[PSUBS-MAILIST] thruster positioning

[T Novak via Personal_Submersibles]

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]
On Behalf Of hank pronk via Personal_Submersibles
Sent: July-28-15 1:38 PM
To: 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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