Engineering school project

CHARGER2

Petty Officer 3rd Class
Joined
Jun 14, 2012
Messages
80
My team (Junior/Senior mechanical engineering undergrad students) needs to make a machine that will propel itself 10 feet in a swimming pool as fast as possible using a small 4 speed DC motor.

General rules:

-Must fit in a shoe box.
-Must contain a 4-bar linkage (even if used to drive a prop/wheel).

Currently investigating "steamboat" style paddle boat, prop driven boat, something that sinks and rolls across the bottom, an oar contraption...

Any interesting ideas/suggestions out there?

Regards
 

Alan_Scott

Seaman
Joined
Nov 25, 2011
Messages
69
Re: Engineering school project

Use the motor to build up kinetic energy in a spiral torsion spring that would drive a prop? Then the 4 bar could be used in the release mechanism.
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Engineering school project

I would bet using a forum for finding a way to do it is not one of the general rules.
 

CHARGER2

Petty Officer 3rd Class
Joined
Jun 14, 2012
Messages
80
Re: Engineering school project

I would bet using a forum for finding a way to do it is not one of the general rules.

Sharing ideas to find the best way to solve a problem in encouraged :D
 

tpenfield

Moderator
Staff member
Joined
Jul 18, 2011
Messages
17,620
Re: Engineering school project

My 2 cents . . .

work the problem/challenge from 2 angles . . .

- The 'boat' should provide minimum resistance to moving through the water . . .

- The propulsion system should make maximum use of the available power from the DC motor . . .

If you can master those 2 issues, then you probably have a 'winner'
 

southkogs

Moderator
Staff member
Joined
Jul 7, 2010
Messages
14,783
Re: Engineering school project

Less resistance on the surface, so you'll get more speed on the dry side. Wonder if you could use the DC motor to inflate a bellows to give you a "jet" effect from the output? If you could build a light 4-bar frame (bicycle type), and put the bellows on a set of catamaran sponsons (high density urethane) you might be able to keep your weight down too.
 

stackz

Master Chief Petty Officer
Joined
May 29, 2008
Messages
830
Re: Engineering school project

so does the machine have to be a shoebox or just fit in one? does the 4-bar linkage have to be function or just be attached to the motor and do something?

I'd get a couple lithium ion batteries (the types for the tiny remote control helicopters) and wire them to get the most power to the motor. get a small plastic kids boat that fits in a shoebox. put the motor in rear and batteries in midway. Toss a prop on the motor out the back.

Use the 4-bar linkage add in steering (I'd get a super cheap remote control car that steers left/right and rip the steering assembly out of it and modify it to a simple 4-bar and probably mount dual fins jutting out the side of the boat while wiring the forward motion to the motor. basically, have the linkage flipped on its side with the middle being the pivot and the outer bars attached to stationary on a boom frame (I guess you would call it). make the outer bars pivot points the front of the fins so they turn left/right. Try to imagine this planar 4-bar setup like that...

300px-Suspension_train_watt.svg.png


if it doesnt have to control the boat in any way, just rob another small motor with separate batteries to make some paper cut people wave or something...

bam, tiny little fast remote control boat that fits in a shoebox and has a 4-bar linkage that does something.

try to imagine this train suspension 4-bar

let that thing rip like a madman across the pool.

I would just approach it like the cubscouts pinewood derby...everyone tries to re-invent it but just shave it down to tiny, insert metal rod in middle and fill ends with epoxy. light, tiny, fast, and wont break to pieces at the other end :p
 

Nickypoo

Petty Officer 1st Class
Joined
Mar 21, 2012
Messages
287
Re: Engineering school project

Sounds like a fun project. I'm majoring in mech engineering too.

I can say that having something sink and roll across the bottom wouldn't be good. You would have to wait for it to sink, and then water resistance would just make it super inefficient and slow.

Unfortunately the "winning" solution would probably be just a standard boat design using a lithium battery and brushless motor and propeller, and do something cheap to satisfy the 4 bar requirement. For sure that would scream across 10 feet. That isn't very interesting though.

It would be cool to make something that can walk on water using surface tension, but I think your design parameters wouldn't allow for that. You could maybe look at some hydrophobic coatings that would enhance the effect, and use incredibly light/small components made out of composite materials. That would be awesome.

Edit: Like this video: Surface Tension - YouTube This is where I'm interning this summer!

It seems a little cheap to allow a prop though. Are there any rules against that?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,296
Re: Engineering school project

small RC cars with paddle wheels (chevrons) will skim across the water, however that is not that interesting.

small boat would fit the bill, however as stated, not that interesting either.
 
Top