Tachometer

DescriptionTachometer (Mechanical)DescriptionA tachometer (revolution-counter, tach, rev-counter, RPM gauge) is an instrument measuring the rotation speed of a shaft or disk, as in a motor or other machine.[1] The device usually displays the revolutions per minute (RPM) on a calibrated analogue dial, but digital displays are increasingly common. The word comes from Greek (tachos "speed") and metron ("measure")

Tachometers (Figure 2-13) are measuring instruments that give a direct and continuous indication of rotary speed in rpm. For submarine diesel engines, the mechanical tachometers are usually permanently mounted on a gage board. They are generally driven from the engine camshaft through a gearing and a flexible shaft. In operation, the force produced by the rotation is balanced against a calibrated spring or against the force of gravity. Those used in submarines are usually of the indicator type in which the pointer registers the rpm at the moment, rising and falling with the fluctuations in engine speed..

History The first mechanical tachometers were based on measuring the centrifugal force, similar to the operation of a centrifugal governor. The inventor is assumed to be the German engineer Dietrich Uhlhorn; he used it for measuring the speed of machines in 1817.[citation needed] Since 1840, it has been used to measure the speed of locomotives.

Components and Parts

Indicator displays rotational speed exerted from the engine camshaft through the flexible shaft assemblyFlexible Shaft transfers the kinetic energy exerted of the engine shaft to the mechanical indicatorEngine Camshaft serves as kinetic energy source

Industrial ApplicationsTachometers or revolution counters on cars, aircraft, and other vehicles show the rateofrotation of the engine's crankshaft.In vehicles such as tractors and trucks, the tachometer often has other markings,usually agreen arc showing the speed range in which the engine producesmaximum torque, which isof prime interest to operators of such vehicles.Aircraft tachometers have a green arc showing the engine's designed cruising speedrange.Tachometers are used to estimate traffic speed and volume (flow). A vehicle isequipped withthe sensor and conducts "tach runs" which record the traffic data.In analogue audio recording, a tachometer is a device that measures the speed ofaudiotape as it passes across the head. On most audio tape recorders the tachometer (or simply "tach") is a relatively large spindle near the ERP head stack, isolated from the feed and take-up spindles by tension idlers.On many recorders the tachometer spindle is connected by an axle to a rotatingmagnet that induces a changing magnetic field upon a Hall effect transistor. Othersystems connect the spindle to a stroboscope, which alternates light and dark upon aphotodiode.

Usage Instructions

Majority of mechanical tachometers operate in the same principles which are following;Principle 1: A Kinetic energy source in the form of rotational displacements such as engine camshafts serves as the registrants of dataPrinciple 2: a gear assembly used to transmit the power from the energy source to the dialPrinciple 3: An indicator assembly (dial) registers the actual power obtained from the source through the gear assembly and displays the registered data (power) due to the mechanical work performed by the indicator assembly pushing the dial to move at a scale.

Maintenance and StorageFor Mechanical Tachometers

Maintenance1.) Proper calibration must be in place2.) Fasteners properly fastened.3.) Periodic checking for the presence of destructive and constructive mechanical and chemical corrosions.4.) Internal mechanical parts must be periodically properly lubricated.