T90 & 16 ACR alternator

[Gordonmc]

A long shot, I know, but does anyone out there know how many pulses per revolution will be generated by a standard 16 ACR alternator on a BMC/Thorneycroft 1.5. T90.
The AC tachometer signal cable on mine has been soldered to one of the field windings and it produces a pulse, but I can't calibrate the rev counter accurately without knowing how many pulses per rev.

Thanks in hope...

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[VicS]

It'll depend on the pulley diameters as well as the alternator design. Can't you measure the engine rpm using a mechanical tachometer, or a strobe, and adjust the tacho to read the same?

<hr width=100% size=1><font color=purple>Ne te confundant illegitimi.</font color=purple>

 

[halcyon]

There are 6 poles on the rotor, so each coil will have 6 pulses per rev, each diode set have three diodes connected to three coils. So if you tap off one coil you would have 6 pulses, or if you connect to the diode set you would have 18 pulses per rev.
I think.
The problem connecting to output side is that you have, or should have battery voltage connected.
How many pulses are you looking for.

Brian

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[Gordonmc]

Thanks for the reply. If push comes to shove I will use a strobe, but as I don't have one I thought I would use the forum as a short cut.
The tachometer is programmable by use of dip switches, so it doesn't matter how many pulses there are, as long as I can establish how many.
I could set up for 18 per rev and drop down to 6 and see what gives a sensible reading.

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[silverseal]

I dont know where you are, but my uncle died about 2 years ago and left me a mechanical tachometer, wtih a variety of attachments for measuring the speed of rotating stuff... he was true engineer. I would love to use it for real.. I am based Hampshire. PM me if appropriate

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[cliff]

The problem is not so much the frequency of the alternator but also the size of the flywheel and alternator pulleys as this will affect the rpm of the alternator for any given crankshaft speed. That is to say the alternator spins faster than the crankshaft, or at least should do.

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[Guest]

Cheap mechanical tachos

Sold by Tandy's, Maplins and in most Model Airplane shops ......
Last one I bought was 9.99 and silly me - I gave it away !!

<hr width=100% size=1>Cheers Nigel http://groups.yahoo.com/group/gps-navigator/ http://groups.yahoo.com/group/searider/