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.
Alternator mod for rev counter signal?
in International Forum
Posted · Edited by 88 Especial
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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!