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Smiths Chronometric mechanical tachometer. This tachometer movement is very much like a chronometric watch or clock and has been used in everything from production motorcycles to Formula 1 race cars. It is a very accurate method of gauging engine revolutions and some of the various models used had a resettable "telltale" needle that recorded the highest rpm the driver reached. If you look at most Formula 1 race car instrument panels you will notice a Smiths Chronometric tachometer being used, maybe even as late as the 1980s. These tachometers were available in different drive ratios depending where the tachometer was to be driven from, crankshaft (Cobras), distributor, camshaft, etc. . SAI transitioned from the SUN electric tachometers on early and up to the first couple of FIA competition 289 Cobras to the mechanical Smiths Chronometric tachometers. Depending on the particular model these can be expensive, STACK makes an electric tachometer that has the appearance of the Smiths but is electrically operated and has "telltale" capability, in fact they even reproduced the needle movement to mimic the Smiths Chronometric tach.
As per the statement above regarding "following the revs", all tachometers follow the revs, that's what tachometers do. Mechanical tachometers are more instantaneous than electric units.
Clocking the tachometer or any gauge for that matter is done so that it is easier to notice through your peripheral eyesight vs directly taking your eyes off the road to look where gauge needles are pointed.
Last edited by CompClassics; 05-23-2017 at 11:50 AM..
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