Would the "S" be safer without airbags and ABS. Peter Wheeler thinks TVR's are!

Pistonheads TVR News

 

Spot on too, IMHO!

 

 

Not sure I agree........

He explains that ABS cars take longer to stop than non-ABS cars, but surely the accident that ABS can prevent is the lock up skid that stops you steering around something? I doubt a shorter braking difference to the extent provided by a non-ABS car is an advantage that outweighs being able to steer while braking hard.

He goes on about his cars all having roll-cages - I would suspect that the roll cages have far more to do with stiffening the chassis to improve the handling than to preserve the life of the occupant (although its a handy by-product).

Curved GRP panels - I don't doubt his safety claims re the GRP absorbing the impact of shunts, but again this would seem to be the happy by-product of a method of building a car for cost and production flexibility benefits rather than purely for safety reasons.

I can understand why he doesn't see ABS as a priority for a lightweight car with great handling and standard brakes given my experience of the S and its reluctance to operate the ABS, but that's not a reason to ignore a feature that might well save someone's life one day when all your competitors are doing it.

 

Interesting point of view.

I don't think I'd buy a car without ABS or airbags.

If nothing else, it does give you a sense of protection, knowing that should the worst happen, there is some active proctection there.

Bharat

 

He's dead right about the airbags in a convertible, for tall drivers anyway. It's something that concerns me if I ever got into a rollover situation. Shame they dont have a switch that stops them deploying if the car is upside down.
I'd personally rather not have ABS either, I've had to learn to cadence brake after driving crappy old cars without abs on ungritted, icy backroads. So far each time it has activated on the S it's been for daft things like braking across a bumpy surface or a drain cover etc.
Not overly bothered about the ABS though overall, that probably won't kill me, but the airbags could, given the right circumstances, ie rollover.

 

I'm not convinced by any of his arguments personally.

ABS - only the very best drivers will be able to improve on the stopping time of an ABS equipped car in one without it.

Airbags - these are most likely to go off in a head on collision which normally happen with the car upright. If the car does subsequently roll which I think unlikely, then they will have deflated. The most likely cause for a car to roll is if it's going sideways, in which case the airbags wouldn't trigger.

Rollcage - excellent idea, not convinced by the entirely rigid chassis though. There are two ways people can get seriously injured in cars, one is through the passenger compartment being encroached on, and the other is through extreme forces being exerted on the body when an extremely rigid car is brought to a stop very rapidly (e.g. the Smart car test on 5th gear). The compressible monocoque chassis with a strengthened passenger compartment helps here and is IMO better than a totally rigid chassis.

Plastic panels - simple fact - they do not absorb as much energy as metal. Look at the number of structures built from plastic rather than metal for strength.

 

Eh? Think this one depends entirely on application - if the car is designed properly the plastic panels never need to absorb as much energy.
The trouble here is that we're trying to compare a metal monocoque car to a car with seperate chassis and panels - 2 entirely different concepts which will perform completely differently in crash. In each case the panels themselves will only be absorbing a smallish amount of the energy involved, it is the structure beneath that saves the driver.

However, if you want to think about panels only, a composite (say 3mm GRP) panel will split, splinter and tear when crashed, all of which will abosrb more energy than simply folding up a thin (iro 0.7mm) steel panel. It'll look a lot worse at the end, but it will have taken more engery to do so - in both cases it's the underlying structure that does the bulk of the work.

Plastics (composites) allow much more freedom in designing a good crash box, and allow the crash pulse to be more easily tuned to whatever is deemed optimal. See F1 nosecones, and the plastic structures (crash boxes or crush cans) in the front of Elises, VX220s, McMerc SLR as 3 cars I can think of off the top of my head that use this technology. In these cases the car has a very stiff chassis, and seperate bolt on bits to absorb the energy, hopefully avoiding replacing the main tub.

 

OK, I'll claim ignorance here, as I assumed that TVRs are made of GRP ala boat building which isn't in the same strength league as carbon fibre as used in F1 (the inside of the boot of a Griffith I hired once certainly looked more akin to a fishing boat than McLaren). The high quality directional fabric used in F1 is much better than the 'random' weave you see for boatbuilding, so I can believe that it would be stronger than steel, but even so, I think there's a difference between strength and energy absorbtion. Once composites fracture, they're done and dusted. Steel will continue to bend, absorbing more energy won't it ?
Don't know for sure, I'm just thinking out loud.

 

Yup, that's why I steered clear of the word "strength".
IMO a 3mm thick GRP panel (alone, with no internal panels) found on TVRs and Lotus etc will probably absorb more energy in crash than a 0.7mm steel panel.
Could be wrong here, but think of a coke can - really strong when it's whole, but introduce one small dent to it and it crushes really easily. A GRP panel keeps on splintering and tearing, and each time it does it's absorbing more energy - albeit a very destructive absorbtion. As far as ultimate strength goes, I dunno, and it depends on what direction we're talking I guess anyway! The shape of the panel will also have a huge bearing on it's ability to absorb energy too..

Either way it's not entirely relevant as the steel panel has 3 or 4 internal panels which make up the body in white, and the GRP panel will be bolted/bonded to an internal panel, then a strong chassis and/or crash structure. And it's those that determine the ultimate strength and ability to absorb energy rather than the panels themselves.

FWIW, whilst the materials and resins used are similar to those used in boat building, the outward appearance of the GRP layup isn't everything. I know in some of our panels there is a directional mat weave sandwiched between layers of CSM (random direction Chopped Strand Mat) - don't judge a book by it's cover and all that!