Front engine safer than rear?

[Mave]

XJ Flyer said:

Although it is obvious that having as much metal as possible out front in addition can only help.

Not really, you want the crumple job to do it's job, not have a big stiff lump of metal keeping the peak deceleration high...

[DonkeyApple]

Mave said:

Not really, you want the crumple job to do it's job, not have a big stiff lump of metal keeping the peak deceleration high...

Yup. Before crumple zone tech and the understanding that it was all about controlled deformation that reduced the shock and impact to internal organs the best you could hope for was a big lump of iron to try and out ram the opposition.

But as something like an engine doesn't dissipate or absorb energy it is as much part of the problem now that crumple zone tech and understanding has got as far as it has. The fact that they try to design it so that the block keeps moving back but under the occupants tells you that it doesn't help but hinders.

[XJ Flyer]

V8forweekends said:

hoegaardenruls said:

As with a lot of things, I think Mercedes just did it first and the rest followed - the original A-class was a mid-90's design, when you average French hatchback would have been lucky to scrape two stars in an NCAP test. The height of the A-class just made it a bit easier to achieve.

I think (but can't find a link to substantiate) this idea was used by Rover in the Early 60s for the P6. Clearly the engine didn't start off under the floor like the A Class, but I'm sure the engine and box were designed to side out under the passenger compartment in an impact.

Plenty of cars had the same system certainly the Volvo 140 series and the old Jaguar XJ uses a similar idea.The key is in the way that the rear of the gearbox is attached to the gearbox cross member mounting.It is either made to shear off and drop the gearbox on impact and/or bend in at 90 degrees thereby lowering the gearbox and allowing the engine to pivot on its mountings and then get pushed under the trans tunnel.

However at that point it will be a massive impact that realistically won't have a happy ending anyway in most cases.There was an article in old issue of Autocar years ago concerning a Volvo 142 that was put on the Volvo stands at numerous motor shows.If I remember it right it had been involved in head on collision with a heavy truck at a combined speed of almost 100 mph and yet still ( just ) remained survivable for its driver who suffered serious injuries by all accounts.With no more than I think it was 18 inches of the car left forward of the bulkhead.

However it is obvious that even the process of shifting the engine in that way would also absorb a lot of energy anyway.Which again is something that a rear engined car wouldn't have the luxury of.

[XJ Flyer]

Mave said:

XJ Flyer said:

Although it is obvious that having as much metal as possible out front in addition can only help.

Not really, you want the crumple job to do it's job, not have a big stiff lump of metal keeping the peak deceleration high...

The problem being that you eventually run out of crumple zone and start penetrating the bulkhead and A post etc area.In which case having a big lump of metal in the way that either has to be shifted or penetrated can only help in that regard.

Hence the rigged Volvo v shopping trolley stunt in which no surprise that's exactly what happened in the case of the unfortunate Volvo when he offset pitted the Volvo's front wing and bulkhead/A post structure against the combined strength of the transverse engine and bulkhead structure of the shopping car.Which had it been a square on hit involving the same combination in the case of the Volvo most likely would have had a very different outcome.

[Finlandia]

It doesn't always help to have a dance floor sized bonnet and a huge engine in front.

https://www.youtube.com/watch?v=joMK1WZjP7g

[skyrover]

Finlandia said:

It doesn't always help to have a dance floor sized bonnet and a huge engine in front.

https://www.youtube.com/watch?v=joMK1WZjP7g

Massive technological gap shown in this test.

Older car's usually perform very poorly in offset crashes due to the complete lack of structural rigidity across the front of the vehicle.

A lack of high strength safety cell for the occupants, zero crumple zones, flimsy x-chassis, no seatbelts, airbags, sharp interior corners, spear-like steering column, low strength steel etc etc etc

Technology has moved on hugely in 50 years

[Mave]

XJ Flyer said:

Mave said:

XJ Flyer said:

Although it is obvious that having as much metal as possible out front in addition can only help.

Not really, you want the crumple job to do it's job, not have a big stiff lump of metal keeping the peak deceleration high...

The problem being that you eventually run out of crumple zone and start penetrating the bulkhead and A post etc area.In which case having a big lump of metal in the way that either has to be shifted or penetrated can only help in that regard.

Having a big lump of metal in the way doesn't help you one bit in terms of energy absorbsion. What does help is having a strong structure transmitting the loads more uniformly back to a crumple zone to take out as much energy as possible, but if you've run out of crumple zone (as you suggest above) then it's like tying yourself to a safe and jumping out of an aeroplane; you just get squashed against the safe instead of against the concrete....

XJ Flyer said:

Hence the rigged Volvo v shopping trolley stunt in which no surprise that's exactly what happened in the case of the unfortunate Volvo when he offset pitted the Volvo's front wing and bulkhead/A post structure against the combined strength of the transverse engine and bulkhead structure of the shopping car.Which had it been a square on hit involving the same combination in the case of the Volvo most likely would have had a very different outcome.

Why are you saying the test was rigged? Surely an offset collision is far more common than a square head on?

[XJ Flyer]

Finlandia said:

It doesn't always help to have a dance floor sized bonnet and a huge engine in front.

https://www.youtube.com/watch?v=joMK1WZjP7g

Another example of a rigged test with predictable results.IE offset head on transverse engine v longitudinal with the even worse factor of stressed monocoque v seperate chassis and unstressed body.With the offset nature of the comparison counting out any contribution of the engine/bulkhead/front chassis structure combination.Like the Volvo example a square on collision might have had a different outcome especially assuming the chassis height was sufficient to meet the floor height of the Malibu.

www.youtube.com/watch?v=vq5cAgTN3zE

[XJ Flyer]

Mave said:

XJ Flyer said:

Mave said:

XJ Flyer said:

Although it is obvious that having as much metal as possible out front in addition can only help.

Not really, you want the crumple job to do it's job, not have a big stiff lump of metal keeping the peak deceleration high...

The problem being that you eventually run out of crumple zone and start penetrating the bulkhead and A post etc area.In which case having a big lump of metal in the way that either has to be shifted or penetrated can only help in that regard.

Having a big lump of metal in the way doesn't help you one bit in terms of energy absorbsion. What does help is having a strong structure transmitting the loads more uniformly back to a crumple zone to take out as much energy as possible, but if you've run out of crumple zone (as you suggest above) then it's like tying yourself to a safe and jumping out of an aeroplane; you just get squashed against the safe instead of against the concrete....

XJ Flyer said:

Hence the rigged Volvo v shopping trolley stunt in which no surprise that's exactly what happened in the case of the unfortunate Volvo when he offset pitted the Volvo's front wing and bulkhead/A post structure against the combined strength of the transverse engine and bulkhead structure of the shopping car.Which had it been a square on hit involving the same combination in the case of the Volvo most likely would have had a very different outcome.

Why are you saying the test was rigged? Surely an offset collision is far more common than a square head on?

Not assuming the driver of the longitudinal engined car knows the weakness and does everything possible to turn an offset collision into a square on one.While in the case of a rear engined car there obviously won't be that choice/chance.

Some say that was the mistake which the helmsman of the Titanic made.

As for the safe analogy you're not actually attached to the safe.In this case the safe is a few feet away acting as an armoured bulkhead which hopefully uses the opposing car as it's crumple zone.

Edited by XJ Flyer on Wednesday 27th August 22:11

[Finlandia]

XJ Flyer said:

Finlandia said:

It doesn't always help to have a dance floor sized bonnet and a huge engine in front.

https://www.youtube.com/watch?v=joMK1WZjP7g

Another example of a rigged test with predictable results.IE offset head on transverse engine v longitudinal with the even worse factor of stressed monocoque v seperate chassis and unstressed body.With the offset nature of the comparison counting out any contribution of the engine/bulkhead/front chassis structure combination.Like the Volvo example a square on collision might have had a different outcome especially assuming the chassis height was sufficient to meet the floor height of the Malibu.

www.youtube.com/watch?v=vq5cAgTN3zE

Rigged how? Of course rigged as in it's a test, not a real smash, but the result is the same. Offset is also a more fair way to test the crash safety of a car, not many crashes are straight head on, most are offset into another car or a structure of some sort or a tree.
The occupants of an older car, no matter how big, will always come worse off against the ones in a modern car.
As for the Jaguar vs Ford, both are old, one is bigger and heavier, very much expected outcome, now put an old Jaguar against a modern one.

[Finlandia]

XJ Flyer said:

Not assuming the driver of the longitudinal engined car knows the weakness and does everything possible to turn an offset collision into a square on one.While in the case of a rear engined car there obviously won't be that choice/chance.

Some say that was the mistake which the helmsman of the Titanic made.

Everything happens in a split second, your human nature is to try to avoid the collision not try to go for a head on.

[XJ Flyer]

Finlandia said:

XJ Flyer said:

Finlandia said:

It doesn't always help to have a dance floor sized bonnet and a huge engine in front.

https://www.youtube.com/watch?v=joMK1WZjP7g

Another example of a rigged test with predictable results.IE offset head on transverse engine v longitudinal with the even worse factor of stressed monocoque v seperate chassis and unstressed body.With the offset nature of the comparison counting out any contribution of the engine/bulkhead/front chassis structure combination.Like the Volvo example a square on collision might have had a different outcome especially assuming the chassis height was sufficient to meet the floor height of the Malibu.

www.youtube.com/watch?v=vq5cAgTN3zE

Rigged how? Of course rigged as in it's a test, not a real smash, but the result is the same. Offset is also a more fair way to test the crash safety of a car, not many crashes are straight head on, most are offset into another car or a structure of some sort or a tree.
The occupants of an older car, no matter how big, will always come worse off against the ones in a modern car.
As for the Jaguar vs Ford, both are old, one is bigger and heavier, very much expected outcome, now put an old Jaguar against a modern one.

As I've said most people know that a longitudinal engined car has less chance in an offset head on with a transverse engined one.While a rear engined one has even less in the case of either square on or offset but for similar reasons.Ironically those reasons actually being all about the advantages of penetration as opposed to crumple zones.

[scenario8]

I promise you "most people" wouldn't have a clue what most of that post meant at all.

[XJ Flyer]

Finlandia said:

XJ Flyer said:

Not assuming the driver of the longitudinal engined car knows the weakness and does everything possible to turn an offset collision into a square on one.While in the case of a rear engined car there obviously won't be that choice/chance.

Some say that was the mistake which the helmsman of the Titanic made.

Everything happens in a split second, your human nature is to try to avoid the collision not try to go for a head on.

In the case of a longitudinal front engined car the natural reaction needs to be try to avoid it.But if you can't avoid it your life might depend on doing everything possible to turn an offset head on into a square on one.Just as shown in the tests.

In just the same way that the correct reaction to a slide is to do everything possible to try to save it.Which might not always be the same thing as 'the natural reaction' to the circumstances which generally are to just panic brake.

While the fact is the offset tests in question were certainly rigged to provide the best example of the conclusion which the testers wanted to prove.

[XJ Flyer]

scenario8 said:

I promise you "most people" wouldn't have a clue what most of that post meant at all.

Possibly.They would probably also be the same people who think that a small shopping hatch would survive a square on head on collision with a big old school Volvo.In exactly the same way as it would in an offset head on collision with same.

[Finlandia]

XJ Flyer said:

Finlandia said:

XJ Flyer said:

Not assuming the driver of the longitudinal engined car knows the weakness and does everything possible to turn an offset collision into a square on one.While in the case of a rear engined car there obviously won't be that choice/chance.

Some say that was the mistake which the helmsman of the Titanic made.

Everything happens in a split second, your human nature is to try to avoid the collision not try to go for a head on.

In the case of a longitudinal front engined car the natural reaction needs to be try to avoid it.But if you can't avoid it your life might depend on doing everything possible to turn an offset head on into a square on one.Just as shown in the tests.

In just the same way that the correct reaction to a slide is to do everything possible to try to save it.Which might not always be the same thing as 'the natural reaction' to the circumstances which generally are to just panic brake.

While the fact is the offset tests in question were certainly rigged to provide the best example of the conclusion which the testers wanted to prove.

The only fact is that most collisions are offset in one way or another, some cars come out better than others in these types of collisions. How can you have a head on crash with a tree?

[Finlandia]

XJ Flyer said:

scenario8 said:

I promise you "most people" wouldn't have a clue what most of that post meant at all.

Possibly.They would probably also be the same people who think that a small shopping hatch would survive a square on head on collision with a big old school Volvo.In exactly the same way as it would in an offset head on collision with same.

The fact is that a modern car is safer than an old one, even if the size is in favour of the old car.

[Finlandia]

Old longitudinal vs. new(ish).

https://www.youtube.com/watch?v=O-WYKYrq5FI

[Mave]

XJ Flyer said:

Not assuming the driver of the longitudinal engined car knows the weakness and does everything possible to turn an offset collision into a square on one.

Are you seriously suggesting that in a head on collision scenario, the driver would turn into the crash rather than swerving to avoid it?

[scenario8]

I concluded some long time ago XJ Flyer must be a wind up.