Tachometer

[fishermantwo]

I have an old Gardner diesel. The engine tacho cable has failed, replacement cables are available and there are companies that will repair the cables. The problem is the price on these articles. What I am considering is making an electronic unit using something like a Halls sensor or a photo interrupter unit on the front pulley. Either a kit car LCD tacho or some alternative. The engine operates between about 350 and 1000 rpm, most aftermarket tachometers are up to 4000 rpm and are ridiculously priced as well.
Would appreciate any input, links etc.

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[snowleopard]

i have an old jaguar with a tacho which is wired in series with the LT side of the coil. it counts the interruptions (3 per revolution - it's a 6-cyl). If you wired one up to your photo interruptor and arranged for say 10 interruptions per rev it would give a reasonable reading though you'd need to re-mark the scale.

you should be able to get a unit of that type from a car breaker.

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[thalassa]

No tacho... but a large flywheel is found on my trusty Volvo MD7a. Went to the bicycle shop, and bought a flashy wireless bicycle computer for the equivalent of 2O quid. Epoxy-glued the magnet to the flywheel. The transducer on a small bracket. No holes to drill. Yes, call me cheap and easy.

Kind regards

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[cats]

There is a design for a DIY tacho. in the Nov. issue of PBO.
good luck

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