Mouse Trap Powered Boat - Looking For Suggestions and Ideas

[Trace]

Basically, I need to power a boat with a maximum of 2 mousetraps. It must fit inside 20cm cube before being sprung.

Mousetrap must transfer power to paddle wheel or propeller.

It will being going around a kiddie pool with a trashcan in the middle.

I'm taking suggestions! Any questions, just ask!


Thanks,
Trace

[d_stilgar]

I would suggest some version of a continuously variable transmission. The mousetrap is going to have the most torque at the beginning and the least at the end. With a propeller on a single gear this will result in a high speed propeller at the beginning when the boat isn't even moving yet and a slow propeller at the end when that speed would be useful.

In middle school we built newton air cars (rubber band powered propeller cars). We had severe limits on what they could be made of. We also had to make our own propellers. My group ended up making a somewhat flimsy propeller that would flatten out at the beginning cutting through the air easier, and then moving back into shape as the rubber band wound down. This acted as a variable transmission of sorts and our car beat the all time school record pulling 9+ Gs.

I'm not sure what kind of resources you have access to, but if you can, I would go with a paddle boat. The paddle wheel should be made out of tiny wings, with aerofoils. This with give you the most forward movement through the water. If you look at this google image search (http://images.google.com/images?q=vertical%20wind%20turbine&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&sa=N&hl=en&tab=wi) for vertical wind turbines you will see what I am talking about.

Also, it looks like the boats use a long arm coming from the rat trap to pull a string on an axle connected to the wheel. This is a simple way to experiment with a "transmission" and "gear shifts." If you have a dowel as your axle, make it out of dowels with varying diameters. The greater the diameter of your dowel, the more torque you will get. If the mouse trap pulls the string one linear inch on a dowel with a 4 inch circumference, then the paddle wheel will only have made one quarter turn. If that same string is wrapped around a dowel with a 1/4 inch circumference, then you will get four rotations from that same inch. By varying these lengths, you can wrap your string so that you get torque when you need it, and speed when you need it.

By experimenting with the above, you should be able to get a boat that can be set for speed or distance during different runs. I should note that the settings for the two will probably not be that far off. In a supermilage vehicle competition a few years ago, a team showed up and ran their vehicle at 32mph (the fastest they could make the corners on the track). The other vehicles ran at 5mph and thought that the fast vehicle was just trying to lose as fast as they could so that the misery could be over. The fast vehicle ran out of fuel a few hours before any of the other vehicles, but they had traveled a much greater distance in that time and ended up winning the competition. Now most supermilage vehicles run at a faster speed. This has to do with Newton's first law of motion. Once the vehicle is at speed, remaining at that speed consumes the same amount of fuel no matter what speed that is (air resistance neglected).

Some things to considered:

1) Use the mousetraps together for increased torque and power.
2) Maybe use them in a multistage configuration (complicated. Not recommended)
3) The longer the arm on the mousetraps, the less torque they have, but the longer linear pull they make.
4) Compensate number three and go with a medium length arm combined with a varying thickness axle to vary the speed/torque.
5) Keep it simple. Pulleys may seem like a good idea given your limited dimensions, but your machine is as reliable as its least reliable component.
6) Resistance is much greater in water than in air. Your time will be equally well spent designing a boat with the least drag possible as it will be spent trying to propel it.
7) Can you modify the traps? The spring will surely bend past 180 if you remove part of the trap. That's potential energy waiting to be harnessed.

Good luck!

[Cryptonic]

I second the boat with a gearing system and paddle boat wheel idea but it'll take time to get the correct gearing. My main concern would be perfecting the angle of the rudder(s) to keep the boat going in a consistent circle. Without them it won't matter how fast the boat goes if you lose all that momentum hitting the bin in the middle or the outer edge of the course.

Also, I doubt he can modify the traps in any way. Heating the springs or bending past 180 would be cheating imo.

Tried my hand at creating a mousetrap boat in sketchup...
http://www.filedump.net/dumped/mousetrapboat1257235787.jpg

[Oneslowz28]

YOu said you can use 2 mouse traps right? Use the first to get the boat moving (larger dowel) and set it to trip the 2nd mouse trap about 3/4 through the first's sweep. Have the second one connected to a smaller dowel on the same axle for extra speed points.

[mDust]

I saw that everyone else took care of the power aspect of the boat...but nobody mentioned the aerodynamics (or fluid dynamics I suppose) side. I don't know if there are more rules other than what you mentioned but I'd recommend doing something like this:

http://img134.imageshack.us/img134/284/trapboat0001.jpghttp://img513.imageshack.us/img513/5489/trapboat0020.jpghttp://img265.imageshack.us/img265/7315/trapboat0040.jpghttp://img692.imageshack.us/img692/9883/trapboat0060.jpg

A little wax on the bottom and sides should make it glide like no other...:up:
That should keep it from nosediving if a little water gets on top, if it does hit the side of the pool or the can it should just glance right off and continue on its way. This or any other effort to reduce drag will be pretty beneficial.

Another thought is to put the mouse traps as far forward as possible and attach 10cm (or the longest that will legally fit) sticks to the trap spring to maximize leverage. The axle-wound string would tie to the tip of the sticks.

...I doubt if anyone else is going to do anything as hardcore as what has been mentioned in this thread (assuming this is a school project) so you'll have the full advantage. This is a physics project right?

[Trace]

Yes, it is a physics project, and all of your guy's help is appreciated.

I like the wax idea! I hadn't really thought about that.

I think the 2-stage mousetrap is a great idea, just a bit hard to implement.

I believe that mousetrap modifying is allowed, I will check into this.

+Rep to everyone!

Keep the ideas coming! :)

Were you talking about a design like:

http://www.inhabitat.com/wp-content/uploads/maglev1.jpg

[d_stilgar]

Yeah. Something like that. Those paddles are airfoils. This design would help in the water as well. The number of foils, their size, and the angle of attack into the water would all be variables you would have to deal with though.

Your other big issue is the size restriction. A 20cm cube is really small in the end.

[Trace]

I know. I'm trying to make the mechanics as small as possible.

[Cryptonic]

mDust got me thinking about possible hull choices with his earlier post. But I want to quote what d_stilgar said also.


"6) Resistance is much greater in water than in air. Your time will be equally well spent designing a boat with the least drag possible as it will be spent trying to propel it."

Now wouldn't a dual hull have less drag then a raft style bottom? Something along the lines of a catamaran/pontoon style hull may work better.

v2
http://www.filedump.net/dumped/mousetrapboatv21257315899.jpg

[Trace]

I like the ideas, it's getting me to think more about things I hadn't thought about.

i built a Gearbox out of Knex last night--for every full turn at the input, i get 6 full turns at the output.

[billygoat333]

I second the dual hull pontoon boat idea. seems like it would work the best, especially with the paddle wheel.

[mDust]

Now wouldn't a dual hull have less drag then a raft style bottom? Something along the lines of a catamaran/pontoon style hull may work better.Much less, yes. The less boat that's actually in the water, the less drag the water will exert on it. I even thought about hydrofoils, but I then I snapped out of my dream world and realized that would never have a chance at working at such slow speeds. Pontoons are definitely a good idea.

[XcOM]

with pontoons you could also shape either the bow or stern (See i know proper terms like!) to stear the boat round, you could even make these ajustable, i assume its with regards the longest distance covered rather than the number of times round the pool,

if the former make the turning circle as wide as possable to reduce drag, if the latter, make the turning circle as small as possable.

i suppose for an idea with the dual mouse trap idea, you could make the second trap trigger by the first, and make the string powered by the first come loose,have a gear box working so it winds the string for the second so it is tight when the first finshes, use the movement of the mouse trap arm to somehow change the gear so the second trap would then power the boat, half the power short term, twice the power long term,

I know what i mean, not sure if anyone else does? will try to do a quick sketch (If i can)

[Trace]

I get basically what you are saying. It is the most times around, so the inside track is where I will be. I'll try my hand at sketchup and see what I can create.

[mDust]

It is the most times around, so the inside track is where I will be.Heh, just put a couple wheels on the 'inside' side to hug the can as your waxed up pontoon powers through it's gears around the shortest laps possible. Win.;)
Make the turn radius the same as that of the can and start the boat right next to it. Even if you don't get to place the boat yourself, and it starts in the middle, it will spiral towards the can...and if you use the side wheel idea, it will just continue around the shortest possible lap.

[Trace]

Side wheel, Check, friend and I thought of this already!

[mDust]

Side wheel, Check, friend and I thought of this already!Awesome! Only other thing I can think of is to mount a wheel on the front and back corners so no part of the boat can possibly touch the can. This would also conform nicely with the curvature of the can.
Graphite lube in the wheel axles and the drive axle could reduce friction there.
I guess shaving mass off the boat could help it ride higher in the water.
You could also paint it black:

By keeping the air near the surface warmer, it reduces the viscosity of the air in the boundary layer. This reduces drag.lol, how far are you willing to take this project?:)

[Trace]

How far? Oh I'd say about as far as 4 loops around the pool :)
Lol, It's going pretty serious. So, I'm willing to take it pretty far.