Continue final finishing of escapement, begin balance springs
- June / July 2016
The pendulum cross arbors and their spacers are now completed.
Notice in this photo
that Buchanan uses a numbering system to match up parts wherever there are
similar pieces that may be confused upon reassembly.
Another example of the
numbering system. Even the individual numerals are beautiful. Next is an
example of a finished screw. The photos tend to make them darker than they
The first photo shows the diagonal bracing for the pendulums. Next the
spacers are assembled.
The finished front pendulum and escapement supports are
The barrel shaped worm gears are
adjustments for the grasshopper
appears to be trying a different approach here for the
process. Remember how a modern torch was used in the prior process.
has gone to an open flame burner. So the process is now completely in
keeping with the old methods.
The front end pendulum assemblies are now complete and ready to accept the
now proceeds onto the grasshopper escapements. While he previously indicated
that these were largely in their final finish form, they were not completely
We now turn to the steel components. First,
all of the jewel escapement
stones must be removed; these are the bird’s ‘beaks’. The jewel pivots are
protected within the body of the part and do not need to be removed.
The remaining escapement components which comprise the allegorical bird’s
bodies, the feathers are finished. Notice how slender the curvaceous
escapement pair appears in the first photo. Next the parts are drying after
The pair of allegorical bird
escapements complete with tail feathers and comb on the heads are now
The second photo shows the complexity of the grasshopper
joint. A dozen components comprise this one small system.
now goes through the steps to make the escapement pillars. These are the
last components to complete the escapements. They have a fairly complex
shape requiring not only conventional lathe turning, but manual filing using
both round and square filing buttons. Filing buttons are used to guide the
file into a particular contour, usually a round or flat profile. The buttons
are custom made just for this step. The first two photos show the initial
Next the flat filing buttons are used to mark off the tabs where the
mounting holes are located behind the flat buttons on each side of the
Much of the original round flange is rough cut away as seen in the first
photo. Next the flat buttons are used to fine-shape the mounting tabs.
In the first photo the round buttons are used for the fine-shaping of the
round portion of the pillar. The second photo shows a before and after shot
in relation to the end flanges and the use of the filing buttons to achieve
this. The turning of the pillar body, though, is already done on the piece
to the left.
The next two photos show this piece reinserted into the completed
escapements and pendulum support rods.
The combination of color and finish is visually compelling.
Now Buchanan tackles the large balance frames. Each one is nearly 24 inches
tall with a lot of internal complex patterns. Buchanan writes:
Both frames are filed up to sanding point. I did an opening count and there
are 85 opening in each balance frame or 170 openings. If I can polish one
opening in 20 minutes (some will be quicker and some longer.) I have 3400
minutes or 56 hours to go. Then there is the outside and the back and front
face. I was asking myself why the filing was taking so long. I have the
first opening polished! 169 to go.
The final finishing steps take a substantial fraction of the time it took to
make these pieces in the first place. While these parts are especially large
and complex in their layout, the machine is filled with such parts.
I was curious how
the frames so I asked him what the procedure was.
a stick charged with grit? Or paper on a shaped surface? There are so many
concave surfaces of differing configurations I’m curious how this is
These photos explain how it’s done. There are five grades of sanding sticks,
red-400 grit, purple-600 grit, blue-1000 grit, green-2500 grit and
yellow-5000 grit. By the time one get’s to that grade it is a pretty fine
The other thing that is being accomplished here is that the geometry of the
curves is being subtly altered to a better refinement.
I have the first of the small panels polished on the
first frame. The blue marker is for a reminder as to which part has had a
certain grit. First as I use 250 grit I mark each facet as I finish
then I remove it with 400 grit then as I finish 100 grit I remark each
section then remove it with 2500 grit and a final polish with 5000 grit.
That is 32 facets times 5 grades of paper. I have 3 more small panels to go
and then the inside of the first frame is complete.
Now the last step is performed. The two large flat sides that compose the
front and rear of the balance frames are now tackled. The first photo shows
the filings left behind on the right leaving a shadow of the frame itself on
the left. Next is a close up that shadow on the wood board.
Buchanan glues the sandpaper to a thick sheet of glass to ensure that the
paper remains perfectly flat and the final finish is as close to an ideal
plane as possible.
Notice the pile of brass dust on the table top. This area is just below the
table top of the custom polishing machine he made last month. Next a shot of
hands after a hard day’s work.
This photo shows the end of an eight hour session. There is a prodigious
amount of used and broken sanding sticks on the floor. Notice the pile of
brass dust under the filing machine’s table in the upper right corner of the
photo. Hope that balance frame doesn’t drop out of the vise!
The balance frames are now brought to their final finish. These were
The frames and escapements are now ready for assembly. In the next
photo the assembly is complete. Unlike in a conventional clock, the pendulum
is not readily separable from the escapement. They are an integrated unit,
excepting the escapement wheels themselves.
Rear three-quarter elevation. Both sets of triple antifriction wheel
support systems are seen in their full complexity.
Front three-quarter elevation. Again, complexity and the visual impact
of the various colors are brought to the fore. This photo better represents
the color of the blued screws. It is the lighter, 'electric blue' seen in
watch work that I was after. While not to everyone's taste in the
horological world, I think it works well in this application; particularly
because these screws are very large.
A view from the inside, rear. Notice how the everything appears to
radiate out from the center axis, especially the six straight rays that
follow the longitudinal orientation. At the 45 degree angle from these it
appears that the metal has peeled away like a delicate sliver of wood under
the application of a wood planer tool. All edges are sharp as they should be
under strict standards. yet the entire polish gives a glowing, 'liquid'
look. Next month the second balance will be finished.
Buchanan now turns to the springs for the balances. With the generous
collaboration of Douglas Drumheller we begin the process of bringing the
machine from a visual attraction to an accurate timekeeper. Or at least as
accurate as can be accomplished in such a complex mechanism.
After Buchanan read
article there were several responses back and
forth. Buchanan and Mr. Drumheller chose to respond with additional dialog
within the original email and with responses in different colored font. The
original letter from Buchanan to Mr. Drumheller's is in black. Mr.
Drumheller's response is in red. Buchanan's next reply is in blue and
Mr. Drumheller's rejoinder in Green. I've included this dialog to give the
reader a taste of how ideas, questions and solutions come about through
collaboration. There will be several such collaborations on the rating of
have read the article and I think I can follow Mr. Drumheller in his
reasoning. I need adjustment on the following points.
I have known of your Harrison for some time and must compliment you on it.
It is beautiful. It would surely be unique to actually navigate by
means of a Harrison Replica.
It’s my dream, but of course it’s hard to
get buy in for the cruise and documentary. At this point I don’t think it
will happen. Anyway I’m off to my boat in the Great Lakes in a few weeks to
dream about such things.
I found your paper fascinating and enlightening. I have always
understood how the temperature compensation worked on H.1 but had not
thought about the effect of moving the point of attachment on it until I had
started to make my adjusters. Your paper answers a number of queries I had.
I have a query about Page 3 middle paragraph. ”An alteration of as little as
1/2mm will MAKE A DIFFERENCE OF SEVERAL MINUTES A DAY. This I would
understand to mean an adjustment on our outer adjusters on the balance or on
the verier adjusters as they are now, but with no temperature compensation
fitted. And not a change in semiarch but a change in spring rate.
I see also the need for an accurate way to measure the arc of our balance,
as we will need to monitor every factor that can change.
Almost all of this observed change in rate is due to the presence of the
temperature compensator which alters the springs to a highly nonlinear
behavior. If the springs themselves are perfectly linear and the cheeks are
perfect circular arc this adjustment will have little effect on the rate of
your system, which does not have a compensator.
Yes you are correct when you take the
temperature compensators into account. I agree with you. I missed this
until I had read through the complete article.
Page 4 last paragraph, first line. I must misunderstand something here but I
never thought of a helical spring as linear. The result of 4 helical springs
in a Harrison system may be linear. I do not have any real life experience
with this yet to be able to comment.
Engineers think of them as linear. Of course a clockmaker looks at very tiny
deviations from linearity as very important. I’ve not measured the force
deflection of one of these springs, but my guess is that it will be hard to
measure the deviation from linear. Now if the spring is grossly extended it
will exhibit a strong deviation from linearity. Measuring the rate as you
change your adjusters will give a very good measure of the deviation
provided the amplitude is held constant.
I think I could plot some sort of deflection Force graph for my springs.
I will see what I can manage. I have a mill with a digital readout on
the z axis if I suspend an overweight weight on a spring but support
the weight on a sensitive balance , as I drop the knee of the mill I will
get a decrease in the reading on the balance. This
will be very useful data.
This system should have no friction involved anywhere. Only the weight of
the spring coils to take into account. I am wondering how we could measure
the force of deflection for the complete balance assembly.
I suggest a series of coast-down tests, which
will yield the rate vs. the amplitude. You’ll also get Q. The version of
MicroSet that I hope you purchased has the capability to measure two things
with the photogate laser. First it measures the period of the beat, and
simultaneously it measures the time that the flag, which you mount on the
balance, blocks the laser beam. These measurements yield values for the rate
and amplitude during operation of the balances. You can repeat the test with
differing amounts of initial stretch of the springs. I suggest you use the
procedure outlined in my HSN article which is attached. This procedure
requires using the MicroSet to capture every beat so the amplitude can be
extracted from these readings. If you send me the Microset files that you
generate, I’d be willing to help you reduce the data. (I suggest starting
with a flag of measured width that is about 1/16” to 1/8” wide.) Often a one
point calibration is needed to determine the extent to which the laser beam
diffuses around the edges of the balance flag. This is accomplished by
comparing a Microset measurement of amplitude to a direct measurement of the
Page 6 second paragraph. Last line. I need convincing that a change in
outer band length produces a change in the 0max Note 3 I
have experimented with this on My No.1 clock and found that shaping the
cheeks can have a major effect on isochronism. But my cheeks were on a
balance with an arc of over 180 degrees. So we are comparing apples with
I do not intend to imply that changing the band length changes Omax. Instead
I was pointing out that with the temperature compensator installed the
average stiffness of the springs can be changed either by changing the
position of the compensator pads or by changing the amplitude of the swing.
Yes I agree.
That is why the compensator is such a bad device. It destroys the
isochronism of the balances. It was one of Harrison’s worst ideas.
Yes I agree.
I also do not mean to imply that you can’t tune the clock by altering the
shapes of the cheeks. Rather I suggest that such an alteration of shape,
while important and useful in many applications, is too weak to overcome the
huge anisochronism produced by the temperature compensator.
Yes I agree.
Page 14, last paragraph. I agree with this paragraph totally .I think
I recall reading that on the return trip Harrison applied a calculated
correction which gave an extremely accurate rate.This
is very important to me. Is there any chance you might remember where you
I thought you would ask that. I will see if I can find it. It is not in
Gould or Sobels book. Perhaps in Such Mechanism. I found a short reference
to a correction after a trip with H.4 but that is not what we want
These comments are my uneducated observations. Any enlightenment will be
gladly accepted . I am not wanting to criticize but want to understand
better what we both are working towards. I found the description of
the arc measurement very interesting.
I really appreciate your interest, and I think that what you are doing on
this project is marvellous. Thank you. If this discussion produces
a better clock or a better understanding of what we are doing it is
I have also a few more ideas on temperature compensation.
I’d be interested in hearing them when you are ready.
I better get on with the polishing. The 6 small frames are finished and
lacquered, polishing screws now.
My dad was a tool & die maker---steel dies for pouring molten zinc and
aluminium. The die faces had to be polished to mirror finish so that they
would release the castings properly. On occasion he would
unintentionally polish his fingernails to paper thin. Mom would help cure
that with her fingernail polish.
I spent most of my early working life
making plastic injection molds. Polishing tool steel is no fun, I
sandpapered my fingertips through on my first clock.
Mr Frank has kindly financed the full suite of sensors for my Microset
timer. I have tested it briefly but do not know if I can use if for accurate
You need the version of Brian Mumford’s MicroSet hardware and software that
allows you to turn on the amplitude display in the computer graphics. The
resulting plot with the amplitude shown as a blue line will not be scaled
properly, but we can solve that problem.
I think it has some feature like that. If not I would most certainly need
to ask you for more detail about your method.
I use the MicroSet with the photogate laser. The sensor needs to be shielded
from ambient light. During my initial tests I didn’t do this and I first
noticed problems after I realized that the readings shifted as I walked past
my clock wearing a bright shirt. The best calibration of the amplitude scale
is obtained by comparing a MicroSet reading to a direct measurement of the
balance amplitude. It’s a one-point calibration.
I am working on finishing my balances to a point where I can start an
accurate analysis of their behaviour. I will, no doubt, call on your
expertise at this point. My only previous experience relates to my first
serious clock which has a horizontal bar balance, two Harrison type springs
and a constant force escapement. I will attach a photo or two of it.
Thanks for the great photos. They make me jealous.
You may be interested in our website: www buchananclocks.com, Mr Frank’s
chronology of his clock on his website is superb.
Mr. Drumheller makes the final line with the
following humorous comment:
We should call this the Rainbow Discussion. At some point we’ll run out of
Buchanan now begins to address the fitting of the new
balance springs. He writes:
Drumheller wrote back:
This last observation about the springs by Mr. Drumheller will turn out
to be exactly correct. We will see how this is resolved in the next few