- Wed Feb 16, 2022 7:00 am
#100127
Guys. A couple of simple questions but maybe complex answers.
My 1996 535cc has a modern 120W Lucas alternator, the ID of which is stated in Mr H’s catalogue as 2 15/16” which equates to 74.6mm. My rotor measures 74.1-74.2mm at many points i.e. a tad too small (although I cannot easily measure this because my verniers are all steel).
Fitting the two together requires an air gap of ~10thou (0.25mm) at all points between stator and rotor. That presupposes that the stator has an ID of at least 74.6mm + 2x0.25mm = 75.1mm. I found that our hosts “alternator clearance setting shim” PN98240 was inadequate to set the airgap because after it was bent around the rotor the laminates separated. But before throwing it away (and keeping the so useful datasheet) I measured its thickness at ~10thou. So;
Q1: If my rotor is that much too small, will the increased air gap reduce the charging?
I assume the rotor is fixed first and tightened onto the crankshaft as it fits onto a keyed (?tapered?) shaft but that there is enough “slop” in the three stator stud holes to allow for that 1/4mm gap.
So I use a system of 10-12 strips of plastic sheet, each 9thou thick and 2cm wide (sorry, all my units are varied), that I place between the two and if they can be freely moved after the stator is tightened, then the gap is set.
I confess when I reassembled it a few days ago after changing the drive sprocket, I got that gap wrong and the rotor ground some of the stator resin with an awful and lasting smell, and with smoke issuing from the chaincase filler bolt hence the new stator on its way from MrH. So, before I muck up the next stator;
Q2: Can anyone confirm if the fixing sequence/method is correct?
Many thanks and cheers, ChrisD
My 1996 535cc has a modern 120W Lucas alternator, the ID of which is stated in Mr H’s catalogue as 2 15/16” which equates to 74.6mm. My rotor measures 74.1-74.2mm at many points i.e. a tad too small (although I cannot easily measure this because my verniers are all steel).
Fitting the two together requires an air gap of ~10thou (0.25mm) at all points between stator and rotor. That presupposes that the stator has an ID of at least 74.6mm + 2x0.25mm = 75.1mm. I found that our hosts “alternator clearance setting shim” PN98240 was inadequate to set the airgap because after it was bent around the rotor the laminates separated. But before throwing it away (and keeping the so useful datasheet) I measured its thickness at ~10thou. So;
Q1: If my rotor is that much too small, will the increased air gap reduce the charging?
I assume the rotor is fixed first and tightened onto the crankshaft as it fits onto a keyed (?tapered?) shaft but that there is enough “slop” in the three stator stud holes to allow for that 1/4mm gap.
So I use a system of 10-12 strips of plastic sheet, each 9thou thick and 2cm wide (sorry, all my units are varied), that I place between the two and if they can be freely moved after the stator is tightened, then the gap is set.
I confess when I reassembled it a few days ago after changing the drive sprocket, I got that gap wrong and the rotor ground some of the stator resin with an awful and lasting smell, and with smoke issuing from the chaincase filler bolt hence the new stator on its way from MrH. So, before I muck up the next stator;
Q2: Can anyone confirm if the fixing sequence/method is correct?
Many thanks and cheers, ChrisD
