Contents
How to Build Your Own Underwater ROV.
Using Thrusters With Props Controlled by a Joystick
Manipulator
Increasing Thrust with Kort Nozzles
Resources
ROV Glider (Just an idea)
Home Page
Contents
How to Build Your Own Underwater ROV.
Using Thrusters With Props Controlled by a Joystick
Manipulator
Increasing Thrust with Kort Nozzles
Resources
ROV Glider (Just an
idea)
How to Build Your Own Underwater
ROV.
"BOB"
My ROV, "Bob" is based on the "Sea Fox". It uses 5, 500 gph Johnson Bilge Pumps ($10 Each) for thrusters. Unfortunately these pumps have increased in cost to $20 since I built Bob in 2002. If you have more time than money you can convert bilge pumps to use propellers similar to a boat and then reverse wire the so you can reverse them. Since each motor can produce forward and reverse thrust you can design and ROV with only 3 motors. The control is an old Atari switch type joy stick ($10 on ebay), that now houses a 9 volt battery, and is wired to mechanical relays on the ROV using Cat-5 (Standard 4-pair Computer Network) cable. An extension cord provides power to the ROV from a 12volt trolling motor battery. And the camera is an Atlantis™ Guide View Underwater Camera System for $250 but the price has now dropped to around $100.
We named our ROV from the tasteless joke: "What do you call a quadriplegic who fell overboard?" ...BOB
My son and I with Bob. Just after completing Bob's pool trials
on a cold
Bob did surprisingly well. It only took a couple of days to build,
after about 2 weeks of getting the parts. The cold was the biggest
problem because it caused the cables to become very stiff making Bob less
responsive.
My wife takes Bob for a spin. She is a public school
teacher, and we see a bright future for Bob in her class curriculum.
Bob on the bottom. All of 5 feet for now.
I used pipe insulation to make the cables neutrally buoyant. The camera
comes with 65 ft of cable. The tether cable is actually 3 cables bound
together with plastic wire ties every 10 inches or so. 1 foot pieces of
foam pipe insulation are wrapped around the cable at 6 to 8 ft intervals again
using plastic wire ties. The wire ties holding the cables together prevent
the foam from slipping along the cable. The 1st float is about 5 feet from
where the cable attaches to BOB. With the first float in place feed
umbilical into the water until the previous float is almost ready to sink, and
add another. I added most of my floats at the lake in 60 feet of water using
BOB (with a little extra weight so it was negative) to pull the floats down.
This is best because the insulation is soft and easily compresses the deeper
your ROV goes. At 40 feet the float nearest the ROV had compressed and lost
some buoyancy, so the float 40 feet above (on the surface) had to be a little
bigger or little closer to the previous float. Then I removed the extra weight
so BOB was slightly positive and was all done. It sounds like I planed it that
way but is was a complete accident and I did not realize what I had done until I
got home and stretched the umbilical out on the lawn so I could wind it up. I
then noticed the the floats further from BOB were closer together.
The Atlantis™ Guide View camera works great and driving Bob is
easy after just a minute. The monitor shows a pile of leaves covering the
swimming pool drain. You can buy a Guide View camera for about $100 on ebay
or at
www.harborfreight.com, or LurkerCam is a less expensive
alternative. See
www.mninter.net/~boardman/ for
details and to purchase a kit.
Looking down on Bob you can also see the a
newspaper on the bottom. We were able to read the larger print adds with the camera.
My son Carl behind the wheel. Sixteen and he can drive anything. Vaya con dios.
Bob is 19 inches long, about 13 inches wide and 9 inches tall including the floats on top. The floats are
2" Sch40 PVC and the rest of the frame is 1/2 inch. The plastic grid is
cut from a panel intended to diffuse light from a recessed florescent lighting
fixture. The bottom PVC pipes running lengthwise hold
3/8 inch steel bar and candle wax for ballast. Plastic wire ties
hold the floats and gird to the frame and machine nuts and bolts hold the 5
Johnson Bilge pumps to the bottom grid.
Here you can see the starboard thruster pipe which is a 45 degree
bend, 1/2 inch electrical conduit that is glued onto one of the bilge
pumps. Also visible is the 2" PVC pipe that houses the relays for
the pumps.
The wires enter the housing thought drilled holes that are sealed with epoxy poured into a form made from PVC pipe.
The old Atari joysticks used simple switches, 1 for each of 4
directions, and 2 additional buttons. 1 on top of the stick that I use
for the down thruster and 1 on the base of the joy stick that I use for the up
thruster. There is also room inside for a 9 volt battery that powers the
relays down on Bob. Cat-5 computer network cable runs from the joystick
to a section of 2" PVC on Bob that houses the relays.
There is a threaded plug on the relay switch housing. I used a total of 7 single pole,
single throw 30 amp relays because they were cheep. 3 amp
would do and 1 double pole double throw would have been nice for full
forward. When the joystick is forward I turn on both the port and
starboard thrusters. Left and Right turns are only made by using only the
Left or Right thruster, and pulling back engages the
single reverse thruster that is mounted in the center. So pulling back
and to the right turns on the reverse and left forward thruster giving a nice
tight right turn. Right on the stick runs the left forward thruster, and center
forward turns on both the left and right forward thrusters.
Below is a wiring diagram for BOB. You can buy the relays for about $1 each. Here is one source: www.allelectronics.com They also have the Cat 5 network cable. The pumps you can get at a boating store like www.boatersworld.com. You can still find Atari joysticks for sale on www.eBay.com. Everything else can be found at Home Depot www.homedepot.com and WalMart.
Remove 4 screws and the top comes off to expose the pumps.
The camera is wired to the top grid with plastic wire ties. These things
are as handy as duct tape.
A tip for building with PVC is that you can bend it like rubber when its hot. If you want a special shape or don't get it
glued together perfectly flat, just put it in the oven for about 15 minutes at
250 F. (Watch it closely!) It will bend easily to the shape you want and
remain in that shape once it cools for a few minutes.
Looking down on Bob shows how the pumps are arranged. All of
the pumps have part of their exhaust pipes cut off and 1/2 inch PVC pipe is
glued on to direct the flow. The left and right side pipes are 1/2 inch Electrical conduit 45 degree turns. Yes, you
can bend PVC yourself, but these are too cheep not to
just buy. The up and down thrusters each have 2, 45 degree turns to
direct their thrust down and up respectively at the center point of the
frame. The reverse thruster uses 2, 45 degree turns to lower its thrust
to the bottom of the frame. This lets me pitch Bob downward a little with
the reverse thruster. This is helpful because I can not pitch the
camera. I have not tried this, but you should be able to get a
little better performance out of the pumps by adding a nozzle at the end of the
thruster pipes. Not too much or you run the risk of burning up the
pumps.
Update
Telling how close BOB is to objects is difficult and a couple of lasers on each side pointing so that their beams crossed about 6 feet away would be a great addition. The visibility was about 12 feet above 25 feet deep and the camera picture was fine, but at 60 ft the visibility was only a few feet. The inferred diodes on the camera were providing most of the light as floating partials would become brighter as they came closer to the lens. An additional light source would possibly help but there is so much suspended particles at that depth that more light could possible do little good. Diving a rock wall was the most enjoyable. Having a visual reference helps greatly. When the camera is staring off into the water column it is impossible to tell if the controls are even working. I tried adding to Bob is a small compass just in the view of the camera but it takes up to much of the field of view. The perch were extremely curious about BOB, three gathered quickly and came in for a close look, until hit with a shot from the reverse thruster. I didn't see them again after that. BOB is fun to play with but is not fast enough and does not have enough viewable camera area to make him a productive search platform. All in all I am pleased with the outcome. For now BOB is going on the shelf because we have hookah diving gear now and can explorer the lakes first hand. But a bigger and better ROV is on the drawing board.
My next ROV will be faster, have multiple cameras, lights, and carry a computer (PC/104). It will provide feedback through and be controlled by a network link to a laptop at the surface. Its hull will counter pressurized by a scuba tank system, and it will be powered by 240V AC generator topside. Hopefully it will reach 1000 feet for something under $2000. Perhaps becoming a crawler once it is on the bottom, with a metal detector and recovery arm. That would be fun!
Increasing Thrust with Kort Nozzles
Many tub boats and most commercial ROV's use Kort nozzles, or propeller shrouds because they significantly improve the thruster performance at low speed. They will give you more power, more speed, and help extend your battery life, so they are worth the effort if you are looking to upgrade. Please see the details about Kort Nozzles on my submarine web site's Thruster page. Click Here
A great resource for the
beginner ROV hobbyist is a book written for kids! "Build Your Own
Underwater Robot and Other Wet Projects" by Harry Bohm
and Vickie Jansen. It contains plans for the "Sea
Fox" and other simple ROV's.
Be sure to see what the model submarine builders are doing. They have lots of good ideas for thrusters, cameras, and ballast control. See Tim Smalley's www.rc-submarines.com He has a Sea Fox type ROV he uses to film model submarines. Go to his "My Projects" page.
I found some very helpful ideas and people at the "ROV Interest Forum" at Delphi.com. This form is a great place to find people who are working with real ROV's as a career. A better forum for hobbyist is RobotROV groups.yahoo.com/group/robotrov/
Links; See: Steve Thone's Homebuilt ROV's page: www.homebuiltrovs.com Steve has multiple ROV's and he maintains a good link page to other home made ROV's.
Send suggestions, comments, questions, donations, and cookies to me at Doug@submarineboat.com Hope you have as much fun with your ROV as I did with BOB.
Keep dreaming, learning,
exploring, playing... and don't forget to love someone.
--Doug Jackson