G'day Chris here and welcome back to Clickspring. In this video I make the user input section
of the mechanism, the Input Crown Wheel Assembly. If I were to make the input crown wheel without
any consideration of the existing artefact, I'd be inclined to start with a solid piece
of round stock, machine the recess, and then finally cut the
teeth. But during his investigation of the mechanism, the historian Derek de Solla Price noticed
evidence of fine cracking around the perimeter of the wheel. A sure sign that this was yet another fabricated
part. Most probably, using a cylindrical piece of
metal for the interior. And then a thin metal strip formed into a
band was either soldered or perhaps riveted to the perimeter. Now much like the main solar drive wheel,
from our modern perspective, this is clearly not the easiest way to construct
the part. So again the question naturally arises, why did The Maker choose this more difficult
method? Its possible that it was due to the turning
limitations of the period. And certainly its easy to imagine that forming
a small recess like this might not have been entirely straightforward. But there are some other features that would
have been much more difficult to form, such as the very precise recess for the front
dial calendar ring. So I'm not convinced that that was necessarily
the reason. For now I'll fabricate it as per the original, and hopefully the reason will reveal itself
during the course of the build. Now for this fabricated approach to work, the brass strip needs to be formed into a
reasonably accurate circular band, with a slightly undersized inside diameter. In fact its just one of several accurate tubes
that are required for the mechanism to function. From an engineering perspective, accurate narrow tubes would probably have
been one of the most challenging aspects of the original construction, particularly if its assumed that the maker
only had access to flat sheet stock to begin with. For the short tube or band that I'll use to
construct A1, I think a plausible suggestion is that a simple
former was used, around which the sheet stock was wrapped and
then lightly hammered into shape whilst heated. The tool is easily made, and I think its conceivable
that a set was made to generate a range of inside diameters. I'll develop this idea a bit further when
making the concentric pointer tubes later in the build. For now though, I used the torch to repeatedly
soften the brass strip, and then slowly work it around the former. Taking care to reheat the work as soon as
it started to cool down, and also being careful to not to overheat
it. It doesn't take much to melt a small piece
of brass like this. A light skim cut on the lathe created a uniform
surface, and widened the inside diameter to be a close
fit with the central cylinder formed earlier. A touch of soft solder bonds the two parts
together, and fills the join in the perimeter of the
band. I'll be sure to position that join to coincide
with the root of a tooth when I form the teeth later. And briefly dipping the part in soda ash neutralises
the flux residue, preventing it from corroding the metal surrounding
the join. The central hole now becomes the register to relocate the part back on the lathe for
some cleanup cuts, matching the spigot turned on the face of
this temporary arbor. The workpiece needs to be flipped so that
I can make some cuts on the other end. But rather than risk loosening the solder
join with heat, I soaked the part for about a half hour in
acetone to dissolve the super glue bond. Now at this point the wheel could be manually
divided, and the teeth hand filed, as will be done
for the rest of the mechanism. But the shape of this wheel allows me to show
you something a little unusual: Wheel cutting on the lathe where the cutter
passes through the work vertically, rather than horizontally. Much of the process for regular wheel cutting
applies, but you'll notice there are a few key differences. The motor, speed control and spindle are all
set up to travel vertically as a self contained unit on the vertical slide. And the depth of cut is now measured along
the length of the lathe bed, requiring something like a dial indicator
to give a precise indication of that depth. Gradual increases in the depth of cut on either
side of a single tooth, eventually leave a small triangular land at
the tooth apex. At which point the carriage can be locked,
and all of the teeth cut at the same setting. I took a light skim cut of the perimeter to
remove the small exit burr left by the fly cutter, and then marked out the rectangular hole that
will receive the driving arbor. Of course I'd like these markings to remain
after I've removed the part from the arbor. So that rules out using either heat or acetone
to break the bond. But fortunately super glue is very hard and
brittle when cured. So a third option, providing the part can
tolerate the impact, is to simply tap it off with a hammer. And that's where I'll leave this part for
now. Now you'll recall from a previous episode, that I'd like to keep the whole structure
open throughout the build to give you a good clear view of what's going
on. So for at least the duration of the build, support for the input arbor will be provided
by this bracket, pinned to the main plate. A key feature of the bracket is that crisp
90 degree bend, which I formed by milling out a V groove in
the raw stock. And the easiest way that I've found to hold
the work to form this sort of groove is by using a cement chuck on the mill. It does have its limits, but its a surprisingly
sturdy way to hold a part. And It also provides access to all 4 sides
as well as the top, making it easy to bring the perimeter to size
as well, all using the single setup. And here's a closer look at the depth of metal
remaining after the V groove has been cut. I've found that around 0.4 of a millimeter
gives a good tight radius to the bend, and allows the metal to bend easily without
cracking. The inside corner on the indexing arm, that
I made in a previous video, serves as a convenient square reference. And I'm being very careful here not to bend
back and forth too much, to avoid work hardening the join which would
increase the risk of cracking the thin metal. A bead of soft solder makes the join permanent, and once again a soda ash solution neutralises
the residual flux. Back on the surface plate, I marked out the
positions for the other bracket features. Now the issue of depthing the input assembly
is a little tricky. I'll go into this in detail for the other
wheels later in the series. But at this point of the build I don't really
have a convenient way to depth a crown wheel, other than by using the device itself. The wheel assembly could be held up to B1
with a toolmakers clamp, depthed, marked and then permanently fixed
in place. But I'd also like to have the back surface
of the bracket flush with the side of the main plate, without having to trim that plate after the
fact. So that meant making my best guess at the
correct depthing at the planning stage, and essentially locking it in at the start
of the project. It was a riskier approach, no doubt about
it. And as it happens, it worked out fine. But I'll be taking a more traditional approach
with the depthing for the rest of the mechanism. The lateral position of the assembly, was
determined based on the main bearing position. And I put in 2 witness marks on either side
of the main plate. Aside from being useful right now, they'll
record the centerline should I need it later in the build. With the input assembly position located, the bracket and underlying main plate were
drilled out to accept a pair of steady pins. The steady pins now ensure the the accuracy
and repeatability of the bracket position. And once clamped firmly, I drilled out the
hole for the bracket retaining pin. A quick tidy up of the holes, and thats the
bracket complete for now. Next up is what I'm calling the driving arbor, the shaft that that transmits the torque generated
by the user, through to the crown wheel. It has a nice straightforward profile that
I formed on the lathe, and then I used the mill to form the features
at each end. And with that rectangular driving section
now formed, I opened up the matching rectangle marked
out in the center of the crown wheel, taking care to ensure a close fit. With the crown wheel assembled on its driving
arbor, I marked the retaining pin position, which will ensure a small clamping force from
the taper pin once its inserted. The final items on the parts list for this
episode are the retaining pin that holds the bracket in place, and a small washer to protect the under side
of the main plate. OK, so thats everything I need for the moment, so lets put it together and see what we've
got. The friction is quite low, with both wheels
showing free and smooth movement. And the gear interaction feels good too, much better than I expected from a triangular
tooth form. In fact based on the feel alone, there's not much to give away the fact that
its not a modern tooth profile. In the next video, the mechanism will continue
to take shape, as I make a start on the calendar and eclipse
gearing. Thanks for watching, I'll see you later. Now if you enjoyed this video, and you'd like to help me make more, then
consider becoming a Clickspring Patron. As a Patron of the channel, you get immediate
access to the patron series of videos. This includes the 5 videos from the Wedge
Style hand Vise build, and at present the first 5 videos of the BSC
build. There's also the first 3 episodes of the new
Tools, Glorious Tools series, with more to come as that series progresses. And don't forget that as a Patron you also
get free access to the plans for the patron series projects, so you can follow along and build the projects
yourself if you wish. visit patreon.com/clickspring to find out
more Thanks for watching, I'll catch you on the
next video.
Although it makes for slow progress, the attention to detail is incredible. Can't wait to see the finished product.
p.s. anyone else think that Dykum blue is incredibly satisfying stuff?
Jesus, either him or Primitive Technology are trolling us. This keeps happening, where the videos come out close together
That satisfying click when the driving arbor was connected with the crown wheel. Dear god.
I've been loving the balance between the ancient fabrication methods and modern technology there has been throughout the series. It pays homage to the original maker and really makes you appreciate the immense amount of time and care that must have gone into the original mechanism.
"Clickspring" sounds like a nonsense start-up company. But it also sounds like a very satisfying, succinct name for a channel about mechanical clocks.
The gear tooth cutting sequence was great. Seeing that final tooth being cut exactly between the adjacent ones is so satisfying.
I love his videos
And on an unrelated note, I swear AvE has ruined my perception of every other youtubers sign off message when they say "Thanks for watching"