BW wrote:
...
a "sliding pin" must be disengaged on the large spindle gear ...
Anybody know where it is and how to disengage it ?

If it is engaged, you *can't* see it! The gear has a recess and the pin
is in the recess when engaged and totally hidden by the gear teeth.
Here is a picture of it disengaged:
http://home.comcast.net/~bobengelhardt/atlaspin.jpg

To find it, you stick your pin tool in the recess and turn the gear
until the pin bumps the tool. I know, you don't have a pin tool. Well
I didn't either and made this one:
http://home.comcast.net/~bobengelhardt/atlastool.jpg
As a matter of scale, the stock is 1/2 x 1/8 more or less. You'll need
the tool to engage the pin as well.

HTH,
Bob