Regarding the frame assembly of the Gingery lathe, MikeM writes:
I built a slightly larger version of the Gingery lathe and may be able
to help. The frame that carries the countershaft is pivoted at the
base on each side so that it can be moved back & forth when neccessary
to shift the belt to the different pulley diameters for changing
speeds, but the frame itself should be as stiff as possible so as not
to upset the alignment of the countershaft bearings. Think of it like
a door, you want the door to easily open and close but you wouldn't
want the door itself to bend or twist.
I understand that the only motion that the frame should allow is in the
direction towards and away from the motor. It also makes sense that the
parts described as pivots ought to move, or at least to be connected by
a movable joint to a part that moves. I would expect that the only parts
that actually move are the release lever (which is rigidly attached to the
release crank and the handle) and the release link, i.e. parts 7,6,10,9,
respectively. From the picture on p.71, I think it is intended that the
release link pivot (part 8, which I think is rigidly attached to the upright
rail, part 4) is intended to block the release crank from moving any closer
to the motor than it is in the upright position of the release lever.
Thus, in the door analogy, this is the part of the frame that keeps the
door from being a swinging door and allows the door to assuming a limiting
position in which it is closed. Such an arrangement makes sense and I think
it was Gingery's intention. It also implies that the upright rail is suppose
to be rigidly attached to the base rails (part 5) and unable to pivot.
The reason I have doubts about that conclusion is that Gingery writes, p.71:
"The mechanics of the assembly are simple. Notice the dotted center line from
the release link pivot to the release lever pivot. When the release lever is
drawn forward, the crank will pull the lower link pivot over the center line,
unlocking the linkage and pulling the upright forward."
In other words, he seems to be saying that the upright does move. If it
moves, I don't see what there is in the construction that keeps it upright.
The motor is going to be turning the motor pulley, which will turn the
outboard pully and the counter shaft. These are mounted on pillow blocks
attached to the upright rail, which is therefore going to be subject
to some significant forces, in my uninformed opinion. It would make sense
for the upright rail to be completely rigid in order to keep from getting
jerked around by the motor.
Since I haven't finished reading the entire book, and don't know yet exactly
how this set up is connected to the pulley in the headstock, I'm not sure yet
exactly how the release lever is supposed to let one change the ratio for
the pulleys and why, once selected, the selection is supposed to remain
stable. Maybe I'll be able to answer my own question after I've read
a lot further. On the other hand, maybe what is making me uneasy about this
is also related to the reason why Gingery writes on p.70 that he has belt
slipping problems when he uses an 8 inch outboard pulley instead of a
6 inch one.
Ignorantly,
Allan Adler
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* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
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