive, they were all dry.
>
> As to Sean's idea of using a positive bias pressure inside the thruster
> and filling the space beween the two seals with oil that has ambient
> pressure via a compensation line, I think this could be done for both the
> original MK-101 brush end assembly and my modified version.  Might be
> tricky to machine the hole beween the two lip seals but I think it might be
> possible.  Not sure how you would keep the oil place as there is no room
> for a bladder. Might be able to use some kind of plug that would transmit
> ambient water pressure to area between the seals.
>
> Before I take my boat out again, I am going to call the  *Parker Hannifin*
> guys and get their take how to modify this seal arrangement. In the spirit
> of KISS,  I am leaning towards just removing the outbound lip seal and
> relying on the pressure compensation system and a single lip seal. We don't
> put a lot of hours on this seal so duty cycle is light.  A single lip seal
> with pressure compensation might be all that is required.
>
> Maybe we could get Jon to post the PP file on the MK 101 thruster project
> to the PSubs web site.
>
> Cliff
>
>
>
>
>
>
>
>
>
>
>
>
>
>   Late year I reverse enginnered
>
> On Mon, Dec 5, 2016 at 8:01 PM, Sean T. Stevenson via
> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
> Do the Minn Kota motors have a dual seal arrangement that would permit you
> to run a compensation line to the void between the two seals?  I am not
> familiar with their design. In designing mission critical sealing
> arrangements, I have always stuck to the rule of thumb of using any single
> seal to change fluid, or to change pressure, but not both simultaneously.
> Thus an ideal arrangement with dual seals would be to run bias compensated
> oil in the housing, unbiased compensated oil in the volume between the
> seals, and then the seawater outside. This way, leakage across the inner
> seal is immaterial because the fluid is the same, and leakage across the
> outer seal is unlikely because there is no delta-P.
> Sean
>
>
> On December 5, 2016 3:58:49 PM MST, Alan James via Personal_Submersibles <personal_submersibles at psubs.
> org <personal_submersibles at psubs.org>> wrote:
>
> Rick,
> one method Psubbers were using to compensate thrusters was to have two
> nipples
> in the thruster with a piece of PVC tube leaving one, wrapping around the
> thruster
> & joining the other. The idea being that the oil filled PVC tube
> compressed to equalize the thruster.
> It's easy to squeeze the tube with your fingers, but when you have water
> pressure
> squeezing evenly, it's collapse pressure is quite high. Also lights are
> compensated like
> this with the wiring running through oil filled PVC tu! be from the back
> of the light fitting
> to the through hull. Again, the tube needs to be crimped to initiate it's
> collapse.
>    With the addition of a bladder there is no need to worry about this, as
> the bladder collapses
> easily. If you semi fill the bladder then it can take any expansion. As
> long as there is enough
> oil in the bladder to cover the compression of any air at the depth you
> are going, then
> you could have quite a bit of air still left in your thruster. But the
> ideal is to have
> as little as possible.
>    I know Cliff mentioned the problem of the dual seals when he was doing
> his Minn Kotta
> modifications. I think he built a new end section to the motor, but aren't
> sure.
>    I have heard that the Minn Kotta seals are rated to 15-30ft but have
> been tested
> to over 100ft in some cases. I have only looked at them from an obscure
> parts diagram.
> There may be such a small void between them that it would be a non issue
> if the seaward seal
> fails. Sometimes in thrusters with dual seal arrangements the seaward seal
> is regarded
> as sacrificial because it sees all the grit etc.
>    Today I am emailing manufacturers to try & find a cheaper version of
> the Parker PR364
> relieving regulator that Cliff is using for compensation.
> Cheers Alan
>
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