Front engine safer than rear?

[ORD]

XJ either really doesn't understand energy transfers or is just a troll. Nobody is that slow to catch on.

[Finlandia]

Mave said:

XJ Flyer said:

I'll go with close enough to be able to make a comparison.In this case it is at least a reasonable assumption that I think I'd prefer to be sitting in the Westminster ( or the XJ ) in the event of meeting a 911 in a head on collision possibly including up to that 100 mph combined speed.As for something with a transverse front engine the answer is not going to be so easy but I still think my money would be on the tank in general in that regard.

Edited by XJ Flyer on Friday 29th August 00:50

Edited by XJ Flyer on Friday 29th August 00:56

See, in that situation you'd be worst off in the Westminster. Stop thinking of it as a competitive with the other car where you need to "defeat" it, and think of it as s competition with energy. Once your Westminster has "defeated" the crumple zone of the other car, it's your body that is taking the brunt. If you had a crumple zone as well, there would be less energy left over for your body to take...

As in the old Caddy vs. the new one, the old one came up better (more left of it) from the crash, but the driver died, while it was the other way around in the newer car.

[XJ Flyer]

Mave said:

XJ Flyer said:

I'll go with close enough to be able to make a comparison.In this case it is at least a reasonable assumption that I think I'd prefer to be sitting in the Westminster ( or the XJ ) in the event of meeting a 911 in a head on collision possibly including up to that 100 mph combined speed.As for something with a transverse front engine the answer is not going to be so easy but I still think my money would be on the tank in general in that regard.

Edited by XJ Flyer on Friday 29th August 00:50

Edited by XJ Flyer on Friday 29th August 00:56

See, in that situation you'd be worst off in the Westminster. Stop thinking of it as a competitive with the other car where you need to "defeat" it, and think of it as s competition with energy. Once your Westminster has "defeated" the crumple zone of the other car, it's your body that is taking the brunt. If you had a crumple zone as well, there would be less energy left over for your body to take...

All of which is based on the flawed idea that the Westminster is just a solid lump with no crumple ability of it's own.Everything after that is about defeating the other car and using that as a reserve crumple zone.Which is exactly what happened in the case of the offset longitudinal engine layout Volvo v the transverse engine shopping trolley shoe box.IE the solid mass of the combined transverse engine and bulkhead assembly went through the Volvo's front wing,bulkhead and A post assembly like a knife through butter and it was that transfer of energy from solid to soft target that saved the shopping car's occupants not the shopping car's ability to crumple which was actually less in that case.

[XJ Flyer]

ORD said:

XJ either really doesn't understand energy transfers or is just a troll. Nobody is that slow to catch on.

If you read my posts you'll see that I understand exactly the idea of using crumple zones to cushion impact loads.However in this case there is a point where the bulkhead area becomes the crumple zone.The argument then just being is it better to have a big lump of engine acting as a barrier to that or to have no engine there at all.

[XJ Flyer]

Finlandia said:

Mave said:

XJ Flyer said:

I'll go with close enough to be able to make a comparison.In this case it is at least a reasonable assumption that I think I'd prefer to be sitting in the Westminster ( or the XJ ) in the event of meeting a 911 in a head on collision possibly including up to that 100 mph combined speed.As for something with a transverse front engine the answer is not going to be so easy but I still think my money would be on the tank in general in that regard.

Edited by XJ Flyer on Friday 29th August 00:50

Edited by XJ Flyer on Friday 29th August 00:56

See, in that situation you'd be worst off in the Westminster. Stop thinking of it as a competitive with the other car where you need to "defeat" it, and think of it as s competition with energy. Once your Westminster has "defeated" the crumple zone of the other car, it's your body that is taking the brunt. If you had a crumple zone as well, there would be less energy left over for your body to take...

As in the old Caddy vs. the new one, the old one came up better (more left of it) from the crash, but the driver died, while it was the other way around in the newer car.

Yes I know.The reason for that being that the solid chassis of the older Caddy couldn't defeat the engine bulkhead assembly of the newer one.Thereby transferring all the impact loads into the older Caddy's occupants.Things might have turnout different in the case of a Corvair ( or a 911 ) v the old Caddy in that comparison.

[blueg33]

Someone has compared having ab engine in front of you as being like having a wall in front of you = safer

I don't get that, because what we should have here as an analogy, is a wall that can be pushed over onto you. Would you rather be behind a wall that can be pushed on top of you, or have specially designed features to ensure that arrows are defected anyway and no wall to squish you?

Personally, the impact on the body, especially legs of an engine being pushed backwards into the passenger compartment doesn't bear thinking about.

[XJ Flyer]

blueg33 said:

Someone has compared having ab engine in front of you as being like having a wall in front of you = safer

I don't get that, because what we should have here as an analogy, is a wall that can be pushed over onto you. Would you rather be behind a wall that can be pushed on top of you, or have specially designed features to ensure that arrows are defected anyway and no wall to squish you?

Personally, the impact on the body, especially legs of an engine being pushed backwards into the passenger compartment doesn't bear thinking about.

There is arguably more chance of an engine acting as a battering ram against the opposing car and an armour plated bulkhead in the direction of travel thereby transmitting the impact loads onto the opposing car.Which is how the small shopping trolley defeated the Volvo in the video posted.

[blueg33]

XJ Flyer said:

blueg33 said:

Someone has compared having ab engine in front of you as being like having a wall in front of you = safer

I don't get that, because what we should have here as an analogy, is a wall that can be pushed over onto you. Would you rather be behind a wall that can be pushed on top of you, or have specially designed features to ensure that arrows are defected anyway and no wall to squish you?

Personally, the impact on the body, especially legs of an engine being pushed backwards into the passenger compartment doesn't bear thinking about.

There is arguably more chance of an engine acting as a battering ram against the opposing car and an armour plated bulkhead in the direction of travel thereby transmitting the impact loads onto the opposing car.Which is how the small shopping trolley defeated the Volvo in the video posted.

It doesnt work like that - you can't turn the force around to make the engine work as a battering ram in the opposite direction.

[XJ Flyer]

blueg33 said:

XJ Flyer said:

blueg33 said:

Someone has compared having ab engine in front of you as being like having a wall in front of you = safer

I don't get that, because what we should have here as an analogy, is a wall that can be pushed over onto you. Would you rather be behind a wall that can be pushed on top of you, or have specially designed features to ensure that arrows are defected anyway and no wall to squish you?

Personally, the impact on the body, especially legs of an engine being pushed backwards into the passenger compartment doesn't bear thinking about.

There is arguably more chance of an engine acting as a battering ram against the opposing car and an armour plated bulkhead in the direction of travel thereby transmitting the impact loads onto the opposing car.Which is how the small shopping trolley defeated the Volvo in the video posted.

It doesnt work like that - you can't turn the force around to make the engine work as a battering ram in the opposite direction.

In this case it is the idea of it coming back through the bulkead which is turning the forces in the opposite direction.The engine more often acting as a battering ram and a barrier ahead of the bulkhead all travelling together at the same speed in the direction they were originally heading and then all coming to a stop in unison.The usual factor then just being a case of which car could stand up to intrusion best not which one crumpled the most.

[blueg33]

XJ Flyer said:

In this case it is the idea of it coming back through the bulkead which is turning the forces in the opposite direction.The engine more often acting as a battering ram and a barrier ahead of the bulkhead all travelling together at the same speed in the direction they were originally heading and then all coming to a stop in unison.The usual factor then just being a case of which car could stand up to intrusion best not which one crumpled the most.

In effect the engine decelerates faster than the rest of the car which moves forwards around it causing the engine to break into the passenger compartment.

The bulkhead may absorb some force and transfer it to the other structures of the car.

Did you do physics at school?

Crumpling dissipates energy, something solid like an engine doesnt

[XJ Flyer]

blueg33 said:

XJ Flyer said:

In this case it is the idea of it coming back through the bulkead which is turning the forces in the opposite direction.The engine more often acting as a battering ram and a barrier ahead of the bulkhead all travelling together at the same speed in the direction they were originally heading and then all coming to a stop in unison.The usual factor then just being a case of which car could stand up to intrusion best not which one crumpled the most.

In effect the engine decelerates faster than the rest of the car which moves forwards around it causing the engine to break into the passenger compartment.

The bulkhead may absorb some force and transfer it to the other structures of the car.

Did you do physics at school?

Crumpling dissipates energy, something solid like an engine doesnt

My physics tells me that something like a solid heavy engine won't decelarate any slower than the rest of the car it is attached to.

The only chance of that happening is if it meets something more solid than it and that thereby refuses to give way and crumple.

In which case it is obvious that,just like in the offset transverse v longitudinal test scenario,a rear engined car won't fit that definition resulting in the typical knife through butter effect which is the idea depending on point of view.

[Finlandia]

XJ Flyer said:

Finlandia said:

Mave said:

XJ Flyer said:

I'll go with close enough to be able to make a comparison.In this case it is at least a reasonable assumption that I think I'd prefer to be sitting in the Westminster ( or the XJ ) in the event of meeting a 911 in a head on collision possibly including up to that 100 mph combined speed.As for something with a transverse front engine the answer is not going to be so easy but I still think my money would be on the tank in general in that regard.

Edited by XJ Flyer on Friday 29th August 00:50

Edited by XJ Flyer on Friday 29th August 00:56

See, in that situation you'd be worst off in the Westminster. Stop thinking of it as a competitive with the other car where you need to "defeat" it, and think of it as s competition with energy. Once your Westminster has "defeated" the crumple zone of the other car, it's your body that is taking the brunt. If you had a crumple zone as well, there would be less energy left over for your body to take...

As in the old Caddy vs. the new one, the old one came up better (more left of it) from the crash, but the driver died, while it was the other way around in the newer car.

Yes I know.The reason for that being that the solid chassis of the older Caddy couldn't defeat the engine bulkhead assembly of the newer one.Thereby transferring all the impact loads into the older Caddy's occupants.Things might have turnout different in the case of a Corvair ( or a 911 ) v the old Caddy in that comparison.

That is why a newer car is safer than an old one, generally speaking, an old S class is probably safer than a new Proton.

The best and fairest way to test the crash safety of a car is to crash it into a solid object, that way you will see how good the construction is at handling the crash energy and how good it is at protecting the occupants.
This will show that the biggest and meanest 4x4 or the largest barge you can find isn't always the safest.


As for rear or front engine being safer in a crash; both drivers survived, sadly the passenger of the car with the engine in the front died.

https://www.youtube.com/watch?v=bDyvOGW_80o

[Mave]

ORD said:

XJ either really doesn't understand energy transfers or is just a troll. Nobody is that slow to catch on.

I dunno. I just think he can't accept that a lowly" shopping trolley shoe box" could possibly have better crash protection than his beloved jag.

Edited by Mave on Friday 29th August 16:22

[blueg33]

He also seems to miss the point that the last thing you want is a solid lump stopping you dead.

Cars crumple to slow down the rate of deceleration so that the g forces don't kill its occupants

[kambites]

I think his point is that you're probably better off using the body of the driver of the car you hit as a crumple zone than your own car.

[Mave]

XJ Flyer said:

All of which is based on the flawed idea that the Westminster is just a solid lump with no crumple ability of it's own.Everything after that is about defeating the other car and using that as a reserve crumple zone

Why are you obsessed with "defeating" the other car? The reason the "shopping car" protected the occupants better than the Volvo was simply because it's crumple zone was more effective. If the Westminster had better packaging with regards to crumple zones, it too would protect its occupants better.

[Finlandia]

From another thread, excuse the DM link.

http://www.dailymail.co.uk/news/article-2737682/Po...

Old car (with lots of tin and a big engine in front) with no crumple zone = relatively undamaged car and dead driver.

[shoestring7]

blueg33 said:

Someone has compared having ab engine in front of you as being like having a wall in front of you = safer

I don't get that, because what we should have here as an analogy, is a wall that can be pushed over onto you. Would you rather be behind a wall that can be pushed on top of you, or have specially designed features to ensure that arrows are defected anyway and no wall to squish you?

Personally, the impact on the body, especially legs of an engine being pushed backwards into the passenger compartment doesn't bear thinking about.

Or.. "If I was to drop you onto a pile of cardboard boxes, would you prefer them to be empty or full of nice strong bricks?"

SS7

[Mave]

kambites said:

I think his point is that you're probably better off using the body of the driver of the car you hit as a crumple zone than your own car.

Ah, forgetting that the longitudinal engine is now in the cabin, so you've got squashy people on either side of the transverse engine throwing themselves at it very hard...

[XJ Flyer]

Mave said:

ORD said:

XJ either really doesn't understand energy transfers or is just a troll. Nobody is that slow to catch on.

I dunno. I just think he can't accept that a lowly" shopping trolley shoe box" could possibly have better crash protection than his beloved jag.

Edited by Mave on Friday 29th August 16:22

I 'actually' said in the case of any longitudinal v transverse offset collision it won't be so easy to reach any conclusions regarding the performance of the longitudinal layout.

Ironically because the transverse design trades crumple zone for the battering ram and barrier capabilities of the lump of engine block ahead of the bulkhead.In order to defeat the crumple zone and exposed bulkhead area of the longitudinal layout.