Tachometer/Alternator

[tertim]

I have recently fitted a new alternator to my thornycroft 108 and have had to fit a different size pulley on the alternator, thus altering the speed of the alternator and the pulse to the tachometer. My question is can the tachometer be re-calibrated to show the correct RPM and how do I ascertain the true RPM

tertim

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[philip_stevens]

Quite often, there is a small adjusting screw on the back of a tachometer - but not always!!

To adjust, you need a mechanical or electronic tachometer so that you can check the speed of rotation of your flywheel.

An mechanical tacho would get its reading from the centre of the flywheel, whereas an electronic tacho would need a small white patch on the side or front of the flywheel to allow the "pickup" to "see" the speed by counting pulses/flashes of white.

I have Japanese clockwork tacho that measures the speed by a timer over about 5 seconds. Unusual but accurate.

<hr width=100% size=1>regards,
Philip