The Challenges of and Solutions for
Engineering your own ROV has construction challenges
beyond designing and building the necessary electronics.
The electronics package for the design is housed inside a six
inch PVC pipe, with a tether cable running topside to a
joystick steering mechanism. The tether is Cat5 cable and
must enter the PVC pipe through a watertight seal.
Additionally, the wires from the motors and optional light
must also feed into the PVC pipe to connect to the motor
The integrity of these watertight connections is an
absolute must as any water leak can be catastrophic to the
electronics inside. My simple solution was to drill holes in
the six inch PVC and then use marine epoxy to glue a 1/2
inch PVC coupling that is threaded on the inside. The wires
are then pulled through a hole drilled in a 1/2 inch PVC
threaded plug, after coating each wire with marine epoxy.
The entire plug is then filled with additional marine epoxy.
It is important that each wire going through the hole in the
PVC plug have an epoxy coat around it before bundling
them and passing them through the hole. The PVC plug is
wrapped with Teflon™tape and screwed tightly into the
A second challenge is achieving neutral buoyancy for
the ROV, as well as a balanced trim. The six inch PVC tube
and the 1/2 inch PVC frame act as floats, while the total
weight of the ROV acts to sink it. These two must be
balanced so that the ROV attains neutral buoyancy, where it
simply hovers and does not sink or float to the top. This
ROV needed additional weight.
After struggling with several ideas, the solution was a
14 inch square of ceramic tile, cemented to the bottom of
the frame with bathtub caulk along with several smaller
four inch square pieces. To fine-tune the buoyancy, a small
petcock was added at the top and bottom of the frame.
With the ROV just barely floating, these petcocks can be
opened allowing a little water to enter the frame and
adding weight. Adjusting how much water is in the frame
can achieve near neutral buoyancy.
The trim of the ROV must be level; the position of the
ballast is used to attain this. The height of the left and right
motors must also match the vertical center of mass of the
ROV. This allows the motors to push the ROV in a level
direction. For example, if the motors are mounted too low,
their thrust would tip the bottom of the ROV forward
Having lived near the water most
of my life and with manatees
showing up regularly in the water
nearby where we live in Florida, I
developed an interest in having
an ROV (Remotely Operated
Vehicle) to video sea life
underwater. Purchasing an ROV
can be expensive, so after several
prototypes, I successfully
constructed an ROV from easily
acquired parts that can be
assembled with basic tools.
Calling this project my ROV
Manatee seemed appropriate.
The ROV Manatee
38 SERVO 03.2016