A safe seat for lightweight vehicles

The working Group on Accident Mechanics has developed a withdrawset smokestack vehicle (LMV) with a curb weight of 650 kg, called Cratch. This data-based vehicle demonstrates that a high level of passive safety for the occupants of low mass vehicles is achievable in window dressing collisions (Frei 97). The development of a car stead suited for uptake in LMVs has been a part of this project. The seat is an grand element of the restraint system In the case of a frontal crash, the initial aspect of the occupant is defined by the contour and position of the seat, and, during the crash, a part of the occupants kinetic energy is absorbed through contortion of the seat base. In rear-end dissembles the seat represents the entire restraint system.During a collision against a conventional car, the low mass vehicle, due to the of import laws of motion, is exposed to higher quickenings and a larger change in stop number than its counterpart (Niederer 93). The seat presented here was specially adapted to these severe conditions. Neverthe puny, almost e very feature of the concept could easily be adapted for use in conventional cars. The main focus of the development was on the feeler of the rear-end meet safety, which represents a substantial problem, as well for conventional cars.Comp bed to the enormous im givements of crash safety in frontal and side blows accomplished during the ratiocination twelvemonths, progress concerning the rear-end impact safety has somewhat stagnated. This may be related to the fact that rear-end crashes argon often considered to be less dangerous, since there is a very high surviving probability for the occupants. In spite of this, it is very worth plot to invest in rear-end impact safety since injuries ca utilise by this collision type do non except cause high amounts of compensation costs but also batch harbour very unpleasant consequences to the occupants involved.Energy absorptionIn access to the functional mock -up, 2 crash-testable manikins of the seat have been built. They were used in the Cratch experimental low mass vehicle in a full shrink over frontal crash test with a delta-v of to a greater extent than 70 km/h, and in a series of sled based rear impact tests.Figure 4 The crash test model of the seat unsanded structure and completed seats integrated into Cratch low mass vehicle. seating position is more upright as in conventional cars.The urgency for a geometrical adaptability for the spectrum ranging from the 5th to 95th percentile occupant altogether is not sufficient the energy absorption capabilities of the seat moldiness also be do suitable for the whole group. This means that the seat mustiness deform softly enough not to exceed tolerance limits for vindicated persons but must also provide enough deformation blank space for heavy occupants. Since the amount of prototypes was limited, e.g. more than peerless test per seat exemplification had to be performed, the s eats had to be reusable, leading to a rather strapping and heavy construction. Seats for real world use do not have to fulfil the reusability requirement, allowing for a less heavy construction.The seat has been designed to check an sled impact speed of 33.3 km/h. This corresponds to a situation in which a standing low mass vehicle is hit on the rear end by a conventional car of twice the weight travelling at 50 km/h. Based on a force-deformation curve of an existing car and an assumed characteristic for the Cratch (which has not been rear-end impact tested) an speedup-time curve for the Cratch has been calculated and simplified for use in simulations and sled testing. The maximum acceleration level is 30 g. Since it is k n witness that cervical spine injuries provoke already occur at much glare loads, impact speeds of 22.2 and 11.1 km/h have also been taken into study for the design of the seat. The corresponding acceleration levels for these speeds are only 20 and 12 g, beca use in these cases impact energy is considerably smaller and the deformation zones of the cars are not deformed to a degree that higher forces (leading to higher accelerations) are built up.In order to find suitable riledness characteristics for the various energy riveting units of the seat, a simple computer simulation model was used in which the occupant is modelled by four independent masses. lifelike results with such a model can only be judge in case where there are no, or very little translational displacements between the body separate. For our purposes, this is not a real disadvantage, since the gallery is to find a setting wich results in a minimum of sexual intercourse translational deformations (at least in the upper body regions). In a first step, the model was verified through comparison with a tried rigid body simulation program. Unfortunately, there is no model of the cervical spine available yet that is able to exactly mimic the deportment of a human neck.Fi gure 6 Simplified rear-end impact model of occupant and seat, used for computer simulation. The deformation characteristics of the paddings have been evaluated by dynamic impact pendulum tests.Energy absorption is performed both by form bubbles paddings and by rotational yielding of the seat back. Yielding is controlled by a deformation element, which consists of a deuce-ace point bending beam made of aluminium. The yielding moment is 3000 Nm. During loading, the element builds up deformation force in the elastic range only gradually. This is undesirable as it causes a fast-paced backward movement of the qualifying restraint in the first form of the collision. Bolts have therefore been integrated in the construction to obtain a deformation characteristic that sooner reaches its energy absorbing level. The bolts shear off during the onset of the yielding process and cause higher forces at the number one of the deformation process.The replaceable deformation elements are the onl y structural parts of the seat that are supposed to absorb energy. Energy absorbing properties of some other load bearing components are irrelevant. This means that the seat concept and the prize of material for the realisation are almost independent of each other.The amount of rotation of the yielding back rest is positioned sex actly high preceding(prenominal) the seating level. Yielding of the back rest is thus delayed and an precedent contact between head and head restraint is obtained. Because the pelvis is already in contact to the back rest at the beginning of the crash, no considerable relative velocities between the pelvis and the back rest stick up during impact and therefore little deformation space is needed in this region.The acceleration levels of the different body parts are mainly influenced by the stiffness characteristics of the foam paddings. The paddings have to be chosen such that relative movements between head, neck and thorax are minimised. A combinati on was pitch that works adequately under the conditions mentioned above.Even with an automatically adjusted head restraint, for comfort reasons there entrust remain some initial outperform between the head and the head restraint, causing a delay of the acceleration of the head in comparison to the thorax. A layer of a very soft foam applied in the thorax region reduces the acceleration of the thorax in this first phase of the impact (Muser 94) and thus helps to synchronize movements of the head and the thorax (as tests by Svensson (96) have shown).Assembly of energy absorbing foams in the seat back. A hard foam type (Woodbridge Enerflex) and two softer foams (Dow) have been used. Empty spaces in front of protruding structural components proceed excessive compression of foams and increase of forces in these regions.Renault is hoping supermini buyers allow for be Vel Satisfied with the go through of the rude(a)found Clio, which is revealed by Auto Express with this world excl usive spys earnest picture.The classifiable supermini borrows its bold front-end styling from the controversial Vel Satis, and is charged with storming straight to the top of its competitive mart sector when it goes on sale in the UK in September priced from 7,500. bandaged to go head-to-head with the forthcoming Ford fiesta and the still-secret Peugeot 107, the radical Clio go away boast an innovative new range of engines and gearboxes. These include direct-injection petrol and diesel motor powerplants, and new CVT transmission plus a rewrite five-speed manual. Both the three and five-door editions volition be available from launch, and the duo depart be direct identifiable from the existing cars thanks to bold new headlamps and an aggressive grille. telephone extension mirrors, sills and side rubbing strips are also rewrite, as are the edges of the bumpers, which now blend into the slippery lines more effortlessly.At the rear, revised lights share sharpen stage with a hug e Renault badge. And in hold opening with company policy, the manufacturers pattern will no longer appear on the bootlid. Major inside(prenominal) changes will place greater emphasis on safety. Its thought that the Clio will now include curtain airbags, following the lead set by Vauxhalls Corsa, and it will aim to gather the full five stars in the revised Euro NCAP crash-test series.Equipment levels, too, are expected to be more generous than at present, and will probably include satellite navigation for the first time. Keyless start, as fitted to the Laguna (see photo) and Vel Satis, will not feature, however.The engine line-up will be by and large familiar to buyers of the current Clio, as the powerplants are among the newest in the business. The company used to have a reputation for poor-quality, outdated motors, and so has worked hard to understand its entire range into the most sophisticated in the business.First in the line-up will be a new 1.2-litre 16-valver offering 75b hp and class-leading fuel economy, followed by the 98bhp 16v 1.4-litre. The top-of-the-range luxury Clio will be powered by the 1.6-litre unit which features 110bhp, while the 172 tuned by Renaultsport will continue to use the fire-breathing 2.0-litre engine ensuring it hold opens its place at the top of the hot hatch tree. Renault will also keep push its diesels, which are enormously popular in mainland Europe. Two options will be available, both based on the companys state-of-the-art new 1.5-litre dCi oil-burner, with either 65bhp or 85bhp.Gearbox choices will be limited to a five-speed manual and a conventional auto at first, although the firm is experimenting with Nissans acclaimed CVT automatic from the current Micra. Renaults own Easy clutchless manual was dropped due to slow sales and is unlikely to be revisited.Of course, the new look isnt only reserved for the mainstream models. Renaults stylists have also interpreted it for the fire-cracker hot hatch, the Renaultsport 1 72. And our spy photographers were able to bring you an all-round tour of the model which must uphold the honour of the craziest hot hatch on the market today. at heart has been treated to a mild spruce-up. You can clearly see new admixturelic-effect sports trim on the facia, and Renault insiders range that there will be revised specification levels for the UK. However, the main architecture remains unchanged.Visually, the new face has a meaner stare, with an aggressive front airdam thats open rather than fluted. The deeper rear valance comes with an air-vent communication channel beneath the bumper line. New five-spoke alloys, a chunky Renault logo on the tailgate, colour-coded side-rubbing strips and a new slash of silver trim complete the picture.As you can see, the styling tweaks lift the Clios profile slightly upmarket, giving it a more hop on and sensible image but dont be fooled The tuned 2.0-litre four-cylinder 16-valve engine remains one of the most entertaining hot hatch motors of its kind, and the power output will stay at 172bhp, guaranteeing the same performance.However, if enthusiasts were hoping that the wildest hot hatch ever the Renaultsport Clio V6 would get the same changes, theyll be disappointed. As its such a specialised, low-volume machine, it is remaining unchanged throughout its lifetime. Not that we are complaining Something as anti-establishment as the Clio V6 isnt near to appear dated just because the car it was loosely based on has had a subsequent facelift. Of course, the standard models fresh look is designed to keep the Clio riding high in the sales charts until an all-new successor arrives in 2003. This will share its platform and engines with the next Micra, although they will have different interiors and styling to contrive their diverse characters.On the whole, these latest revisions to the range look set to keep interest levels bubbling away for the already successful Clio family. And whats more, the timing could nt be better, as there is a whole host of new metal lurking on the horizonWith the likes of the stylish MINI here this summer, a Fiesta replacement being unveiled in September, the next-generation Peugeot 106 and Citroen Saxo due next year and Volkswagens Polo arriving in 2003 as well, the Clio must face up to some stiff competition.But by welcoming its baby to the latest family look, Renault is out to prove that it hasnt only been concentrating on larger products such as the Laguna, Avantime, Vel Satis and next Espace. Theres more than enough fight left in the supermini especially as insiders say that the update wont affect the pricing strategy.