Saturday, March 4, 2017

Triumph Spitfire Engine Rebuild #13 - Generator

Much like the starters, I had three generators, or dynamos as the Brits called them. For the little time that Dorothy was running, the generator never charged the battery. I suspected a wiring issue, though I never found a smoking gun in the harness. Of course, the generator itself could also be the problem, but it would take some disassembly to investigate.

As with the other two posts, I'll refer to the numbers in the diagram below for clarity.

The obligatory reference drawing.

I was hoping I would get lucky and, like with the starter, find a generator that was a rebuilt unit. I picked one of the two that wasn't on the car and started taking it apart. One had a Lucas Exchange Unit sticker, so I started with that one.

Old sticker. Unfortunately, it crumbled as I carefully tried to peel it off.

I undid the two bolts (1) and pulled the armature (16) and the entire front end of the generator out of the housing (called the yolk in the starter, but not identified on the drawing). Looking down into the brush box, it was evident that this generator had seen some pain.

Blurry, but you can see the brushes are all chipped up and there appears to be charring on the bottom box.

Speaking of charring. Again, sorry for the blurriness. This one is toast.

In addition to the brush box damage, one entire segment of the commutator on the armature was burned away. This baby suffered a short at some point and was trash.

I tore into the next one and, lo and behold, found the rebuild. Much like the starter, things were done to make this generator serviceable. The rivet where the field coils (7) are tied to the case was drilled out and replaced with a screw. The brushes (2), brush springs (4) and bushing (5) appeared nearly new.


Dirty on the outside, not so bad on inside.

With that, I cleaned it all up, painted it and put it back together. Because this is a generator, which is DC, and not an alternator, which is AC, it is very similar in construction to the starter and went together in a very similar manner, so I won't repeat a lot of that.

After wire brushing the outside.


Brush box all good to go.

Fan end, sans fan.

Top view.

Rear view.

That was about it, really. I did investigate the one that was on the car and the brush springs had lost their tension so were not keeping the brushes on the commutator. I can only assume this is why it was not functioning. That one requires new brushes, springs, a bearing and bushing, which I have not sourced yet. I'll eventually rebuild it, however.

Oh, and much like the starter, I was able to test that the generator spins. I stole the setup from Moss Motors and their awesome series of videos, this one specifically. Quite a bit more polished than mine below!



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