Formulas for building jumps
Is there a formula for figuring out the best height, length, curvature and angle of a jump to achieve the longest distance and height? And what would be the differences if you had the angle of the take off at say 35, 45 and 55 degrees?
Of course there’s a formula! Actually, there are a bunch of formulas.
For the longest distance, you want a 45-degree lip.
If you carry 15 mph off a 45-degree lip, you’ll fly 15 feet beyond and 3.8 feet above the lip. On a 35-degree lip you’ll fly 14 feet out and only 2.5 feet up. On a 55-degree lip you’ll fly 14 feet (the same as the 35-degree lip) but fly twice as high: 5 feet.
For the greatest height, make the lip as steep as you can handle. At 15 mph, an 80-degree lip will launch you seven feet into the air. A vertical lip will shoot you 7.5 feet up, but you’ll land where you took off. Tricky.
Check out this chart action. 45 degrees gives you the most distance. As you get flatter, distance and height go down. As you get steeper, distance drops but height increases.
NOTE: This totally ignores suspension, technique and every other variable. You can make a jump tiny or huge by sucking it up or pumping it hard.
By the way, speed dramatically increases distance and height. 2x speed = 4x height and distance. Nifty!
For the equations and an online calculator, check out hyperphysics.phy-astr.gsu.edu
Length, height and curvature are trickier. You basically want to place the rider at the end of the ramp, at the proper launch angle, without subjecting him to forces he or she can’t handle. The details are too involved to reveal on this site (for free), but here are some basic ideas:
Whew! I hope that helps. Email me if you want help designing a jump park.
Ouch, my brain hurts
Just build a lip, launch your test bike (a cheap one as not to damage your own), where it lands, thats where you build the landing, enjoy!
hey, I really like this, please lee help me designing a backyard bmxrace / jump track!
I’d love to, but I have to charge for my time. Got two dogs to feed and a pump track to pave …
First off I love the book! It has helped me advacne alot. Second what do you call the dip it front of the jump. How deep should that be for tall jumps. Thanks for the info to. Now i got to get my friends to understand.
I don’t know what you’d call that. The transition, I guess. A lot of dirt-jump lines start with a little roller, then this downward transition, then the first face. It’s funny: Just today I was working with a racer, and we were concentrating on this part of the set.
The purpose of the transition is to 1) Give you a little extra speed, and 2) To gradually build up the pressure as you reach the lip. This gradual build-up gives you more pump and a better jump.
When you make this transition, make sure the curve from the beginning of the dip to the top of the lip is nice and gradual. That’s the key. For a 5-foot lip your transition might be one to two feet deep. Don’t worry about the exact measurements — each jump is different, and you can vary the feel by changing the depth and length. Just make sure you enter the lip smoothly.
you nerd lee!. PS the thing before the jump is called a pump hole.
Lee thanks so much i just read your article and i built three jumps on thjis already they’re alot of fun thx
I’ve also seen/heard the dip infront of – and between – doubles called the “pit”. Between doubles the pit serves to allow more distance to pump, more transition space in case of overjumping, a bit more gravitational pull and a smoother change from coming down to going back up. In front of the first jump, the pit allows for pump, smooth transition and serves as a set-up… kinda like pushing down on the bars before a textbook bunnyhop.
This is not to be confused with a hole dug to supply dirt or for drainage of water out of a pit. That said, the term “pump hole” is a bit mor interesting.
Hey I need some help on designing a few jumps. Some that you get plenty of hight on but don’t go very far so if anyone can help please do!
How tall do i have to make my lip for these trajectories to work. and how big does the landing have to be.
I have that info, but I’m saving it for an ebook. It was way too much work to put out there for free.
– The face should be long enough to transition from flat to the takeoff angle without it feeling bucky.
– The steeper the lip, the longer it has to be.
– The faster you’re going, the longer it has to be.
– The landing is usually the same height or a bit taller, and not quite as steep.
Look at pictures of good jumps. Figure that a MTB wheel is about 26″ in diameter. Calculate from there.
Stay tuned for the ebook. I have a lot of other stuff that has to be done first …