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Trebuchet CATAPULT Project/Worklog Updated 12/12/06 Please COMMENT

Discussion in 'General' started by scarecrow, 21 Apr 2006.

  1. scarecrow

    scarecrow What's a Dremel?

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    yeah but as I said before this thing I estimate to weight 2000 pounds loaded I prefer if it didn't roll around lol. Plus its going to most likely be launching on grass so yeah. This think isn't moving will be too hard logistically.
     
  2. JCBeastie

    JCBeastie What's a Dremel?

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    Usually it moves on it's base, but I can understand how that would be hard for you to implement. I wouldn't fancy something that size tumbling my and landing a washing machine on me! :p

    I've made several "mini" ones, the biggest throws an 8 pound shot around about 180ft. Don't ask me for any maths I just build and modify until they work. :D

    JCBeastie
     
  3. scarecrow

    scarecrow What's a Dremel?

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    JC just wondering how long was your throwing arm and how heavy was your counter-weight. Cause I am going to be throwing simmilar sized projectiles. I am aiming for a goal post to goalpost shot or at least 300 feet or more.
     
  4. Tibby

    Tibby Back Once Again

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    Umm not to sound dim, but the wheels idea sounds good purely for the fact..

    How you planning on moving something this big and heavy?
     
  5. scarecrow

    scarecrow What's a Dremel?

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    this thing will be dissasemblable. If you read earlier I am using bolts for that reason exactly. Plus I can unload the counter-weight making the machine weigh only 700-1000 pounds ish. But yeah I am breaking it up into 4 major sections. The arm being one the base another and the 2 support struts with the triangles attached. The heaviest piece will be the support struts weighing in at around 140-200 pounds. So yeah it will be ok with a couple cars and some strong burley men :).
     
  6. Tibby

    Tibby Back Once Again

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    Ahh kk.

    I think the most important fact you missed is.

    Colour Scheme? :p

    Varnish or Funky Paint Job?
     
  7. scarecrow

    scarecrow What's a Dremel?

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    Lol good point. I havn't thought about that at all. But I using wood from the sets at school so yeah for now it is going to be funky colored. OMG I FORGOT ABOUT THE MODS I NEED TO DO ON THE TREB ok I say paint it in uv and get a **** load of blacklights. Got to sleeve your cables too... Lol ok seriously had a genious idea. Night launch with glow in the dark projectile:)

    Give me ideas I personally don't care about the paint job and I still need a name for this thing.
     
  8. Tibby

    Tibby Back Once Again

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    Man I would love to see a massive glow in the dark washing machine at night!
     
  9. scarecrow

    scarecrow What's a Dremel?

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    well I will make sure to make a video for you guys to see when this thing is completed ;)
     
  10. Rocket733

    Rocket733 Austerity - It's the only way

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    For my ap physics class someone built a similar device and found out that even a bench pressing bar bends and that was with only about 400-600 pounds worth of weight. Perhaps if you can find a car axle or something similar from a junk yard it might prove to be stronger. What is your firing mechanism going to be? Good luck with this project.
     
  11. scarecrow

    scarecrow What's a Dremel?

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    I am getting my firing mechanism from www.trebuchet.com the one rated for 160 pounds of load weight as easy release. As for the bench bar did he use the whole thing? cause I am cutting it down so it is shorter and stronger so it only has to span a gap a little wider then a foot.
     
  12. JCBeastie

    JCBeastie What's a Dremel?

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    4'6" arm m8! And about 30 pounds of sand...

    It might be less I've not weighed it and I'm crap at guessing. I did say don't ask.

    My maths suck by the way.

    JCBeastie
     
  13. scarecrow

    scarecrow What's a Dremel?

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    Diagram Schematic Thing

    These are some quick drawings so you guys arn't in the dark so much. I added some of the numbers so you know the size of some of the parts. Really rough though .

    [​IMG]
    That is the side view. Not really complicated but part D the support struts will be 7 by 1 and 96 inches long. Set at 45 degrees from the ground and there will be 8 of them in total on the machine. 4 for every support strut. How they are arranged will make more sense latter. Part f if you see is how I am attacking the struts to the base making a sandwich so that I can take the bolt off and take it off latter.

    [​IMG]

    This is a top view I left out how d is connecting to the struts cause it will get to crowded but it will connect basically where f is just higher. Here you can see the sandwich more clearly with the 2 a pieces coming to the c support strut. then sandwiched between two f pieces. If you see I am not taking any chances and putting 3 support struts way more then I need but better safe then sorry.

    [​IMG]

    Final image is a frontal view here you can see how d connects. The space between the support struts will be most likely filled with wooden spacers but havn't decided if I want to do something else. So I left them empty. But those gaps will be filled with something eventually probally just more wood to make it solid all the way down to the ground. In this diagram you can see also how the counterweight is going to be connected also. I didn't do any of my ideas for the arm axel just put it there cause I still thinking on it. What I want to do in terms of bracing.

    Oh and thanks for the info I just wondering. I also need any ideas for where to attach the winch which I should be getting pictures of latter.

    Oh also the diagrams are not to scale I eyeballed it. So yeah.
     
  14. profqwerty

    profqwerty What's a Dremel?

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    When the counterweights reach the bottom of the swing, does the downwards velocity being converted to upwards increase the downwards force on the structure?
     
  15. scarecrow

    scarecrow What's a Dremel?

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    WINCH OBTAINED

    [​IMG]

    Winch Obtained from my good friend IAN. This thing is meant to pull cars out of ditches and such. I think it will do the job nicely. But I have one prob I don't think I can attach it to anything like a tree or such but to the structure itself. Any ideas on mounting?

    [​IMG]
    Don't know if you can read it but 4000 pound limit :) Hurray for overpower.

    Um to answer you question it will not add more stress downward. But it will increase stress foward and back hence why I got 8 support struts to prevent this thing from toppling over.
     
  16. MaximumShow

    MaximumShow Minimodder

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    This thing is going to rock... and I mean that literally. With that much counter weight and only a swinging bucket to absorb the stresses, it could easily vibrate it self apart on the first test.

    You show in your diagram that the arm is 14' total, but you don't list the length of the swing section nor the counterweight section.
     
  17. scarecrow

    scarecrow What's a Dremel?

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    the counterweight part of the arm is 64 inches or 5 feet 4 inches. Then the swing part for the bucket I believe will be those 2 little arms around 5 inches. It will have plenty cause the bucket and the arm will be allowed to swing. It won't rock plus on my first test I am going to start with a much lower weight like 100-200 pounds. Then work my way up to the full 800.
     
  18. MaximumShow

    MaximumShow Minimodder

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    The total arm length is 14', and of that 5'4" is counter weight arm length??? Thats nearly half the total arm length!

    You will have very little acceleration with an arm length ratio like that. You need a short counterweight arm length, with a longer tossing arm (measured from the fulcrum to the tip). This is the reason why need need a large counter weight mass.

    Gravity will, at the absolute max, accelerate the counterweight at 9.8 m/s^2 (if it was falling straight down). Adding a million lbs of weight will not make it swing any faster if you are not converting the torque into motion properly.
     
  19. scarecrow

    scarecrow What's a Dremel?

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    Good point that is 1 to 3 sorry I am looking at my notes that was for prior plans of a 26 ft long throwing arm which I had to drop due to unavailability of materials. So I downscaled to a 14 ft one. Sorry as I said I have not done a formal schematic of the design plan yet. The cw will be 33.6 inches or 2 feet 9 inches. Sorry my mistake. Yeah sorry but thanks for the catch. And you do make a good point anybody that is making a treb just adding more weight doesn't necesarily help. It just adds to how much you can throw. My ratio is 1 to 4 by the way.

    If you see any other mistakes please point them out. Nobody's perfect. I will be submitting my design to the rest of my physics class also for analysis. Build is scheduled to start after May 7th so yeah I got a good amount of time.
     
    Last edited: 23 Apr 2006
  20. DarkReaper

    DarkReaper Alignment: Sarcastic Good

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    I'm still insistent on adding wheels but apart from that, not much really :)

    For mounting the winch, use some of your bar through your long horizontal base pieces and thread the big eyelet of the winch onto that.
     

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