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I added the image of the camdrive in my car, but I'm not completely sure that this is the right image to use here. My car repair handbook calls these things valve lifters, but reading this article on tappets, it does seem that it is what the term tappet should refer to. The specific part I'm referring to is the metallic cylinder that sits between the actual cam lobe and the valve stem itself (the latter of which obviously isn't visible in the image, as the tappet covers it) in order to take up the sideways friction of the moving cam lobe (or at least that is what I'm assuming is its purpose). --Dolda2000 23:46, 5 October 2006 (UTC)

Diagram needed[edit]

{{Reqdiagram}} The picture shows a lot of complicated parts. It would be nice to have a simple drawing with the tappet(s) clearly labeled. -- Beland 08:23, 14 February 2007 (UTC)

These apparently include tappets, although I myself can't tell which bit is the tappet. --pfctdayelise (talk) 11:00, 10 August 2008 (UTC)

Disagree with the opening definition[edit]

  • I disagree with the current (March 9, 2010) opening definition of a tappet. I propose to replace it with the following: "A tappet in mechanical engineering is that end of a push-rod which contacts the cam. The cam turns, and when the enlarged part of the cam reaches the tappet, it pushes the tappet (and, through the tappet, the push-rod) away from itself. A tappet is thus a cam follower. There are various designs of tappet." This is based on examining Fundamentals of Motor Vehicle Technology, pp. 44 and following, and Light and Heavy Vehicle Technology, p. 49.
    • I would changed your definition to: "A tappet is that end of a push-rod which contacts the cam. As the cam turns it actuates the tappet, which actuates the push-rod. There are various tappet designs." The cam doesn't actually move the tappet away from the cam, it stays the same distance from the surface. Also, a tappet is more than a cam follower; see cam follower. Wizard191 (talk) 18:51, 9 March 2010 (UTC)
  • I disagree with the second sentence, which currently states that "Properly speaking, a tappet is only that part of a rocker arm which makes contact with an intake or exhaust valve stem above the cylinder head of an internal combustion engine." In Fundamentals of Motor Vehicle Technology, p. 46, Fig. 8.17, and Light and Heavy Vehicle Technology, p. 49, Fig. 1.88 , the sequence is cam, tappet, push-rod, rocker, valve stem. The tappet is nowhere near the valve. I propose to delete this sentence.
    • Perhaps in the example given above the tappet doesn't contact the valve stem, but in OHC applications the tappet does contact the valve stem directly. Wizard191 (talk) 18:53, 9 March 2010 (UTC)
  • I disagree with the final two sentences of the current opening paragraph, which say "Without a tappet (and with the cam acting directly on the valve), the sideways force would cause the valve stem to bend. With a tappet, the sideways force is transferred to the cylinder head so only the downward force acts on the valve stem." As noted above, the tappet is nowhere near the valve or its stem. I propose to amend these sentences to remove the implication that the tappet touches the valve stem, or that the cam could. UBJ 43X (talk) 11:00, 9 March 2010 (UTC)
    • See my note above. The sentence can be reworded to note that it is only applicable in applications where the tappet does contact the valve directly. Wizard191 (talk) 18:54, 9 March 2010 (UTC)