i did my biggest move ever today!

hey everyone… just got back from a ride in my city. i was hanging out with the skaters as i usually do (showing them up) and one of them heard that i was trying to hop down a whole nine set of stairs last saturday but couldnt make it. so they of course didnt believe it and told me to go do it. after a little bit of hesitation, i decided to go for it. so my filmer turns on the camera… tells me not to hirt myself and i go for it. first try i fll quite hard but was ok. then second time came… i start pedalling… i hear the cheers of the hundreds of people watching me… i jump, i see each of the 9 stairs flying below me. i tweak the unicycle out in front of me… i hit the ground… and… I RIDE AWAY!!! yipee!! the crowd went wild!! then the security guard came and kicked us out… but not before i jumped down a whole 9 set of stairs in one hop! it felt pretty crazy.

so i was wondering if anyone has ever done more than 9. i saw dan doerkson do a nine set, but have never seen any more than 9. so if youve done a 10 or 11 set, or no someone who has, then tell me!

Kevin… and i might put the video of the nine set up soon.

WOW! 5 is my max, and come to think about it, maybe it was even only 4 :o

good job!

Nice work! I’ve only ever ridden down 9 and that was hard enough for me. You’re a machine.


Wow. I’d love to see. How long did it take to remove the grin?

Tell us about your Uni. It must be beefy. And your weight.

Now someone (Klaas Bill?) (Harper?) can extrapolate the force exerted on your poor wheel.

32 ft per second squared…

it took me about 20 seconds for the grin to go away (thats when the security guard came)… im riding a summit trials with a reeder handle. that KH splined hub and crank set is holding up awesomely!! anyways, im still looking for someone who can show up a 9 set… later, Kevin

oh forgot about my weight… im 147 lbs and my uni is like 15 or 16 i think. buh byes

Re: i did my biggest move ever today!

You have a video? Please post it. Do you have the fall, also?

it is on camera. i dont know if i can post it or not because im filming for my own video. i’ll probably keep the footage for myself until my video is complete. but if you really want to see it… then wait for my video to come out and then buy it. and who knows… maybe ican make it into universe 2?? gets hopes up anyays, later

This is the simplest impulse approximation. The assumption is that the tire is inflated to the pressure that will allow it to compress fully without bottoming. The velocity of the rider drops linearly as the tire compresses. Then you cheat and say that the velocity is constant for the duration of the compression. The distance dropped is D, the amount of tire compression is C, the mass of the rider plus unicycle is m, the acceleration of gravity is a, and the force during the impulse is F. Within a factor of two, then:


D/C is the ratio of two lengths so who cares what consistent unit is used. ma is a force and, if you are a US guy and like pounds then ma is just that, the weight of the rider and the unicycle in pounds.

In the case given, the unicycle and rider weigh about 160 pounds. He jumped down nine stairs which are usually about 8 inches each for 72 total inches of drop. The tire is a fat one and compressed 3 inches. Change these values as you like.

F=160(72/3)=3840 pounds (probably within an order of magnitude).

Oh, by the way, the tire probably has to be at 50 psig or so for this to work.



F=160(72/6)=1920 pounds, or about a ton. Sorry. Still about 40 psig in the tire, though.

wow… very impressive formula. i didnt know i could make that much force by jumping down 9 stairs. i would tell you how much pressure was in my tire, but i dont know. i just jumped. i never really pay attention to my psi. but next time i air it up, what should i be putting in it?

Harper you crack me up. You’re a great reference. I didn’t even get a nose bleed on that one.

Tug, go have tons of fun.

How much for the vid?

This doesn’t tell you how much air to put in your tire. This is about how much that would be required to keep the tire from bottoming. I assumed you used a 24" tire. For a 20" tire, more pressure would be required because the flattened footprint wouldn’t be as big. Put whatever air you like in the tire. Make it easy for yourself, not me. I can tell you with modest accuracy what’s going on when you do the jump, but I’d much rather be able to do the jump. YOU should be telling ME how much air to put in MY tire.

Re: i did my biggest move ever today!

On Fri, 4 Apr 2003 05:24:56 -0600, tugboat
<tugboat.lczko@timelimit.unicyclist.com> wrote:

>wow… very impressive formula. i didnt know i could make that much
>force by jumping down 9 stairs.

Well, Harper said it was the simplest approximation and I’m sure he
also knows what the main weakness in the approximation is.
Specifically, he treats the rider and unicycle (except the tyre) as
one rigid body. In reality, you are absorbing most of the downward
impulse in your legs, and probably also in bending forward. That makes
the forces involved less (as the impulse can be taken up in more
distance, hence more time). Still, jumping down 9 stairs is utterly
impressive and no physics reasoning detracts from that!

Klaas Bil - Newsgroup Addict

“Ford, you are turning into a penguin again. Stop it.”

woooooooooooww just wow. that is what i like to hear about. showing up those stupid skaters is fun and easy. but you just crushed them. what city are you from?

I jumped down 4 stairs once… ah, yes. It was at school. The buses were loading, and all eyes were on me. Go Steve, go Steve… and then, I jumped. Down all four, with nary an ouchie to be seen. And you should have heard them. Had they seen the 9 set, there would have been multiple heart attacks in the audience. The commoners are easily amused.

actually, i was on a 20". i don’t even own a 24. never even ridden a 24 for that matter. but anyways… my video is probably going to come out near the end of the summer and it will be completely street riding. maybe some bike trials and some skateboarding in it too. its gonna be called “monkeylamp” and it will be 20$ canadian probably. so hope you buy one. lates, Kevin

Re: i did my biggest move ever today!

I’ve aired a 9 set from a stand still on Dan Heaton’s Trials uni. Dan Heaton
has aired 13. If I ever get profiles for my trials uni I want to try a 15


I guess the underlying question is:

What Uni setup would be required for a 195 pounder to “air” 9 steps?

Or is this a guaranteed bent metal scenario?

you did 9 from a stand still? thats ridiculous. and a big grrr at dan. he just has to go and beat everyone doesnt he? hehe just joking, he’s amazing!

glad to see someone giving that kh hub a good thrashing.
now we can be fairly sure its going to take a good bit of abuse.

i’ve jumped down stairs before but i never counted them because all stairs are diferent in both width and height. stairs can be as small as 4" wide and 2" tall or as wide as 12" and 8" tall.
how big where your stairs?

its realy about how far you went forwards relative to how far you dropped, but still i’m impressed.

somebody cheeky could make a realy steep staircase with like 100 tiny stairs 1" by 1"

jumping from a still stand forwards or sideways.?
sideways from a standstill is easier to learn but now the limits are starting to be pushed by people doing rolling hops

you can always “cheat” by riding up to the edge, hopping into position and then riding backwards so you’re sure that when you do your rolling jump you’ll be in the perfect position for take off, and not have to waste up to 6" waiting for your feet to be level.