[PSUBS-MAILIST] thruster positioning and compass thoughts

Thu Jul 30 23:57:34 EDT 2015

Hank,

Will the four thrusters be mounted high on the hull like the single vertical one you showed me last week?  If so then this position would probably be beneficial for three dimensional maneuvering close to the bottom as the thrusters would be less likely to stir up the silt and mud.  Less likely doesn't mean won't.  I am imagining that you will have four thrusters mounted high, horizontal and canted 45 degrees to the long axis.  Toss a photo or drawing our way so that we can see your plans.

An aircraft compass may be your best bet since you can adjust the internal magnets to "swing" the compass.  It's hard to say how even that would work inside an all steel boat, especially when that big electric motor powers up.  Scuba with a DPV made my wrist compass useless while under power.  What are the K-subs using for compass nav?

Tim

From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of hank pronk via Personal_Submersibles
Sent: July-30-15 5:34 AM
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] thruster positioning

Tim,

I learned a lot yesterday, I repositioned my test thrusters from strait ahead to angled almost 45 degrees.  My concern was the forward speed would suffer greatly.  In fact the forward speed is still very good, and the turning performance is also good.  I am now  thinking I will use  4 thrusters.   I am not sure about the DW set up because the DW is a short wide machine compared to Gamma.  I am thinking the same for the vertical thrusters, but the forward thrusters might be in the front on an angle.  I will test with the thrusters in the rear before I commit.   If the forward thrusters are in the front, I can see them and it is easier to make them jettisoning .

The viz in Premier lake is still 15 feet and I am still struggling with my compass.  I think I will have to go electronic because what I have is useless.

Hank

On Tuesday, July 28, 2015 9:26 PM, T Novak via Personal_Submersibles <personal_submersibles at psubs.org <mailto:personal_submersibles at psubs.org> > wrote:

Hey Hank,

Take note of the DW configuration.
Four fixed reversible thrusters, two horizontal and two vertical but canted
out by 45 degrees.
The two horizontal control surge (both powered forward or in reverse) and
yaw (one powered forward, the other in reverse).
The two vertical control heave (both powered up or down) and translate (one
powered up, the other down).
There is no roll or pitch control, the ballast block (batteries and lead)
keep the vehicle level on those axis (slight roll during translate
operation).

Some ROV's have four fixed reversible horizontal thrusters, one on each
corner, with the front two pointed 45 degrees inward and the aft two pointed
45 degrees outward, and one vertical reversible thruster.
The four horizontal control surge (all powered forward or reverse), yaw (one
side forward the other side reverse), and translate (one aft thruster
forward, the other reverse, and one front thruster forward and the other
reverse).
The vertical thruster controls heave.

Minimum two axis control is one steerable reversible thruster to control
surge and yaw.  Control heave with buoyancy or dive planes which really is
pitch control rather than true heave.
Minimum three axis control is two independent rotating non-reversible
thrusters, one on each side, to control surge, heave and yaw by the
direction they are pointed (the SportSub has this but they must rotate
together and are therefore reversible).  If they are also canted out 45
degrees then you also get to control translate.

Pitch and roll are necessary in airplanes, but not in personal submarines
(okay sometimes pitch is useful for powered ascent and descent). 

I think three reversible thruster do the trick, the primary in the stern
that is steerable for surge and yaw, and one canted reversible rotatable on
each side for heave, translate, surge redundancy, and yaw redundancy.  Place
those two on the sides just forward of hydrodynamic centre and you also get
a bit of powered pitch.

What configuration were you thinking about with six thrusters? Eight?  Are
you looking for redundancy or only non-reversible thrusters?

Tim

-----Original Message-----
From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org <mailto:personal_submersibles-bounces at psubs.org> ]
On Behalf Of hank pronk via Personal_Submersibles
Sent: July-28-15 1:38 PM
To: personal_submersibles at psubs.org <mailto:personal_submersibles at psubs.org> 
Subject: [PSUBS-MAILIST] thruster positioning

I am trying to figure out the thruster position for all my thrusters before
I take Gamma apart.  I have tested with two thruster pointing strait ahead.
That worked well, now I have the same two thruster on angles opposing each
other.  I notice on some  commercial subs that the thrusters are vectored,
in fact four forward facing thrusters, one at each corner. I assume the way
it works is, all four thrusters are turned on, two in forward and two in
reverse.  To go strait ahead all four turn on in the same direction.  I am
trying to keep it at 6 thrusters but may need 8.
Hank 
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