Misplaced Pages

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57-401: Many later automobile rear swing axles have universal joints connecting the driveshafts to the differential , which is attached to the chassis . Swing axles do not have universal joints at the wheels — the wheels are always perpendicular to the driveshafts; the design is therefore not suitable for a car's front wheels, which require steering motion. Nevertheless, a simplified variant, wherein

114-793: A 1 cos ⁡ β 1 − sin 2 ⁡ β cos 2 ⁡ γ 1 − ω 1 2 cos ⁡ β sin 2 ⁡ β sin ⁡ 2 γ 1 ( 1 − sin 2 ⁡ β cos 2 ⁡ γ 1 ) 2 {\displaystyle a_{2}={\frac {a_{1}\cos \beta }{1-\sin ^{2}\beta \,\cos ^{2}\gamma _{1}}}-{\frac {\omega _{1}^{2}\cos \beta \,\sin ^{2}\beta \,\sin 2\gamma _{1}}{\left(1-\sin ^{2}\beta \,\cos ^{2}\gamma _{1}\right)^{2}}}} A configuration known as

171-430: A better compromise of handling and comfort to be tuned in. The bushing in line with the wheel can be kept relatively stiff to effectively handle cornering loads while the off-line joint can be softer to allow the wheel to recess under fore-aft impact loads. For a rear suspension, a pair of joints can be used at both ends of the arm, making them more H-shaped in plan view. Alternatively, a fixed-length driveshaft can perform

228-407: A cross shaft. The universal joint is not a constant-velocity joint . U-joints are also sometimes called by various eponymous names, as follows: The main concept of the universal joint is based on the design of gimbals , which have been in use since antiquity. One anticipation of the universal joint was its use by the ancient Greeks on ballistae . In Europe the universal joint is often called

285-402: A double Cardan joint drive shaft partially overcomes the problem of jerky rotation. This configuration uses two U-joints joined by an intermediate shaft, with the second U-joint phased in relation to the first U-joint to cancel the changing angular velocity. In this configuration, the angular velocity of the driven shaft will match that of the driving shaft, provided that both the driving shaft and

342-923: A rotating joint will be functions of time. Differentiating the equation of motion with respect to time and using the equation of motion itself to eliminate a variable yields the relationship between the angular velocities ω 1 = d γ 1 / d t {\displaystyle \omega _{1}=d\gamma _{1}/dt} and ω 2 = d γ 2 / d t {\displaystyle \omega _{2}=d\gamma _{2}/dt} : ω 2 = ω 1 ( cos ⁡ β 1 − sin 2 ⁡ β cos 2 ⁡ γ 1 ) {\displaystyle \omega _{2}=\omega _{1}\left({\frac {\cos \beta }{1-\sin ^{2}\beta \,\cos ^{2}\gamma _{1}}}\right)} As shown in

399-424: A spindle to which the wheel bearings are mounted. To resist fore-aft loads such as acceleration and braking , the arms require two bushings or ball joints at the body. At the knuckle end, single ball joints are typically used, in which case the steering loads have to be taken via a steering arm, and the wishbones look A- or L-shaped. An L-shaped arm is generally preferred on passenger vehicles because it allows

456-474: A swing-axle front suspension, derived from the Ford E93 sedan. Universal joint A universal joint (also called a universal coupling or U-joint ) is a joint or coupling connecting rigid shafts whose axes are inclined to each other. It is commonly used in shafts that transmit rotary motion . It consists of a pair of hinges located close together, oriented at 90° to each other, connected by

513-579: A true independent rear suspension (IRS) system. The Hillman Imp designers learned from the problems with the Corvair, having crashed one at a relatively low speed, and they designed their rear-engined car with a semi-trailing arm suspension at the rear. To attain correct handling balance, they actually used swing-axle geometry at the front, with the steering pivots mounted at the outer ends of single swing wishbones. These caused too much understeer and uneven tyre wear, and modifications were made to reduce

570-463: A very high roll centre which causes detrimental jacking effects and camber change when cornering and lateral cornering forces are applied. Its simple geometry limits design freedom to a great extent. Swing axles can also be used on as a low cost and durable independent suspension solution for non-driven front or rear axles, the Tatra 17 which had swing axles front and rear being an early example. It

627-516: Is at angle γ 1 {\displaystyle \gamma _{1}} with respect to its beginning position along the x axis and x ^ 2 {\displaystyle {\hat {\mathbf {x} }}_{2}} is at angle γ 2 {\displaystyle \gamma _{2}} with respect to its beginning position along the y axis. x ^ 1 {\displaystyle {\hat {\mathbf {x} }}_{1}}

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684-918: Is confined to the "blue plane" in the diagram and is the result of the unit vector on the x axis x ^ = [ 1 , 0 , 0 ] {\displaystyle {\hat {x}}=[1,0,0]} being rotated through Euler angles [ π / 2 , β , γ 2 {\displaystyle [\pi \!/2\,,\,\beta \,,\,\gamma _{2}} ]: x ^ 2 = [ − cos ⁡ β sin ⁡ γ 2 , cos ⁡ γ 2 , sin ⁡ β sin ⁡ γ 2 ] {\displaystyle {\hat {\mathbf {x} }}_{2}=\left[-\cos \beta \sin \gamma _{2}\,,\,\cos \gamma _{2}\,,\,\sin \beta \sin \gamma _{2}\right]} A constraint on

741-559: Is confined to the "red plane" in the diagram and is related to γ 1 {\displaystyle \gamma _{1}} by: x ^ 1 = [ cos ⁡ γ 1 , sin ⁡ γ 1 , 0 ] {\displaystyle {\hat {\mathbf {x} }}_{1}=\left[\cos \gamma _{1}\,,\,\sin \gamma _{1}\,,\,0\right]} x ^ 2 {\displaystyle {\hat {\mathbf {x} }}_{2}}

798-523: Is especially manifested in long 6+ wheel vehicles where off-road chassis twisting can be a major issue. Another use of the swing axle concept is Ford's "Twin I-Beam" front suspension for trucks. This system has solid axles, and may transmit power in four-wheel-drive versions, where it is called "Twin Traction Beam". It is an independent suspension system, as each tyre rises and falls without affecting

855-628: Is far less hazardous than powered swing axles for the rear wheels listed above, where the pivot point is approximately on the same side frame rail. The Twin I-Beam suspension includes an additional radius arm link on each side to control caster. Although the camber change is reduced with the Twin I-Beam suspension, the A-arm suspension system constrains the wheel into a parallelogram motion, further minimizing camber changes throughout suspension travel. The 1956 Series 1 Lotus Eleven sports racers used

912-408: Is mentioned between the forks.) A double Cardan joint consists of two universal joints mounted back to back with a centre yoke; the centre yoke replaces the intermediate shaft. Provided that the angle between the input shaft and centre yoke is equal to the angle between the centre yoke and the output shaft, the second Cardan joint will cancel the velocity errors introduced by the first Cardan joint and

969-540: Is no genetic relationship between MacPherson strut and double wishbone suspension. Double wishbones have traditionally been considered to have superior dynamic characteristics as well as load-handling capabilities and are therefore commonly found on sports cars and racing cars throughout automotive history . Examples of cars with double wishbone suspension include the Aston Martin DB7 , the Mazda MX-5 , and

1026-982: Is not unique since the arctangent function is multivalued, however it is required that the solution for γ 2 {\displaystyle \gamma _{2}} be continuous over the angles of interest. For example, the following explicit solution using the atan2 (y, x) function will be valid for − π < γ 1 < π {\displaystyle -\pi <\gamma _{1}<\pi } : γ 2 = atan2 ⁡ ( sin ⁡ γ 1 , cos ⁡ β cos ⁡ γ 1 ) {\displaystyle \gamma _{2}=\operatorname {atan2} \left(\sin \gamma _{1},\cos \beta \,\cos \gamma _{1}\right)} The angles γ 1 {\displaystyle \gamma _{1}} and γ 2 {\displaystyle \gamma _{2}} in

1083-450: Is seen that the output drive is just 90 degrees out of phase with the input shaft, yielding a constant-velocity drive. NOTE: The reference for measuring angles of input and output shafts of universal joint are mutually perpendicular axes. So, in absolute sense the forks of the intermediate shaft are parallel to each other. (Since, one fork is acting as input and the other fork is acting as output for shafts and above 90 degree phase difference

1140-496: Is the Czech truck manufacturer Tatra , which has been using swing axles on a central 'backbone' tube since 1923 (model Tatra 11 ) instead of more common solid axles. This system is claimed to give greater rigidity and better performance on poor quality roads and off-road. There the inherent reduced stability on roads is compensated by an increased stability on rough terrain, allowing for higher off-road speeds, all else being equal. This

1197-608: The x ^ 1 {\displaystyle {\hat {\mathbf {x} }}_{1}} and x ^ 2 {\displaystyle {\hat {\mathbf {x} }}_{2}} vectors is that since they are fixed in the gimbal , they must remain at right angles to each other. This is so when their dot product equals zero: x ^ 1 ⋅ x ^ 2 = 0 {\displaystyle {\hat {\mathbf {x} }}_{1}\cdot {\hat {\mathbf {x} }}_{2}=0} Thus

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1254-618: The Packard One-Twenty from 1935,[1] and advertised it as a safety feature. During that time MacPherson strut was still in the area of aviation technology and was derived from aircraft landing mechanisms. Later on, in 1951, Ford Company decided to use the MacPherson strut on small production cars, the English Ford Consul and Ford Zephyr.[2] Thus, the double wishbone was applied early in automobile history and there

1311-588: The Spicer Manufacturing Company , as well as the Hardy Spicer successor brand, helped further popularize universal joints in the automotive , farm equipment , heavy equipment , and industrial machinery industries. The Cardan joint suffers from one major problem: even when the input drive shaft axle rotates at a constant speed, the output drive shaft axle rotates at a variable speed, thus causing vibration and wear. The variation in

1368-400: The planes of rotation of each axle. These planes of rotation are perpendicular to the axes of rotation and do not move as the axles rotate. The two axles are joined by a gimbal which is not shown. However, axle 1 attaches to the gimbal at the red points on the red plane of rotation in the diagram, and axle 2 attaches at the blue points on the blue plane. Coordinate systems fixed with respect to

1425-489: The unsprung mass , and also allows the designer to make the suspension more aerodynamic. A short long arms suspension ( SLA ) is also known as an unequal-length double wishbone suspension. The upper arm is typically an A-arm and is shorter than the lower link, which is an A-arm or an L-arm, or sometimes a pair of tension/compression arms. In the latter case, the suspension can be called a multi-link, or dual-ball joint suspension . The four-bar linkage mechanism formed by

1482-495: The 19th century. Edmund Morewood's 1844 patent for a metal coating machine called for a universal joint, by that name, to accommodate small alignment errors between the engine and rolling mill shafts. Ephriam Shay's locomotive patent of 1881, for example, used double universal joints in the locomotive's drive shaft . Charles Amidon used a much smaller universal joint in his bit-brace patented 1884. Beauchamp Tower 's spherical, rotary, high speed steam engine used an adaptation of

1539-606: The Cardano joint (and a drive shaft that uses the joints, a Cardan shaft), after the 16th century Italian mathematician, Gerolamo Cardano , who was an early writer on gimbals, although his writings mentioned only gimbal mountings, not universal joints. The mechanism was later described in Technica curiosa sive mirabilia artis (1664) by Gaspar Schott , who mistakenly claimed that it was a constant-velocity joint . Shortly afterward, between 1667 and 1675, Robert Hooke analysed

1596-406: The aligned double Cardan joint will act as a CV joint. A Thompson coupling is a refined version of the double Cardan joint. It offers slightly increased efficiency with the penalty of great increase in complexity. Double wishbone suspension A double wishbone suspension is an independent suspension design for automobiles using two (occasionally parallel) wishbone -shaped arms to locate

1653-954: The angles for the input and output of the universal joint connecting the drive and the intermediate shafts respectively, and γ 3 {\displaystyle \gamma _{3}\,} and γ 4 {\displaystyle \gamma _{4}\,} are the angles for the input and output of the universal joint connecting the intermediate and the output shafts respectively, and each pair are at angle β {\displaystyle \beta \,} with respect to each other, then: tan ⁡ γ 2 = cos ⁡ β tan ⁡ γ 1 tan ⁡ γ 4 = cos ⁡ β tan ⁡ γ 3 {\displaystyle \tan \gamma _{2}=\cos \beta \,\tan \gamma _{1}\qquad \tan \gamma _{4}=\cos \beta \,\tan \gamma _{3}} If

1710-485: The arms themselves can be A-shaped or L-shaped. A single wishbone or A-arm can also be used in various other suspension types, such as variations of the MacPherson strut . The upper arm is usually shorter to induce negative camber as the suspension jounces (rises), and often this arrangement is titled an "SLA" or "short, long arms" suspension. When the vehicle is in a turn, body roll results in positive camber gain on

1767-431: The beginning of jounce travel and then reverses into positive camber gain at high jounce amounts. Double wishbone suspensions are more complex, impose more difficult packaging constraints, and are thus often more expensive than other systems like a MacPherson strut . Due to the increased number of components within the suspension setup, it takes much longer to service and is heavier than an equivalent MacPherson design. At

Swing axle - Misplaced Pages Continue

1824-476: The differential remained fixed to one of the halfshafts, was offered optionally on the 1963 Jeep Wagoneer 's front axle, upon its market introduction. Swing axle suspensions often used leaf springs and shock absorbers , though later Mercedes-Benz applications used coil springs and the VW beetle swing axle was torsion bar sprung. One problem inherent in the swing axle concept is that it almost enevitably results in

1881-485: The driven shaft are at equal angles with respect to the intermediate shaft (but not necessarily in the same plane) and that the two universal joints are 90 degrees out of phase. This assembly is commonly employed in rear wheel drive vehicles, where it is known as a drive shaft or propeller (prop) shaft. Even when the driving and driven shafts are at equal angles with respect to the intermediate shaft, if these angles are greater than zero, oscillating moments are applied to

1938-427: The effect of moving each joint, so the kinematics of the suspension can be tuned easily and wheel motion can be optimized. It is also easy to work out the loads that different parts will be subjected to which allows more optimized lightweight parts to be designed. They also provide increasing negative camber gain all the way to full jounce travel, unlike the MacPherson strut , which provides negative camber gain only at

1995-768: The equation of motion relating the two angular positions is given by: tan ⁡ γ 1 = cos ⁡ β tan ⁡ γ 2 {\displaystyle \tan \gamma _{1}=\cos \beta \tan \gamma _{2}\,} with a formal solution for γ 2 {\displaystyle \gamma _{2}} : γ 2 = tan − 1 ⁡ [ tan ⁡ γ 1 sec ⁡ β ] {\displaystyle \gamma _{2}=\tan ^{-1}\left[\tan \gamma _{1}\sec \beta \right]\,} The solution for γ 2 {\displaystyle \gamma _{2}}

2052-501: The function of a wishbone as long as the shape of the other wishbone provides control of the upright. This arrangement has been successfully used in the Jaguar IRS . In elevation view , the suspension is a 4-bar link, and it is easy to work out the camber gain (see camber angle ) and other parameters for a given set of bushing or ball-joint locations. The various bushings or ball joints do not have to be on horizontal axes, parallel to

2109-428: The joint and found that its speed of rotation was nonuniform, but that property could be used to track the motion of the shadow on the face of a sundial. In fact, the component of the equation of time which accounts for the tilt of the equatorial plane relative to the ecliptic is entirely analogous to the mathematical description of the universal joint. The first recorded use of the term 'universal joint' for this device

2166-439: The lightly loaded inside wheel, while the heavily loaded outer wheel gains negative camber. Between the outboard end of the arms is a knuckle. The knuckle contains a kingpin for horizontal radial movement in older designs, and rubber or trunnion bushings for vertical hinged movement. In newer designs, a ball joint at each end allows for all movement. Attached to the knuckle at its center is a bearing hub, or in many older designs,

2223-408: The plots, the angular velocities are not linearly related, but rather are periodic with a period half that of the rotating shafts. The angular velocity equation can again be differentiated to get the relation between the angular accelerations a 1 {\displaystyle a_{1}} and a 2 {\displaystyle a_{2}} : a 2 =

2280-403: The position of the other. Although each tyre still moves in an arc as in a standard swing-axle suspension, the lower control arms effectively are lengthened by attaching the axle pivot point to the bottom of the opposite frame rail (i.e., the left lower control arm pivots on the right frame rail and vice versa). The lowered pivot point and longer arm length reduce the change in camber and the effect

2337-578: The positive camber of the front wheels by lowering the swing-axle pivot points. Aftermarket kits were also available to do this, and an inexpensive alternative was to insert a tapered shim to change the inclination of the kingpin carrier relative to the wishbone. Swing axles were supplanted in general use by de Dion tube axles in the late 1960s, though live axles remained the most common. Most rear suspensions have been replaced by more modern independent suspensions in recent years, and both swing and de Dion types are virtually unused today. One exception

Swing axle - Misplaced Pages Continue

2394-418: The rod must be joined to the bottom of the upright and angled upward). As the wheel rises, the push rod compresses the internal spring via a pivot or pivoting system. The opposite arrangement, a "pull rod", will pull on the rod during bump travel, and the rod must be attached to the top of the upright, angled downward. Locating the spring and damper inboard increases the total mass of the suspension, but reduces

2451-488: The rotating axles are defined as having their x-axis unit vectors ( x ^ 1 {\displaystyle {\hat {\mathbf {x} }}_{1}} and x ^ 2 {\displaystyle {\hat {\mathbf {x} }}_{2}} ) pointing from the origin towards one of the connection points. As shown in the diagram, x ^ 1 {\displaystyle {\hat {\mathbf {x} }}_{1}}

2508-974: The second universal joint is rotated 90 degrees with respect to the first, then γ 3 = γ 2 + π / 2 {\displaystyle \gamma _{3}=\gamma _{2}+\pi /2} . Using the fact that tan ⁡ ( γ + π / 2 ) = 1 / tan ⁡ γ {\displaystyle \tan(\gamma +\pi /2)=1/\tan \gamma } yields: tan ⁡ γ 4 = cos ⁡ β tan ⁡ γ 2 = 1 tan ⁡ γ 1 = tan ⁡ ( γ 1 + π 2 ) {\displaystyle \tan \gamma _{4}={\frac {\cos \beta }{\tan \gamma _{2}}}={\frac {1}{\tan \gamma _{1}}}=\tan \left(\gamma _{1}+{\frac {\pi }{2}}\right)\,} and it

2565-468: The shortcomings in 1960–1963 models of the first generation Chevrolet Corvair 's swing-axle design. Nader identified a Chevrolet engineer who had fought management after the management had eliminated a front anti-roll bar for cost reasons. The 1964 models were fitted with a front anti-roll bar as standard equipment, in addition to a rear transverse leaf spring, thus improving stability during emergency maneuvering. Second-generation Corvairs (1965–1969) used

2622-438: The speed of the driven shaft depends on the configuration of the joint, which is specified by three variables: These variables are illustrated in the diagram on the right. Also shown are a set of fixed coordinate axes with unit vectors x ^ {\displaystyle {\hat {\mathbf {x} }}} and y ^ {\displaystyle {\hat {\mathbf {y} }}} and

2679-592: The third through eighth generation of the Honda Accord . Short long arms suspension, a type of double wishbone suspension, is very common on front suspensions for medium-to-large cars such as the Peugeot 407 , Citroën C5 , and the first two generations of the Mazda6/Atenza . The double wishbone suspension provides the engineer with more design choices than some other types do. It is fairly easy to work out

2736-580: The three shafts as they rotate. These tend to bend them in a direction perpendicular to the common plane of the shafts. This applies forces to the support bearings and can cause "launch shudder" in rear wheel drive vehicles. The intermediate shaft will also have a sinusoidal component to its angular velocity, which contributes to vibration and stresses. Mathematically, this can be shown as follows: If γ 1 {\displaystyle \gamma _{1}\,} and γ 2 {\displaystyle \gamma _{2}\,} are

2793-401: The tire and the upper ball joint sits above the tire. Short spindle SLAs tend to require stiffer bushings at the body, as the braking and cornering forces are higher. Also, they tend to have poorer kingpin geometry, due to the difficulty of packaging the upper ball joint and the brakes inside the wheel. Long spindle SLAs tend to have better kingpin geometry, but the proximity of the spindle to

2850-533: The tire restricts fitting oversized tires or snow chains. The location of the upper balljoint may have styling implications in the design of the sheet metal above it. SLAs require some care when setting up their bump steer characteristic, as it is easy to end up with excessive, or curved, bump steer curves. The double wishbone suspension was introduced in the 1930s. French car maker Citroën began using it in their 1934 Rosalie and Traction Avant models. Packard Motor Car Company of Detroit, Michigan , used it on

2907-416: The unequal arm lengths causes a change in the camber of the vehicle as it rolls, which helps to keep the contact patch square on the ground, increasing the ultimate cornering capacity of the vehicle. It also reduces the wear on the outer edge of the tire. SLAs can be classified as short spindle, in which the upper ball joint on the spindle is inside the wheel, or long spindle, in which the spindle tucks around

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2964-555: The universal joint c.  1885 . The term 'Cardan joint' appears to be a latecomer to the English language. Many early uses in the 19th century appear in translations from French or are strongly influenced by French usage. Examples include an 1868 report on the Exposition Universelle of 1867 and an article on the dynamometer translated from French in 1881. In the 20th century, Clarence W. Spicer and

3021-522: The universal joint, giving rise to the name Polhemsknut ("Polhem knot") in Swedish. In 1841, the English scientist Robert Willis analyzed the motion of the universal joint. By 1845, the French engineer and mathematician Jean-Victor Poncelet had analyzed the movement of the universal joint using spherical trigonometry. The term universal joint was used in the 18th century and was in common use in

3078-409: The vehicle center line. If they are set at an angle, then anti-dive and anti-squat geometry can be dialed in. In many racing cars, the springs and dampers are relocated inside the bodywork. The suspension uses a bellcrank to transfer the forces at the knuckle end of the suspension to the internal spring and damper. This is then known as a "push rod" if bump travel "pushes" on the rod (and subsequently

3135-555: The wheel. Each wishbone or arm has two mounting points to the chassis and one joint at the knuckle. The shock absorber and coil spring mount to the wishbones to control vertical movement. Double wishbone designs allow the engineer to carefully control the motion of the wheel throughout suspension travel, controlling such parameters as camber angle , caster angle , toe pattern, roll center height, scrub radius , scuff ( mechanical abrasion ), and more. The double-wishbone suspension can also be referred to as " double A-arms ", though

3192-453: Was also used in early aircraft (1910 or before), such as the Sopwith and Fokker , usually with rubber bungee and no damping. The swing axle suspension has two advantages over the typical live axle : Several engineering options can limit swing axle handling problems, with varying success: Ralph Nader in his 1965 book Unsafe at Any Speed detailed accidents and lawsuits related to

3249-529: Was by Hooke in 1676, in his book Helioscopes . He published a description in 1678, resulting in the use of the term Hooke's joint in the English-speaking world. In 1683, Hooke proposed a solution to the nonuniform rotary speed of the universal joint: a pair of Hooke's joints 90° out of phase at either end of an intermediate shaft, an arrangement that is now known as a type of constant-velocity joint. Christopher Polhem of Sweden later re-invented

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