Lifter
In engineering, lifter has a some unrelated meanings.
Signal processing
In signal processing, a lifter (anagram of filter) is a signal transform consisting of taking the decibel transform of a signal, convolving it with some function, and taking the inverse Fourier transform of the result after undecibelizing. The effect is to enhance or attenuate the gamnitude of certain quefrencies (anagrams of magnitude and frequency, respectively).
Propulsion device
In electrical and mechanical engineering, a Lifter is a field-effect propulsion device powered by high-voltage in the range of several 10s of kilovolts. A lifter is basically an asymmetric capacitor, asymmetric meaning that the size of the two electrodes is significantly different. The diameter of the electrodes are usually about 0.1mm and 2cm, respectively.
The underlying principle is called the Biefeld-Brown effect. Lifters exhibit Vertical take-off and landing characteristics when powered. They are composed of aluminum or other lightweight conductive materials and usually have no moving parts. Small Lifter models powered by high-voltage flyback transformers have been made and successfully tested by several companies and hobbyists.
Lifters usually have a triangular shape or are built of many triangular submodules. The usual side length is between 15cm and 1m. The smaller electrode usually consists of a thin copper wire and the larger electrode is built using aluminium foil. The supporting frame is made of a light material such as balsa wood, straw blades, or styrofoam. This frame ensures a constant distance of a few centimetres between the two electrodes.
Automotive
In piston engines, a lifter, cam follower, or tappet is a device that actuates a poppet valve through rocker arms and pushrods. Cam followers are needed to transfer the radial forces caused by the rotating cams on the camshaft to the engine block, leaving only an axial force on the pushrod.
Use of Hydraulic lifters eliminates the need to regularly adjust the valve play, but can be inefficient. Solid lifters are used in performance applications.
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