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| Figure 9. SeeSaw Gravity Escapement |
Summary
This article
describes a novel clock escapement, termed The SeeSaw Gravity Escapement1,2,
in which, paradoxically, the pendulum controls the escapement, but the pendulum is 'unaware that the escapement exists'.
A proof-of-concept model is described which demonstrates the feasibility of the escapement3. In addition, two alternative modes of impulse are described.
Background
The escapement
has three important functions:
1. Maintain oscillation of the
pendulum.
2. Provide a means of indicating the time.
3. Control the release of energy in order to perform the aforementioned tasks.
Furthermore:
In
an ideal escapement, the pendulum controls the escapement, but, paradoxically, the pendulum should be
'unaware that the escapement exists'.
Many
different types of escapement have been described. The reasons why escapements adversely affect the consistency of oscillation
of the pendulum is mainly due to friction. The word friction, in this context, refers to any source of friction (mechanical
or viscous) or, more precisely, variation in friction related effects.
More
specifically, and without describing a myriad of escapements, sources of frictional and other errors include:
1. Friction as the escapement drives (impulses)
the pendulum.
2. Friction as the
pendulum releases (unlocks) the escapement.
3. Variation in driving torque – particularly in spring driven clocks.
4. Imprecision and friction variation in the gears driving the escapement
and clock hands.
5. In the case
of public clocks, external forces, such as wind rain and snow, acting on the hands.
The nearest 'relative' of the SeeSaw Gravity Escapement (SGE)2, is the delightfully named Double Three Legged Gravity Escapement (DTLGE), invented by Edmund,
First Baron Grimthorpe, in about 1854, and used in the Great Clock of Westminster (Big Ben). Big Ben was considered more accurate
than similar clocks of the period (probably because of the DTLGE). The original specification required an accuracy of
one second per day. To put things into perspective, observatory clocks of the period, were about 20 times better, or within
about 0.05 seconds per day. Most of these had a one second pendulum and, for whatever reason, that seems to be a sort of optimum.
Gravity-type escapements largely obviate variation in pendular
impulse caused by 3 – 5 above. However, two problems remain: Firstly, the pendulum unlocks the escapement, and any variation
in unlocking friction affects timekeeping. Secondly, the impulse arms, which act on the pendulum, are pivoted; again, variation
in friction affects timekeeping. The problem of unlocking friction was solved by Jim Arnfield, in 1987, using his Inertially
Detached Gravity Escapement. As far as I know, the problem of friction associated with the impulse arms remained unsolved.
Basic
Ideas
Before describing the SGE concept model,
it will be useful to discuss the four basic ideas on which it is based:
Energy interchange
Figures 1a - d show a simplified pendulum (blue), pivoted at two points A
and B (yellow), and having LH and RH arms located at the pivot region. Towards the end of each arm is a weight (pink). The
weights straddle the arms (blue), and can periodically rest on weight supports (green), at each side of the arms. When the
pendulum rod is vertical, the top surfaces of the arms are just below the weight supports. Hence, the weights just rest on
the weight supports.
Imagine that the pendulum is
caused to swing to the left (Figure 1c). The amplitude of the swing is exaggerated for clarity, and the weights do not slide
down the arms. The LH arm raises its weight clear of the weight support. The pendulum reaches its extreme left position and
begins to swing to the right. As it does so it lowers the weight back on to the weight support, and the arm continues to lower.
A similar action occurs to the weight on the RH side (Figure 1d).
Neglecting
acceleration and retardation, the amount of energy abstracted from the pendulum, as it raises a weight, is exactly the same
that the weight delivers to the pendulum, as the weight is lowered back to its original position. But there is also energy
interchange as the pendulum accelerates and retards the weight. However, over the cycle of raising and lowering the weight,
the net affect on the pendulum is zero. In addition, there is a small loss of energy as the weights impact the weight supports
and pendulum arms (similar to that in the DTLGE). So, the pendulum continues to oscillate (at least for some time). The weights
add inertia to the pendulum, so that the cyclic period will be a little longer than the pendulum without the weights. However,
since the mass of the weights is constant, and if the pendulum's amplitude is constant, the periodic time will also be
constant.
A similar energy interchange occurs in
the DTLGE and other escapements. The important difference is that, in the SGE, there are no frictional losses. More specifically,
no sliding occurs between the weights, arms and weight supports. However, friction at the pendulum pivot/suspension remains,
but this is common to all pendulum clocks, and is just one of the energy losses to be 'made up' by the escapement.
Impulse and reset
In order for the pendulum to continue to oscillate, the escapement must make up the losses, that is, impulse the pendulum.
Imagine that after the weights are lifted clear of the weight supports by the arms, the weight supports are lowered a little.
Hence, when the arms lower the weights back to the weight supports, the weights will have moved a greater distance downwards
than upwards. The difference between these two distances, together with the value of each weight, impulses the pendulum.
When
an arm is below a weight, that is, with the weight resting on a weight support, the weight support and hence weight needs
to be raised (reset), ready for the next cycle. In this way, the pendulum will be 'unaware' that the weights have
been reset. Lowering and
resetting the weights, at just the right time, is the job of the escapement. Paradoxically, the pendulum needs to control
the escapement, but must be oblivious to the escapement's existence! The key mechanism of the SGE that does this is called
'the prop'.
 The prop
Figures 2a & b
show a simplified prop and weight support assembly. The upper vertical arm of the prop supports a pivoted weight support,
on top of which is a weight. Incidentally, the horizontal arm of the prop is used to lock and unlock the escape wheel, and
the lower arm is used to reset the prop (to be explained later). The prop is biased to turn clockwise by a counterweight.
With the weight in position on the
weight support, there is sufficient frictional resistance between the end of the prop and underside of the weight support
to prevent the prop from turning clockwise. As soon as the weight is lifted clear of the weight support, the resistive force
is reduced, and the prop pivots clockwise against a stop (Figure 2b). The weight support lowers, and is constrained by a stop.
It will be appreciated that
as the weight is lifted, the weight, and weight support, move in opposite directions. In fact, the weight is quite oblivious
to the fact that the prop and weight support have moved. If the weight is replaced on the weight support, resetting the prop anticlockwise raises the weight
support and weight thereon. Because of the weight, there is again sufficient frictional resistance to retain the prop in the
vertical position.
The weight, in this
description of the prop, corresponds to the weights shown in Figures 1a - d. Hence, the pendulum is also quite oblivious to
the fact that the escape wheel has been unlocked. In fact, the SGE has two props, each controlling its own impulse weight.
Escape wheel assembly The escape wheel assembly ensures that all the various actions described above occur in the correct order. It
is similar to the escape wheel assembly of the DTLGE, since it consists of two 'three legged' escape wheels mounted
either side of three resetting rollers (to be described in detail later).
Concept Model
The
description that follows is of my proof-of-concept model3. I emphasize that the methods and
materials used are not necessarily those recommended for use in a 'real clock'. I chose the simplest, cheapest, quickest
ways to explore the validity of the invention, without regard for optimization or longevity. Nevertheless, to give the escapement
the best chance of working, ball bearings were used in 'important places'. I have used simplified drawings in this
description for clarity.
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| Escapement - 3a front view (front plate omitted for clarity), 3b side view. |
Parts Figures 3a – 8c show a SGE in which impulse occurs twice during each complete cycle
of the pendulum. Figures 9 – 14 are photographs of the proof-of-concept model.
The components of the mechanism are mounted on and between front and back plates. The pendulum
assembly is shown pivoting on knife-edges (in the actual concept model pointed screws were used for simplicity and adjustment).
The escapement was tested with 1 second (0.994m long) and 0.68 second (0.462m long) pendulums (time of swing in one direction).
Extending each side of the pendulum are LH and RH arms.
 Sharing the same pivotal axis as the pendulum are
LH and RH weight supports (Figures 4a – 5b, and Figure 12). The weight supports
are provided with Vee notches in which periodically rest the LH and RH weights (Figure 13).
Each weight is provided with an inverted Vee notch, and these locate on the pendulum arms. The flanks of the inverted Vees
are slightly convex so the weights are self-aligning to allow for any slight misalignment in the aforementioned Vees.
As the pendulum oscillates, the weights are alternately
lifted from the weight supports and then replaced, as described above (Energy interchange). The weight supports are fitted
with counterweights so that the distal ends are biased gently downwards. Fitted to the underside of the weight supports are
'flat' cams.
 The LH and RH props act on the cams to raise
or lower the weight supports (Figures 6a – 7b). Adjustable stops restrict the
movement of the weight supports and the props.
The upper ends of the props terminate in rollers, which incorporate
one-way ball bearing clutches (MF-CB-10, modelfixings.co.uk). The clutches are arranged so that as the upper ends of the props
move towards the centre of the mechanism, the rollers are free to roll against the cams. Conversely, as the ends of the props
move away from the centre, the rollers are prevented from rolling against the cams. Hence, the frictional resistance between
rollers and cams is greatly increased in the outward direction. The escapement may work without one-way clutches (Figures 2a and b), but more force would be needed to reset the impulse weights.
Fitted to the props are locking arms. The ends of the locking arms terminate in ball bearings (SMR83ZZ EZ0, SMB Bearings
Ltd), which act against the teeth of the escape wheel. Extending downwards from the props are reset levers. On the opposite
side to the locking arms are adjustable counterweights. These lightly bias the LH and RH props anticlockwise and clockwise
respectively.
 Below the prop assemblies, is the escape wheel assembly
(Figures 8a – c, and Figure 14). This comprises a rear escape wheel with three
teeth, and a front escape wheel, also with three teeth. Interposed between the two escape wheels are three ball bearing resetting
rollers (S604ZZ EZ0, SMB Bearings Ltd), which act on the reset levers. Mounted on the shaft of the escape wheel assembly is
a gear, which is driven by a drive means (not shown). In the actual concept model the gear was replaced by a pulley, which
is driven via a line and weights. In an actual clock, the shaft would be fitted with a seconds indicating hand. Further hands,
indicating minutes and hours, would be incorporated into the drive means (not shown). The shafts of the prop assemblies and
escape wheel assembly are supported on ball bearings (S604ZZ EZ0, SMB Bearings Ltd).
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| Figure 9. Front view |
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| Figure 10. Rear view |
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| Figure 11. Side view |
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| Figure 12. Top view |
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| Figure 13. Close up of weight and weight support |
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| Figure 14. Close up of escape wheel and prop assembly |
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Materials
As
I explained at the beginning of this section, the methods and materials used in my concept model are not necessarily those
recommended for use in a 'real clock'.
The fame of the escapement is made of wood. This is not as
silly as it sounds – John Harrison, probably the world's most famous clockmaker ever, began his working life as
a joiner. His early clock mechanisms were made of wood, and several remain working after nearly 300 years!
The
plates are made from 9.5mm thick, 7 ply, birch plywood. The traditional material is of course brass, but for a concept model
brass was considered far to expensive. In any case, I am not a great fan of brass in 21st century clocks, and prefer anodized
aluminium or stainless steel. Alternatively, carbon fibre plates may be considered for thermal stability and visual interest.
The plates are spaced apart with pillars made of beech, and the blocks holding the adjustable stops are also beech. The whole
frame is held together with TurboUltra stainless steel wood screws (ScrewFix Ltd). The frame was given a coat of Osmo TopOil
(Sykes Timber Ltd), to seal the grain and stop it getting too grubby. Of course, in a 'real clock', these aspects
would be 'sympathetic' to the material of the plates.
The pendulum pivots each comprise two TurboUltra wood screws,
the pointed end of the upper screw pivoting in the cross head of its partner below. I am not suggesting this as an alternative
to proper knife-edge pivots – it certainly is not. However, it is quick, cheap and adjustable, and ideal for the concept
model. For 'a proper' knife-edge suspension, I would turn to Riefler astronomical clocks of the early 20th century
for inspiration.
The adjustable stops were also made from wood screws. Ideally, in a 'real
clock', adjustable stops should be avoided since they can result in dimensional instability. Furthermore, to minimize
wear, the stops may be jeweled.
The pendulum arms were made from aluminium tube (which I happened
to have). A better material would be carbon fibre tube; its very low coefficient of thermal expansion being more in keeping
with a precision, temperature compensated, pendulum. The weights were made of brass, but stainless steel would be better to avoid
oxidation.
The weight supports were made from 1mm thick aluminium and skeletonised for lightness. Carbon
fibre might be a better alternative since it is light, strong, and thermally stable. I confess to not having bushed the weight
supports. In a 'real clock' these would have brass or bronze bushes, or be jeweled.
The
props were made from beech for lightness, and the locking arms from grey PVC, again, for lightness. I decided against wood
for the locking arms in case the delicate regions by the rollers split off. The reset levers were made from aluminium alloy.
The prop parts were held together on polyacetal hubs. Again, carbon fibre components may be incorporated for thermal stability,
strength and lightness.
The shafts were made from silver steel, but stainless steel is preferred.
The
escape wheels were made from aluminium alloy, but titanium is preferred.
Adjusting the escapement With
the pendulum rod vertical and still, and the weight supports in the up position, the top surfaces of the arms were arranged
to be below the weights by half the impulse distance. Hence, when the pendulum swings past the vertical, the arms lift the
weights. The weight support stops were adjusted, so that with the weight supports in the down position, the pendulum arms
lifted the weights clear of the weight supports, again, by half the impulse distance (the full impulse distance being about
0.5 to 1.0mm). In other words, impulse is symmetrical about the pendulum's vertical position. This satisfies what is known
as 'Airy's Condition'. Sir George Biddel Airy was an English 19th century mathematician and Astronomer Royal.
He showed that this condition negates escapement error. A further implication is that this minimizes timing deviation due
to changes in impulse. Of course, the whole idea of the SGE is that the impulse does not change. Nevertheless, as an added
precaution, the escapement may be set to satisfy Airy's Condition.
It will be appreciated that as a pendulum arm lifts its weight
clear of a weight support, the other arm lowers its weight onto its weight support. This weight support is then reset, to
its original height, as the escape wheel indexes, and the resetting roller turns the reset lever. However, there is always
a slight delay before the prop resets the weight support and weight thereon. This occurs as the prop turns and the unlocking
roller rides up the escape wheel tooth. Further delay occurs due to clearance between the reset roller and reset lever. Hence,
the pendulum arm is below the weight (has released the weight), before the weight support raises the weight. So the pendulum
is quite oblivious to the fact that the weight has been raised (reset). Alternatively, the weight support stops may be set
just a little higher (say 0.1mm), than the optimum Airy requirement. This further ensures that resetting only begins when
the pendulum arms are below the weights.
The weight supports are fitted with counterweights. These are
adjusted so that, with the weights lifted clear of the weight supports, and with the props in the lower position, the distal
ends of the weight supports lower against the stops. The pivotal action must be reliable, but not too forceful, since excess
force interferers with the unlocking action of the props.
The prop counterweights are adjusted so that, with a weight
resting on a weight support, there is insufficient torque on the prop to overcome the frictional resistance between the roller
clutch and cam of the weight support, to allow the ball bearing roller of the locking arm, to roll off a tooth of an escape
wheel. It will be realized that in this condition, the frictional resistance between roller clutches and cams is greatly increased
because the roller clutches cannot turn. Hence, the escape wheel remains locked. Conversely, when
a weight is lifted clear of its weight support, the frictional resistance between the roller clutch and cam is reduced. The
torque applied to the prop, via its counterweight, is then sufficient to cause the prop to pivot. Hence, the roller of the
locking arm rolls up the flank of an escape wheel tooth, allowing the tooth to 'escape', and the escape wheel assembly
to index. It will be appreciated that during 'unlocking', the periphery of roller clutch does not roll, but slides
against the cam. However, as mentioned earlier, without the weight in place, the force between cam and roller is minimal.
The torque provided to drive the escape wheel must be sufficient to reliably index the escape wheel once within half the cycle
time of the pendulum, but not enough to prevent the roller of the locking arm from unlocking the escape wheel.
Operating sequence (first impulse
mode) Figures
15a – d show the operating sequence of the SGE in which the pendulum is impulsed first in one direction and then
the other.  The oscillation is begun by displacing and releasing
the pendulum manually. The oscillation then continues as long as the drive means in active. Figure
15a shows the pendulum swinging to the right from the centre position. As soon as the arm of the pendulum begins to
lift the RH weight, the frictional resistance between the roller and cam of the weight support is reduced, and the prop pivots
clockwise against its stop. The RH weight support lowers and is restrained by its stop. Meanwhile, the weight continues to
be lifted by the arm of the pendulum. It will be appreciated that as the weight is lifted clear of the weight support,
the weight and weight support begin to move in opposite directions as described above (Prop). Hence, any friction at the weight
support pivot, or the weight of the weight support itself, has no affect whatever on the pendulum. Furthermore, the
action of lifting the weights out of the Vees of the weight supports does not involve sliding or rolling friction, so this
action also has no affect whatever on the pendulum. There is no need to provide lubrication between the arms, weights, and
weight support. Indeed, this is highly undesirable since it would have an adverse affect on the timekeeping, due to the variability
of viscous and surface tension forces.
Concurrent with prop pivoting clockwise, the distal end of
the locking arm lifts, causing the escape wheel assembly to unlock and index clockwise. The LH resetting roller of the escape
wheel assembly turns the LH resetting arm clockwise. This causes the LH prop to become vertical, and the locking arm to lower,
thus locking the escape wheel. Also, the LH prop raises its weight support and weight thereon. It will be appreciated that
when this happens the LH pendulum arm is lower than the weight. Hence, raising the LH weight has no affect whatever on the
pendulum, as described above (Adjusting the escapement). At this stage in the sequence, the positions of the components are
shown in Figure 15b.
Meanwhile, the pendulum continues to swing to the right. After
reaching its maximum amplitude, it begins to swing left. The distal end of RH pendulum arm lowers and places its weight in
the Vees of its weight support. As the pendulum continues to swing left, the pendulum arm continues to lower.
The
difference between the height, when RH arm begins to lift weight from the weight support, and the height when it replaces
the weight back onto the weight support (now in the low position), provides the impulse to the pendulum for the first half
of its cycle, as described above (Impulse and reset). The impulse for the second half of the cycle is provided by the LH weight.
The pendulum continues to swing left so that the pendulum arm lifts the LH weight clear of its
weight support. The frictional resistance between roller and cam of the weight support is reduced, and the prop pivots anticlockwise
against its stop. The weight support is now in the low position - supported by its stop, and is ready to allow the LH weight
to impulse the pendulum for the other half of the cycle. Concurrently, the escape wheel is unlocked and the RH resetting roller
of the escape wheel assembly turns the RH resetting arm anticlockwise to raise the RH prop to the vertical position which,
in turn, raises weight support and weight thereon. At this stage in the sequence, the positions of the components are shown
in Figure 15c.
The pendulum continues to swing left until it reaches the extremity
of its swing, and then it begins to swing right. As the pendulum reaches the centre position, it will be noted that Figures 15a and 15d are identical (except that the escape wheel has indexed). In other words,
the pendulum has completed one oscillatory cycle. The escape wheel continues to index as the pendulum continues to swing,
and all the other components move cyclically according to the aforementioned sequence.
The concept model of the SGE can be seen working on YouTube.
Alternative
impulse modes
In the above example, the SGE provides impulse
at every swing of the pendulum, that is, first in one direction and then the other (first impulse mode). This is by far the
most common mode of impulsing used by escapements. A second mode of impulsing involves impulsing the oscillator (pendulum
or spring balance), in one direction only. The most well know example of this type is the marine chronometer escapement and
the lesser-known pendulum version. A third mode of impulsing involves impulsing the pendulum after it has made a predetermined
number of oscillations. The most well known example is the escapement used in the Synchronome clock. A fourth mode of impulsing
involves impulsing on demand so that, as the pendulum's amplitude drops below a certain value, it is automatically impulsed.
The most well know example involves the ingenuous mechanism know as Hipp's toggle. It is beyond the remit of this article
to discuss the merits and uses of these various forms of impulsing. They are mentioned simply as precedence for adapting the
SGE to work in additional impulse modes.
The SGE may be adapted to work in the second and
third of these impulse modes and these will be described next. Adapting the SGE to work in the fourth mode: 'impulse on
demand', is a challenge for the future!
Second impulse mode Figure 16 is a front view of a SGE in which the pendulum is impulsed in one direction only.
 The construction is virtually identical to that shown
is Figures 3a – 8c. However, the LH flat cam is replaced by a concave cam, and
the LH weight support stop is no longer needed. The radius of cam is struck from the pivotal centre of the LH prop assembly.
Hence, as the prop pivots, it supports the weight support, but the weight support does not move up or down. Furthermore, the
length of the cam, and the prop assembly stops, constrain the roller to move within the radiused surface of the cam.
Oscillation is begun by manually displacing and releasing the
pendulum, in the normal way. The LH Prop and its coacting components continue to lock and unlock the escape wheel as described
previously. However, because of the radiused cam, the LH weight support does not move up and down, and the LH weight does
not impulse the pendulum. The RH prop, and its coacting components, lock and unlock the escape wheel, and impulse the pendulum,
as described previously. Hence, the pendulum is impulsed in one direction only.
Third impulse
mode
Figures 17a and b are front and side views of a SGE, where the
impulse occurs once for every complete cycle of the escape wheel.
 The construction is similar to Figures 3a – 8c and Figure 16, but with the following differences:
The RH flat cam is replaced by concave cam, and the RH
prop stop is no longer needed. The radius of the cam is struck from the pivotal centre of the RH prop assembly. Hence, when
roller acts within the radius of the cam, it supports the RH weight support but does not cause it to move up or down. However,
the length of the RH cam is shorter than the LH cam and, as the RH prop pivots fully clockwise, its roller exits the edge
of the cam causing the RH weight support to lower, and be constrained by its stop. The RH reset lever is replaced by bent
reset lever. The bend gives clearance to the resetting rollers of the escape wheel assembly, prior to their resetting action.
The pivotal shaft of the RH prop assembly extends though the front plate and on it is fixed an
impulse control lever (Figure 17b). The distal end of this lever terminates in a ball
bearing roller. The roller acts on an impulse control cam, which is mounted on the shaft of the escape wheel assembly. The
control cam has major and minor peripheral regions. In this example, which provides a pendular impulse once per revolution
of the escape wheel, the minor diameter encompasses teeth 1 and 6, relative to the escape wheels. For two impulses per revolution
of the escape wheel, the minor diameter would be extended to encompass teeth 3 to 6. For less frequent impulsing than once
every revolution of the escape wheel, the control cam, with an appropriate form, would be driven via the escape wheel shaft,
but at a slower speed.
When the RH prop pivots clockwise, as the RH weight is lifted clear of weight
support, and roller of the impulse control lever coacts with the major diameter of the control cam, the prop roller is constrained
to remain within the confines of the radius region of the RH weight support cam. Hence, the weight remains at the same height,
and no impulse is imparted to the pendulum by the RH weight. However, when the roller of the impulse control lever coacts
with minor diameter of the control cam, the roller of the RH prop exits the edge of the cam, causing the RH weight support
to lower. Hence, impulse is imparted to the pendulum by the RH weight (as described in modes 1 and 2). As the escape wheel
assembly continues to index, the control cam controls when impulse occurs. In this example, it is once every complete turn
of the escape wheel, or every sixth swing of the pendulum.
Discussion
The concept model of the SGE, in which the pendulum
is impulsed in both directions, has been tested. Frankly, because of its departure from convention, I was surprised it worked
at all! But, work it does. Furthermore, it is robust, and can handle a wide range of periodic times and pendulum amplitudes,
ranging from a fraction of a degree to several degrees.
What of its limitations: Like its nearest relative the DTLGE,
and particularly if weight driven, the SGE needs a higher gear ratio between the driving weight/s and the escapement, than
conventional escapements. This, together with greater inertia of the moving parts, means that the mechanical efficiency will
be lower. However, similar clocks were made successfully in the mid 19th century ('Big Ben' being the prime example).
These days, high precision gears, and the use of ball bearings, make light work of high gear ratios.
Like
the DTLGE, the tick of the SGE is louder than conventional escapements. It is thought that the strategic use of resilient
materials, and/or damping elements, will reduce the noise of the tick to an acceptable level, which is particularly important
for domestic or 'boardroom' clocks.
As I mentioned earlier, no attempt was made to optimization
the concept model or seek longevity at this stage. I have already alluded to some possible improvements, particularly regarding
the materials used. These relate mainly to the thermal stability and wear of the SGE mechanism itself. In this respect, I
do not know if the SGE is potentially better or worse than other escapements. At least in the SGE it is easy to see how components
affect the stability of impulse, and to design and choose materials accordingly.
The
question is: will the SGE be a good timekeeper, and will it be reliable? In theory, it should be – but that's hardly
an answer! The only way to test the escapement is to build it into a precision clock. The most important component of such
a clock is the pendulum. I see no reason to break with tradition and not use a one second pendulum - but what sort of pendulum?
Should it be a simple, compound, or Schuler-type; and what of temperature and barometric compensation? Then there is the question
of which mode of impulse is best?
But, traditionally, clock makers have never confined themselves
to purely functional aspects. Reifler precision clocks of the early 20th century were beautifully elegant with their etched
glass cases, nickel plated columns, and maple back boards. These days', mechanical clocks are not built primarily for
timekeeping accuracy; quartz clocks and atomic clocks are far superior in that respect. My own interest in designing and making
contemporary mechanical clocks lies in the way the technology and aesthetics may be combined to enhance visual interest. So,
if a clock has a particularly interesting mechanism or pendulum, then these become important aesthetic features. But that
is not as easy as it sounds because a precision clock needs to indicate the time clearly, and making a feature of the mechanism
must not distract from that.
These are challenges for the future - which will not be solved
'overnight'.
Conclusion
The feasibility of the SGE has been demonstrated using
a concept model. In addition, alternative modes of impulse have been considered and appear possible. However, further work
is needed to examine the performance of the SGE in a complete clock. Only then will the utility, or otherwise, of the SGE
be established.
1. The SGE is the
subject of a recent patent application.
3.
General arrangement drawings can be found on: 4. The concept model of the SGE can be seen working on: YouTube.
Copyright (c) 2010 Roger Bunce
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