Mousetrap Cars/Planes

[PoWn3d_0704]

Alright! So... this is my first post on this website and i need some ideas. I currently have a school project that requires me to build a mousetrap powered cars. Well, vehicle. We are allowed to use ANYTHING we want I i can say with confidence that i will have every kind of tool i might need. So far i'm going to be using a sail servo for gears (pretty good idea i think considering i'm 14 and thought of it all by my lonesome) and a lot of carbon fiber. (i love Carbon fiber.) the servo is a 1:110 ratio so for every one turn of the largest gear, the smallest turns 110 times. It should be really good considering i'm most likely going to be using 5-6 inch wheels. I'm also going to but a half-circle on the swing arm of the mousetrap to keep all of the force on the string all the way through the pull of the trap. (if you can picture that.) I can't really decide what to do about the rest of the car, however. The whole airplane post will be right below this one...

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And then there is the airplane problem. Like I said, there is basically no rules except that the mousetrap can be the only thing powering the car/plane/whatever. My friend/competitor wants to make his into an airplane which i also believe is a great usage of another sail servo. I'm not really an expert of the matter, but i can again, say very confidently, I will have/can get all of the supplies you can come up with. Here's a great chance to really let all of your engineering loose and i challenge you to think of something good before i do, regardless of my age.

[CaptainPanic]

Sorry for not being very helpful, but you're basically asking us to completely design two machines? Do you have any specific questions?

 

It seems to me that you have figured out the car already (you have a source of energy and you know how to convert it to spin the wheels)... so no question there? My only advice is: reduce weight wherever you can.

 

About the airplane. I am not sure about this sail servo. It's a nice idea, but I get the feeling it's a bit heavy. But if it needs to fly, I would start with finding an old RC (= remote controlled) airplane. Then remove the engine, and probably also replace/redesign the propeller (because I doubt you'll reach the rpm that the old engine did, if it's a real RC airplane with engine).

 

But without any specific questions, I could talk forever and still give no relevant feedback.

[PoWn3d_0704]

Yes... i see your point... sorry. I was basically wondering about how to get the RPMs up high enough for lift off. If you look on the side of the mousetrap, the arm has a little thing tat spins... i know it's not very specific... but you have to look at trap to really get it. I was wondering if cutting the bottom part of the mouse trap off to let the thing spin constantly at just hooking that straight up to the prop. That should give me the torque to get lift off, but i don't think it would spin for very long. Gear reduction is the only other idea... and i need to decide. Thanks for the input anyways, and my entire car is carbon fiber. Not the lightest material i could have used... but defiantly the best (i think)

[CaptainPanic]

Just a thought: why not go for a helicopter?

Then you only need to worry about the propeller and the rpm's... no wings that will cause any trouble.

 

Did you calculate the energy stored in the spring? It's not much anyway, so I wouldn't worry too much about flight time. Just lift off is an achievement.

 

To overcome the gravity, you need to create a force (however brief) that is greater than the gravitational force. Since your spring contains so little energy, you'll have to focus on releasing this energy in a very short time (a matter of seconds).

 

Since this is a school project, I think your teachers would be pleased if you actually work out how much energy you can store in your spring.

[PoWn3d_0704]

Yes.. I can also see your point there... A helicopter could get complicated on the whole balance aspect. It still has to move forwards. We (well they, i'm just giving advice and ideas) are making a model of the Kittyhawk. That first airplane by the wright brothers. We're not sure if we're going to use the prop at all for the actual competition, but just the body w/ wheels. We are defiantly going to get this to work afterwards though. Like you said though... the sail servo is way too heavy and the mouse trap itself is almost too much. The reason they are using the Kittyhawk is because of the two wings, one in front and one in back. It SHOULd provide lift from both ends of the airplane. Thoughts?

[cameron marical]

There has actually been like 3 other threads regarding very similiar assignments, wich, in my opinion, Is quite strange due to the relatevelly different means of achieving kinetic energy. You can check them out too, for extra info. {search at the top}

 

How big would this thing be? Sorry if you already said it, I just skimmed over it, but would something with 2 ski paddle looking things on the sides, and then have the mousetraps move them up and in a circle so it progresses the device forward work? {sorry I cant find a pic to help out, I know that similiar designs were used for early moon rover ideas}

 

Good luck.

Edited June 7, 2009 by cameron marical

[PoWn3d_0704]

Welll..... it's due tomorrow and i've pretty much already built the whole thing. Here's what it's like... (i'll post a picture later) It's base is like a block of Balsa wood about 1 inch thick, 2.25 inches wide and just over 10 inches long. We cut a long slit towards the back half of the wood to allow the drive wheel (yes... only one drive wheel) through to touch the ground. For ther front axle, I found a nice piece of 1 inch square steel tubing. I drilled a 5/8 hole through both sides of it with a drill press for the carbon fiber axle. I went out and bought some Ball Bearings to slip into the holes i drilled for the axle. I slipped the axle through the ball bearings to complete the axle. I'll put the rest up later... since we're testing it right now... well.. we know it works... it's just the radio controlled part we're testing now. (yes... we put a servo on it. just to turn it... not to push it.)

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HAHA! 191 feet. 2nd place was like 87 or something.