Help on school science expo

[seeker7805]

My 6th grader has been assigned the task of building a submarine for under $50 out of a 2 liter bottle. It must submerge, go forward and backward. These are the mandatory requirements.

So I came to you guys as the experts in subs.

We were looking at http://www.instructables.com/id/RC-Subm ... an-RC-Car/ , but I think we need a better propeller/motor system. Does any one have any suggestions? A cheap wtc built with a lego propeller system in it that will aid the bottle to go up and down?

Thanks in advance for your help!

Regards,
seeker7805

[JWLaRue]

Re: Help on school science expo

We need BigDave to chime in here...he likes to develop interesting one-off sub projects. Here's one that comes to mind given your requirements:

http://www.subcommittee.com/phpBB3/viewtopic.php?f=36&t=8753

-Jeff

[raalst]

Re: Help on school science expo

There is one important requirement missing, making this an easy assignment
it is not a requirement that the thing can resurface....

[Guest]

Re: Help on school science expo

Indeed. So get a cheap R/C toy car, waterproof the electronics, add some weight so it sinks to the bottom, and drive along, forwards and backwards.

[seeker7805]

Re: Help on school science expo

First I just want to say thanks for your advice.

This organization is really cool, and the subs you have all made are excellent!

So here are their "Constraints/Rules/Guidelines"

"1. You should use 2 liter soda bottle no glass material
2. the cost of the material is limited to $50
3. In water it should be very stable and balanced not flipping over
4. It should have a propeller with no more than 4 fins
5. You should be able to measure speed in water going forward, backward, up (float) and down (sink)
6. You should be able to measure buoyancy
7, If you are using pressure then you should be able to measure the pressure without touching the submarine
8. Be creative to make the bottle look like real submarine

Project should be turned in on May 9th on the blacktop at 1pm..."

My questions are
1.How much is it to have a simple motor inside a wtc that can do these things?
a. Is it possible to build an engine and propeller unit inside a wtc so we can put it in 2 liter bottle?

Once again, thanks for your help.

Regards,
seeker

[JWLaRue]

Re: Help on school science expo

There doesn't appear to be any restriction in taking the 2-liter bottle and cutting it in half so as to place something inside that is larger that would be possible through the necked opening……

Can you provide any additional insight as to what these two requirements mean?

• 6. You should be able to measure buoyancy
  7. If you are using pressure then you should be able to measure the pressure without touching the submarine

-Jeff

[seeker7805]

Re: Help on school science expo

Hi Jeff:

Thanks for your reply.

I for one have no idea what that means, but I will try to scour google on measurement tools regarding that issue. perhaps some kind of buoy to attach to the sub so we can measure the depth but as to pressure I have no idea how we are to measure that, or what pressure they are referring to. They said we can ask one of the monitors questions.

Thanks again!

Regards,
seeker

[raalst]

Re: Help on school science expo

a cheap electro motor can be operated in water, it does not need to be kept dry.
of course this limits it's lifetime, but a few trips will be possible. I had the motor running in the water
in a sub and the motors lasted more than a year (in my case a year was about 3 events).

running the motor(s) in the water simplifies your design.

just keep the electronics (receiver, speed control and the electronics of servo's) dry.
for a once-off you might consider "potting" the non-moving electronics in candle wax (or anything
else that can be poured, withstands water when hardened and falls within budget).

[seeker7805]

Re: Help on school science expo

Thanks! So earlier Jeff cited this url ,
viewtopic.php?f=36&t=8753, i clicked on it but did not have access. Do I need to become a member to access that link and talk to Big Dave?

I looked at the MIT Sea Perch, and I thought it looked too complicated, there must be a simpler and more elegant way that comes close to getting what we need.

[JWLaRue]

Re: Help on school science expo

Oh…I didn't realize that it was in the members only section. Let me see if I can get BigDave to respond here.

-Jeff

[seeker7805]

Re: Help on school science expo

Thanks!

At this point, I am thinking of getting two of those rc mini subs that are selling for 11.00 a piece and strapping them to top of a two liter bottle.

Or maybe cannibalizing them and modifying them to fit somehow on the bottle.

Once again, thanks for your help!

Regards,
seeker

[bigdave]

Re: Help on school science expo

Hi guys
I just checked and all the photos that were on my build are gone?
I will try to find some. BD.

[scott t]

Re: Help on school science expo

Pictures from thread listed above.

[seeker7805]

Re: Help on school science expo

Thanks! The pictures are cool! Now I just have to learn how to build it.

Regards,
seeker

[petn7]

Re: Help on school science expo

Out of curiosity, is this a school assigned project?

I know I'm not that that smart, but I can't even do this project now, let alone in elementary school. Is it due on May 9, 2024?

I feel so inadequate.