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Mechanical clocks (and watches) all work in the same basic way.
There is an oscillator (a pendulum or a hairspring) which has a
constant natural frequency and will swing steadily until friction stops
it. Then there is the pallet, which does a double job: it is rocked to
and fro by the oscillator
and, as it does so, allows the toothed escape
wheel to turn one "click" at each oscillation; and, because the escape
wheel is being driven by a spring (or weight on a pulley), the escape
wheel nudges the pallet as it "clicks", which in turn gives the
hairspring or pendulum the nudge it needs to keep oscillating.
This is a very clever and ingenious arrangement, in which the driving
source is regulated by the natural period of the oscillator, and the
oscillator reciprocally is driven by the driving source.
None of these clever features apply to the MacTime Bouncing Ball
escapement, but I thought to hell with it.
So.
The Bouncng Ball Escapement Clock is driven (like a regular clock) by
a heavy spring which is wound up. The pallets consist of a long see-
saw-like structure (maybe 2-20feet across, depending on the desired
effect), pivoted in the middle and with a large flat, horizontal
paddle at either end. Underneath the pallets sits the escape wheel
which, by means of the usual arrangment, is driven by the
mainspring but is allowed to turn only one step for each time the
pallet rocks, see-saw-like, to and fro.
The pallet, and the profile of the teeth on the escape wheel, are
cunningly designed (but not, in fact, very different from those in a
conventional escapement). When one end of the see-saw-like pallet
is pressed down, the escape wheel is released and, as it moves
forward one "click", it vigorously pushes that end of the pallet back
up. The same process happens reciprocally at the other end of the
pallet.
We now add the key component: a steel ball-bearing. This ball
bearing will be tossed from one end of the pallet to the other,
performing the necessary functions of pressing down one end of the
pallet and, in turn, being thrown in an arc to land at the opposite
end, where the process repeats.
If all of this has failed to make any sense, I can only suggest the
mental image of a sort of clockwork juggler with only one ball,
acting as the regulator of a clock.
This clock will be infuriatingly inaccurate, because the thrown ball
has no "natural" frequency of its own. Instead, the rate of the clock
will depend largely on the height of the arc of the ball, which will in
turn depend on how recently the mainspring has been wound. This
could be partially circumvented either by using a fusee to regulate
the driving power of the mainspring or, more effectively, by using
weights to drive the clock (a la grandfather clock).
It will be appreciated that a more elaborate version of this clock
could, in actual fact, juggle three (or more) balls in non-intersecting
arcs, using several sets of interconnected pallets.
Although such a clock might well be wildly inaccurate, it would be
incredibly irritating.
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Is this like a Congeve escapement? |
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[+] and your mainspring problem isn't one: don't connect it directly to the paddle, have it arm a dedicated paddle spring, otherwise not only do you have a 'second" that varies but you couldn't wind the mainspring up more than the force of the bouncing ball... and it's about 4' high arc. |
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//Is this like a Congeve escapement?// |
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Yes, except that it's different in two respects. The Congreve
escapement uses rolling balls, and would probably work. |
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[FT] I think I follow - good idea! |
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//juggle three (or more) balls in non-intersecting arcs, using several sets of interconnected pallets// only one pallet required shirley, if the left hand end bats harder than the right? |
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a one second arc is roughly 4' high... I'm surprised 8/7 hasn't signed in on the inevitable cat<>ball-bearing interface yet. |
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The clock would be more accurate (I think) if the action was to bounce a ping-pong ball against the floor, or against the wall. With each release of energy from the escapement wheel, the table tennis bat gaffer-taped to the end of the pallet imparts a little extra energy to the ball. An additional feature of this approach is that two clocks can be made to keep perfect time with each other by setting them up to play table tennis against each other. |
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The interclock synchronisation aspect is interesting. In
fact, with a sufficiently dense network of clocks, this
could replace the Rugby time-signal system. |
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However, I'm not convinced about your proposal for
increasing the accuracy. Whether the ball travels in an arc
or on a rebound, its frequency will depend heavily on the
amount of energy-boost which its given at each bounce. I
think [FT]'s suggestion of arming springs (which will deliver
a constant impulse for as long as enough arming energy is
available) is the better. |
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[Ian] I thought the epitrochoid was one of those
cartilaginous bones in the throat? |
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A higher boucing ball goes further, up & horizontally. So compensate for higher bouncing, and going further, by making the ball fall less. Cunningly, the time of flight will be the same. |
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// cat<>ball-bearing interface // |
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Yes, well, we had to go and do a practical test before we annotated the idea ... |
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Anyway, the ball will be affected by changes in gravity (tidal changes) which are significant. |
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We like the idea of cat heads, plastinated and then embedded in spheres of acrylic or clear PVC, bouncing through the air ... [+] |
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//with a sufficiently dense network of clocks, this could replace the Rugby time-signal system// Or, long-range ballistic clocks. A long-range clock could use, as its escapement, a pair of repeating field guns a mile or two apart, each beside a large target. The near gun would fire; the shell would arc a mile or so though the air, and land on the distant target. This would trigger the far gun to fire, its shell arcing through the air to land on the near target. This would trigger both an advance in the escape wheel, and the firing of the next shell from the near gun. |
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The noise of the guns would allow anyone within a 10 or 20 mile radius to hear the clock ticking. Perhaps a 21-gun-salute could be triggered on the hour, or some kind of anti-aircraft round or (at night) a magnesium flare could be fired high into the sky. |
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Tidal changes could be compensated for by having the weight of the throwing arm similar to the weight of the ball (I think). And given a vacuum or an enclosure with still air this could be made fairly accurate, there are multiple ways to produce a constant force out from a given spring, pulling down with a ratchet mechanism against a secondary spring as mentioned is probably the best. |
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pocmloc - I am amazed and impressed, and will berate my
own development team for not having thought of this. |
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Hippo, ling et al: I don't think either of your schemes
(unless I misunderhend them) will help. The basic
problem is that, if the impulse given to the ball depends
on the degree of winding left in the mainspring, then the
timing will vary. If the ball travels in an arc, then more
impulse=slower rate. If the ball rebounds from a wall,
then more impulse=faster rate. I don't see a way around
that, other than the alternative proposed ( but now
seemingly edited away) by FT. |
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umm what ?.... I've sorta moved on to paddle-ball-on-a-string and yoyo variants but I may have cut too deep editing the 3rd from the top anno: err, basically "keep the mainspring tension from affecting the period in the same manner as in other clock designs with mainsprings". |
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FT, I think your original anno was suggesting having little
"flipper" springs which were "armed" by the mainspring; this
would work, since the "flip" would be of constant strength as
long as the mainspring had enough force to arm them. |
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whoops yes, indeed though I think somebody else may have expanded on it... but I think that's how clocks generally work... as long as there's enough oomph in the storage mechanism to arm the escapement, you're all set. I imagine the mechanism would have a fine-tuning knob to account for air-density and manufacturing vagaries. |
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//I think that's how clocks generally work// Well, not really.
In regular clocks, the period is set by either a balance wheel
and hairspring, or by a pendulum. In either case, it has a
natural frequency which does not vary (much) with the
amount of "push" (ie, a balance wheel or a pendulum will
swing back and forth at the same rate regardless of whether
it's a small to-and-fro or a large one). The power train serves
only to nudge the balance wheel or pendulum to keep it
going. That's the beauty of these systems. |
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okay, so the mainspring powers two functions: the UI and the topping-up the period mechanics... so: |
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The ball hits the paddle which triggers the UI *tick*: the paddle itself doesn't power the hands movement because then the clock would be slower at 8:44:45 than it would be at 3:15:15. |
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When the ball is in its most compressed state (immediately after the UI trigger trip), the topping-up mechanism is triggered which adds enough energy to the ball to let it make another complete cycle in one second |
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The UI trigger is rearmed by the paddle returning to it's original position (via a very weak spring or balance weight) |
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But we have to repower the topping-up mechanism somehow. |
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I am kicking myself for not using the word "trebuchet" before
now.. |
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//Can a ball be made into a three dimensional epitrochoid?//
I'm not sure, but with correcct application of heat and pressure, maybe a kitten could. |
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I was just about to repost this... |
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Hmm, how did I come up with 4' for a one second arc ? (should be 8', yes ?) |
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