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(R) Connections for Fluid Power and General Use – Hydraulic Couplings – Diagnostic

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2nd Edition, May 2013

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Description

  • Revision:2nd Edition, May 2013
  • Published Date:September 1, 1996
  • Status:Active, Most Current
  • Document Language:English
  • Published By:SAE International (SAE)
  • Page Count:642
  • ANSI Approved:No
  • DoD Adopted:No
  • Introduction and History

    The automobile, or horseless carriage, as it was originallyknown, appeared at the end of the 19th Century, approximately onehundred years ago, a direct consequence of the availability ofsuitable internal-combustion engines.

    The design of automobiles evolved from that of the horse-drawncarriage, itself the culmination of several thousand years of slowevolution from early carts and chariots. At the time of arrival ofthe automobile, carriages already had suspension systems, verydesirable in view of the poor roads at the time. There wastherefore already a body of knowledge regarding ride quality andsuspension systems. However, virtually no published materialexisted concerning investigation of handling qualities.

    It is interesting to speculate what sort of concept of handlingthe earliest chariot engineers may have had. Perhaps the mostobvious requirement of a high-performance chariot is a small mass.Certainly, the importance of this was appreciated at least 2000years ago. The wheels were so light that they were removed when notin use (e.g., overnight) to obviate eccentricity and lack ofroundness due to creep.

    Early carts had steering in which the entire front axle pivotedabout a vertical central pivot. Lightweight chariots weretwo-wheeled, so yawing could be achieved by relative rotation ofthe wheels, and the need for steering as such did not arise. Thetraditional horse-drawn carriage of the 18th and 19th Centuries hadrigid axles front and rear; steering of the complete front axleabout its central pivot naturally left the wheels perpendicular toradii from a notional center of the path arc. However, steering bymovement of the complete axle was inconvenient, requiring largeclearance around the wheels, so steering by pivoting the wheelsseparately on stub axles was introduced. In 1816 GeorgesLangensperger stated the geometric condition required for stub-axlesteering to maintain the wheels perpendicular to their arc ofmotion. Such an arrangement was highly desirable to minimizefriction at the wheels during low-speed maneuvering on small radii.This is still the case, although conditions are different at higherspeeds. Ackermann recognized the importance of this invention; byagreement with Langensperger, acting as his agent in London, hetook out British patents in 1817, and hence this arrangement iswidely known as Ackermann steering. Some sixty years later, AmadéeBollée, in designs of 1873 and 1878, achieved a similar effect,possibly independently. From 1878 to 1881 Jeantaud arrived at thesame arrangement, and performed some more scientific assessments.As a result, Langensperger's principle is known in France as theJeantaud diagram. In 1893 Benz was granted a German patent foranother arrangement, similar to Bollée's later type. By the time ofthe introduction of the automobile, then, stub axle steering waswell established, and cars adopted this system from thebeginning.