Part 13 (2/2)

131 It will now be seen that the angular extent is 196 degrees If we draw the line _e can see in what proportion the measurement should be made between the outer diameter of the cylinder and the measure of the half shell It will be seen on measurement that the distance between the center _e_ and the line _w_ is about one-fifteenth part of the outer diameter of the cylinder and consequently with a cylinder which measures 45/1000 of an inch in diameter, now the half shell should measure half of the entire diameter of the cylinder plus one-fifteenth part of such diameter, or 25 thousandths of an inch

After these proportions are understood and the drawingpretty near what is required; but much the safer plan is toso Most workmen have an idea that the depth or distance at which the cylinder is set from the escape wheel is a matter of adjustment; while this is true to a certain extent, still there is really only one position for the center of the cylinder, and that is so that the center of the pivot hole coincides exactly with the center of the chord to the curve of the i 130 Any adjuste the depth could only be de in the cylinder or where it had been enius as an experi the drawing at Fig 131 that when the cylinder is perfor an arc of vibration, as soon as the entrance lip has passed the point indicated by the radial line _e x_ the point of the escape-wheel tooth will coh an arc of forty degrees, or from the lines _x_ to _l_

MAKING A WORKING MODEL

To practically study the action of the cylinder escape model It is not necessary that such a model should contain an entire escape wheel; all that is really required is two teeth cut out of brass of the proper forms and proportions and attached to the end of an ar with studs riveted to the U ar ar of heavy sheet brass is shaped to represent a short transverse section of a cylinder This seg such a model we can eer drawings reat service in learning the i the lips of the cylinder And right here we beg to call attention to the fact that in the ordinary repair shop the proper shape of cylinder lips is entirely neglected

PROPER SHAPE OF CYLINDER LIPS

The workman buys a cylinder and whether the proper amount is cut away from the half shell, or the lips, the correct fornored, and still careful attention to the form of the cylinder lips adds full ten per cent to the efficiency of thestudy drawings of the cylinder escapee that we can establish upon it the center of the arc which represents the periphery of our escape wheel, as we have at our disposal two plans by which this can be obviated First, placing a bit of bristol board on our drawing-board in which we can set one leg of our dividers or compasses eep the peripheral arc which we use in our delineations; second,three arcs in brass or other sheet metal, viz: the periphery of the escape wheel, the arc passing through the center of the chord of the arc of the ih the point of the escape-wheel tooth Of these plans we favor the one of sticking a bit of cardboard on the drawing board outside of the paper on which we are132]

At Fig 132 we show the position and relation of the several parts just as the tooth passes into the shell of the cylinder, leaving the lip of the cylinder just as the tooth parted with it The half shell of the cylinder as shown occupies 196 degrees or the larger arc e the entrance lip the acting face is made almost identical with a radial line except to round the corners for about one-third the thickness of the cylinder shell No portion, however, of the lip can be considered as a straight line, but ht be described as a flattened curve

[Illustration: Fig 133]

A little study of ould be required to get the best results afterat the proper shape, especially when he remembers that the thickness of the cylinder shell of a twelve-line watch is only about five one-thousandths of an inch But because the parts are s the most we possibly can out of a cylinder watch

The extent of arc between the radial lines _k f_, as shown in Fig 132, is four degrees Although in forrees, as we show the lip _ The space _k f_ on the egress or exit side is intended to be about four degrees, which shows the extent of lock We show at Fig 133 the tooth _D_ just having passed out of the cylinder, having parted with the exit lip _p_

In132 by establishi+ng a center for our radius of 10” outside of our drawing paper and drawing the line _A A_ to such center and sweeping the arcs _a b c_ We establish the point _e_, which represents the center of our cylinder, as before We take the space to represent the radial extent of the outside of our cylinder in our dividers and from _e_ as a center sweep a fine pencil line, represented by the dotted line _t_ in our drawing; and where this circle intersects the arc _a_ we name it the point _s_; and it is at this point the heel of our escape-wheel tooth must part with the exit lip of the cylinder Froh the point _s_ we draw the line _e l''_ With our dividers set to the radius of any convenient arc which we have divided into degrees, eep the short arc _d'_ The intersection of this arc with the line _e l''_ we name the point _u_; and from _e_ as a center we draw the radial line _e u f'_ We place the letter _f''_ in connection with this line because it (the line) bears the sa 133 that the line _f_ does to the half shell (_D_) shown in Fig

132 We draw the line _f'' f'''_, Fig 133, which divides the cylinder into two segrees each We take the same space in our dividers hich ept the interior of the cylinder in Fig 132 and sweep the circle _v_, Fig 133 Fro 133, and frorees on said arc _d''_ and draw the line _e' k''_, which defines the angular extent of our entrance lip to the half shell of the cylinder in Fig 133 We draw the full lines of the cylinder as shown

We next delineate the heel of the tooth which has just passed out of the cylinder, as shown at _D'_, Fig 133 We now have a drawing showing the position of the half shell of the cylinder just as the tooth has passed the exit lip This drawing also represents the position of the half shell of the cylinder when the tooth rests against it on the outside If we shouldof an escape-wheel tooth shaped exactly as the one shown at Fig 132 and the point of the tooth resting at _x_, ould show the position of a tooth encountering the cylinder after a tooth which has been engaged in the inside of the shell has passed out

By following the instructions now given, we can delineate a tooth in any of its relations with the cylinder shell

DELINEATING AN ESCAPE-WHEEL TOOTH WHILE IN ACTION

We will now go through the operation of delineating an escape-wheel tooth while in action The position we shall assume is the one in which the cylinder and escape-wheel tooth are in the relation of the passage of half the impulse face of the tooth into the cylinder To do this is si 133, as directed, and then proceed to delineate a tooth as in previous instances To delineate our cylinder in the position we have assumed above, we take the space between the points _e d_ in our dividers and setting one leg at _d_ establish the point _g_, to represent the center of our cylinder

If we then sweep the circle _h_ fro_ we define the inner surface of the shell of our cylinder

Strictly speaking, we have not assumed the position we stated, that is, the i half way into the cylinder To comply strictly with our statement, we divide the chord of the iht equal spaces, as shown Now as each of these spaces represent the thickness of the cylinder, if we take in our dividers four of these spaces and half of another, we have the radius of a circle passing the center of the cylinder shell Consequently, if with this space in our dividers we set the leg at _d_, we establish on the arc _b_ the point _i_ We locate the center of our cylinder when one-half of an entering tooth has passed into the cylinder If now from the new center with our dividers set at four of the spaces into which we have divided the line _e f_ we can sweep a circle representing the inner surface of the cylinder shell, and by setting our dividers to five of these spaces we can, fro the outside of the cylinder shell For all purposes of practical study the delineation we show at Fig 133 is to be preferred, because, if we carry out all the details we have described, the lines would become confused

We set our dividers at five of the spaces on the line _e f_ and fro_ as a center sweep the circle _j_, which delineates the outer surface of our cylinder shell

Let us now, as we directed in our former instructions, draw a flattened curve to represent the acting surface of the entrance lip of our cylinder as if it were in direct contact with the impulse face of the tooth To delineate the exit lip we draw fro k_, said line passing through the point of contact between the tooth and entrance lip of the cylinder Let us next continue this line on the opposite side of the point _g_, as shown at _g k'_, and we thus bisect the cylinder shell into two equal parts of 180 degrees each As we previously explained, the entire extent of the cylinder half shell is 196 degrees We now set our dividers to the radius of any convenient arc which we have divided into degrees, and fro_ as a center sweep the short arc _l l_, and fro k'_ we lay off sixteen degrees on the said arc _l_ and establish the point _n_, frorees from the same parent arc and establish the point _n'_ and _g m_ limits the extent of the exit lip of the cylinder and the arc between the lines _g k'_ and _gsurface of the cylinder shell

[Illustration: Fig 134]

To delineate the U arain, we draw the arc _a b c_ and delineate a tooth as before From the point _e_ located at the heel of the tooth we draw the radial line _e e'_ Frorees and establish the point _p_; we halve this space and draw the short radial line _p' s'_ and _p s_

Frorees and establish the point _t_, which locates the heel of the next tooth in advance of _A_ At two and a half degrees to the right of the point _t_ we locate the point _r_ and draw the short radial line _r s_ On the arc _b_ and half way between the lines _p s_ and _r s_, we establish the point _u_, and fro the curve of the U ar a cylinder escape slot of the cylinder, which is usually rees; consequently, the pillar of the cylinder will not ular extent

There is no escapes tend e of the action than the cylinder But it is necessary with the pupil to institute a careful analysis of the actions involved In writing on a subject of this kind it is extre to knohen to stop; not that there is sothe words read with attention