GB2327649A - Suspension safety system - Google Patents

Abstract

A suspension safety system, eg for a racing car, comprises at least one tendon (b,g,m,r,s) incorporated within a suspension member (a,l,n,q), interconnecting the vehicle chassis (k) and a hub and wheel assembly (c,d,e). Should a suspension component (a,l,n,q) fail, eg in an accident, the hub and wheel assembly (c,d,e) and any fragments of broken suspension component (a,l,n,q) will be restrained. The tendon (b,g,m,r,s) may terminate at the hub and wheel assembly (c,d,e), the other end being attached to the vehicle chassis (k), or may pass through attachment means in the assembly (c,d,e) and have both ends attached to the chassis (k).

Description

TITLE: Structural members for vehicles This invention relates to structural members, particularly those used in vehicles, comprising a hollow tubular member formed from a frangible material such as fibre reinforced plastics, carbon fibre or the like used as a structural component or a reinforcement member, Tubular members of carbon fibre, plastics and the like possess considerable strength to weight ratios but have the disadvantage against steel, for example, that they can catastrophically fail and break into fragments which may depart at high velocity posing a serious hazard. Although this invention is primarily concerned with tubular members used in vehicle, more particularly vehicles used in sports competitions the principle can equally well be applied to components in aircraft, spacecraft and consumer items such as sports racquets and domestic equipment.

An object of this invention is to provided, for a frangible structural member, a means of constraining any major fragments occurring on catastrophic destruction.

Broadly and in accordance with this invention there is provided a structural member, preferably of hollow tubular construction and of a frangible material adapted to connect together two parts of a structure, there being located within and extending through the hollow structural member a flexible strapping means of high tensile material the ends of which are secured to the relevant parts of the said structure.

The strapping means will preferably comprise a cable of, for example, high tensile steel.

In an embodiment the hollow member comprises a fibre reinforced plastics material including end fittings forming a structural connection with the strapping means being bonded or looped around parts of the structure joined by the hollow member.

In a preferred application the hollow member forms a suspension component of a vehicle. In motor sport, as well as other applications, the structure of a vehicle is such that components forming chassis framework or suspension assemblies are designed to deform to provide energy absorption in the event of impact primarily to protect occupants or equipment. When the body of a vehicle is of a high strength composite there is little, if any, deformation of the body itself on impact, and the suspension components provide the only means of cushioning. However when such components themselves are formed of high strength composites there is the risk of sudden fracture under certain loads with the result that parts broken-off can form a serious hazard. In this invention by the provision of a high tensile strapping means such as a steel wire or cable any broken parts will, in most cases, be retained.

In another aspect of this invention the strapping means itself may initiate the fracture following impact which assists the energy absorption process.

A further advantage of this invention is that the strapping means may be connected securely to the fittings connected by the hollow member and thus can act to assist breaking of the hollow member on impact but nevertheless still retain the broken parts.

This invention as it is applied to a motor racing car previously referred to, is illustrated in more detail in the drawings showing an embodiment by way of example and wherein: Fig 1, shows schematically in plan view the front chassis components of a racing car, the left side showing the lower suspension components and the right hand side showing the upper suspension components, and Fig 2, shows schematically and in plan view the rear suspension and drive components of a racing car, the left side showing the lower suspension components and the right side showing the upper suspension components.

In the drawings the reference letters denote the following component parts: Referring to Fig 1: a upper wishbone b upper wishbone safety cable c kingpin d brake calliper e front stub axle f brake disc g steering tie rod safety cable h steering rack safety cable anchorage plate nose cone k monocoque chassis steering tie rod m lower wishbone safety cable n lower wishbone o kingpin p suspension pushrod mounting bracket q suspension push rod mounting bracket q suspension push rod r lower wishbone safety cable s suspension push rod safety cable Referring to Fig 2.

a engine b gearbox housing c upper wishbone d upper wishbone safety cable e driveshaft f brake calliper g stub axle h brake disc rear hub carrier j suspension pushrod safety cable k suspension push rod lower wishbone safety cable m lower wishbone n suspension pushrod o universal joint p safety cable anchorage plate In so far as competition racing cars are concerned they include suspension components which serve several purposes.

Basically, single seat racing cars have two wishbones (a) and (n) on each side at the front and rear of the car. Also at the front, there is a suspension pushrod (q) on each side, and a steering tie rod (I) on each side. At the back, there is a suspension pushrod (k) on each side, and also a driveshaft (e) on each side. In total, there are six members between each wheel and the chassis. In Formula One and Indycar style racing cars, these members are mostly made from carbon fibre to save weight. They are very directionally strong; tremendously strong in one direction, but very easily broken in another. They can be likened to a paper drinking straw, that is very strong in compression along its length, but while any load of this kind is applied it is easily destroyed by applying a force across the straw. It will collapse very easily.

In one aspect, these components are forced to collapse completely, even if the forces applied during the accident would not normally cause this. By installing a cable (b), (g), (m), (r), (s) Fig 1 and (d), (j), (I) Fig 2 inside the hollow struts which is extremely strong in tension, but totally flexible and fixed very strongly to the chassis, the struts will still be able to collapse or be broken in an accident to absorb some of the energy, but the broken ends of the struts that could otherwise be exposed will be kept away from the driver as the broken parts are still threaded onto a cable. The wheel, in most cases, will not be able to break away from the chassis, which will prevent the possibility of a suspension strut fixed to a flying wheel departing the chassis. In the wish bones, the cable passes from the chassis anchorage (i), through the hollow wishbone, around the kingpin (c), and back to the chassis inside the other wishbone leg. One complete cable is used for safety. This is the same in each wishbone on the front, and at the rear, the cables pass around the pivot bolt for the rear hub carrier, so failure is only possible on the wheel side of the hub carrier.

In the extreme case of a wheel becoming detached, and it would be extremely unusual and also necessary if sufficient energy was available to cause such a failure, it would be a blunt object, as failure would have to occur on, the wheel side of the kingpin or hub carrier, and all the parts on this side of the kingpin or rear hub carrier are inside the back of the wheel, rendering a piercing wound of any depth whatsoever virtually impossible. The suspension struts, steering components, etc would all be left safely fixed to the chassis by the cables. The chances of this happening are very remote, as a tremendous force would be required.

However, if such a force was applied it would be essential that the wheel did become detached because much more serious damage could result, such as failure of the cables or indeed the chassis itself, which would be far more dangerous than a large blunt object flying off, stripped of its sharp components.

The cables have two purposes. In the wishbones, where movement is minimal, and the exit of the cables is easy to design, the cables have the purpose of deforming the wish bones, and also to restrain the collapsed assembly on the chassis. Both the upper and lower wishbone in each corner of the car has a safety cable installed for this purpose. However, on the steering tie rod, the end of the carbon fibre shaft moves in and out of the monocoque by several centimetres as the steering wheel is turned because one end of these rods is attached to a steering rack. Hence, exit of the cable from this tie rod to the chassis is very difficult to achieve and chafing and failure is thus more likely. For this reason the cables preferably do not exit the rods in the same way as the wishbones, but are fixed to the adjustment ends of the tie rods, so they will collapse the steering rod in an accident, and serve to prevent any piercing edges being exposed, but do not have a main purpose of restraining the destroyed wheel and suspension components on the chassis. The cable within the suspension pushrod will have a similar purpose to that of the steering tie rod cable for similar reasons. So, the wishbone cables will have the task of restraining the destroyed components on the wreckage.

At the rear of the car (Fig 2), the wishbones have cables with exactly the same purpose as those at the front, as do the suspension struts. However, the driveshafts do not have any such cable inside them.

It would be very difficult to safely install a cable inside the driveshaft as it spins at a high rpm., and a cable would cause imbalance and possibly failure through fatigue. A much simpler solution is to affix the driveshaft at only one end, at the gearbox. The driveshaft could be splined to sit in the stub axle of the rear wheel, and if the rear wishbones were deformed, it would simply pull out of the rear hub, but remain fixed to the vehicle. It has to be splined somewhere to allow for suspension movement, so this is a feature that would require little or no new technology to be developed.

The condition of the cable could easily be checked if made from steel or titanium etc. by passing an electric current down it and measuring its resistance. To save weight, the cable could be made from kevlar.

Preferably the cables can be used to pre-compress the wish bones, increasing their tensile strength.

Advantageously, instead of simply anchoring the cables strongly to the chassis, pre-tensioners, similar to those on car seat belts could be installed, to tension the cable much more in the event of an accident.

They would need to be slightly stronger than those used in cars however, and once operated, the cable end must still be fixed to the chassis as securely as without the pre-tensioner.

With the use of these cables, some of the carbon fibre members may be able to be removed if the suspension components were redesigned.

By keeping all of the wreckage together, drivers arriving at the scene of the accident at high speed will have a better chance of avoiding heavy debris if it is all held together in one place.

The chances of heavy pieces of dangerous, sharp debris flying into crowds is reduced. A wheel and broken suspension components travelling at 100 mph could prove to be fatal to a spectator on impact.

If development showed better safety, a single piece of cable could be used in each wishbone leg rather than one long continuous one. This would reduce the amount of movement of the damaged wheel etc. but this may not be desirable. Also, the long cable could be fixed at the kingpin, which would have a similar effect to using separate cables.

Another field of application, not illustrated, would be for space vehicles which have protruding components and struts. In such constructions the strapping means can be used in order to retain any parts to prevent them becoming free moving debris and to facilitate repair.

Although this invention is described in relation to hollow tubular members it is also possible for the strapping means to form an integral part of the member, for example by embedding a cable in the member or casting or moulding the member around the cable.

Claims (4)

1. A suspension safety system for a racing car wherein one or a multiplicity of tendons are incorporated within the suspension members, the first end of said tendon being attached to the chassis and the second end attached to the hub and wheel assembly in order to restrain the hub and wheel assembly and fragments of broken suspension components should said assembly become detached due to failure of a suspension component.

2. A susepnsion safety system for a racing car incorporating one or a multiplicity of tendons within the suspension members, the first and second ends of said tendon being attached to the chassis and the tendon passing through suspension members and through an attachment means in the wheel and hub assembly in order to restrain said assembly should it become detached due to failure of a suspension component.

3. A suspension safety system as claimed in Claim 2 wherein the attachment means in the hub and wheel assembly will allow said assembly to slide along the tendon.

4. A suspension safety system for a racing car substantially as described herein with reference to Figures 1 and 2 of the accompanying drawing.