Science Project, building a small car

Discussion in 'General Off-Topic Chat' started by Salamantis, Jan 25, 2008.

Jan 25, 2008
  1. Salamantis
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    Member Salamantis GBAtemp Advanced Maniac

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    Hello,

    Well a week ago our science teacher gave us a project. We need to build a small car using a plastic bottle (591 ml), that can advance using no electricity whatsoever, and must be propelled automatically (eg. no pushing the car). There's a list of materials you can use, and you can only use these and no others:

    Materials:
    2 balloons from a height of 30 cm when they are inflated
    An elastic band with a length of 1 meter
    20 wooden sticks (the type that they use in the doctor's office)
    Glass beads or other objects that may give weight to the vehicle
    A piece of wood with the dimensions of 305 mm x 10mm x 10mm
    2 sticks of wood with a length of 450 mm and a diameter of 7 mm
    2 sticks of wood (kebab-style) with a length of 305 mm and a diameter of 2 mm
    A plastic bottle of 591 ml (such as sports drinks, used for main structure of the car)
    2 pieces of foam core board 305 mm x 305mm x 5mm
    A paperboard of 305 mm x 305 mm
    10 rubber elastics
    4 gears
    3 strings a length of 1 m
    10 straws
    A mousetrap
    A plastic tube with a length of 70 mm and a diameter of 8 mm
    A plastic tube with a length of 70 mm and a diameter of 16 mm
    A plastic tube with a length of 70 mm and a diameter of 23 mm
    A piece of corrugated polyethylene 205 mm x 300 mm x 5 mm
    A piece of polystyrene rigid foam (non-expanded) 305 mm x 180 mm x 3 mm
    4 pulleys
    2 tension springs
    4 styrofoam cups

    And the things you can use to attach them together:
    Finishing nails
    Carpenter's glue
    Hot glue
    Iron wire
    Contact glue
    Masking tape

    The bottle's cap will be mounted on the car to transport a regular golf ball. It cannot be attached permanently (the golf ball) to the cap.
    The car must be light enough to be easily transportable by hand.
    The car must look good.

    It must drive on a flat floor and there can be no human factor to propel it. It must travel the longest distance possible.
    We just can't think of a way to make it move!

    Thanks for helping me out!

    EDIT: For the french people, here's the original paper: http://i18.photobucket.com/albums/b127/sal...02/Materiel.png, and the paper with the rules: http://img177.imageshack.us/img177/9241/conceptzt1.png
     


  2. FAST6191

    Reporter FAST6191 Techromancer

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    Movement huh. First your conceptqo2.png image is a bit hard to read in basic firefox at all but a fairly ridiculous resolution but that is nothing major.
    Second these sort of things are really designed to test you guys so me doing it all is probably not a good idea. Hence concepts and possibilities are what I offer. I will say keep it simple: too many contraptions if you do not know what is what will likely doom you.

    Self contained vehicle seems to be the order of the day (otherwise I would say making a launching platform: it is very debatable as to whether it is allowed in the rules but you could make a kind of self carried platform by pressing down on two sticks attaching the springs to the sticks, pulling back and letting go of the car: it shoots forward and you let the sticks go. They get dragged off.....).

    Anyhow 1st rule of thermodynamics goes roughly energy can not be created or destroyed only converted or stored.
    Stored energy conversion it is then.

    Energy storage
    You have two reasonable possibilities (I am assuming they will not be too impressed if you burn stuff or use compressed gas other than air (or burn stuff to create compressed gas)):
    energy storage via elastic (I am counting the balloon in this despite it technically being air pressure for the most part)
    1) elastic band/mousetrap/Tension springs and 2) balloons.

    gravitational potential energy
    I see a limit is less than or equal to 2KG (if you were using imperial units I would suggest a dodge of using helium but that is getting into semantics and a different discussion) which limits this one a bit. You could also have problems with centre of gravity being too high (a slight kink in the wheel resulting in a sharp turn and you fall over: solved by making a wide base). I mention torque later but if the pulleys are beyond the basic wheel on an axle you can alter speed (by and large in these sort of things it is he who moves fastest with some semblance of stability with a nod towards friction issues goes furthest)

    energy conversion:
    It is all well and good having a rubber band/some other elastic storage or something heavy and high in the air but unless you can make mechanical work occur then it useless.

    Two simple methods:
    For gravity a water wheel approach is probably the simplest (and a bit problematic as the rules appear to say no shedding of stuff en route) but you could also do a coiled string tied to a mass: raise the weight and have the string around the wheel/axle the weight drops and the string gets pulled turning the wheel. You could also adapt this for a spring quite easily.

    Mousetrap: it is crude but it could be used as a lever/ land based oar. The springs are usually fairly tightly wound too giving a nice shunt. This oar approach can be adapted too for other elastic storage. Consider as well as an oar a piston approach (you do not have to make a push if you have a something already moving).

    Air propulsion.
    I am assuming at some point you had an expanded polystyrene plane you twisted at the propeller and watched it fly into a wall/power line/sibling/pet before either shattering or bending in half nicely. Basically one twisted/wound rubber band and a propeller (this will be the hard part as you will likely have to look up some basic stuff on propeller design)
    Your main problem would be regulating the output (which with a 1m band wound to give some decent output is far easier said than done).
    We have all had a balloon fly around the room so that one does not need to be explained, 2 balloons can be used to create a more stable output too. I suggest fixing the business end of the balloon rather than trying to contain it.

    I know I said keep it simple but some timing mechanisms (i.e. have the mousetrap hit something that holds the springs in place as it finishes its rotation) can allow you to combine multiple methods making for a nice distance travelled.

    Also the gears what sizes are they or are they 4 gears of any size (within reason). You can use these to modify speed and torque but be warned a gear going one way makes a joining gear go the other.
    [​IMG]

    A tip: grease your axles (or whatever is turning) or make something low in friction for them to run it (a bit of set glue will do nicely).

    Have fun.
     
  3. jgu1994

    Member jgu1994 GBAtemp Advanced Fan

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    Wow, what an awesome project imo. The only time I had a chance to do something half as cool as this was for an afterschool engineering activity. Good luck dude!
     
  4. test84

    Member test84 GBAtemp's last ninja 2.

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    wow, I love to see these kind of conversations.
    sorry for being off topic, couldnt resist of saying this.
     
  5. OSW

    Former Staff OSW Wii King

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    I think that this kind of project is so common in lower high school levels in australia too [​IMG]
     
  6. rhyguy

    Member rhyguy GBAtemp Maniac

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    why not cut a hole in the bottle and put balloons in it
     
  7. Salamantis
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    Member Salamantis GBAtemp Advanced Maniac

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    Wow dude, thanks for taking the time to help me! And sorry about the concept page, I've resized it now [​IMG]
    I don't understand the water wheel approach, if you could explain a little more. And for me, what would be the best possibility?

    Thanks man! [​IMG]
     
  8. Sinkhead

    Former Staff Sinkhead yay p1ngpong.

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    What about something like this. I only briefly read through the guidelines though, so I'm not sure if it's allowed. I'll take a proper look now.

    [​IMG]
     
  9. Salamantis
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    Member Salamantis GBAtemp Advanced Maniac

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    Hrm, I'm pretty sure that will work out fine. I'll print that out and show it to my friend (we're in teams of 2). We also need the design to be approved by the teacher [​IMG]

    Thanks Sam, I'll get back to you on what he thinks of it [​IMG]
     
  10. notnarb

    Member notnarb Not narbing it up

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    can't you just make a mousetrap powered car? Or are you not allowed to add any energy to it yourself?
     
  11. Salamantis
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    Member Salamantis GBAtemp Advanced Maniac

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    It has to move in an automated manner. And what is a mousetrap car?
     
  12. notnarb

    Member notnarb Not narbing it up

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    edit: Just read your signature, can't help you
     
  13. Salamantis
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    Member Salamantis GBAtemp Advanced Maniac

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    Ugh! I don't effing get the mousetrap car! I've looked at tutorials, YouTube vids, and still don't know how it works!
     
  14. notnarb

    Member notnarb Not narbing it up

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    Edit: just read your signature, can't help you
     
  15. Salamantis
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    Member Salamantis GBAtemp Advanced Maniac

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    ?
     
  16. FAST6191

    Reporter FAST6191 Techromancer

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    I think it refers to your like of Mr Jobs.

    sinkhead already gave a picture better than I could have cooked up on the water wheel.

    The mousetrap car works in a similar manner to the coiled weight approach I suggested, you tie one bit of string to the mousetrap err trap part and when it slams shut it pulls the string which is tied to the wheel (see ripcord) thus moving the car. Probably a better approach that the oar/shunt thing my sleep deprived brain was cooking up in my reply.
     
  17. Salamantis
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    Member Salamantis GBAtemp Advanced Maniac

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    If it's not too much for you, could you make me a simple diagram like sinkhead's but with the mousetrap car? It would help a lot.

    Thanks!
     
  18. FAST6191

    Reporter FAST6191 Techromancer

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    Behold the power of paint:
    [​IMG]
     
  19. Salamantis
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    Member Salamantis GBAtemp Advanced Maniac

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    Dude thanks! Now I understand! They should include that diagram in the construction tuts on the internet. Thanks man!
     
  20. Little

    Member Little I r Little

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    I guess this is old old now =p but when I was at school we had to do a similar project... my group spent ages on ours. We had two CD's with an empty cotton reel and an elastic band running through the cotton reel... one side had a match stick (not glued or anything) and the other had a pencil. you turned the pencil lots and lots, put it down and off it went. Very simple idea and worked really easily. Then another group had completely forgot about the project and grabbed 2 lollipop sticks an elastic band and an empty washing up liquid bottle, pretty much while the other groups were doing theres. They simple put the band between the sticks, pulled back on the bottle and let go... of course they pretty much just threw the bottle. Of course, they ended up winning because theirs went the furthest. The moral of the story.... if you're allowed some form of propulsion at the start then use it... if you could have some kind of elastic band thrust off the starting point, followed by some stored energy... you'd win for sure. to make sure you dont just throw the device, you'd have to mount the lollipop sticks on some kind of base, and have some kind of pull tab on the elastic band so that you don't touch the main vehicle.
     

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