Magnetic coupling Thruster design (Some big challenges!)

[VegardP]

Hi there Deepsea explorers.
I am still gathering information on my hobbyproject and trying to get a proper design up for prototyping and testing for my longterm ROV build.
I try to share some of my experiences and hope that some of you might help out as well.
If any of you have some interest in working together withe me on developing an opensource model for a magnetic thruster feel free do drop me a PM or reply below

After ALOT of reading about different approaches to building my own ROV Thruster i made my mind and am avoiding the bilge pump thruster method and going for the more heavy design.

Using a magnetic coupling to connect the propellershaft to the motorshaft and by using a smallscale brushless dc motor and a ESC motordriver i plan to take on much heavier depths than i could using either the O-ring, Face-seal or lip-seals on the thruster housing.
There is alot of commercially availiable couplings allready built so this may be an easier approach than building the whole system from scratch.

Since the brushless motor is designed to work when submerged in mineraloil the possibility to flood the motor housing with mineraloil and completely seal of the housing from the outside pressure using magnetic drive this design should handle almost as much as the other commercially availiable thrusters.

As this forum is quite new i will put out some links to stuff that might get things going.

Some thruster references from other ROV enthusiasts: (may save you a google search or two)
http://aquaticus.info/thrusters
http://www.rcgroups.com/forums/showthread.php?t=580739
http://www.cnczone.com/forums/rc_roboti ... seals.html
http://www.physicsforums.com/archive/in ... 81533.html
http://www.physicsforums.com/showthread.php?t=150247

commercially available thrusters is
http://www.tecnadyne.com/faqs.htm
http://www.deepseasystems.com/4000.htm
but soooo expensive...

Here is some interesting finds about underwater connections and other stuff you might want to check out for your design.

http://www.subconn.com/default.asp?objt ... ch&id=2451 - underwater ethernet connections through hull without comprimising the integrity of the chassis.
http://www.mtroniks.net/details1.asp/Pr ... an68.5.htm (built for model planes but i have read about some people trying it for underwater though).
http://www.aero-model.com/ - brushless motors for model planes. (to high rpm on most motors but if it was possible to gear down the axis with some worm gearing or such it could work)

Also do check out some of the FPV community when it comes to OSD and small camera tips.
http://www.decadenet.com/bob4/bob4.html - build your own On screen display with this OSD module
http://www.rangevideo.com
http://fpvpilot.com/default.aspx

And ofcourse the microprosessor Arduino is becoming an altime favorite so check out www.arduino.cc for Atmel PIC controller to run the electronics in your ROV. Using an ttl to RS-485 converter you can run serial link for 100meters or more through regular cheap cat5e TP cable. Check out the MAX485 chip for this.
I will post alot on this another time.
More on cameras on my other post in the cameraforum

[OCE Student]

SeaBotix makes what is probably the best thrusters for homebuilt use
www.seabotix.com
These will run you about 600 USD a piece
If you are interested in magnetic coupling you might want to check out this paper
http://www.marinetech.org/rov_competiti ... 0Final.pdf
Looks like you have been doing your homework goodluck

[Spadinator]

I like the magnetic coupler idea. Are they rare earth magnets that are on the coupler?

[VegardP]

Regular strong neodyme magnetcs will do

[ROV-Control]

We built our thruster with brushless motors running with no housing (principle these motors are "magnetic couplers") and made very good experiences with them. 65m depth in mediterranean sea and no problems with the electric in the saltwater. The only thing: It is very important to clean them with fresh water after diving! T

[Spadinator]

We built our thruster with brushless motors running with no housing (principle these motors are "magnetic couplers") and made very good experiences with them. 65m depth in mediterranean sea and no problems with the electric in the saltwater. The only thing: It is very important to clean them with fresh water after diving! T

Interesting....I wondered if a outrunner brushless would work. I plan on exclusively fresh water dives less that 100 ft and I can get brushless outrunner motors pretty inexpensively.

[ROV-Control]

On my opinoin it is the best an cheapest way to build thrusters. You just have to paint and seal the wires. But this isn't a real bigh problem.

[VegardP]

We built our thruster with brushless motors running with no housing (principle these motors are "magnetic couplers") and made very good experiences with them. 65m depth in mediterranean sea and no problems with the electric in the saltwater. The only thing: It is very important to clean them with fresh water after diving! T

Like the idea but you may want to protect yourself from the sea with some sort of housing anyways.
Do you have some reference website link or project info i can have a look at ?

[ROV-Control]

http://www.rov-er.net/images/P5040005.MOV

http://www.rov-er.net/images/P9090001.MOV

http://www.rov-er.net/index.php?option= ... ry&catid=1

Here are two videos testing the thruster
The brushlessmotors run direct in the water. We tested 13 thruster in seawater like them with no problems. The only problem is sand. The motors will be damaged after a certain. So we painted it with a special electric plastic paint so that they cannot corrode so fast.
Hope your answer is solved

[VegardP]

Do you have the spesification on what kind of brushless motors and esc u guys used?
Btw. Great work on the webpage and the german rov forum is brilliant. Just one thing sucks, and that its all in german.
I have to use Google chrome to translate all the pages and the translator isnt that good
Still a great ressource for people!