Front engine safer than rear?

[ikarl]

hoegaardenruls said:

Baryonyx said:

The original A Class was notoriously unstable though, wasn't it?

Yep, as hinted at in my original post. Sorted to some extent I believe - much like the handling of early TT's which also liked going off the road backwards even though the engine was in the front.

hoegaardenruls said:

Wasn't the original Merc A-class designed so that the engine went under the passenger compartment in a frontal collision? Still, that assumes it didn't see an elk and topple over..

Thought it was the A2 that was designed to send the engine under the car in a crash

[JoeMk1]

Does the Elise have a reinforced windscreen frame? If not the strength is impressive to deflect a Laguna!

[B'stard Child]

JoeMk1 said:

Does the Elise have a reinforced windscreen frame? If not the strength is impressive to deflect a Laguna!

No idea but it's not the first time I've seen that.....

[james_gt3rs]

kambites said:

I think if you submarine under another car, you're generally fine with that tub. The problem comes if you hit something that wont move upwards, like a motorway central reservation.

I saw a post on the VX220 forum of someone who crashed into a central reservation. He survived, but had a cut on his head, and concussion IIRC. Lucky not to be beheaded!

[kambites]

JoeMk1 said:

Does the Elise have a reinforced windscreen frame? If not the strength is impressive to deflect a Laguna!

No there is no structural strength in the frame. It's so weak that if you pull yourself up on it getting out of the car you can break the windscreen. It's purely the tub that's deflected the Renault upwards.

That sort of accident happens quite a lot with Elise-type cars (well the accidents are presumably no more common than with any other car, but that result is) and I've never heard of the car not being deflected well over the driver's head.

[DonkeyApple]

ZesPak said:

you'll die with an Audi rim in your face.

I imagine that dying with four rings jammed in your face is how Hugh Heffner plans to go.

[k-ink]

That elise crash pic is damn impressive for a small kart!

I do wonder if anyone has fitted a cage into a street use elise?

[ORD]

All of this assumes that the Elise has not disintegrated of its own accord once it hits motorway speeds.

[k-ink]

ORD said:

All of this assumes that the Elise has not disintegrated of its own accord once it hits motorway speeds.

They are good for 140 with the top down, no issues at all.

[Some Gump]

To be honest, if I was forced to pick a car to crash in, a 911 would be right up there. They're built like tanks!

[JonnyVTEC]

One thing to consider with Rear engine and indeed the Telsa is that although you have more length available it has to do more to slow the car as the powertrain mass remains 'working mass' during the whole event. At some point a front engine hits the object and the car mass suddenly loses 200kg.

kambites said:

Surely it can't be hard to design a system which deflects the wheels out beyond the sills in an impact?

Issue is supension linkages are trying to do the exact opposite thing. You cant let a wheel go that far outboard to miss foot zone anyway unless you are able to actually detach the wheel from the hub even then it may not escape the zone. Small offset crash the NHTSA highlights this issue where the wheel is collected as the offset missed the main structure.

Edited by JonnyVTEC on Saturday 23 August 13:21

[kambites]

Surely that's an advantage for the rear engined car? It means your entire crumple structure is having to deal with decelerating the same mass, rather than the complexity of a varying mass as it crumples. Making the crumple zone strong enough to bare the brunt of the force has never been the problem; it's making it crumple linearly at the correct speed to dissipate as much energy as possible that's the challenge.

Front engined cars will have a slightly easier job keeping the passenger cell in tact for a given force transmitted through the crumple zone, but since the force transmitted through the crumple zone will be larger due to having less space to crumple I'd think that's more than cancelled out.


Ultimately, I suspect any funamental difference made by the engine placement is far less than the difference in design quality of different cars with the same layout, anyway. The hardest accidents for cars to deal with seem to be those where the offset of the impact is so small that the engine plays little or no part anyway.

Edited by kambites on Saturday 23 August 11:07

[JonnyVTEC]

I didnt suggest it was worse, just not quite as clean cut The Tesla in reality can not use all of the zone as it is less tolerant to lower dash/floor deformation.

Also a Rear engine car with a lower bonnet will also take avantage of moving the occupant forward for a more cabin forward package which reduces the length you have remaining as either the front overhange shortens or the driver gets closer to front wheel.

Especially when you start thinking about about a Telsa deals with a 500kg battery for a car that weighs similar to 7 series with a 350kg engine/gearbox. Have to be careful what you put in that frunk.

Edited by JonnyVTEC on Saturday 23 August 11:22

[kambites]

Again though, as long as the weight can be anticipated in the design of the crumple zone, more weight to slow down is not a negative. Quite the opposite in fact if you're hitting a deformable object because the more weight your vehicle has the more the other object will deform (of coures it's a rather different matter for the thing you hit).

The point about rear engined car stending to seat the driver further forward is certainly a valid one, although that's arguably not a fundamental problem with the engine placement but a choice of the designer.

In the case of the Tesla, I'd imagine the batteries start behind the drivers' feet, in which case the front floor section can deform as much as the front of any internal combustion engined car could without causing an issue.

Edited by kambites on Saturday 23 August 11:28

[anonymous-user]

DonkeyApple said:

I imagine that dying with four rings jammed in your face is how Hugh Heffner plans to go.

Keeping it classy

[shoehorn]

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.

Peugeot/Talbot was doing this stuff back in the 70`s.

[XJ Flyer]

There is a point where crumple zones are defeated by sheer non deformable mass.IE a tank has no 'crumple zone' whatsoever but it doesn't need it because it will just use whatever it hits,assuming it's something softer than another tank,as its crumple zone to cushion its impact against the softer target.By the same logic I think I'd prefer to be in something like an E Class or an S Class Merc ( or for that matter an old Austin Westminster or the XJ ) in a head on crash involving the 911.On the basis that that in addition to the crumple effect that they contain in the front structure,the remaining combination after that of engine and bulkhead will probably defeat what remains of the Porsche's bulkhead structure first.

[kambites]

Unfortunately that's the logic which is slowly leading to everyone driving twenty five tonne SUVs. Car safety should not, IMO, be an arms race.

Edited by kambites on Sunday 24th August 18:28

[XJ Flyer]

kambites said:

Unfortunately that's the logic which is slowly leading to everyone driving twenty five tonne SUVs.

Or E/S Class Mercs.Or partly old classic Austins and Jags etc instead of Volkswagen Beetles etc.

[montytom]

I think front engined would be safer in my opinion.
Also The Rover P6 a late 50s early 60s design had the same thing where if you were in a smack the engine would go down under the passenger compartment.
The ideas have been around for a long time