Vienna Regulator in the Laterndluhr style
Since this
is a wall clock, and due
to the length of a seconds beating pendulum, I decided to hang the pendulum some 5" higher than
normal, right up in the pitch of the case roof as shown. An asymmetric crutch,
with a rolling wheel contact, engages the pendulum. This had a most remarkable
effect on the performance of the clock. Rather than being a detrimental feature
as I at first thought, it proved to be a major design improvement in increasing
the efficiency of the weight drive by nearly four fold. Basic details of the movements are: Eight day going
Module .6 on all wheels. high count pinions: 12 leaves
3mm plates, six pillars Graham dead beat escapement, maintaining power using a circlip Ball races on all arbors including the pallet arbor All wheels, escape wheel, and plates machined with CNC The case is constructed in the Laterndluhr style Vienna regulator
(circa 1820),
and made from Australian red cedar. Details are shown below. High Pivoted Pendulum Concept The diagram illustrates the virtue of this approach since it
reduces the pendulum amplitude by more than 2:1. Pendulum power absorption
varies with the amplitude squared, so halving the amplitude reduces the power
required to a quarter. So the drive weight is similarly reduced, and circular
error is also reduced. The rolling wheel contact with the pendulum is to
compensate for dL in the diagram. Because of this overall design improvement,
this clock will run on a 400gm weight. In practice, dL is very small being
approximately .002".
Dial, Case, and Pendulum Construction The dial was made by matte cello
glazing a print of the dial which
was printed on my laser printer from a CAD drawing. This was attached to the
brass dial plate with spots of Araldite placed every 40 mm, and the bezel around
the periphery. It worked well. The bezel was made from a straight
length of 3/8" square brass bar which was annealed, then bent into a 200mm
diameter ring, ends trimmed then silver soldered. It was machined on an MDF face
plate as if it were a casting. The bending worked well, but the holding and
machining was rather pains taking. The case was made from Australian
red cedar, with stringing made from 2.5mm Venetian blind slats. It is a complex
construction with removable hood. There are nine pieces of glass and three
doors. The hood door is hinged on hidden pivots, while the lower two doors are
lift out as was the tradition of these clocks. Much use was made of my radial
arm saw and the router table. The basic section for frame timbers was
20mm x 10mm, and the stringing 4mm x 2.5mm. Corner joints were mostly small home
made "biscuits" in grooves. The case was finished by filling
the grain with water based acrylic wood filler, stained with penetrating spirit
stain, then shellacked using a soft shellac brush. Each part was given a few
external coats of shellac before assembly to prevent the PVC glue from sealing
the wood. The pendulum has a carbon fibre
rod, while the 155mm bob is made from hand beaten brass shells filled with
rutile sand which has a SG of about 4. The rod extends down through a sealed
tube to isolate the sand from the rating mechanism. Araldite was used to
assemble the shells and central tube. The Second Vienna Regulator The wheels, pinion length, and some
pillars are now complete. It will be made in the Dachluhr style which has
straight sides up and down and is a much easier case to make. I also plan to use
a centre sweep seconds hand on this movement. It too will be
seconds beating. Updated 28 May,
2009
email me with your comments.
I
started out making two of these clocks at the same time to my own CAD designs.
However I have concentrated on the first movement and incorporated several
rather novel features, the main one being a high pivoted pendulum as shown by
the red arrow. Shown here on a test stand. It is seconds beating, and
has a centre sweep second hand. This
complicates the assembly at the dial centre due to the three concentric arbors.
The hour hand and motion work have not yet been fitted when the photo was taken. All upper arbors,
including the pallet arbor, run on miniature stainless steel ball races, 2mm x 5
mm. Bigger races are used for the great wheel and weight pulley. The effect of the sweep seconds hand is to
increase the inertia of the escape wheel and train by about 35%, according to a study I
did with 3D solid modelling.
