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swinny

Alternator ppr...? Anyone heard of it or know anything about it?

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As you say W terminal feeds rev counter on vehicles.

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1 hour ago, htb said:

As you say W terminal feeds rev counter on vehicles.

But how or what do I need to put into my new clock for it to calibrate the reading? 

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2 hours ago, swinny said:

Right, the wires already there from the old clock so that's OK, I just need to calibrate it to read correctly the rpm of the engine...

I remember years ago using a timing lightning my college days back in 2006/7 ish, never used one since lol. Can't even remember what's what.... something else I'll have to buy then I suppose 🤔

 

And I always thought they were for dizzy cap timing?

 

Infact the wire feed is that red one on the w post that feeds the clock  to give the rpm

I was wrong about the poles on the rotor, it is one field coil but the iron is shaped to give 6 poles so the W terminal will see 3 cycles per revolution, . My guess is 3 if it senses ac with possibly just one diode. none of my working alternators have a w terminal.

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Just getting round to this now.... and I've taken covers off and found that my Alternator pulley is 70mm and the crank is 140mm

 

PPR = P x R /2

 

“P” is the number of poles in the alternator. “R” is the pulley ratio. Determine the pulley ratio by dividing the crank pulley diameter by the alternator pulley diameter

 

So my r value is 2....

 

How do I work out how many poles on this alternator? It's the last piece of the puzzle lol  😆  helllllllpppppp 😀 

 

Edited by swinny

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If I remove the alternator is it easier to work out? I've not a clue what I'm looking for    .... anyone help? Many thanks

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I would say that if you have a rev counter and can check the actual rpm of the shaft in question,  be it engine or flywheel shaft speed  , then guess at a pulses figure to input and try it to see what speed is displayed  ?

For example an alternator on a Greenmech 19-28 mk1 has a pulses per rev of 20.9 if I remember rightly. 

By doing this   if you know the actual speed using a rev counter then just keep trying inputting different pulse settings until the display shows the correct speed.

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4 minutes ago, Jase hutch said:

For example an alternator on a Greenmech 19-28 mk1 has a pulses per rev of 20.9

So the alternator runs about 1.5 times engine speed?

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1 hour ago, Jase hutch said:

I would say that if you have a rev counter and can check the actual rpm of the shaft in question,  be it engine or flywheel shaft speed  , then guess at a pulses figure to input and try it to see what speed is displayed  ?

For example an alternator on a Greenmech 19-28 mk1 has a pulses per rev of 20.9 if I remember rightly. 

By doing this   if you know the actual speed using a rev counter then just keep trying inputting different pulse settings until the display shows the correct speed.

I know flat out the machine runs 2600rpm or so the old display said..... I will start on this guesstimate route 😀 

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If it's not exact, maybe best to aim a bit high with the PPR so the computer thinks the engine is running slower than it really is. That way the stress control will cut in early, rather than other way round and stress control cuts in late.

My dad bought a tachometer from Machine Mart a few years ago for his boat engine, don't think it was hugely expensive.

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