[PSUBS-MAILIST] Brushless Thrusters
via Personal_Submersibles
personal_submersibles at psubs.org
Sun Sep 7 18:49:13 EDT 2014
Hank,
Harbor Branch used o-rings on the reduced output 1 1/4 thrusters on the JSLs. The mid-body on the hard can (actually the back 25% or so of the cylinder section) was machined on the output side for planetary gears, and machined on the motor side to replace the entire output plate/bearing case for the motor itself (like a golf cart motor bolts into a differential). Pretty nice and compact for the day.
The rear section of the hard can behind the gear case is a hollow sand casting shaped like the long end of an egg, webbed internally to support a 1" shaft, double bearings, with double thrust bearings, and a tapered, polished, hardened aluminum sleeve pressed in from the pressure side.
The shaft itself was machined to carry double o-rings in square cross section grooves and terminated on the internal end with a flex-coupling which mated (obviously) to the output of the planetary output. A big shaft was necessary to keep the jitters down to more or less zero. Everything needs to stay exactly centered, as the O-rings will go to pot a whole lot faster if there is any flex or vibration at all in that prop shaft shaft.
Lots of development to get it right, finally, but the props turned about 275-300 rpm (I don't remember exactly, but something like that). 14" X 14" Kort style prop in a machined syntactic foam nozzle supported on a 4-legged frame welded to the aft part of the shell. I actually have a blueprint of it, somewhere around here. For those interested, the tip clearance between blade end and nozzle sleeve was about 50-thousandths. NOTE: That would be of an inch, Emile.
There were no speed controls on the boats. Fwd-Off-Rev only. You just turned thrusters on or off to vary the push. When I was there, we had 5 for forward and reverse (3 in a row on the centerline with 1 each to port and starboard aft) plus a vertical and horizontal pair forward and aft for steering and fine maneuvering (fine maneuvering my ass!!!). That's right. NINE thrusters that probably with cabling weighed over half a ton. Plus two or three spares in the kit ready to bolt up at a moment's notice as replacements. We were definitely in the motor business with those babies.
They were home grown but worked reasonably well, although they were a little noisy with the gear case and whatnot. That said, I never saw the electrical side flooded on one of those things. Not once. Ever. We had a routine service schedule and changed a thruster every so many hours of service. Just put a fresh one on (two people could do a change-out in about three minutes), then tear the to-be-serviced unit down to check brushes and bearing lube and change the shaft o-rings (which would be looking a little fuzzy by then, but still worked fine--and even if they looked brand new, we changed them). It needs a really, really first rate waterproof lubricant, as the internal shaft o-ring runs hotter than the one in contact with the water, and was often in worse shape than the one primary as a result.
Once the JSLs re-certified to 3000 feet, engineering redesigned the seals for better service, using a ceramic cartridge seal in place of the o-rings, but that was after my day. I'd hate to even think what one would cost today, built commercially. You wouldn't use them, probably, as a unit with twice that power is probably a third the size and weight.
Those thrusters on the Tritons, for instance, look positively tiny by comparison, and they're rated at over 2 hp. Then there's our own Uncle Dr. Phil's new mag coupled ones. Now there's a Christmas present to ask Santa for.
All that aside, the o-rings will work if you plan regular service (ie, scheduled o-ring replacement) and don't wait for water intrusion. They have to be done right during construction, though. Those surfaces have to be mirror smooth.
Vance
-----Original Message-----
From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Sent: Sun, Sep 7, 2014 4:51 pm
Subject: Re: [PSUBS-MAILIST] Brushless Thrusters
Brian,
Vance would know better than me, but I think if you keep the rpm under 1,000 you
can use an o ring for a seal. I thought Perry did that in the early subs to
1,000 feet.
Hank--------------------------------------------
On Sun, 9/7/14, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
wrote:
Subject: Re: [PSUBS-MAILIST] Brushless Thrusters
To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
Received: Sunday, September 7, 2014, 4:42 PM
Brian,
You can use a simple
mechanical seal, that is what the K subs have. An 891
Chesterton mechanical seal is good fo 600 psi, that is what
Gamma had when I got it. You can buy them on ebay for 100
bucks. Build the shaft to fit the seal, and your
sailing.
Hank--------------------------------------------
On Sun, 9/7/14, Brian Cox via
Personal_Submersibles <personal_submersibles at psubs.org>
wrote:
Subject: Re:
[PSUBS-MAILIST] Brushless Thrusters
To:
"Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
Received: Sunday, September 7, 2014, 4:29
PM
I
talked to a hydraulics guy a few days ago about making a
seal for my motor pod. I told him I had a
high pressure
tank that I wanted to turn a
shaft inside the tank to stir
the contents
at 250 psi, ( didn't want his eyes to
glaze over if I mentioned submarine !) Anyway he
directed
me to a system using a bronze
fitting that would tighten
down these rings
he called "cheverons" they are
mating rings of a very high durometer . the bronze is
for
mating with stainless . I would have
to machine an
assembly for this , but once
I have my shaft size (1 inch
most likely) I
will be able to size everything
accordingly. Brian
---
personal_submersibles at psubs.org
wrote:
From: hank pronk
via Personal_Submersibles
<personal_submersibles at psubs.org>
To:
personal_submersibles at psubs.org
Subject: Re:
[PSUBS-MAILIST]
Brushless Thrusters
Date:
Sun, 7 Sep 2014 07:07:20 -0700
Alan
When I upgraded the
cartridge seal in Gamma, I needed a pretty
Beafy thrust
bearing, it was no problem to
get. have since changer to
Magnetic. I think you could replace the bushing
in a
thruster with a ball bearing and never
look back.
Hank
From:
Alan via Personal_Submersibles
<personal_submersibles at psubs.org>;
To:
Personal Submersibles General
Discussion <personal_submersibles at psubs.org>;
Subject:
Re: [PSUBS-MAILIST] Brushless
Thrusters
Sent:
Sun, Sep 7, 2014 1:43:49 PM
Hi Hank,the kort
nozzle on the Indonesian thruster looks a bit
Naff. ( I am designing an art work
here.)I could get a price for the unit
without
kort nozzle, butI'm wondering
if I could
build something for 1/2 that
price.There are some
reasonably priced
brushless motors about.I
don't know
that I could just retro fit a thrust bearing
inside the can of the motor.I tried to put
a
thrust bearing for reverse inside my
brushed thrusters,
butcouldn't find one
with a thin enough
section to fit.Also the
motors are a bit
expensive to just buy
& hope you can fit
one.How did you fit
the thrust bearing on Gamma?
Did the
propellor shaft extend out the backof
the
motor?Alan
Sent from my
iPad
On 7/09/2014, at 7:22 pm, hank pronk
via
Personal_Submersibles <personal_submersibles at psubs.org>
wrote:
Allan
Dont
worry about
thrust bearings to much. They are aesy to get,
I bought one for Gamma , real heavy duty for
80 dollars.
Personally I would just use a
good quality bearing and
replace it once a
year for 8 bucks, if it is a small
thruster. Are you not happy with the
Indonesia thrusters?
Or to pricey?
Hank
From:
Alan via
Personal_Submersibles
<personal_submersibles at psubs.org>;
To:
Personal Submersibles
General
Discussion <personal_submersibles at psubs.org>;
Subject:
[PSUBS-MAILIST] Brushless
Thrusters
Sent:
Sun, Sep 7, 2014 11:58:56 AM
Hi people,
I've
spent several hours today looking at brushless
thrusters
& wonder if anyone else has
looked at them or got any
ideas. There is
the Indonesian thruster I posted a few weeks
back at US 2,200. There is also the Haswing
Protruar 2hp
that Emile has; however they
state that it's for fresh
water only,
& I think Emile said it was a bit noisy.
The inrunner motors that have the winding
on
the outside, seem a good option as they
cool through
convection to the can. They
also need higher revs for torque
&
require a planetary gear box or similar. ( which a lot
have built in)
I was
looking at the
option of making my own
thruster, however the motor would
require a
thrust bearing & I don't
know of
any that would have one other than
maybe
a high powered battery operated drill.
Any
thoughts, suggestions thanks.
Alan
Sent from
my
iPad
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