[T3] Generator ... Again

[Jim Adney]

On 3 Sep 2012 at 13:54, Max Welton wrote:

> Jim, I did the field test. This generator isn't generating much of
> anything at the D+ with the DF grounded. 
> 
> Here's the installation. No issues I can see.
> 
> http://www.maxwelton2k.net/squareback68/IMG_7480.jpg

That looks perfect to me, too. A typical '68 setup, except that 
you're missing the rubber seal between the end of the generator and 
the pulley housing. I have those if you need one.

> But if I understand you, these are bug brushes?
> 
> http://www.maxwelton2k.net/squareback68/IMG_7479.jpg

Hard to see for sure, but it appears that, yes, the ramp slopes the 
wrong way on those brushes. What's clear is that the brushes are worn 
out, since they have sunk well below the top of the holders. There's 
also a LOT of black buildup around the opening in the generator body. 
What is that? It can't all be brush material.

One thing that can cause rapid brush wear is abrasive grit that gets 
embedded in the copper armature. That can come from the wrong kind of 
airborn dust or from polishing the armature with the wrong kind of 
sandpaper. I believe the common kind of sandpaper is the wrong kind 
in this case.

Do you drive in a dusty climate?

> Would those type-1 brushes wear faster than the correct brushes?

No, they just tend to stick in the brush guides.

> I could not feel any pulsation up and down. But they probably aren't
> touching the armature anymore. 

Look at the slot in the brush guide where the copper pigtail comes 
out. Once the pigtail hits the bottom of that slot the brush can't 
advance any more. That's when it is completely worn out. Until then, 
you may get a little more time by pushing the brushes in farther with 
your fingers.

It looks to me that your original question was the right one: Why did 
these brushes wear out so fast? I don't have a good answer for you.

-- 
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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