Thread: 2nd Christmas fatality involves Defender towing trailer.

Originally Posted by numpty

But, how many people buy a car based on how well it will crash. Safety would be a secondary consideration (if considered at all) in most peoples choice.

Actually I do. The defender isn't great but the "shopping trolley" that mum drives the kids around in was bought primarily for safety. Apart from a few people wanting to commit suicide no one leaves home thinking they will be a number in the road toll

i think what a few people arnt realising is that on those tests that they do it is a perfect crash.also im not sure what the speed limit is there but lets say they were both doing 75km/h then they coliding at 150km/h aslo on the videos it was a head on im guessing this was not completely head on(face to face) therefore the crumpling works differently so lets just say that there is 10kn of force in the test crash well that is spread evenly but in this case it is not so therefore you get a twisting action.i think taking everything into consideration like look what it did to the other car,the weight that it was towing and where it ended up it didn't to do badly.but it doesnt matter as much how or where it crumpled.but did it save lives and the answer is YES

Originally Posted by schmierer LR at singleton

i think what a few people arnt realising is that on those tests that they do it is a perfect crash.also im not sure what the speed limit is there but lets say they were both doing 75km/h then they coliding at 150km/h aslo on the videos it was a head on im guessing this was not completely head on(face to face) therefore the crumpling works differently so lets just say that there is 10kn of force in the test crash well that is spread evenly but in this case it is not so therefore you get a twisting action.i think taking everything into consideration like look what it did to the other car,the weight that it was towing and where it ended up it didn't to do badly.but it doesnt matter as much how or where it crumpled.but did it save lives and the answer is YES

I take on board what you've said. The crash tests are offset at 64kph into a deformable barrier because that is the hardest of tests. It's only in the last couple of years that cars are now starting to perform well in these tests. Safety is advancing **really** quickly at the moment thanks to computer sims.

In regards to the defender, sometimes, the simple answer is that on the day you can be LUCKY.

[ame="http://www.youtube.com/watch?v=Ad8dHYAIhZ4"]YouTube- Fifth Gear: 4x4 Crash Test[/ame]

Originally Posted by numpty

But, how many people buy a car based on how well it will crash. Safety would be a secondary consideration (if considered at all) in most peoples choice.

I remember reading an article a few yrs back when many of the Jap vehicle manufacturers had "safety paks " as an option.These included ABS brakes,air bags,TC,etc.
They couldn't sell them,most people wanted a flashy set of wheels,leather pack,or something similar.

Originally Posted by schmierer LR at singleton

.also im not sure what the speed limit is there but lets say they were both doing 75km/h then they coliding at 150km/h

This is a common missconception.

For the sake of simplicity (in the example I am about to give) imagine you have two identical vehicles traveling towards each other. Because this is AULRO I am going to say they are both Defenders .

Each Defender has a certain amount of "energy" which is a factor of its speed and weight. I will call this a Defenders worth of energy. If they are both going at the same speed they both have the same amount of energy to be dissapated in a crash.

If they collide head on, they both have one Defenders worth of energy to use in the collision. In a perfect crash they would both crumple the same amount, both using their energy the same way.
The entire crash would have two Defenders worth of energy, but each vehicle would use only there own energy in the crash (remember the energy is partly derived from vehicle speed).

To further explain, imagine driving the Defender into a brick wall that won't collapse. One Defenders worth of energy is used in the crash.
Now drive another Defender into the opposite side of the wall at exactly the same time. The second Defender will also use one Defenders worth of energy in the crash.

Now take the wall out of the middle. There is now a head on crash, but the energy that each vehicle brings to the crash is the same as before, therefore the crash is the same per vehicle as if the wall was there.

In the real world there are many other factors to consider. As noted by others, crash design is a huge factor when considering how safe a car is.

Another big factor is size and weight. In my example above, both Defenders are identical in size, weight and speed.
In the real world it is not always the case.
Generally speaking, in a head on crash the bigger vehicle "wins". Some of the larger (and possibly "stronger", think full chassis) vehicles energy will be trasferred to the smaller vehicle. This is great for the occupants of the larger vehicle, but really bad news for the smaller vehicles occupants.

In that case, the energy dissipation of the collision isn't equally shared and the smaller vehicle has to do more than its fair share.

I hope that clears things up a bit ...

Originally Posted by BigJon

This is a common missconception.

For the sake of simplicity (in the example I am about to give) imagine you have two identical vehicles traveling towards each other. Because this is AULRO I am going to say they are both Defenders .

Each Defender has a certain amount of "energy" which is a factor of its speed and weight. I will call this a Defenders worth of energy. If they are both going at the same speed they both have the same amount of energy to be dissapated in a crash.

If they collide head on, they both have one Defenders worth of energy to use in the collision. In a perfect crash they would both crumple the same amount, both using their energy the same way.
The entire crash would have two Defenders worth of energy, but each vehicle would use only there own energy in the crash (remember the energy is partly derived from vehicle speed).

To further explain, imagine driving the Defender into a brick wall that won't collapse. One Defenders worth of energy is used in the crash.
Now drive another Defender into the opposite side of the wall at exactly the same time. The second Defender will also use one Defenders worth of energy in the crash.

Now take the wall out of the middle. There is now a head on crash, but the energy that each vehicle brings to the crash is the same as before, therefore the crash is the same per vehicle as if the wall was there.

In the real world there are many other factors to consider. As noted by others, crash design is a huge factor when considering how safe a car is.

Another big factor is size and weight. In my example above, both Defenders are identical in size, weight and speed.
In the real world it is not always the case.
Generally speaking, in a head on crash the bigger vehicle "wins". Some of the larger (and possibly "stronger", think full chassis) vehicles energy will be trasferred to the smaller vehicle. This is great for the occupants of the larger vehicle, but really bad news for the smaller vehicles occupants.

In that case, the energy dissipation of the collision isn't equally shared and the smaller vehicle has to do more than its fair share.

I hope that clears things up a bit ...

To add to this, the energy of a moving object is a function of the square of its velocity. Energy = half mass x velocity x velocity. Double the speed = 4x the energy.

Many modern vehicles which can be written off in relatively low speed collisions are far safer than older truck like vehicles like our land rovers.
Defenders in particular dont give good outcomes in frontal, side impact and rollover accidents. There are also valid arguments that certain design aspects can make a Defender more prone to rollover than many other makes of 4WD. I say this not to stir the pot but because a healthy awareness of these vulnerabilities is a good thing when it comes to driving attitude.

I think you guys are being a bit hard on the Defender in this case.

That's a pretty complex crash. From the pic it looks like the vehicle being towed moved forward and bashed into the back of the Defender and judging by the deformation of the back doors of the towed vehicle, and the popped boot, it hit pretty hard.

It also looks to me like the Defender has almost been bent in half, but again, from the picture, I can't see a clear impact point. Looks to me like the chassis rail has bent under driver's seat, which to me reads like a hit big enough to compact most cars.

Originally Posted by BigJon

Now take the wall out of the middle. There is now a head on crash, but the energy that each vehicle brings to the crash is the same as before, therefore the crash is the same per vehicle as if the wall was there.
...

I disagree, as you haven't taken into account that both vehicles are moving towards each other at whatever velocity they have. The wall, on the other hand, is standing still.

It therefore stands to reason that the impact would be more acute, as each vehicle is trying to push the other vehicle backwards, in addition to colliding with it.