Machining the Packing Glands
The original plans, and the prototype, have two studs on the heads, and
tightning a pair of nuts pressed on the packing glands which in turn
presses on the packing
material, sealing the
rods. There are lock nuts that prevent the other nuts from vibrating
loose.
After fiddling with tightning the packing on the other models in our
locomotive roster, and after urging from Gorden, I decided to adopt a
threaded packing gland nut, as Gorden did on his Shay engine.
The first step is to choose the size and thread pitch. This usually
involves intense engineering. That means choosing what taps are on
hand. Gorden had two taps the fit the bill. One 5/8 x 24 TPI, and the
other 3/4 x 24 TPI. Since I was going to thread the Packing Glands Nuts
on the lathe,
the same threads per inch made a lot of sense. Not to mention the
adjustment of the valve and cylinder packing nuts will be similar.
Valve Packing Gland Nut
Cylinder Packing Gland Nut
Even
though I had a tap that what the correct size, I started the treading
process on the lathe. This will help keep the treads concentric with
the bore. I will finish the thread depth with the tap.
This
show the completed Cylinder Heads.
Here
is the almost completed Packing Gland Nut. I fininhed the part by
facing the side just parted off, and then drilled the aqdjustment
holes. See more pictures here.
Here
is the Valve Head with the Valve Packing Gland Nut installed.
Karl
Kobel
With
the help of Matthew Kobel and Gordon Carlson
(see his
work on http://www.locogear.com/page15.html).