IN this chapter we are going to overhaul a simple p e n d u l u m clock of the lower priced domestic variety. It seems reasonable to say t h a t these clocks are one of the m o s t p o p u l a r clocks in the h o m e t o d a y .
T h e i r low price is b r o u g h t a b o u t by the high r a t e of mass p r o d u c t i o n . Large quantities are manufactured in G e r m a n y , the U n i t e d States a n d G r e a t Britain.
T h e m o v e m e n t s themselves are readily recognized. T h e plates a n d wheels are coated with lacquer a n d m a n y of the p a r t s are pressed out by m a c h i n e . Providing they a r e kept clean, oiled a n d adjusted these clocks give excellent service over long periods.
In C h a p t e r 15 we spoke a b o u t taking m o v e m e n t s from their cases a n d removing dials a n d h a n d s . Let us a s s u m e t h a t this h a s been d o n e a n d t h a t we are n o w ready to proceed with the overhaul.
First of all we need a small b u t strong c a r d b o a r d b o x on which to place the m o v e m e n t a n d so prevent the m a n y p r o t r u s i o n s from d a m a g e . Better still of course would be a h o m e - m a d e box of ply- wood cut to fit the m o v e m e n t .
N o w let the m a i n s p r i n g d o w n . If the m o v e m e n t is very old the chances are t h a t the m a i n s p r i n g will n o t be contained in a barrel in which case a m a i n s p r i n g c l a m p will h a v e to be fitted.
Place the key on the winding square a n d t u r n it in the direction of winding. This will t h r o w the ratchet click o u t which m u s t then be held in this position. Allow the tension of the spring to t u r n the key b a c k w a r d s until y o u r h a n d can go no farther. Release the ratchet click back into the ratchet a n d then you may let go of the key. R e p e a t this process until t h e spring is completely u n w o u n d .
These springs are very powerful a n d could cause personal injury to h a n d or fingers if allowed to r u n d o w n o u t of c o n t r o l . A p a r t from this, to do such a thing would m o s t probably result
in a b r o k e n spring. So take care a n d m a k e sure t h a t the m o v e m e n t is held firmly, t h a t the key will n o t slip in y o u r h a n d a n d t h a t the click can be released immediately and at any time.
R e m o v e t h e m i n u t e wheel collet, lift off the h o u r wheel a n d then remove the m i n u t e wheel.
W o r n pivots a n d pivot holes h a v e an effect on the depth of mesh between the wheels a n d their pinions a n d the locking of the escapement. H o l d each a r b o r between the finger a n d t h u m b , or stout tweezers if the a r b o r is n o t accessible, as n e a r the pivot as possible a n d check the a m o u n t of side-shake. M a k e a n o t e of any holes t h a t are considered to be in need of bushing. T h e best way of assessing w h e t h e r or n o t the side-shake is excessive is to c o m p a r e it with a m o v e m e n t of similar size t h a t has h a d little or n o wear.
Once having experienced the a m o u n t of side-shake in a new clock, subsequent inspections will prove less difficult.
Examine each a r b o r to m a k e sure it h a s e n d - s h a k e . T h e r e m u s t be sufficient clearance to prevent the shoulders of the pivots binding against the plates.
Providing there is no excessive side-shake in the pallet a r b o r pivot holes a n d the escape wheel a r b o r pivot holes we can go on to check the recoil escapement, otherwise checking the escape- m e n t m u s t wait until the worn pivot holes have been bushed.
Wind up the mainspring a few clicks, hold the m o v e m e n t in the left h a n d a n d o p e r a t e the crutch with t h e right h a n d . Examine the faces of the pallets for wear. Observe t h r o u g h an eye-glass the action of the escape wheel teeth d r o p p i n g on to the pallets a n d at the same time form an idea of the angle of swing the p e n d u l u m m u s t m a k e to release the escape wheel teeth.
It will be seen t h a t deep locking will necessitate the p e n d u l u m passing through a large angle of swing which in turn d e m a n d s m o r e power. R e m e m b e r also t h a t if the pallet fails to release an escape wheel t o o t h just once, the clock will s t o p .
If on the o t h e r h a n d the d e p t h of locking is t o o shallow mis- locking is likely to occur.
a n d the solid pallet fitted to the G a r r a r d escapement (Fig. 73, right), b o t h of which are provided w i t h m e a n s of adjusting the d e p t h .
In the case of the m o v e m e n t fitted with a strip pallet, the screw holes in the pallet cock a r e elongated a n d all t h a t h a s to be d o n e is slacken off the t w o screws, reposition the pallet cock a n d tighten the screws. It is a m a t t e r of trial a n d e r r o r b u t t h e correct position is quickly found.
Adjusting the d e p t h of a solid pallet is d o n e by altering the position of a screw on t o p of the back plate. Slacken off the t w o
Fig. 73. Recoil escapements. Strip pallet {left) and solid pallet (right). pallet cock screws, r o t a t e the adjusting screw a n d tighten the pallet cock screws. By t u r n i n g the adjusting screw in a clockwise direction the pallet cock is raised which reduces the pallet d e p t h , a n d of course, to increase the depth the screw m u s t be t u r n e d counter-clockwise.
H a v i n g checked a n d adjusted the pallet d e p t h we have ensured t h a t the escape wheel teeth will be properly locked. N o w we can examine the a m o u n t of d r o p .
T h e d r o p of an escape wheel is the distance it travels from the release of a t o o t h from one pallet to the next arrest of a tooth by the o t h e r pallet.
To check the d r o p apply the same technique as was used when checking the pallet d e p t h . In determining w h e t h e r the a m o u n t of d r o p is correct, again t h e best advice is to c o m p a r e it with a similar clock t h a t h a s had little wear. M a k e a note of the adjust-
merits t h a t are needed then r e m o v e the pallet cock a n d lift the pallet a r b o r from the m o v e m e n t .
If the pallet is the strip type all t h a t is needed is to bend the offending pallet or pallets. Bending the entry pallet o u t w a r d will decrease the d r o p on t h a t pallet, a n d b e n d i n g the exit pallet o u t w a r d will increase the d r o p on t h a t pallet.
These strip pallets are quite soft a n d can be bent cold b u t as a precaution against cracking it is advisable to h e a t t h e m first.
N o w t h a t the pallet is o u t of the m o v e m e n t this is a good o p p o r t u n i t y to deal with w o r n pallet faces. U s e a d e a d - s m o o t h file to restore the faces to their original surface, s m o o t h off with the finest emery stick a n d finish with a burnisher.
W i t h the solid type of pallet the d r o p can be increased by reducing the entry faces. These pallets are t o o h a r d to file a n d a stone m u s t therefore be used. An oilstone such as is used by a cabinet m a k e r is best for this j o b . M a k e sure the stone is kept flat a n d t h a t it follows the c o n t o u r of the pallet.
T h e m a r k s from the oilstone are then r e m o v e d by an oilstone slip keeping the grain flowing w i t h the pallet. Finish off with a very fine emery stick a n d then burnish.
Little can be d o n e to decrease the d r o p in the solid type of pallet b u t this is n o t i m p o r t a n t . W h a t is i m p o r t a n t is to avoid having t o o little d r o p . Such a condition can, after pivot holes are w o r n , lead to the pallets fouling the t o p s of the escape wheel teeth a n d stopping the clock.
O n e last w o r d a b o u t checking the d r o p of the escape wheel. All escape wheel teeth m u s t be checked with b o t h entry a n d exit pallets. A n y variation in d r o p on one side of the wheel to a position diametrically opposite will indicate the wheel being out of r o u n d .
With the pallet a r b o r o u t of the m o v e m e n t we are n o w ready to check the depth of mesh between the wheels a n d their pinions.
G e a r i n g is a subject a b o u t which complete b o o k s h a v e been written. It m a t t e r s little whether we are interested in horology or civil engineering, the theory of gearing is the same. Correct
depth of mesh, one of the m a n y aspects of gearing, plays a very i m p o r t a n t part.
Figure 74, a, shows a wheel a n d pinion in correct m e s h , b the mesh is t o o deep, a n d c it is n o t deep e n o u g h .
O u r m a i n concern is to ensure t h a t the wheels a n d pinions in the clock m o v e m e n t do not suffer from t o o m u c h d e p t h of mesh causing harshness in o p e r a t i o n . This can be checked by the sense
Fig. 74. Gear wheel and pinion in mesh, (a) Correct, (b) Too deep, (c) Too shallow.
of touch a n d is n o t as difficult as it m a y seem. After a little p r a c - tice y o u will soon be able to detect those gears whose mesh is causing trouble.
We will c o m m e n c e with the third wheel a n d the escape wheel pinion. H o l d the escape wheel by the tip of the first finger of the left h a n d a n d with the o t h e r h a n d rock the third wheel backward a n d forward. A l t h o u g h the m o v e m e n t is small any stiffness present can be felt.
N o w press d o w n lightly on the escape wheel a r b o r a n d slowly rotate the third wheel. A p a r t from y o u r finger pressure causing slight resistance the action s h o u l d be s m o o t h a n d free from any roughness.
If tightness is experienced in o n e position b u t n o t in a n o t h e r the possible causes are :
(a) d a m a g e d teeth (b) bent a r b o r (c) wheel o u t of r o u n d
W A T C H A N D C L O C K R E P A I R S
If the teeth are b r o k e n or d a m a g e d beyond repair, new teeth c a n be fitted as explained in C h a p t e r 6. If a t o o t h is b e n t t o w a r d s an adjoining t o o t h it can be straightened by inserting the blade of a pocket knife between the t w o teeth a n d levering the bent t o o t h back into position. If the tooth is bruised it can be shaped with a thin s m o o t h file a n d finished with a very s m o o t h emery stick.
A bent a r b o r can be straightened cold. F i n d o u t first of all where the bend is by spinning the a r b o r a n d then place it on a flat steel stake a n d t a p it straight with the peening end of a w a t c h m a k e r ' s h a m m e r .
If a wheel is o u t of r o u n d it can only be put right by renewing the wheel or by recutting the teeth with a topping tool.
T h e e q u i p m e n t for t o p p i n g wheels is unlikely to be in t h e possession of a beginner, therefore this j o b will have to be sent away to be d o n e . T h e same c o m m e n t s apply to bushing worn pivot holes. In b o t h cases the repairer will require the front a n d back plates, pillar n u t s a n d the wheels a n d pinions t h a t are causing trouble.
To continue with the dismantling. R e m o v e the pillar n u t s a n d carefully lift off the back plate. T a k e out the escape wheel, third wheel, intermediate wheel a n d barrel. Hold the front plate in the palm of the left h a n d with the c a n n o n pinion u p p e r m o s t . Strike the centre a r b o r a s h a r p blow with a brass-faced h a m m e r , this will free the c a n n o n pinion allowing the centre wheel to be lifted out.
N o w the barrel needs inspecting. Hold the square end of the barrel a r b o r between the jaws of the brass-faced pliers a n d try the end-shake. If there is n o n e , place the barrel over a piece of tubing a n d gently t a p the a r b o r a n d try the end-shake again. R e p e a t this until the end-shake is just perceptible.
It m a t t e r s little which end of the a r b o r is tapped by the h a m m e r but r e m e m b e r t h a t the end-shake has an influence over the position of the barrel in the m o v e m e n t . Consideration should be given therefore to other p a r t s in the immediate vicinity of the barrel in deciding which end of the a r b o r to hit.
with a screwdriver. M a k e sure it is m a r k e d before you t a k e it off so t h a t there is no difficulty in p u t t i n g it b a c k into its correct position.
Examine the condition of the spring. If it is clean a n d oiled with no signs of corrosion d o n ' t d i s t u r b it. If the spring is b r o k e n , or if it h a s to be r e m o v e d for any o t h e r r e a s o n , then first r e m o v e the a r b o r . To do this it will be necessary to t u r n it b a c k a little to u n h o o k it from t h e eye of the spring.
Pull o u t the centre of the spring very carefully using the brass- faced pliers. As soon as e n o u g h spring to h o l d h a s been pulled o u t , the rest of the spring is allowed to uncoil itself from the barrel. This operation m u s t be d o n e slowly a n d carefully.
If the spring were allowed to fly o u t , it is doubtful whether it could be used again d u e to distortion.
This completes the dismantling of the m o v e m e n t .
It is a recognized fact t h a t when t w o dissimilar metals m o v e against each other, such as a steel pivot revolving in a brass plate, the h a r d e r of the t w o metals will show signs of wear first. This is because fine particles of d u s t e m b e d themselves in t h e soft metal which then becomes a n abrasive a n d cuts the h a r d metal.
It follows then t h a t if pivot holes need bushing the pivots themselves will m o s t certainly need polishing, a n d further to this, bushing c a n n o t be carried o u t until the pivots h a v e been polished because the bushes have to be drilled to suit t h e pivots. W h e n the w o r k of bushing the plates is sent away the repairer will polish the pivots at the same time.
H a v i n g carried o u t all necessary repairs we are n o w ready to proceed with the cleaning. We will need a tin m e a s u r i n g a b o u t 6 in. x 4 in. a n d a b o u t 1 1/2 in. deep to h o l d the cleaning fluid. A 1/2-in. p a i n t brush m a k e s a g o o d b r u s h for washing t h e p a r t s .
We will also require a tapered strip of c h a m o i s leather, a piece of soft linen, s o m e pith sticks, some p e g w o o d a n d a folded newspaper.
H o l d the p a r t s over the cleaning fluid a n d well brush t h e m with the wet b r u s h , continually dipping the b r u s h i n t o the fluid. M a k e sure all the wheel teeth a n d pinion leaves a r e well b r u s h e d . Treat
all the p a r t s alike, b o t h brass a n d steel, a n d lay t h e m on the folded n e w s p a p e r to d r a i n . U s e the linen cloth to dry t h e m a n d to polish the a r b o r s . Lightly b r u s h the parts with a m e d i u m watch b r u s h charged with c h a l k .
Shave a p o i n t on the e n d of a p e g w o o d stick a n d peg o u t the bearing holes. L a r g e r holes can be cleaned o u t by the strip of c h a m o i s leather. C l a m p the wide e n d t o the b e n c h , t h r e a d the n a r r o w end t h r o u g h the hole a n d r u n the plate u p a n d d o w n the strip.
Push the pith stick well on to each pivot a n d twist it r o u n d a few times.
If the m a i n s p r i n g h a s been washed, dry it with the piece of linen.
Finish off by b r u s h i n g all the p a r t s with a clean soft watch b r u s h .
N o w wind the m a i n s p r i n g i n t o t h e barrel. Start off by h o o k i n g the o u t e r e n d to the barrel wall a n d then slowly feed the spring in a n d at the same time r o t a t e t h e barrel. W h e n the spring is in do n o t a t t e m p t to p u s h it d o w n because of t h e possibility of causing d a m a g e . T a p the barrel on the bench t w o or three times, this will cause the spring to settle d o w n to its correct position.
N o w p u t the a r b o r in m a k i n g sure t h a t t h e eye of t h e spring is properly h o o k e d a n d w r a p p e d a r o u n d the a r b o r .
Oil the edges of the m a i n s p r i n g a n d s n a p the cover o n . Oil the a r b o r bearing hole in the cover a n d in the barrel. T h e m o v e m e n t is n o w ready for assembly.
Lay the front plate over the c a r d b o a r d b o x a n d place the barrel a n d the wheels in position. L o w e r t h e back plate on to the m o v e m e n t a n d with a p a i r of tweezers m a n i p u l a t e the pivots into their respective holes
W h e n all t h e pivots a r e in, t h e back p l a t e should be resting on the pillars. T h e pillar n u t s can then be p u t on finger tight.
M a k e sure t h a t all the a r b o r s h a v e e n d - s h a k e a n d then tighten d o w n the back plate. Oil all the pivots in b o t h plates.
W i n d up the m a i n s p r i n g t w o or three clicks a n d check the wheel train for freedom.
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N o w fit the c a n n o n pinion. Place the m o v e m e n t on a block of h a r d w o o d front plate u p p e r m o s t . P u s h the c a n n o n pinion o n t o t h e centre a r b o r a n d drive it h o m e using a hollow p u n c h a n d a h a m m e r . Check the centre a r b o r to m a k e sure it has e n d - s h a k e . Again wind up the mainspring a few clicks to m a k e certain everything is free.
Refit the m o t i o n w o r k , the pallets a n d the pallet cock. A p p l y a spot of oil to each pallet a n d oil the pallet a r b o r pivots.
T h e m o v e m e n t is n o w ready to be fitted i n t o its case. W h e n this h a s been d o n e , h a n g the p e n d u l u m a n d the m o v e m e n t s h o u l d function.
Refit the h a n d s m a k i n g sure t h a t when the h o u r h a n d p o i n t s at o n e of the n u m e r a l s the m i n u t e h a n d is immediately over the 12.