Steering Electro-hydraulic power steering (EPHS) Hydraulic: A

Steering System A steering system, is a collection of components andlinkages, which allows vehicles (car, bicycle, motorcycle) to follow a desiredcourse. Its main purpose, is to allow the driver guide the vehicle.

There are two main types of steering systems:·        Mechanical·        Power Mechanical:This is a steering system in which a mechanical or manualforce is used for steering. It is also known as manual or non-power steering.  Power:Power steering, also known as power-assisted steering (PAS),helps drivers steer by augmenting steering effort of the steering wheel. It isa system that helps in steering the wheels by using some source of power orpower of engine. It is the preferred steering system, when quick turns need tobe taken.There are three main Power steering components – powersteering pump, power steering fluid reservoir and steering gear box. We have three typesof Power steering systems. They are considered types of power steering systemsbecause they possess all the features of a power steering system.

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These are:·        Hydraulic power steering,·        Fully Electric power steering (EPS) and the·        Electro-hydraulic power steering (EPHS) Hydraulic:A hydraulicpower system uses hydraulic pressure supplied by an engine-drivenpump to assist the motion of turning the steering wheel. It acts as a transmission system that usespressurized hydraulic fluid to power hydraulic machinery. The hydraulic pressuretypically comes from a generator or rotaryvane pump driven by the vehicle’s engine.

A double-acting hydraulic cylinder applies a force to thesteering gear, which in turn steers the road-wheels.  It add controlledenergy to the steering mechanism, so the driver can provide less effort to turnthe steered wheels when driving at typical speeds, and reduce considerably thephysical effort necessary to turn the wheels when a vehicle is stopped ormoving slowly. Hydraulic power steering systems for cars, augment steeringeffort via an actuator, a hydraulic cylinder that is part of a servo system.

These systems have a direct mechanical connection between the steering wheeland the linkage that steers the wheels. This means that power-steering systemfailure (to augment effort) still permits the vehicle to be steered usingmanual effort alone.A hydraulic drive system consists of three parts: Thegenerator (e.g. a hydraulic pump), driven by an electricmotor, a combustion engine or a windmill;valves, filters, piping etc. (to guide and control the system); and theactuator (e.g.

a hydraulic motor or hydraulic cylinder) to drive the machinery. Electro-hydraulicpower steering system (EPHS):The electro-hydraulic system, (sometimes abbreviated EPHS orEHPS) is also sometimes called ‘hybrid’ system. It uses the same hydraulicassist technology as the standard hydraulic system, but the hydraulic pressurecomes from a pump driven by an electric motor instead of a drive belt at theengine.The customary drive belts and pulleys that drive a powersteering pump are replaced by a brushless motor.

It is driven by an electricmotor and thus also reduces the amount of power that needs to be taken from theengine otherwise. Electricpower steering system (EPS):In this kind of system, an electric motor replaces thehydraulic pump and a fully electric power steering system is established. Theelectric motor is either attached to the steering rack or column. The importantcomponent is the electronic control unit because it controls the steeringdynamics.Sensors detect the position and torque of thesteering column, and a computer module applies assistive torque via the motor,which connects to either the steering gear or steering column. This allowsvarying amounts of assistance to be applied depending on driving conditions. Amechanical linkage between the steering wheel and the steering gear is usuallyretained in EPS. This means that in the event of a failure that results in aninability to provide assistance, the mechanical linkage serves as a backup.

Thedriver then encounters a situation where heavy effort is required to steer.Depending on the driving situation and driver skill, the steering assist lossmay or may not lead to a crash. Electric systems have an advantage in fuel efficiencybecause there is no belt-driven hydraulic pump constantly running, whetherassistance is required or not. This was the main reason for their introduction.Another major advantage is the elimination of a belt-driven engine accessoryand several high pressure hydraulic hoses between the hydraulic pump, mountedon the engine and the steering gear, mounted on the chassis. This helps tosimplify manufacturing and maintenance.

Electric power system, is necessary for some power steeringsystems, like those in the largest off-road construction vehicles. Theirsystems, sometimes called ‘drive by wire’ or ‘steer by wire’, have no directmechanical connection to the steering linkage and thus require electricalpower. In this context, ‘wire’ refers to electrical cables that carry power anddata, not thin-wire-rope mechanical control cables.

 Most of the cars today, have power steering systems. Veryfew use mechanical steering. EPS is often preferred, for the fuel economy andlower emission.

Mechanical steering systems use the power of human muscle. Inthis system, more effort is required to steer the vehicles. The only energysource is the force the driver applies to the steering wheel. However, in powersteering, mechanical steering is always allowed to be available, in case of aproblem in the engine or in the case of a power assist system failure. EPS ismore efficient than hydraulic power steering, since the electric power steeringmotor only needs to provide assistance when the steering wheel is turned,whereas the hydraulic pump must run constantly.

In EPS, the amount ofassistance is easily tuneable to the vehicle type, road speed, and even driverpreference. An added benefit is the elimination of environmental hazard posedby leakage and disposal of hydraulic power steering fluid. In addition,electrical assistance is not lost when the engine fails or stalls, whereashydraulic assistance stops working if the engine stops, making the steeringdoubly heavy as the driver must now turn not only the very heavy steering(without any help) but also the power-assistance system itself.There are two basic steering mechanism:·        Rack and pinion steering and·        Recirculating ball steering Rack andpinion steering In this system apinion gear is attached to the steering shaft. This means that as the steeringwheel is turned it turns the pinion gear (circular) and then moves the rack(linear). It basically uses the rotational motion of steering wheels and convertsthis rotational motion into the linear motion. Alternatively, it could bedescribed as a circular gear called the pinion, engages the teeth on the lineargear bar called the rack. Rotational motion is then applied to the pinion whichcauses the rack to move relative to the pinion, thereby translating therotational motion of the pinion into linear motion.

This linear motion isrequired to turn the wheels. It provides a less efficient mechanical advantagethan other mechanisms, like the recirculating ball, but less backlash andgreater feedback or steering feel. In mechanical steering systems, this processis done manually while in power steering systems, it is power-assisted, usuallyby hydraulic or electrical means. Recirculatingball steeringAlso known as recirculating ball and nut or worm and sector.Here, a box with a threaded hole is fastened over a worm drive that containsmany ball bearings. These ball bearings loop around the worm drive and theseballs moves out into a recirculation channel and again gets back into the wormdrive. This block gear has teeth cut into the outside to engage the sectorshaft (also called the sector gear) which moves the pitman arm. Because thesteering wheel is connected to a shaft which rotates the worm gear inside theblock, instead of twisting further into the block, the worm gear is fixed sothat when it spins, it moves the block, which transmits the motion through thegear to the pitman arm, causing the road-wheels to turn.

When the steeringwheel is turned, the worm drive turns and forces the balls to press against thechannel inside the nut. Now the forces the nut to move along the worm drive. Itis a steering mechanism found in older automobiles, off-road trucks and sometrucks.

Finally, listed below are mechanical steering systems. Theyalso occur as power steering systems, with the power supply being eitherhydraulic or electric or electro-hydraulic, instead of manual. These include:·        Worm and sector (Recirculating ball steering)·        Worm and roller·        Cam and lever·        Worm and nut·        Rack and pinion Worm androllerThis is quite similar to the worm and sector, except aroller is supported by ball or roller bearings within the sector, mounted onthe pitman arm shaft. The sliding friction is changed to rolling friction sothat less effort is required to turn the steering wheel. This is only possiblebecause the sector teeth are machined on a roller. As the steering wheel turnsthe worm, the roller turns with it, forcing the sector and pitman arm shaft torotate. Friction is reduced further by mounting the roller on bearings in asaddle at the inner end of the pitman arm shaft. The hourglass shape of theworm which tapers from both ends at the centre, affords better contact betweenthe worm and the roller in every position.

This design provides a variablesteering ratio to permit faster and more efficient steering. ‘Variable steeringratio’ means the ratio is larger at one position than another. Therefore, atcertain positions, the wheels are turned faster than at others. At the verycentre, the steering gear ratio is high, giving more steering control. When thewheels are turned however, the ratio decreases so that the steering action ismuch more rapid. This design is very helpful for parking and manoeuvring thevehicle.

 Cam andleverIn the cam and lever steering gear, the worm is known as acam. The inner end of the pitman arm shaft has a lever that contains a taperedstud. The stud engages in the cam so that the lever is moved back and forthwhen the cam is turned back and forth.

If the tapered stud is fixed in the leverso that it can’t rotate, it creates a sliding friction between the stud and thecam. Therefore, on some vehicles that have this type of steering gear, the studis mounted in bearings so that it rolls in the cam groove (threads) instead ofsliding. A cam and twin-lever steering gear is used in some large trucks. Thisis essentially a cam and lever gear with two tapered studs instead of one. Thestuds sometimes are fixed in the lever, or they may be mounted on bearings. Worm and nutThis steering gear is made in different severalcombinations. The nut is meshed and screws up and down on the worm gear.

Thenut may operate the pitman arm directly through a lever or through a sector onthe pitman arm shaft. The recirculating ball is the most common type of wormand nut steering gear. Here, the nut (that is in the form of a sleeve block) ismounted on a continuous row of balls on the worm gear to reduce friction.

Theball nut has grooves cut into it to match the shape of the worm gear. The ballnut is then fitted with tubular ball guides to return the balls diagonallyacross the nut to recirculate them, as the nut moves up and down on the wormgear. With this design, the nut is moved on the worm gear by rolling instead ofsliding contact.

Turning the worm gear moves the nut and forces the sector andpitman arm shaft to turn. Stubhub steering system? What typeof steering system did we use? WheelsTires are designed to not only support the weight of avehicle, but to absorb road shocks, transmit traction, torque and braking forceto the road and maintain and change the direction of travelThe vehicle was built to be a lightweight off-road vehicle.This means it is suitable for use on and off paved or gravel surfaces. For thisvehicle, we went with radials. A radial tire is a particular design of tire,where the cord plies are arranged at 90 degrees to the direction of travel, orradially. For a regular off-road vehicle, the tires have thick, deep threads.Knowing our buggy would not be used on very sandy terrain, we selected tireswith threads that don’t run too thick.

The exposed edges of the threads diginto soft ground, giving more traction than rolling friction alone. Since ourtires have less aggressive knobs, it means we can also have adequate tractionto enable motion on a pavement, unlike the typical off-road tires. They areusually bigger where there is more weight in the vehicle.

Hence the back tiresin our vehicle are larger. It is also larger at the back because, we designedthe vehicle to be a 2 wheel drive, with the drive axle at the back tires. Inrear-wheel drive vehicles, the engine or power source, turns a driveshaft (alsocalled a propeller shaft or tailshaft) which transmits rotational force to adrive axle at the rear of the vehicle.

To enable the vehicle move, the wheelshave to be big enough to not only carry the weight of the vehicle (when it isempty or otherwise), but also move when power is transmitted to it. Material sourcing and cost Material of choice: SteelSteel is fairly cheap to get, it is also very widelyrecycled. It is a material that does not lose its special properties (i.e.

Strength, hardenability, weldability, ductility etc.) after being recycled.This makes it a good choice because we have the option of using new steel orrecycled steel to reduce cost, without compromising on quality.

The other material we researched was Aluminium, but evenwith corrosion, steel is harder than aluminium. Mostalloys of aluminium dent, ding or scratch more easily ascompared to steel and its alloys. Steel is strong and lesslikely to warp, deform or bend under force or heat. To make our buggy, thematerial will be undergo a lot of welding and we wouldn’t want our material todeform or warp during this, or any other production process.The price of steel and aluminium is continuallyfluctuating based on global supply and demand, fuel costs and the price andavailability of iron and bauxite ore; however steel is generally cheaper (perpound) than aluminium. There are exceptions, but aluminium will almost alwayscost more because of the increase in the raw material price. CostingTo get some of each part we needed at a discounted price (orfree if possible), we visited the following scrapyards:·        JAP city auto salvage Ltd, EMR Middlesbrough·        C L Prosser & Co Ltd The only things we were allowed to buy were some motors butwe did not get them because they were not the appropriate ones for the vehicle.Not to mention, motors at scrapyards can sometimes be unreliable and there wasno way we could test them on site, to make sure they worked.

Moving on fromthere, we contacted a well-known motorsport company that deals in dirt buggies:·        Rage Motorsport Ltd We called to ask if they had any spare parts we could buy.They were unfortunately unwilling to sell us anything for cheap. After that, wecalled multiple steel companies and got some quotes. These included:·        Parson and Crosland – located on forty foot road                              £90 for 3 metres(uncut)·        Brettle – located on 5A Bowes road                                                         £75·        Q A Weldtech Ltd                                                                                             £60·        Jones D K Ltd                                                                                                     £45.60for 3 metres (cut) We ended up going for the Jones D K Ltd option because itwas better value for money. In my table below, I outline the different parts weneeded to source, the quoted or estimated price (as seen online) as well as theprice we obtained them for.

Next we contacted Teesside Karting, where the owner Paul,was more than happy to help us with the project. He gave us a chassis and aseat, at absolutely no cost. Materials or Parts Estimated or Quoted Price Actual Price Motor £35   Motor controller £11.99 £12.99 Twist Throttle £6.99 £13.99 Wheels (4) £27.00 £20.00 Batteries (3) £30.00 £30.00 Steel Piping £45.60 £45.60 A Seat £10.00 FREE Sprockets (2) £3.90   Steel Plate £4.65   Steering wheel £6.99   Stubs £3.92   Jubilee Clips £1.96 £5.82 Wiring £11.00 £12.72 Wiring connector terminals £1.00   TOTAL £200.00 £141.12


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