On Wed, 23 May 2007 12:33:59 -0700, "Jay Beattie"
<
[email protected]> wrote:
>
>"DougC" <[email protected]> wrote in message
>news
[email protected]...
>> G.T. wrote:
>>>
>>> Yeah, he's amazing from a technical standpoint but the guys with
>>> BMX/freestyle backgrounds have so much more flow that I find them more
>>> fun to watch. The trials guys do too much hopping.
>>>
>>> Greg
>>
>> The BMX guy is awesome, doing all that on what is basically a normal
>> BMX/freestyle setup.
>
>I can't believe the apparent elevation these guys can get (in all of the
>clips) -- hopping up to walls or rails that appear to be four or five feet
>off the ground. This is with both wheels, or on a rear wheelie (not the
>front wheel up, hoist the rear wheel thing). There is one shot with a guy
>hopping over a shopping cart. Is that the low-angle/wide-angle affect, or
>are these guys doing the equivalent of a standing jump of four feet straight
>up with a bike? If so, they should be playing with Spud Webb. I have
>enough trouble hopping my road bike over a 5" curb. -- Jay Beattie.
Dear Jay,
Those evil little wretches do jump like the dickens, but they aren't
leaping quite as high as we think at first, curse them.
First, go and measure a shopping cart--they're not 48 inches high.
Next, remember that the horrible little creatures start out with their
feet at the height of the horizontal pedals. They jump their scrawny
little 140-pound bodies from that initial height, not the ground, and
then yank up the 20 pound bike after them.
The vile little monsters are also yanking their legs up and their
upper bodies down. The result is that their belts (center of mass) are
reaching more modest heights than we think because their feet are
coming up while their heads are coming down.
If you're looking at other sites, where the miserable little beasts
are riding bikes with suspension, you'll see them getting even more
height by slamming down to compress the springs so that they can start
their leaps with an extra assist.
But I still hate them, one and all.
None of these tricks work in the kind of vertical-leap measurements
that you see basketball players doing against walls.
Here's a link to the Sargent test:
http://www.topendsports.com/testing/tests/vertjump.htm
For that kind of leaping, 27.6 inches is excellent for humans, while
the record is probably somewhere over 48 inches for basketball players
(who are sometimes photographed deliberately hovering and must then
return to their home planets). Here's a typical page squabbling about
the maximum:
http://answers.yahoo.com/question/index?qid=20060605153957AA1zGiG
Cheers,
Carl Fogel
