Subject:
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Re: running the motors underwater
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Newsgroups:
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lugnet.robotics.rcx
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Date:
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Thu, 29 Jun 2000 23:38:52 GMT
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Viewed:
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1370 times
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Ben Erwin wrote:
> A few years ago some kids I was working with were trying to outfit a LEGO boat
> with a paddle wheel and micromotor. While they were working, one kid got the
> idea that he was going to put a propellor onto one of the 4200 rpm motors, add
> wheels, and have it drive around the bottom of our water tank. He used LEGO
> weight elements to make it sink.
>
> Somewhat to my surprise, the thing worked. The wire was connected to one of
> the 9V battery packs, which remained above water in his hand as he drove it
> back and forth. (and then he would make it rise to the surface and splash
> everyone -- that was the end of that game)
>
> So about a year ago or so I decided to try a similar thing with the gear
> motors and the RCX. Except this time I had read a book about underwater
> robots, and i really wanted to make a sub. To make a long story short I have
> a working underwater submarine, with the motors are exposed to the water, and
> it works.
>
> I told some people at Mindfest about this and they were pretty shocked that
> the motors would work underwater. Well... they do... for a while... and I had
> fun making the thing drive around my industrial size sink, do turns, etc...
> But I have had motors resurface and then the axle makes a little noise when it
> spins... or I've had them seize altogether.
>
> Needless to say, I haven't played with the sub much.
>
> QUESTION STARTS HERE:
>
> But I was wondering if anyone has done any experimentation with blocking up
> those holes at the back of the top of the gear motor and doing underwater
> tests then? These are the holes that allow you to stick in a small
> screwdriver and pop off the back panel (which doesn't do much good). Do these
> holes serve any purpose? i.e. if they help cool the motor or something than
> perhaps I shouldn't block them up with silicon?
>
> Curious,
>
> Ben
The main problem is that the motor isn't water prof. It's rusting inside and or
the grease is breaking down.
The motor will heat up while in use. This would cause a sealed motor to push the
air past the rotating axle.
Ok, now when the motor cools down, (Stops running for even a second) your going to
get the inverse, it's going to suck water INTO the motor. Since water is on the
bottom it will continue to blow air and suck water until it's dead... Same effect.
Your best bet would be to use an enclosure or to make a motor out of a waterproof
one and add lego bumps.
I hope that helps.
Dean
--
Coin-Op's For Sale!: http://www.akasa.bc.ca/tfm/coin-op.html
Dean's Lego Workshop: http://www.akasa.bc.ca/tfm/lego_wr.html
Vancouver Lego Club: http://www.akasa.bc.ca/vlc
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Message is in Reply To:
 | | running the motors underwater
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| A few years ago some kids I was working with were trying to outfit a LEGO boat with a paddle wheel and micromotor. While they were working, one kid got the idea that he was going to put a propellor onto one of the 4200 rpm motors, add wheels, and (...) (24 years ago, 29-Jun-00, to lugnet.robotics.rcx)
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