[Alternator mod for rev counter signal?]

Hello,

New to the forum, first post.

For what it is worth, I installed a tachometer from a Kenworth tractor in my SIII diesel several years ago.

I added a wire from a stator winding output, where it connected to the diode pack/rectifier.

Counted the number of poles on the rotor. I have a Delco-Remy alternator and it has 14 poles. I believe the Lucas has 12.

Measured the diameter of the alternator and crankshaft pulleys. Don't remember the sizes, but it was 2 +/-  revolutions of the alternator for each revolution of the crank.

My multimeter has a frequency function, used this to measure the signal from the alternator.

I used the formula:  f=p/2 X r/60.

Where:  f is the signal frequency in cycles per second,    p is the number of poles, and r is the speed of the rotor in revolutions per minute.

Knowing the frequency and number of poles, manipulate the formula to get the rotor speed. r=120 x f/p.

The tachometer had a number of dip switches, adjusted these till the reading on the tachometer was as close as possible to the calculated speed.

I lost most of my data in a hard drive failure, the attached spreadsheet has some data..Calculated speed.xls

This was almost 10 years ago, so I may have forgotten something. Also I am retired so this project was something to pass the time.

 

Cheers from Central America!