Sprinting and going fast
- Thread starter Andywinds
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ColinJ
Puzzle game procrastinator!
- Location
- Todmorden - Yorks/Lancs border
I think it rather funny that "you cannae change the laws of physics" but you are trying to! 
You need to work out what the components of the various forces are and remember that the hands are connected to the arms, the arms to the shoulders, the shoulders to the back, the back to the pelvis and the pelvis to the legs.
Pedals are way away from the sprockets and the forces on them act in different directions throughout the pedal stroke but the pedals still manage to propel the bike forwards!
Anyway, I am off out on my bike! If somebody else has not managed to convince you, then I might have another go if I am bored this evening ...
You need to work out what the components of the various forces are and remember that the hands are connected to the arms, the arms to the shoulders, the shoulders to the back, the back to the pelvis and the pelvis to the legs.
Pedals are way away from the sprockets and the forces on them act in different directions throughout the pedal stroke but the pedals still manage to propel the bike forwards!
Anyway, I am off out on my bike! If somebody else has not managed to convince you, then I might have another go if I am bored this evening ...
Dogtrousers
Kilometre nibbler
This is why it's always better to take your water bottle off your frame and put it in your jersey pocket at the bottom of a climb, it helps you press down harder on the pedals. Even better, if there is a small boy handy at the bottom of the climb you should get him to ride on your shoulders.
marzjennings
Guru
- Location
- Houston, Texas, USA
In this video, for the first few seconds, do you think Chris is applying a down force greater than or equal to his body mass?
If you think equal to, then why is he pulling so hard on the bars?
If greater than, how is his body staying put, and hardly bouncing up and down?
Citius
Guest
The point is moot anyway, because NOT holding onto the bars is not an option. Assuming you accept that, then the only other question is how much more force is it possible to apply to the pedals by pulling up. Some, but not much, by definition. Principally because of the angles of the forces, as mentioned earlier.
Besides - accelerating from a standing start and sprinting while already underway are totally different in almost every aspect.
Besides - accelerating from a standing start and sprinting while already underway are totally different in almost every aspect.
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Citius
Guest
I think it rather funny that "you cannae change the laws of physics" but you are trying to!
Nobody's trying to change them. But it helps if you could at least understand them properly.
Citius
Guest
Strictly speaking, the small boy should be placed on your lower back, for maximum offset.*
(*not a serious reply)
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marzjennings
Guru
- Location
- Houston, Texas, USA
Nice try at deflection, but we're not talking about pulling up through the pedals, but pushing down and whether one is able to apply more downward force through the pedals than one's own mass. Have you changed your mind and now accept than a 90kg rider can apply 100kg force to a pedal?
Citius
Guest
I mean pulling up on the bars. Nobody is talking about pulling up through the pedals.
You will only exert anything like a maximal force on an object while it is stationary. As soon as the pedal starts to move (ie a split-second later), the application of a maximal force is no longer possible, regardless of how much you pull up (on the bars). Could you perhaps remind yourself what the thread is about before you go off on a complete tangent?
marzjennings
Guru
- Location
- Houston, Texas, USA
What? Ok, so your sentence wasn't clear as I thought you had started talking about pulling up through the pedals.
You don't have to pull up much on the bars to increase the downward force to the pedal. If a 90kg rider is applying 100kg at the pedal, then he only has to apply a pull of ~10kg at the bar. And that force is applied generally through a segment of the pedal stroke, not as an instantaneous effort or only applied to a stationary pedal.
Citius
Guest
Your rationale is utterly absurd. Think about it.
marzjennings
Guru
- Location
- Houston, Texas, USA
Ok, let's make this a bit simpler. If a 90kg person stands from sitting, using one leg, with a 10kg weight in hand, how much force are the applying to the floor? More or less than their mass?
marzjennings
Guru
- Location
- Houston, Texas, USA
And yet still wrong and still no clue. Did you even watch the Chris Hoy video? Can you even imagine how much force he is applying to his pedals for the first half dozen pedal strokes?
Do you think he squats 227kg (or at least used to) just to push 90kg of force down through the pedals?
Joshua Plumtree
Approaching perfection from a distance.
And yet still wrong and still no clue. Did you even watch the Chris Hoy video? Can you even imagine how much force he is applying to his pedals for the first half dozen pedal strokes?
Do you think he squats 227kg (or at least used to) just to push 90kg of force down through the pedals?
Not sure who's right on this one, but that photo makes me cringe.
Knew someone (on the strongman circuit) whose knees, in effect, exploded from the sheer pressure of such a large force and the over extension in the knees.
Still can't walk without the aid of walking sticks.
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