[PSUBS-MAILIST] Minn-Kota Shaft Seals

Mon Apr 10 19:12:04 EDT 2017

I think this could work Alec and it does fit the KISS principle but I don't
think it an optimum solution.  I like the feed back I got to day from the
Parker seal guy to pull both seals and reset with the inbound set to resist
high internal pressure and the outbound seal set for higher ambient
pressure and grease  in place of the dead air space.  This is going to be
the arrangement I try next.

 I don't have a good feel of how much  differential pressure across a
backward facing lip would cause it to leak air.  I really think we need to
put one of the Minn-Kota 101 units in a controlled test chamber and try out
some of these variables, test them to depth and then tear them down for
inspection.  Seem with psubs, there is always one more thing to research.

Cliff

On Mon, Apr 10, 2017 at 4:57 PM, Alec Smyth via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> That's a good conundrum. Let's assume the pressure compensation is to a
> very small pressure above ambient (one could also compensate slightly below
> ambient, but I suspect everyone goes above). With the seal in the direction
> to keep water pressure out and in the wrong direction for the internal
> pressure, it could leak air - but the question is how many psi it would
> take for that. On the other hand, if you were below whatever threshold that
> is and there isn't any leak, I actually still like the idea of having the
> seal oriented to keep water out, as it's better than nothing in the case of
> a compensation failure.
>
> I still have both seals in and am scheduled to test Shackleton later this
> week. These are going to be very shallow dives, so the air gap between
> seals isn't an issue I've bothered with yet. But I think at the end of the
> day, if all is working well and we've got some dives in, I'm going to go
> ahead and drill the outer seal of one of the thrusters and just see if any
> bubbles escape. My pressure compensation is set at 5 psi over ambient. If
> that turns out to be below the reverse blowout threshold, I like the idea
> of drilled outer seals for its simplicity.
>
> Best,
>
> Alec
>
> On Mon, Apr 10, 2017 at 5:29 PM, Cliff Redus via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>> Inbound functioning seal will be facing the wrong direction for a
>> pressure compensated unit if you left the seal set in place that comes with
>> the unit.
>>
>> Cliff
>>
>> On Mon, Apr 10, 2017 at 3:17 PM, Alec Smyth via Personal_Submersibles <
>> personal_submersibles at psubs.org> wrote:
>>
>>> What if we just drill a little hole in the outer seal, and leave it in
>>> place?
>>>
>>> Best,
>>>
>>> Alec
>>>
>>> On Mon, Apr 10, 2017 at 3:11 PM, Alan via Personal_Submersibles <
>>> personal_submersibles at psubs.org> wrote:
>>>
>>>> Jon,
>>>> just be careful you don't damage the seal seat ( bore) or future
>>>> seals may leak.
>>>> You could try threading an over sized bolt in to it & pulling on the
>>>> bolt with a hammer. Maybe hit the bolt in to get it started.
>>>> You could also heat the housing around the bore first.
>>>> There is a plethora of tools if you google on image search; but
>>>> these are on the small size.
>>>>  I have said before that there is a use to the outer seal as a "dust
>>>> cover" function to keep muck away from the more important inner seal.
>>>> A cheap protective seal that is easy to replace!
>>>> Alan
>>>>
>>>> Sent from my iPad
>>>>
>>>> > On 11/04/2017, at 2:32 AM, Jon Wallace via Personal_Submersibles <
>>>> personal_submersibles at psubs.org> wrote:
>>>> >
>>>> >
>>>> > Ok, what's the secret here?  Poking around one of my MK101 lower
>>>> units to get familiar with it and I have hacked up the outer seal trying to
>>>> remove it.  I assumed these things were entirely rubber fabricated and just
>>>> fit tightly into the cylinder that surrounds the shaft.  However, it looks
>>>> like they are rubber over metal and press-fit into the aft section of the
>>>> motor housing.  Anyone removed these things?  I can't find anything on the
>>>> internet with instructions on how to remove them.  I can't just pull them
>>>> out with plyers...tried that and now I'm going to have to purchase new
>>>> seals.   :)
>>>> >
>>>> > Jon
>>>> >
>>>> >
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>>>
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