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crank pulley for Isuzu 42 alternator drive


rogerc

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im not getting sufficient charge from my 70 A alternator HMI 900021ALS. it delivers about 30A  at 1800 RPM engine speed  (4700RPM alternator). 12-15A at tickover.  i would like to get 50-60 A. the alternator pulley is 6 cm external diameter ( i believe this is about the smallest practical size) and the one on the engine that only drives the domestic alternator is 16cm. i would like to change this to about 24cm to give a 4:1 ratio.

does anyone know where i can get a replacement pulley?

and how to remove the existing one?

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I do not know the alternator but have you checked its output curve to see what it can produce at 4800 rpm. It may be that it is the battery limiting charge and not the altetnator.

Additionally, if you gear it up to about 4:1 will the alternator speed at engine full revs be in safe limits for the rotor?

60A is close to the limit for a Z section belt without good wrap angles on both pullies so you might want to look at using a poly V (ribbed) belt.  That would also stand a smaller alternator pulley.  My 6PK  ribbed belt will do 60 A OK from an A127  onto a 50 mm alternator pulley with a 320 mm engine pulley at about 350 engine rpm.  I doubt it would like doing it all day though but it gets the initial charge in.

N

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As above re battery limiting so when do you measure this current and how well charged is the battery?

 

Are you sure you do not have a phase out in the alternator. With one generation coil  out you get lower than normal volts (so less charging current) and a lower maximum charging current.

 

The engine will probably rev to about 3500 rpm or more so what current do you get then?

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