where did you ride this weekend?

open topic, for anything cycling related.

Postby tuco » Wed May 09, 2007 11:28 am

Bnej wrote:e.g, riding at 55kph through a bend, hit loose gravel on the road, tyres slide, you fall about 1.2m out of the lean directly onto the road. Yes it's going to hurt, and you're going to lose a fair bit of skin - but you may be saved from severe head injury.


Remember high school physics?

Vector forces?

The speed of the 55km/h force is added to the 1.2m fall force. The head hit is going to be greater than a 1.2m vertical fall.
Last edited by tuco on Wed May 09, 2007 11:40 am, edited 1 time in total.
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by BNA » Wed May 09, 2007 11:30 am

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Postby Bnej » Wed May 09, 2007 11:30 am

MJF wrote:When did I say that there wasn't evidence? Just because I linked to a fringe nutbag position paper, doesn't mean I agree with their position, I just though what they said was interesting in terms of the reasoning behind the mandatory rules and the effects.

Fair nuff.

Obviously, helmets help - I just don't think they went far enough with the standards. My cruddy helmet from the 80's had an ABS plastic shell with high density polystyrene foam - a lot safer than my current helmet IMHO, except the way the straps attached (to the shell) created a peripheral vision blind spot.


The problem of the old Stackhat helmets and other heaver ABS shelled jobs is that people didn't want to buy them. Rosebank doesn't make them any more either.

They could probably make a really strong, effective, helmet with a carbon fibre shell and just enough vents to reduce the sweating, but the high end market is dominated by lightweight and comfortable, not high safety features.

Which is a shame.
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Postby MJF » Wed May 09, 2007 12:33 pm

Just read the AS/NZS vs. Snell ATSB document, and from comments in the document it appears the Rosebank failed the energy attenuation testing.

Then again, a number of the current style helmets failed as well. From reading the report, the most obvious message is : don't get hit by a car.
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Postby Bnej » Wed May 09, 2007 12:48 pm

tuco wrote:Remember high school physics?

Vector forces?

The speed of the 55km/h force is added to the 1.2m fall force. The head hit is going to be greater than a 1.2m vertical fall.


I would have thought that the 1.2m fall would be the more dangerous component, since you're risking slowing down in the least amount of space.

The 55km/h is going to wash off over some distance on the road as you slide, so is not going to subject you to the same g force as striking the road. Motorcycle racers fall off at 100km/h routinely and are not seriously injured, because they slide a long way.

As long as you're sliding rather than striking you're going to get abrasions rather than blunt force trauma.
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Postby europa » Wed May 09, 2007 1:08 pm

Hmm, it doesn't matter how bad the gravel rash is as long as you're still alive to enjoy it eh? :?

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Postby Bnej » Wed May 09, 2007 1:22 pm

europa wrote:Hmm, it doesn't matter how bad the gravel rash is as long as you're still alive to enjoy it eh? :?


When asked to choose between ouch and dead, I'll have ouch every time.

You could try riding with motorcycle leathers? :)
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Postby tuco » Wed May 09, 2007 1:24 pm

Bnej wrote:
tuco wrote:Remember high school physics?

Vector forces?

The speed of the 55km/h force is added to the 1.2m fall force. The head hit is going to be greater than a 1.2m vertical fall.


I would have thought that the 1.2m fall would be the more dangerous component, since you're risking slowing down in the least amount of space.

Not really, 1.2m down would be bang and "Ouch!" and 55km/h would be bang, bounce, bang, grate, bounce, bang, scrape, bounce, bang, slide, scrape, etc.
Bnej wrote:The 55km/h is going to wash off over some distance on the road as you slide, so is not going to subject you to the same g force as striking the road. Motorcycle racers fall off at 100km/h routinely and are not seriously injured, because they slide a long way.

As long as you're sliding rather than striking you're going to get abrasions rather than blunt force trauma.


The motorcycle racers' gear is designed to slide they plus they have built in titanium pads in the vital areas.
If we wore their gear when we routinely fell then we'd not be seriously hurt either but our race times may suffer.
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Postby Bnej » Wed May 09, 2007 1:34 pm

tuco wrote:Not really, 1.2m down would be bang and "Ouch!" and 55km/h would be bang, bounce, bang, grate, bounce, bang, scrape, bounce, bang, slide, scrape, etc.


Well, yeah, you're not losing all that energy in a single collision. I mean, you'll be in a world of hurting, but you don't have that massive deceleration force that can jelly your brain in an instant.

Ideally you slide off towards a grass verge and the grass can take the energy instead of your body.
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Postby sogood » Wed May 09, 2007 5:27 pm

Bnej wrote:The 55km/h is going to wash off over some distance on the road as you slide...

That obviously assumes that you slide. Chances are, there'll be plenty of potential obstracles in your way.
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Postby Bnej » Wed May 09, 2007 5:59 pm

As long as it doesn't stop you completely, it's not that bad. You're far better off bouncing over a kerb than hitting a cement barrier.

Most of the places where I'd fall off at speed, I'd have a good 15-25m of road & verge before hitting anything solid. You're not going to slide as far as a motorcyclist.

I mean really, given the choice, I'd lose the speed by breaking my legs rather than my skull. The main thing in terms of crash survival is not to have too much g-force on your head & not break your neck. After that, most injuries can be survived provided that you get medical help quickly.
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Postby millynumb68 » Fri May 11, 2007 6:26 am

They could probably make a really strong, effective, helmet with a carbon fibre shell and just enough vents to reduce the sweating, but the high end market is dominated by lightweight and comfortable, not high safety features.

Which is a shame.


Not trying to be nit-picking, but in actual fact carbon fibre has bugger-all impact resistance. It's most valuable property is it's stiffness. If they really wanted to get serious they'd make them out of a mix of Carbon (for stiffness) and kevlar (aramid) for impact resistance........
..... or you could just get around with a bullet-proof vest strapped to your head.....
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Postby Bnej » Fri May 11, 2007 7:49 am

They use carbon fibre outer shells of high end helmets now to distribute the force around the foam - but they use this to reduce the total amount of material to make the helmet lighter and more comfortable, rather than to make it safer.

That's the sort of construction I'm talking about, not an all CF helmet.
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Postby sogood » Fri May 11, 2007 8:29 am

Bugger with those helmets that'll protect your skull 100%. At some point to that 100% holy grail, your neck will snap, and depending the level of break, you may still die. a horrible death. Bottom line, speed kills!
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Postby Bnej » Fri May 11, 2007 8:32 am

sogood wrote:Bottom line, speed kills!


Stopping too quickly kills. ;)
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Postby sogood » Fri May 11, 2007 9:37 am

Bnej wrote:Stopping too quickly kills. ;)

Without speed, there's no stopping in it. ;)
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Postby MJF » Fri May 11, 2007 3:09 pm

millynumb68 wrote:If they really wanted to get serious they'd make them out of a mix of Carbon (for stiffness) and kevlar (aramid) for impact resistance..


Actually, most helmets advertised as 'carbon' are carbon/kevlar or carbon/fiberglass. Often advertised as carbon composite.

From my car hoon days, I'm pretty sure the argument for carbon etc. helmets is that they attenuate energy as the shell fractures, as opposed to polycarbonate which tends to just deform without absorbing energy.

BTW - the head acceleration standard used for bike helmets is 300G. Read this.
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