Skateboarders v cyclists..amazing footage

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Tonyf33
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Re: Skateboarders v cyclists..amazing footage

Post by Tonyf33 »

How does it not show physics?
These boarders are clearly able to present a lesser frontal area thus are able to go faster, that's physics. The ceramic bearings that most top end trucks have roll forever from one hand spin (okay over 6 minutes) The aerodynamic drag differential between 4 small trucks compared to bicycle wheels is huge, that's physics.

And sorry but lowering your CoG does help to corner more quickly :? , I don't know what bath tub physics you know but inertia has a huge effect on cornering speeds and cycling will give you greater forces going into a corner like for like weight of person and speed compared to a skateboarder that's why they (boarders) are able to get around these corners quicker than a cyclist would.
Oh yeah, inertia, that's physics too 8) :lol:
700c
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Re: Skateboarders v cyclists..amazing footage

Post by 700c »

These are not skateboards that everyone knows and recognises as a skateboard. These are longboards designed to do upwards of 60mph and are up to 6 feet long.

There is no possible way that a cyclist, any cyclist, could keep up with the insane speed and cornering skills of a longboard rider.
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Mick F
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Re: Skateboarders v cyclists..amazing footage

Post by Mick F »

Give me the chance to try, and I'm sure you'll be proved wrong.
That video had the cyclists doing maybe 20mph when they could have been doing 50mph plus.
Mick F. Cornwall
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[XAP]Bob
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Re: Skateboarders v cyclists..amazing footage

Post by [XAP]Bob »

The physics I'm looking at is fairly simple, but I can go to degree level if you like...

The height of the CoG is irrelevant on a bike.
The reason low CoG is good in a car is that you need to keep the net force vector within the wheelbase of the car, else it will fall over. Cyclists, and long boarders, don't have that restriction - they lean over, and none of the cyclists were (they were all taking it easy)

The boarders will have a small aero advantage (bike frames are rubbish, far too many separate elements, all somewhat controlled by the UCI), but they will have a rolling resistance disadvantage. Anything that can be done on a truck bearing can be done on a high end bike wheel bearing, and probably has been. You are then looking at the RR of a wheel doing an order of magnitude less rpm, that will be lower.

The boarders have very limited means to add speed - gravity is their main source of speed although I'm sure some pumping can help as well. A cyclist pushing it down there would be pedalling, certainly out of each corner, and would therefore achieve significantly higher speeds on the road.
Cyclists would also be able to brake more consistently, allowing them to brake later (again a speed advantage).

In the corner I believe that the traction available to a cyclist would be greater than that for a long boarder - based on nothing more than hand-wavy intuition. And it that traction which provides the force to accelerate the person around the corner. The difference in mass between the board and the bike (in terms of all up vehicle mass) is <5%, so any advantage here translates into higher cornering speeds.

Put Paolo Savoldelli on a bike down there and there is no way the long boarders would be keeping up - he'd power away from the start using pedals, brake later then go faster through the first corner, accelerate quicker into the next straight, brake later, corner quicker....

Even if my intuition is wrong, and the longboarder can carry more speed through a corner the acceleration potential of the bike will win the day.


The video shows cyclists virtually upright, cruising and enjoying the view, whilst reckless (assuming the road is open) long boarders hare down as fast as they can, with a car in pursuit?
All that is is a demonstration of bravery/stupidity...
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Postboxer
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Re: Skateboarders v cyclists..amazing footage

Post by Postboxer »

Was looking to find a proper race, all I've found so far is this braking test-

http://www.skatetheeast.net/2013/06/bra ... kateboard/

But doesn't look to me like the bike is braking as much as possible, they also don't seem to be having to try too hard to match speed with the skateboard.
Postboxer
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Re: Skateboarders v cyclists..amazing footage

Post by Postboxer »

Or figure out where it is and check Strava?
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[XAP]Bob
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Re: Skateboarders v cyclists..amazing footage

Post by [XAP]Bob »

That video demonstrates that the traction available is similar - when the cyclist has knobblies and full suspension - My expectation remains that a road bike would stop a shade quicker (and therefore would be able to corner quicker).

The text in the link needs serious proof reading...
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.
Bonefishblues
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Re: Skateboarders v cyclists..amazing footage

Post by Bonefishblues »

[XAP]Bob wrote:That video demonstrates that the traction available is similar - when the cyclist has knobblies and full suspension - My expectation remains that a road bike would stop a shade quicker (and therefore would be able to corner quicker).

The text in the link needs serious proof reading...

What surprised me was how easily they were able to side-slip. What are those wheels made of?
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[XAP]Bob
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Re: Skateboarders v cyclists..amazing footage

Post by [XAP]Bob »

From what I can gather it's generally urethane - various grades allow for trading speed, grip and lifetime (sound familiar?)
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.
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[XAP]Bob
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Re: Skateboarders v cyclists..amazing footage

Post by [XAP]Bob »

Downhill speed record for longboard is ~80mph, seems this was also the speed of some random bloke on the bedoin descent of Mt Ventoux...

[youtube]EahajVER2mo[/youtube]
[youtube]dI3UNU_n50U[/youtube]
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.
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[XAP]Bob
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Re: Skateboarders v cyclists..amazing footage

Post by [XAP]Bob »

From the captions (distance left) and the timing...

These guys are averaging a little over 60kph, including corners...

[youtube]MSmhgOFGl_M[/youtube]
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.
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Mick F
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Re: Skateboarders v cyclists..amazing footage

Post by Mick F »

I'd keep up.
I doubt our skateboarders could.
Mick F. Cornwall
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Mick F
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Re: Skateboarders v cyclists..amazing footage

Post by Mick F »

Just a quickie calculation.
1 mile is 63,360 inches.
60mph is 1 mile per minute.
27" bicycle wheel is 85" circumference.
2" skateboard wheel is 6.3" circumference.

At 60mph .....
27" bicycle wheel is doing 745rpm
2" skateboard wheel is doing over 10,000rpm.
Mick F. Cornwall
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Vantage
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Re: Skateboarders v cyclists..amazing footage

Post by Vantage »

Mick F wrote:I'd keep up.
I doubt our skateboarders could.


How's your ego these days?
At 1.27, could you do that on your Mercian? Doubtful.
The speeds might not be as fast as your bike, but when you consider that those guys are flying round those bends with 2" wheels made from solid rubber bolted to wooden boards and without brakes, a small degree of respect for their skill might be in order. :)
Bill


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Mick F
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Re: Skateboarders v cyclists..amazing footage

Post by Mick F »

Hey!
Respect from me!
I found the video amazing!

I'm just arguing the point that the subject was skateboarders being faster than cyclists.
Those skateboarders were faster than those cyclists, we can plainly see. The trouble is, the statement seems to be inferring that skateboarders are faster than cyclists ......... and I do not agree in the slightest.
Mick F. Cornwall
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