The CycleChat Helmet Debate Thread

[martint235]

Yet nobody wants to discuss it.

I'm willing to. I've yet to hear of a test standard that involves a scenario similar to coming off a bike at speed on tarmac. Most tests seem to rely on dropping onto a flat surface so no sliding, rolling etc

 

[winjim]

I'm willing to. I've yet to hear of a test standard that involves a scenario similar to coming off a bike at speed on tarmac. Most tests seem to rely on dropping onto a flat surface so no sliding, rolling etc

So how do you arrive at your figure of 15mph?

 

[martint235]

So how do you arrive at your figure of 15mph?

Vague memories of that being the speed reached by a helmet dropped from 1 metre.

 

[ufkacbln]

All you could wish to know about helmet standard tests... and so much more that you didn't.

 

[winjim]

Vague memories of that being the speed reached by a helmet dropped from 1 metre.

OK. I think the test is actually from 1.5m which gives 12mph but the actual figure is unimportant. If this drop test is to simulate a seated rider falling onto a level surface, which seems reasonable, and given that vertical velocity of a falling object is independent of velocity in the horizontal plane, how can there be a rider speed which puts the helmet outside the limits of testing?

 

[glasgowcyclist]

OK. I think the test is actually from 1.5m which gives 12mph but the actual figure is unimportant. If this drop test is to simulate a seated rider falling onto a level surface, which seems reasonable, and given that vertical velocity of a falling object is independent of velocity in the horizontal plane, how can there be a rider speed which puts the helmet outside the limits of testing?

The rider's helmeted head in a collision may strike some solid upright surface long before it hits the ground. If his forward speed is 20mph and he T-bones the side of a motor vehicle, the helmet's impact will exceed its design.

GC

 

[martint235]

OK. I think the test is actually from 1.5m which gives 12mph but the actual figure is unimportant. If this drop test is to simulate a seated rider falling onto a level surface, which seems reasonable, and given that vertical velocity of a falling object is independent of velocity in the horizontal plane, how can there be a rider speed which puts the helmet outside the limits of testing?

Surely by not testing it, it's outside the limits of testing?

Other than that if 1.5m gives 12mph, any helmet I wear will be outside its design parameters unless I crouch down before I decide to fall over.

 

[martint235]

You would be within parameters if you were to fall sideways onto a stationery car bonnet, just about.

But that would open a whole new can of worms around testing because a car bonnet doesn't behave the same as a solid object.

Maybe I'll just stick to wearing my Lelly cap and only banging my head against dumper trucks.

 

[ufkacbln]

The other question about responsibility

There are tests for vehicles that show "safety"

The Euro NCAP is typical

One of the tests is about pedestrians
The vehicles gain points if there are features that reduce injury in a pedestrian impact

Some vehicles score a big fat Zero
Is the fact that a driver has decided to drive a vehicle that they know will increase pedestrian injuries really acceptable

Should manufacturers be allowed to produce these vehicles when the technology and design is there to reduce injury ?

If a cyclist impacts a vehicle with a low safety rating and suffers an increased injury ... Is there a moral responsibility with the manafacturer or owner

 

[winjim]

The rider's helmeted head in a collision may strike some solid upright surface long before it hits the ground. If his forward speed is 20mph and he T-bones the side of a motor vehicle, the helmet's impact will exceed its design.

GC

That may or may not be the case, but it is not the point I am contesting.

Surely by not testing it, it's outside the limits of testing?

Other than that if 1.5m gives 12mph, any helmet I wear will be outside its design parameters unless I crouch down before I decide to fall over.

But do you accept that this is independent of the speed of forward travel? Do you still claim that there is an arbitrary, non-zero maximum speed above which one should not ride for fear of taking one's helmet outside its design and testing parameters?

 

[martint235]

That may or may not be the case, but it is not the point I am contesting.


But do you accept that this is independent of the speed of forward travel? Do you still claim that there is an arbitrary, non-zero maximum speed above which one should not ride for fear of taking one's helmet outside its design and testing parameters?

If something is tested to hit a hard object at 15mph, it doesn't matter which plane that speed is achieved in. It is still hitting an object at that speed.

Secondly, when did I say you should not ride at any speed? And thirdly, and most importantly, when did I say you should be wearing a helmet to ride at any speed?

 

[mjr]

If this drop test is to simulate a seated rider falling onto a level surface, which seems reasonable, and given that vertical velocity of a falling object is independent of velocity in the horizontal plane, how can there be a rider speed which puts the helmet outside the limits of testing?

The level surface is not perfectly smooth. The falling object decelerates in the horizontal plane as a result of the impact by a nonzero amount. The effect of that is untested, ergo the helmet is outside the limits of its testing, isn't it? That's not to say it won't work but we just don't know.

 

[martint235]

So if a helmet is tested in a vertical fall where it strikes perpendicular to a flat surface at 6m/s, how is that different to a horizontal crash at 6m/s where the helmet strikes perpendicular to a vertical flat surface?

 

[winjim]

If something is tested to hit a hard object at 15mph, it doesn't matter which plane that speed is achieved in. It is still hitting an object at that speed.

I am talking about a very specific set of admittedly idealised circumstances, namely a vertical drop onto a flat, level surface.

Secondly, when did I say you should not ride at any speed?

These are the specific claims I am contesting.

Not much faster than that and you're outside the tested limits of your helmet so to stay on the safe side, yep 10mph max.

If you fall off while moving at above say 15mph and hurt your head though, don't go crying to the manufacturer as they'll just tell you that you were outside the design parameters.

The implication being that merely by riding one's bike at a given, arbitrary speed, one's helmet is placed outside its design parameters. I do not believe this to be the case, for the reasons I have given upthread, unless you take the extreme view that any non-zero speed is outside these parameters.

And thirdly, and most importantly, when did I say you should be wearing a helmet to ride at any speed?

I did not intend to imply this, I merely thought that we could dispense with the small print which would otherwise read "should one happen to be wearing a helmet". I am not claiming that helmet testing standards are either adequate or realistic. I just think that the comments you are making are worth discussing in an open forum so that others may see both sides of the argument and make up their own minds.

 

[winjim]

The level surface is not perfectly smooth. The falling object decelerates in the horizontal plane as a result of the impact by a nonzero amount. The effect of that is untested, ergo the helmet is outside the limits of its testing, isn't it? That's not to say it won't work but we just don't know.

If that's the case then the forward speed which is still within the testing parameters must be zero.