how big of jump

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#1
ok one night I had a dream that I built a nice big stepup.
it is like this there is a run then a dugout right at the bottom of a hill
that is about 30 feet high I would have to clear probably 80 feet far.
how big of jump would I need and what angle should it be at?
ho fast would I have to hit it and would it be ok to have a flat landing because you don't drop down?
thanx sorry for punctuation
later
 
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#2
Sorry I can't help you, but I have the some what of the same problem.I am building a jump have the dirt, but do not know what angle to build it at 45 degrees or more around 50?How long should I try to make it from the base of the jump to the lip?Its around a 50 ft. gap the spot where the landing is lower than where the spot the jump is.Is around 5ft. tall for the jump good?I am not expert on jump building and do not want to hurt myself from making it wrong or one of my friends get hurt doing it.Thanks:think
 
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#3
boys boys boys... (dont ask why i put that) Really i've found the best thing to do is just build a nice hefty pile of dirt up. Then make what you think looks like a nice lip, then once its good to go... HIT IT! The only way to know if you have a good jump is to build one and work from it. If it kicks you butt high, then shave the lip down and so on. Thats what i've found is the best thing to do.
 
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#4
That can work but it can also get you injured. That might work for small jumps but when your messing around with bigger jumps , you dont have too many chances. My friends built this 50ft+ double in a field. Well lets just say one of them broke their wrist on it, and the other one broke his ankle twice(same ankle, different times) on the jump. Another good example is me. Last spring i built a 50 ft step up in a gravel pit. I hit the thing in 4th tapped, and lanched straight up. The lip on that thing was way to steep and my helmet paid the price that time. When i build jumps now, i let someone else hit them 1st.

Originally posted by YZDezertGuy
boys boys boys... (dont ask why i put that) Really i've found the best thing to do is just build a nice hefty pile of dirt up. Then make what you think looks like a nice lip, then once its good to go... HIT IT! The only way to know if you have a good jump is to build one and work from it. If it kicks you butt high, then shave the lip down and so on. Thats what i've found is the best thing to do.
:)
 

Jaybird

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#5
According to the laws of physics, a 45 degree launch will take an object farther than any other degree. You must be able to control the attitude of the bike after launch or those same laws will bite you hard!
 

motometal

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#6
Cool Jaybird, I didn't know that.

Another thing to keep in mind is that the jump will tend to become less steep over time, because dirt from the upper part of the jump will get roosted towards the bottom and packed in. In other words, you should build it on the steep side, and after a few rains and some riding it should be just right.

On a brand new jump, depending on how you pack it you will notice it shrinks considerably with rain and time.

If you can build the ramps wide enough, a 4 wheel drive truck works great for packing!
 
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#7
I don't think it will be a jump I hit all the time only a few so if I bilt a jump that was 20 feet long and at a 45 degree angle how fastshould I hitthat sucker?
howhigh should it be?
and yzdguy you are nuts if I do thatI will hit the hill or the dugout that would be good (for laughs not pain)
thanx for replyes guyes
 

Jaybird

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#8
I'm not much up on how the tundra up there works for jumps,:) but if you can get some clay hauled in, it's your best type of medium. It will pack good and tends not to wash away so bad. Rototilling sawdust into the landing side makes things a bit nicer....you'll appreciate the more forgiving flavor. :D
 
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#9
One thing, make SURE that your landing is not too abrupt. I was racing this weekend and went off a double (too bad I never scouted out the track before going full tilt) and smashed straight into the landing. The landing on this jump was pathetic. It was about two feet tall, and it had a sharp lip on top of it. The back side of it was really steep as well, as I went from second gear wide open to almost a dead stop. No one else was hitting that jump, just rolling over it. I should have taken the hint. Both my ankles are fractured, but I never crashed and the bike doesn't have a mark (thank God). If the landing was flatter and more spread out, I wouldn't have has this problem.
 
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#10
how big of a jump

Hey Wiz69,
Heres what I saw at my local MX track last weekend, this jump was about
6 feet high, about 15 feet long (from flat base to peak) and I would estimate
the angle to be between 45 and 50 degrees, ( I knew I forgot my protractor!)

The gap between the jump and the landing, which was a tabletop, was
probably between 55 and 60 feet. Everybody I talked to, was hitting the
jump in the top of 4th and sometimes 5th gear. There was a long runup to
give you plenty of speed.

Heaven help you, if you hit that jump at that speed and you dont have
enough to clear, you will probably get a trip to the local hospital!

I dont even want to think about what would happen if you hit the landing
face w/ your front wheel, its way too scary! I dont know about you, but I
would definitely watch someone w/ lots of fexperience jump it first.
They can pretty much tell if something is "jumpable"
Be safe and have fun!

bermbuster

:eek:
 
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#11
Bermbuster, casing a jump that big would most likely break your entire leg! I don't think I wanna find out what would actualy happen either, though. :scream:
 

sfc crash

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#12
i'm building a track now on four acres. i've never done this befor, but what i'm using as a template is the local club track. i'm just puting the same stuf i like out there here on my own track. that way i know the doubles and step ups are already tried and true. i've got a 50ft tape measure and a little metal protractor w/ a string and a weight attactched to it. that gives a pretty good reading. i did screw up already tho and had 45 tons of top soil delivered:( i thought i was getting clay fil. oh well, the topsoil'l make good loose track base. i don't think i'd just dream up or whip up a double or tripple without seeing the dimensions proven first.:think
 

funktree

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#13
I know you cant do it with the step up, but a good way to build doubles is to build the first one. Jump it mellow a few times to get the shape right, then jump at full speed and land on flat ground mark where you landed and put the landing there. The other thing you can do is build it short and easy and keep moving the landing out farther. All this is much easier if you have acsess to a tractor.
 
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#14
for one thing I was talking about building a jump and landing 30 feet uphill on a flat the distance gap is like 80 feet over a dugout Idon't wan't to build a double and if I hit it "mellow" I will kill my self and funk tree how come I can't do it ?
I can't use trial and error or I would be in pain
Did I say the landing is flat
 
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#15
Here is a distance formula for you:
d= distance traveled
v^2=velocity in feet per second squared
a=angle of projectile

d = (v^2/32)(sin(2a))

so if the angle is 45 deg. and the speed is 35Mph:

d = (51.3^2/32(1)
d = 82.347
The Maximum distance that is physicaly possible at the stable velocity of 35 Mph is 82 ft. (That is if you are on earth [gravity] , the wind is not blowing, and you are not accelerating or decellerating.)

Here is another for height: (ill let you work it yourself! :eek: :eek: )
y=height
x=horisontal distance
a=angle
h=height from ground level from which you are shooting (ramping) the object.
v=velocity in ft/sec

y = -(16/(v^2*(cos*a)^2)*(x^2 + (tan*a)x + h)

FYI this materiel was taken directly form an algebra2 book.