I decided to fit an aluminium pulley to my alternator. Then things went a bit too far and my next post will take this further, but for now i thought someone out there would appreciate seeing some components and their masses from a 100A alternator, and also a quick 120A comparison.
All pictures can be clicked on to make them bigger.
We begin with the rotor. This is the rotor from a 100A unit:
This rotor is the same mass at 2.562kg and dimensions on both the 120 and 100A. They are interchangable.
Next part is the pulley:
This is a steel unit and weighs 0.327kg. It is identical to the 120A version.
The front casing is next.
This weighs 0.962kg and is identical to the 120A alternator.
The rear casing is where the action is.
The part weighed here is the 100A case:
It is the lighter case at 2.017kg
This rear casing is from the 120A unit. It weighs 2.226kg.
I did not count or measure anything, but I surmise that the 120A unit has more turns of wire or different magnets.
I also did not remove the coil from the 120A case, so there may be some other difference in there, but from inspection I doubt it.
There is a slight difference in design of the rectifier packs. The heatsink and the winding connectors are a different design.
Left is 100A, Right is 120A:
I have no photo, but the 120A was 0.012kg heavier.
In case you were wondering, yes, I did get a new brush cap for the 100A, and that was the weighed part.
After establising that the parts and bearings were all in good order, and giving them a clean the madness descended.
This is a aluminium pulley. It was made up with 6 ribs because I had a drawing from a supercharged installation, and forgot to count the ribs on the crank pulley.
Still, at 0.107kg it is a lot lighter than stock.
Then it was time to turn up Jazz FM and get the drills and grinders out.
This yielded 0.128kg from the front casing. Not bad as a %.
I needed to get the car back on the road, and by this time I had already decided to go further on alternators, so with the aluminium pulley and the lightened front case I decided to put it all back together.
The finished item, as built:
This alternator was then fitted and driven about but then removed becuase of the next stage of Operation Alternator (coming soon).
If anyone wants to buy a slightly lightened and rebuilt 100A alternator let me know and i'll put it in the For Sale section. It does not have the aluminium pulley on it now though - I re-used that.
Summary - I compared a 120A alternator with a 100A, found it to be heavier but with the same rotating mass and then took some rotating mass and static mass out of the 100A alternator, refitted it, drove it, and decided I can go further.
Edited by blackoctagon, 04 June 2020 - 01:35 PM.