. Watch and clock escapements; . than we might at first thought have imagined,consequenty, we shall dwell upon it at some length. HOW TO SET THE DISCHARGING JEWEL. Theoretically, the escape-wheel tooth should encounter theimpulse jewel at the time—instant—both are moving with the samevelocity. It is evident then that there can be no special rule givenfor this, i. e., how to set the discharging jewel so it will free thetooth at exactly the proper instant, from the fact that one chro-nometer train may be much slower in getting to move forward fromsaid train being heavy and clumsy in construction
. Watch and clock escapements; . than we might at first thought have imagined,consequenty, we shall dwell upon it at some length. HOW TO SET THE DISCHARGING JEWEL. Theoretically, the escape-wheel tooth should encounter theimpulse jewel at the time—instant—both are moving with the samevelocity. It is evident then that there can be no special rule givenfor this, i. e., how to set the discharging jewel so it will free thetooth at exactly the proper instant, from the fact that one chro-nometer train may be much slower in getting to move forward fromsaid train being heavy and clumsy in construction. Let us make anexperiment with a real chronometer in illustration of our do so we remove our balance spring and place the balance The Chronometer Escapement. 143 in position. If we start the balance revolving in tne directionof the arrow y, Fig. 140, it will cause the escapement to beunlocked and the balance to turn rapidly in one direction andwith increasing velocity until, in fact, the escape wheel has but very. little effect on the impulse jewel ; in fact, we could, by applyingsome outside source of power—like blowing with a blow pipe onthe balance—cause the impulse jewel to pass in advance of theescape wheel; that is, the escape-wheel tooth would not be able tocatch the impulse jewel during the entire impulse arc. Let us sup-pose, now, we set our unlocking or discharging jewel in advance, 144 Watch and Clock Escapements. that is, so the escapement is really unlocked a little before thesetting parts are in the positions and relations shown in Fig. the new conditions the escape wheel would commence tomove and get sufficient velocity on it to act on the impulse jewel assoon as it was inside of the periphery of the escape wheel. If thebalance was turned slowly now the tooth of the escape wheel wouldnot encounter the impulse jewel at all, but fall into the passinghollow n ; but if we give the balance a high velocity, the toothwould again encounter a
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