The mechanical system consists of everything
outside the main tube, including the tube itself. The only major mechanical
change to the submarine this year has been the addition of two new Seabotix
Thrusters. On the whole, we have kept to the mechanical system developed last
year, as it functioned well.
Here are the main components that makes up the
mechanical system:
The Tube
The structural support of Barracuda consists of a 6’’ diameter
by 17’’ long acrylic tube and two parallel aluminum rods. The tube is 3/16”
thick and is secured to two acrylic cradles, into which holes were drilled to
allow the rods to pass through. These rods are the equivalent of traditional
frame and hold all of the external components using ring clamps. Two metal
handles attach to the top of the tube for transport and deployment. Both ends of
the tube have metal end caps. They are secured by metal latches with compress
o-rings to create a water-tight seal.
Front End Cap
The front end cap consists of a clear acrylic dome. The flange
of the dome is sandwiched between on the front end cap and another metal ring on
top of it. This assembly is secured by eight screws with compress o-ring. The
dome allows the cameras greater freedom in collecting visual information, and we
are very pleased with its clarity.
Rear End Cap
All through-the-hull connections are made on the rear back plate and use Brad
Harrison Waterproof connectors. These connectors are IP67 rated and can handle
1000PSI spray down.
These connectors are a major advancement from our original connections made
via epoxied wires through the hull. They add to the modularity of the design and
for rapid assembly and disassembly as well as rapid replacement if for instance
an engine were to fail, it would be very simply to replace the engine with one
of our prebuilt spares.
Horizontal Thrusters
This year, for horizontal thrust, we upgraded to SeaBotix
thrusters from our previous bilge pump combinations. We are very pleased with
this change, as they draw much less current; approximately 3.3 amps each, to our
original 8 amps. These new thrusters come with the shroud, propeller and engine
all in one unit, each is mounted via an aluminum plate to our horizontal engine
bar.
Vertical Thrusters
The vertical thrusters control the depth and pitch of the
submarine. The front vertical motor is Mayfair Marine 750 GPH bilge pump while
the back engine is 500 GPH. The 500 GPH was chosen for its low power
consumption; the front, on the other hand, is equipped with the stronger motor
to compensate weight of the treasure. The bilge bump motors are attached to
Rivabo 90mm propellers via custom machined connectors. This yields a very cheap
and effective solution for the low power motors. Protective acrylic shrouds
surround these as well for safety.
Dropper and Markers
Our markers are ¾ inch diameter stainless steel spheres with
our school logo
(AV) engraved into them. They rest in a hollow acrylic tube mounted on the side
of
the vehicle. A sprinkler solenoid is used to retract a pin that allows a hinge
to drop, releasing both of the markers. The solenoid is designed to work
underwater so the only water proofing that needs to be done is to connect it to
the endcap.
Hydrophones
The submarine is equipped with 4 Reson model 4013 omnidirectional hydrophones oriented in such way a that they are non-coplanar.
This array is designed to be able to detect phase difference of the underwater signals and is mounted in an acrylic block machined
by Amerimade. The hydrophones attach to waterproof Brad Harrison connectors, using shielded wires to reduce noise.
Tether
A communications link to the main computer is required to facilitate testing.
This is provided by a wireless access port attached by tether, which can float
along with the vehicle.
This Ethernet connection is connected to the OQO via a
USB-Ethernet adapter. It can also be used to remotely program the
microcontroller. Furthermore, the tether, when connected, enables usage of a
remote engine kill.
Kill Switch
The kill switch is a modified off-the-shelf jet ski kill. The diver
need simply pull on the red tag for immediate engine kill.
Copyright 2008 Amador Valley High School Robotics Club
