[GreenKeys] Spacing problem on a model 15

[John Nagle]

> Date: Tue, 1 Nov 2016 10:58:11 -0700
> From: Audin Malmin <amalmin at okb-1.org>
> Subject: [GreenKeys] Spacing problem on a model 15
> A friend and I are restoring a 15-KSR.  We got it in a partially
> disassembled state and have reassembled it enough to get it running.
> ...
> But, there is still a spacing problem at two portions of each line.  The
> carriage assembly slides very smoothly, we have not been able to feel any
> drag at any point (including those two areas).  The supporting rods and the
> rack all look straight.  The gears that drive the spacing all seem to be
> nice and round.  We've played around with different return-spring tensions,
> up to the point where there isn't enough tension to consistently trip the
> carriage release return, to no avail.
>
> So, does anyone have any suggestions?

    Sure. The first thing to check is the carriage return clutch, which 
is underneath the horizontal fiber gear which meshes with the spacing
worm on the main shaft.  Check that it is engaging fully and
that all those levers which drive it are moving smoothly.  See
Fig. 49 in the adjustments manual.

http://www.aetherltd.com/public/model15manuals/138_Model15_Adj_Oct41.pdf

If something is slipping, it's probably that. There are adjustment
procedures for this in the manual.

    The next thing that might be slipping is the clutch on the main
shaft which drives the worm gear.  This you can check by watching.
Mark it in some way, and while typing manually, make sure it
makes exactly one turn for each key typed.

    Less likely possibilities are loose meshing or tooth damage on the
horizontal fiber gear.   In operation, for each spacing character,
the worm on the main shaft makes one turn, which advances the
fiber gear one tooth, which advances the carriage rack one character 
position.  So the carriage is rigidly locked to the spacing drive.
Unless gear teeth are not meshing or are damaged, that drive
train can't slip.  But you've already checked for gear damage.

    A useful thing to do if you have a Model 15 with a keyboard is
to provide loop power through the keyboard and printer with
the motor off. You can then hand-crank the fan on the motor
(counterclockwise), push a key, and run the machine through
its cycle at slow speed.

				John Nagle