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Difference between revisions of "Desmodromic valve"
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to reveal that cam dynamics are not what they seemed. With proper analysis, valve adjustment, hydraulic [[tappet]]s, push rods, rocker arms, and above all, [[valve float]], became things of the past...without desmodromic drive. | to reveal that cam dynamics are not what they seemed. With proper analysis, valve adjustment, hydraulic [[tappet]]s, push rods, rocker arms, and above all, [[valve float]], became things of the past...without desmodromic drive. | ||
Today most automotive engines use [[overhead camshaft|overhead cams]], driving a flat tappet to achieve the shortest, lightest weight, and most inelastic path from cam to valve, thereby avoiding elastic elements such as [[pushrod]] and [[rocker arm]]. Computers have allowed for fairly accurate acceleration | Today most automotive engines use [[overhead camshaft|overhead cams]], driving a flat tappet to achieve the shortest, lightest weight, and most inelastic path from cam to valve, thereby avoiding elastic elements such as [[pushrod]] and [[rocker arm]]. Computers have allowed for fairly accurate acceleration modeling of valve-train systems. | ||
Before numerical computing methods were readily available, acceleration was only attainable by differentiating cam lift profiles twice, once for velocity and again for acceleration. This generates so much hash (noise) that the second derivative (acceleration) was uselessly inaccurate. Computers permitted integration from the jerk curve, the third derivative of lift, that is conveniently a series of contiguous straight lines whose vertices can be adjusted to give any desired lift profile. | Before numerical computing methods were readily available, acceleration was only attainable by differentiating cam lift profiles twice, once for velocity and again for acceleration. This generates so much hash (noise) that the second derivative (acceleration) was uselessly inaccurate. Computers permitted integration from the jerk curve, the third derivative of lift, that is conveniently a series of contiguous straight lines whose vertices can be adjusted to give any desired lift profile. | ||