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Need Help Making Good Jump (Not Dirt)

Discussion in 'BMX & Dirt Jumping' started by p8ntballguy 666, Aug 29, 2005.

  1. p8ntballguy 666

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    Right now I have a 2 1/2ft tall dirt jump (im not very good so I do small stuff) but my little cousins keep on messing it up (they climb all over and mess up the lip and jsut make itnot pleasent at all) so I decided I was going to make a 3 1/2 mabey 4ft tall wooden jump but dont have any idea how. I want it to be pretty steep but not to steep, I want it to have a curve, and I would like it if I could just make it out of 4 by 4's and plywood. If anyone can give me some advice on how to make it sturdy or if anyone knows of any websites that I can get plans for 1 from that would be great!

    p8ntballguy 666
     

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  2. namaSSte

    namaSSte Chimp

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    Youll be surprised how easy this really is. for the size you are talking, you'll need 2-3 sheets of osb (much cheaper than ply) and 10-12 8' studs. Also, use Deckmates screws to hold it all together (a tip I got from Nate Wessel so trust me on this one). Okay, here you go:

    start by scribing your side pieces, this will determine the radius (curvature) of your ramp. The best method is to use a long piece of string with a pencil tied to one end. Pull the string tight and scribe a line. For the size you are talking, I'd consider no less than a 9' radius or the ramp will be really tight for 26" tires (assuming you stick to 3') You can probably get both sides cut out of one 4x8' sheet. Id use 5/8" for this. Get a jigsaw and have it!

    Next, determine how wide you want it. You're going to be cutting the studs to form ribs between the two sides you scribed and cut earlier.The materials I mentioned above are based on using 48" studs so you can get two ribs per board. Cut enough so that you can space the ribs no more than 8" apart. Note: 2x4"s are fine for this, don't let anyone convince you to use bigger, itll just make the ramp unmanageable to move without adding any real structure). Another note here is to cut them slightly shorter than 48" so that the sheeting fits correctly over the entire ramp since the outboard edge of your ramp is roughly 1.25" wider than the inside - rememeber your side pieces? Okay, now mark the sides at 8" intervals on the outside edge so you can line up your studs and decking (later) easily. You'll need a partner here and I found that it alos helped to just tack it together with nails first then screw it together after. Its up to you. Start with the bottom...laying a cut stud flat on the ground, push the two sides up to it and tack em together. Now do the same on the top but use two studs on top of each other with one protruding above the edge of the sides by roughly an inch so that it makes a nice flsuh edge once the sheeting goes on (studs parralel to the ground). Now the frame will stand on its own. Next, begin tacking the ribs you cut into placeat the marks you made. Be sure they are running perpendicular to the ground and flush to the top edge of the sides.

    Now you have the structure ready for sheeting. People do this many ways but I use two sheets (1/2" on the bottom, 3/8" on top - this is personal choice so do what you will...). Again, you'll need help here to bend the osb onto the frame. Start securing it to the frame at the top! Have your partner bend and push it up to the top as you tack it down. Use a chalk line to mark where the studs are (based on the 8" marks you made on the outside earlier). Now continue bending the osb and tacking it down as you move down the ramp. Your osb should overhang the end of your frame just slightly on your first sheet. Now that its tacked down, go back over the sheeting and screw it into the frame. Now do the same on sheet two allowing the osb to overhang until its flush to the ground. Almsot done now....simply go over all the spots you tacked with nails and screw the ramp together. You cn use brackets, etc, but screws are really all you'll need if you did it right. You might consider a brace along the bottom of the open end of the ramp for even more stability if you think you need it.

    Guess that's it. If you have questions you cn drop me a pm or email and I'll try to answer them. Its really not tough to do this though and once youve done one, you can rip em out like nothing. My first took me a little over an hour, now I can put one together in 20 mins. Have fun, good luck, go big!
     
  3. p8ntballguy 666

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    Thanks man! Il deff give you a pm or email if I have any questions. at first il be using 26" tires but once i get my new bike il be using 20". I think I wills tick to 3ft then ifI ever want something bigger i can just make another one. Thank a ton man! Anyone else got any suggestions?
     
  4. formermtboarder

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    FEAR ME ^
    that descripition is soooo much better than how i did mine though it works too

    i found the height i wanted and then the approximate length i wanted the base
    use the pytharogan therom (im in high school so i do this alot a squared+b squared=c squared) to find the length of the hypotenuse. then take a compass and spread it super wide till u find the curvature u want in the jump, draw it then measure it w/ a piece of string (i use a 1" = 1' scale to simplfy things) measure and thats the length ull need.


    i think thats the best way to find size, but whatever floats ur boat
    as to construction follow namaSSete (or whatever)'s instructons for structure theyre good.

    remember its alot better to have too many braces than not enough so use more than u think

    good luck