Rex Swensen's Web Site
Vienna Regulator in the Laterndluhr style
I started out making two of these clocks at the same time to my own CAD designs. However I concentrated on the first movement and this was finished in 2006. The case was designed in the Vienna regulator Laterndluhr style, which I particularly liked. It is typical of the Viennese clocks made in about 1820.
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. All upper arbors, including the pallet
arbor, run on miniature hybrid ceramic 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.
Basic details of the movements are: Eight day going
Module .6 on all
wheels. High count pinions: 12 leaves
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 as a spring
Ball races on all arbors including the pallet arbor
All wheels, escape wheel, and plates machined with CNC
The movement incorporates several rather novel features, the main one being a high pivoted pendulum as shown by the red arrow with the clock on its test stand. The hour hand and motion work had not yet been fitted at this stage.
Since this is a wall clock, and due to the length of a seconds beating pendulum, I wanted to reduce the case length, so 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.
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 PVA 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
This clock will have all the visible components made in brushed stainless steel in a black ebonised case Work is progressing slowly. The movement is about 60% done. The dial and bezel about 80%.The pendulum components about 60%. It will be made in the Dachluhr style which has straight sides up and down and is a much easier case to make. It will also have a centre sweep seconds. It too will be eight day going and seconds beating.
Updated 27 April, 2015
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