Chapter 10 Cornering - Driving Guide PDF

Cornering forces Chapter 10 A moving vehicle is most siabie when its weight is evenly distributed, its engine is just palling without increasing...

Cornering forces Chapter 10 A moving vehicle is most siabie when its weight is evenly distributed, its engine is just palling without increasing speed, and it is travelling in a.straigiit line. It will continue to travel in a straight line unless you apply some other Cornering D alter its direction. When you steer, the turning force to alter direction comes from the action of the front lyres on mad. You saw in (ihapler 5 (page 8”) ih.al this force dqx'nds on lyre grip. If the front lyre grip is broken, the car u continue in a straight line. On lighter bends, at higher speeds and in lieavier vehicles, the deni.iiids on lyre grip ar greater. Learning outcomes Tlic learning in this chapter, along with driver training, should enable you to: c.\p!ain Ihe principles of safe cornering describe the forces involved in cornering and the factors that alfcet your vehicles abilit)’ to corner show how to use the limit point to assess your speed for bends and corners Grip a’.afable Grip usc-d for braking oi siiow how to position your vehicle for the best view wheit cornering lot sloi'i'inq acceleraling show how to use the system of car control for cornering. ihree forces reduce stability and, ultimately, lyre grip: Developing your co.mpctencc at cornerin^ a steering.iccelcrating Cornering - driving a car round a comer, curve or bend - i.s one of the main driving activities, and it is importani it right. When you corner, your vehicle loses.stability and you place extra demands on the tyre grip available. Ihe br.tking. you go and the lighter the bend, the greater tlie.se demands arc. Ibe more you brake or :icceler:ile, the le.ss lyre grip yon have for.steering. 'Hie faster you go into a corner or bend, more you reduce stability and the more I\tc grip you need to keep your po.sition. Almost lialf ofall fatal collisions for drivers under 30 arc llie result of the driver losing control on a bend or a cui If one or more of these forcc.s causes lo.ss of tyre grip, the vehicle will continue in a slraiglii line rather than uiriiin a lefi-liand bend, as you lose lyre grip, your vehicle drifts to the rigln of your intended position and in a right-ban Ibis chapter explains boss' to apply the system of car control to cornering. We start sviih some general principles ,i it dribs to the left. Tlie design of the veliide will reduce or increase this elfect. look at ilie forcc.s invols-ed in cornering, the factors affecting yours'ehiclc's ability to corner.safely, and boss' to use sy.stem of car control in conjunction svjlli limit point analysis to corner safely. CVifljriVri, VKsyiWin ofi nutlfol [yc 2S. Using the system to corner safely Cornering is potentially ilangerous so you should use the system of car control to help yon carrj' out the manoeus safely. Ivach phase of the sy.stem is relevanl but processing information is e.specialiy important. Correctly assessing severity of the bend is essential for safety. Key principles for safe cornering Make sure that your vehicle is in the correct position on the approach. Travel at the correct speed for the corner or bend. Select the correct gear for that speed.. Be able to stop safely within the distance you can.sec to be de.ar on your own side ol the road. Applving these principles to the variations in bend, visibility, trafiic coiidilions, road surface conditions and other I Ar« t «! ' i« r«' lU.. r/sl  Uiidersteer ami oversteer Understecr is (he tendency of a veliicle to turn less, and oversteer is the tendency of a vehicle to turn more, in resp a given turn of the steering wheel. Tlie tendency to understcer or oversteer i.s a characterLstic of the vehicle it.selt a depends mainly on what sort of drive the vehicle has. Make sure you know the different steering characteristics ol vehicle you drive and adapi your driving on corners and bends. Sfp Ouif'tfv.7 Meinteiniiig veiiiJe fidb'iHly. ttJge 1.^5. UndenUtr euoth directions (similar to banking on a race track). line and only turns into the bend because it ir> forced to by the car. Pick out one or two sections of familiar road where cornering is tricky and workout whether unexpected cambe factor. Analyse how you took the corner and make an honest assessment ofyour driving. Did you make the correct dec Vehicle characteristics about the best position and speed to adopt for the bend, for example? Roadworthiuess Vehicles vary in their capacity to corner, and they only comer efficiently if they are well maintained. Steering, susj shock absorbers, tyres, tyre pressures and the loading of the vehicle all affect its balance and tyre grip when cornci Position loads evenly.so they don’t upset the balance ot the vehicle. I Make sure that your vehicle and tyres are in good condition and that you keep your t>TC pressures at the recommended levels. Crown camber Vehicle specification The specifications that affect the handling characteristics of a vehicle include: the type of drive - front wlieel. rear wheel or four wheel ^suspenrion and damping the drive ratio and central diilerentiai characteristics on a loui wheel drive vehKie active vehicle safety s)-stems the tvneand.si7C of vehicle, whether commercial vehicle or car : Superelevation  i I  Read the diagram from the bottom of the page upwards. Summar)’ of factors affecting cornering T5ie factors that determine your vehicle's ability to corner are: the specification and condition of your vehicle, including the tyres your speed 6 the amount of steering you apply the amount of acceleration or braking 5 the slope across the road surface - camber atid superelevation 4 the road surface and how the weather has atfecled its grip. Tlie system of car control and the limit point To drive safeJy you must be able to slop within die distance you can see to be clear on )our own side of the road - the distance between you and the limit point. Think of the limit point as a perception tool that will help you to aci 3 negotiate a corner or bend. The system of car control helps you plan how to approach and negotiate comers and bends. Intormaiion proccssii the four phases of the system - position, speed, gear and acceleration - are the key factors that you must consid* 2 cornering. As you approach a bend, seek as much information as possible about the severity of the bend using all the observ; dues (weather, road surface, road signs, road markings, the lino made by lamp posts and trees, the speed and posi 1 oncoming Irnffic, the angle of headlights at night, etc) that are available to you. The more information you gather: the bend, the more accurately you will be able to judge the besi position and speed to negotiate it. The limit point gives you a systematic way of judging the correct speed to use througJi the bend. Cha^Kr X U\forrTUiU\>». iAnfi rd/ion ond anUap*Utvr\. 46. How to use the limit point to help you corner Approaching the bend The limit point is the furthest point to which you have an uninterrupted view of the road surface. Tliis is where ih hand edge of the road appeals to meet the left-hand edge in the distance. The more distant liie limit point, the fasi At first the limit point appears to remain stationary. can go because you have more space to stop in. The closer the limit point, the slower you must go because you ha\ Adjust yuur speed so you can slop safely within the remaining distance. space to stop in. As you approach the bend, take information about the sharpness of the bend and carefully assess the appropriate: for cornering. On a left-hand bend, you should drive a.s though the limit point is where the edge of the road meets the central \ line (or the centre of the road if there is no svhite line) so that you can stop safety on your own side of the road. Watching the lunit point enables )’oulo match your speed to the speed at which this point appean to move. If it is moving away from you, you may accelerate. If it is coming closer to you or standing still, you must decelerate or b Even when the bend is not constant, you can still match your speed to the apparent movement of the limit point, 1 this will vary with the curvature of the bend. Acceleration sense is useful here. Using the limit point together with the system helps you: adjust your speed so you can stop safely within the distance you can see to be clear on your own side of the road decide the correct.speed to approach and iicgoti.iic tHchcnd -- — select the correct gear for the speed decide the point at which to start accelerating.  9 jl: 8 4 7 Just before you enter the bend Just before you enter the bend the limit point ^ begins to move round at a constant speed. Adjust your speed to t speed of this movement. You now have the correct speed to go round the bend. Select the gear to match this speed before entering the ben< the accelerator to maintain a constant speed lor maximum stability through the hend. Going through the bend As ihe bend starts to straighten out your view begins to open up, and the limit point ^starts to move away more quickly. You can tlten accelerate steadily as you straigliten your steering. The limit point technique is self-adjusting - as road visibility and conditions deteriorate you need more distance i to stop, and so you must reduce your speed to compensate. Use the limit poiiit as well as other observation links - get into the habit of looking across or beyond the bend as) approach it. You may spot a hazard just after the bend - for example, a warning sign or a chevron marker indicati further bend. In this case it would be inappropriate to use the limit point alone to set your speed. Where a road i.s not wide enougli for two vehicles to pass, consider doubling your stopping distance to give an on^ vehicle enough space to stop as well. On a left-hand bend on a single track road, the limit point is where Ihe two k lines meet. Practise matching your speed to the movement of the limit point. TryUIis bn adjust to tlie characteristics of each bend. Always adjust your speed so that you can slop.safely withm thcdistalti lo hfi rles»r i I I 1 I i ll \i I  Make a special point of using the limit point to set your speed for bends and comers on roads you know well. It On the approach to a corner or bend you should be constantly scanning the road for information, especially abou fomiliar routes that your attention is most likely to wander. tralllc in front and behind tlhe road surface and the effect of weather conditions on it llie double apex bend the limit point. Some bends have been deliberately engineered with a tightening curve or 'double apex’. This has proved a cause ol Whenever you can, look across the bend through gaps in hedges or between buildings for more informalion. Use crashes on left-hand bends, particularly for motorcyclists. In this type of bend, the curve that the driver initially ,si curved line of hedgerows and lamp posts to give you information about the severity of the bend. Look for early w: the approach to the bend continues to lighten so the final curs'e is much sharper. If you plan for the whole bend o ofollicr hazards as well. basis of the curve that you see initially, you run the risk of ending up in the path of oncoming traffic. Orcl'ul observation and using the system of car control to match your speed to the limit point should help you to accurately negotiate deceptive bends like the one below. Match your speed to the speed at which the limit point moves away from you, provided you can slop safely with: distance that you can see to be clear on your own side of the road. On an unfamiliar bend, be prepared if necessary to adjust )”our steering as you travel around the bend. Pusilidii When positioning your vehicle for cornering you need to consider: safetv view stability. Thfe cur\' speed, choose the appropriate gear for that speed. Select the gear thalg you the greatest flexibility to leave the bend safely..Acceleration tin.L_ I 1.. -U. I:.  I I 1.