CONSTRUCTING A YEAR CLOCI(bv c. B. Reeve

PASSIN G one day with a friend through themedieval section of the Briti sh Museum, the

writer's attention was called to the fine exampleof Tompion's very tall one-year clock with itshandsome dial and beautifully shaped and chasedhands. A closer inspection through the sides ofthe case revealed that the great or first wheelof the movement was of enormous size, probablyabout seven or eight inches in diameter. Thisgave the writer the urge to construct a yearclock, but he considered it would have to be onsomewhat different lines, as his domain, having

102

low-pitched ceilings, no clock of more thanfive or six feet would fit in comfortably. It isproposed in this article to state briefly how thisclock was made and to give some details to enableinterested readers to construct a similar clock.

It is generally thought that horological toolsare essential for a job of this description; this isnot so, really. Such tools, of course, are con­venient, but ways and means will be shown howthe ordinary run of tools of the average modelengineer's workshop will accomplish the job. Astart on the movement was made during the

THE MODEL ENGINEER JULY 26, 1951

):0

@111/1 1I II! I I I i 1111 1,111 ~.o "I @)

(j) t}lm@

!1n=p(§)m:r:~:J.. , I 'f}! I I '\' I , I I Ii , I I 'I' @

@ ®

~ ' i !lmJl@ jJ HB li ll l l l l i "I H H f@lH!iRI l1 l m ®op ening week of th e Model Engineer Exhibitionof August 17th , 1949.

The two dri ving barr els were built up in thefollowing way : a 12 in . length of § in . diametersilver-steel was cut in hal f to form the arborsof the barrels and were turned to the shape andsize as indicated in the data table and shown inthe drawings, which are to scale. It will be seen

from the drawingthat part of the arbor is roughfiled eight-sided with a slight tap er; next, acircular brass blank t in . in thi ckness by 21 in.diameter was centrally drilled of such a sizehole tha t it could be filed eight-sided and made adriv e-on fit on this arbor; it was driven wellhome and form ed a nice snug fit on the arbor.The latter was then placed between centres in

103

THE MODEL ENGINEER JULY 26,

Front view of movement

the lathe and a step turned on th e flange slightlyless than k in. in width and the diameter in sizeto fit closely a piece of previously prepared bra sstube 3/32 in. thick and to the dimensions shownin the drawings. The back flange on which theratchet teeth were cut later was turned on aseparate mandrel. The arbor, with the alreadymounted front flange, was then turned parallel,as shown in the drawing, for the reception of theback flange which was a good pres s-on fit. Withall three parts finally fitted together, three locking

104

pins were put through the tube at either end intothe steps of the flanges as shown. Finally, aslight turning all over of both flanges and tubeproduced a perfectly true barrel and arbor. Thebarrel was next screw cut for the reception of thedriving line. It is worth mentioning that thebarrels will work quite satisfactorily if they arenot screw cut for the driving line. Many of theold clock-makers did not trouble to do this .Ratchet teeth were then cut on the back flangeof the barrel with the aid of a home-made cutter,

THE MODEL ENGINEER JULY 26 1951

@ @@}~) @

6) ®.-

--8 @~

~ ~tj

~

@, @@® @

®

o,

o

@ ®

the barr el being placed betwee n centres with th edivision plate on th e end of the mandrel and thecutter frame on the slide-res t.

Maintaining RatchetThis was rna'de as shown in the dr awing, th e

same home-made cutter being used as that withwhich the barrel teeth were cut.

CliCA and SpringT he components were qui te a straight­

forwa rd job, being a pure handwor k opera tion, th eclick being made of steel and the spring cut frombrass shee t with a piercing saw and afterwardsbent to the required circular shape.

The wheel s were next taken in hand ; circularmilling-cutte rs were used for cu tt ing the teeth.

105

THE MODEL ENGINEER JULY 26, 1951

Details of the pitches and diameter s are shownin the data table. The following method wasadopted for producing the larger wheels : Acircular brass blank for the great wheel of theappropriate thickness and ! in. in diameterlarger than the required wheel was to bedrilled and bored, a good revolving fit on thebarrel arbor, the blank being held in the self-

was no w screwed home, taking care not to for cethe latter too much. The blank wheel held thuswas th en turned down to size. The divi sionplate was then fitted on the tail-end of the mandreland the cutter frame fitted to the slide-rest, thecutter being driven from th e countershaft.Wheels produced thi s way came out with theteeth and bores dead true with one another. The

Data Table to Drawings

ReferenceDescription of items

Numberof

teeth

FullDi ameter Width

(in .) (in.)

Diame­tricalpit ch

Quantityrequired

Sh~ckle'~nd ~ull~y

Front flange of driving barrel

K~y or slip w~~he;' .. . .Locking screw to slip washer . .Back flang e of dri ving barrel ..

Ass~mbled'bar:~l : : : :Partly machined arbor of barrelCock for back pivot of centre

arbor . . . . . .Fixing screw for above ..Plan view of cock for back pivot

of centre arbor . . . .Maintaining click . . . .

Gre;; or firs~~heel of ~~ain : :2

222

2

222

2

222

2

2

2

4II

II

12I2

34

4°

1/16

31II2

"roo

II212

10812

" """ " "M aintaining ratchet

Set s~rew for 'holding' mov~:ment to seat board ..

Hook ' for holding ends ofdri ving line of barrel ..

Maintaining spring . . . .Click for barrel teeth . . . .Spring for click . . . .Back plate of movement . .Cock for escapement pivot and

pendulum s us p e ns io nbracket . . .. . .

Bearing for great wheel pivot . .Second wh eel of train . . . .Pini on on zn d wheel of arbor . .Third wh eel of train .. . .Pinion on 3rd wheel of arbor . .Ring nut for pill ar . . . .Crutch of escapem en t . .Winding arbor of movement ..

1.2.

3·4·5·6.7·8.9·

10.II.

21.

12.

13·

14·15·16.17·18.

19·20.

22.

23·24·25 ·26.

27·28.32.29·33·30.31.

34·

""

"

""

"

"""""

"""""""

"""

"""""

"

Fig.A.

centring chuck for this purpose. Next, a shortpiece of round brass or steel rod was chucked inthe self-centring chuck with the lathe jaws inposition, so arranged as to leave about three­quarters of an inch protruding beyond thelongest steps of the chuck jaws. This was nowturned down to fit the previously prepared holein the blank wheel. Afterwards, the end of therod was threaded with a die and a nut made andfitted. The blank wh eel was now pushed on \to the short end of the truly running rod andresting firmly against the chuck jaws, th e nut

106

smaller wheels were produced the same wayexcept that these were fitted to some small home­made chucks made to fit the mandrel bore of thelathe. The wheels were next crossed out, apiercing saw being used for thi s purpose, followedby files and emery sticks for fine finishing. Apiercing saw is an extremely useful tool for anyform of model engineering or instrument work;steel up to a quarter of an inch can be cut with .it, the finishing required afterwards being farless than when other tools 'have been used.

( To be contin ued)

*CONSTRUCTING A YEAR CLOCI{by C. B. Reeve

T H E pinions were next taken in hand . T hesewere mad e from standard pinion wire, but not

in the ort hodox way of solid pi nions. A sho rtlength of the pinion wire, jus t sufficient to formthe head , was cut off th e length with th e piercingsaw. Next , a short length of brass rod somewhatlarger in ·diame ter th an th e piece of pinion wirewas chucked in th e three-jaw chuck, drilled andbored of such a size th at th e piece of pinion wirewas a drive-in fit, care being taken to leave th ewire just proud of the brass bu sh thus formed .The pr otruding end of the pin ion wire was th enfaced off and turned as smoothly as possibl e.Aft erw ar ds it was centred with th e Slocombecentring drill and then drilled through and boreda s low taper. Next , it was tapped out of thebrass bush with a piece of rod passing throu ghthe mandrel and then replaced in the brass bushand th e other end faced off. Afterwards, theleaves of th e pinion head were well shaped withthe aid of a knife-edge file fini shing withcarborundum grit No. 120 and oil , th e grit andoil mixture being worked be tween the leaves witha small piece of .end-grain wood. At this stagethe pinion head was now hardened by heatingto cherry red and plunging into cold water.Afterw ards, it was let down to a purple blue and

*Continu ed from page 106, " M .E.," J uly 26,951. .

finall y poli shed with rouge and oil. The pini onarbors were ma de from tempered steel rod (bluedsteel) which is now obtainable in lengths of ab out6 in . A piece sufficient for one arbor was cutoff from the rod , cone centred at each end, aft erwhi ch one end was taper turned to match thetapered hole in the pini on head. If this is welldone the pinion head literally screws on to thearbor and will never move.

A short len gth of brass rod to form the colletfor mounting the wheel on was pressed on to theother end of th e arbo r and a seating was thenturned to such a size to sui t the previouslyprepared hole in the wheel. The wheel wasth en riveted on to the collet . The latter wasthen finally turned to shape and fini shed off withbuff sti cks. All the wheels and pinions weretreated this way, but the pivoting was left to bedone later.

While in London on holiday I obtained th ebrass for the plates for the movement, also thebrass tubing for making the weight cases . Onunpacking these items it was noticed that thebrass plates were far from flat, and knowing thatbrass of ,\ in . thickness would be no easy ta sk toplanish, the following method was tried out andproved fairly successful :

Each plate in turn was placed in the wood­worker's vice and two small pieces ofwood arranged on either side of a hollow in the

Data Table to D rawings .Number Full D iam e-

of diameter Width tri cal QuantityR eference Description of items teeth (in .) (in .) pitch r equir ed

F ig.C. 35· Front plate of movement . . - - - - I

" 36. Pillar of small auxiliary frontplate . . .. .. - - - - 4

" 37· Centre wheel of movem ent 96 I t 3/64 72 I

" 38. Pinion on centre wh eel arbor .. 12 .185 I

" 39· Upper 3rd wheel of movement 90 I t 3/64 72 I

" 4°· Pinion of upper 3rd wheel arborof movement .. .. 12 .185 I

" 41. Escape wheel dead- bea tstraight-sided teeth . . 30 I t 1/16 I

" 42. Pinion on escape wheel arbor 12 .185 I

" 43· Dead-beat adjustable pall ets . . - - - - 2

" 44· \Vinding gear on arbor of greatwheel .. .. .. 78 I 13/16 ! 40 2

" 45· Intermediate winding gear .. 36 ·95 t 4° 2

" 46. Gear mounted on winding arbor 36 ·95 t 4° 2

" 47· 24-hour wh eel . . .. .. 144 3 3/64 5° I

" 48. Hour whe el .. .. .. 72 I t 3/64 5° I

" 49· Minute wheel on centre pinion 44 t 3/64 52 I

" 50. Rever sed minute whe el .. 44 t 3/64 52 I

" 51. Minute wh eel clock .. " - - - - -" 52. Bridg e for ho ur wheel .. - - - - -

F ig. D. 53. Pill ar to main clock frame .. - - 6

" 54· Weight case .. .. .. - 3 Length: 15 in. 2

131

THE MODEL ENGINEER

@

f0\\to

' . 1

@

@

- • __1.-. •• • ", "

'/ "<_,-.f, " .\ -·f"::":':·.: - ~I O } • :0 .'..J .....-, ~_";'I_-....

" ,

o

@'- \

AUGUST 2, 1951

@

plate whil e a third piece of wood was placed onthe opposite side of the plate immediately over

_ the bump. The jaws of the 'vice were then. carefully closed, causing the bump to be flattened

out. Both plates were gone . over thus 'and al­though the result was not exactly sur~ace-plate

finish, it was reasonably good for the purposein hand.

Pillars were then made. This was a straight­forward turning job, the ends being threaded witha fine pitch home-made die; after this , ring nutswere made and tapped to suit the ends of the

132 \ ' .

THE MODEL ENGINEER AUGUST 2. 19Si

Front view with cam wheel and finger removed

pillars. The plates were now drilled to receivethe pillars. After fitting the pillars, the framewas ready to assemble and it went together quitewell. The various wheels and pin ions were nowlaid across the edge of the frame and it was theneasy to see to mark them out for the pivots to beturned. The turning of the pivots was donewith a graver and handrest, running the workfairly fast in the lathe, and afterwards they were

smoothed with a pivot file followed by oil-stonedust on a polisher, and finally finished withrouge and oil. The next operation was theplanting of the train of wheels in the frame.This was accomplished without any mistakeswith the aid of a depth tool.

By the end of the -writer's two weeks' holiday,all the inside wheels were planted and also theupper wheels contained between the main front-

133

TH E MODEL ENGINEER AUGU ST 2, 195 J

plate and the upper small auxiliary plate. Itwill be seen from the drawing that the backpivot of th e centre wheel is held in a cock screwedto the underside of th e main front plate, thepinion on the centre wheel arbor engaging withthird whe el of the train. After th is the workprogressed rather slowly, being mai nly done atweek-ends; but by Christm as, 1949, the dead­beat escapement and pendulum were mad e andthe exciting moment arrived when it was pos sible

west comer contains double the number ofteeth of the hour wheel with whi ch it meshes,and, therefore, makes one revolut ion in twenty­·four hours . There is a pin situ ated in one of itsarms which, as the wheel turns anti-clockwise,moves the lever to the right, which in turn movesthe big arm or detenr also to the right. Att achedto the detent are two clicks and weak springspointing in opposite directions to one another .T hat on the left is for moving the seven days of

Fig. D

to see if the movement would go. As the weightshad not yet been made, weights from other clockswere quickly borrowed and a short length ofwire line was attached to each barrel. A total'weight of abo ut seventy pounds on a double linewas required to get way on the wheelwork.After adjusting the crutch in beat the clock wasstarted, and, strange to say, it went for the firsttime of asking. The pendulum rating-nut wasadjusted by pure gues swork and the movementwas left going for a fortnight during which periodit kept time with Big Ben within a minute or so.It was then decided to add the perpetual calendarattachment.

This part of the job took about three months toconstruct, and the followin g is a brief descriptionof its action, which is on Broco's principle:

The drawing of the calendar work shows thevarious parts as they appear with the clockdial removed. The large gear wheel in the north-

134

week star wheel, whilst that on the right is formoving the thirty-one days of the month wheel.As the detent travels towards the right, the twoclicks will slip past a tooth of their respective 'wheels without the wheels moving in any way,but when the pin in the twenty-four hour wheel hasmoved past the extremity of the curved arm, thedetent will suddenly return again to the ' left­hand position and in so doing both clicks willadvance their respective wheels one tooth. Thishappens every time th e detent travels to th e left,whether it happens to be a short or long month.It will be seen from the drawing that th e weekand month wheels are stea died in th eir positionsby rollers shouldered on screws fitted to arms;the lower extremities of th e arm s carry lightweights. This idea, th e writer considers, isbetter practice than using springs . A similarweighted arm is also used for returning the det ent.

,( To be continued)

*CONSTRUCTING A YEAR CLOCI(by C. B. Reeve

T H E action for the short and long months willnow be described. Fixed to the axis of the

month wheel and turning with it is a pinion of tenleaves which engages the teeth of an intermediatewheel of any number of teeth. This int erme diatewheel meshes with another wheel containing

*Cantin uedfrom page 134, " M.E. ," August 2 ,

1951.

12 0 teeth and is the year wheel which makes acomplete revolution in twel ve months. Thiswh eel is shown in the drawing occupying thelowest central position in the movement. On theaxi s of thi s whe el is fitted the hand that indicatesthe vari ous months of the year . Also superim­posed on this wh eel is a smaller wheel containing36 teeth, whic h drives a larger wh eel containing144 teeth which turns on its axis once in four

V iew of movement f rom above

179

1m~ II £ r-~.Ij;j

cf r--f---

i=I

E ..f

:~'---- "l

~.. ~ .

~ ~

~h

ID II~ ¥:~ ~

..r1l""

L-UL: II '=-.

Q..J'1

~0

lli~

rt '=: /"'--

",...

:T~

THE MODEL ENGINEER

years. This last wheel is indicated in the drawingon the left-hand side of the movement beneaththe cam wheel to which the latter is screwed.There are 48 divisions on the circumference ofthe cam wheel, this being the number of monthscontained in four years. There are 28 un cutportions on the rim of the cam wheel corre­sponding to the 31-day months, 16 shallow slotscorresponding to the 3o-daymonths, 3 deep slots corre­sponding to the months ofFebruary with 28 days eachand on e slightly less deepfor th e month of Februaryin Leap Year . There i.a pin placed in th e 31-daymonth wheel opposite thetooth representing the zsthday of the month. Situatedon the detent is a bell cranklever freely pivoted andon its lower extremity is apin which rests on thecircumference of the camwheel and by its own weightthe bell crank lever willcause the pin to enter anyof the slot s on the camwheel as it rot ates the four­year wheel beneath it.

It will be easy to see thatwhen the pin rests on thehighest step on the camwheel the opposite end ofthe bell crank will also bein the highest position andwill be out of reach of thepin in the 31-day monthwheel, but wh en the pin onthe lower end of the bel1crank has fallen into oneof the shallow slots (corre­sponding to the 3o-daymonth) the upper end of thebel1 crank will have arrivedat a lower posirion and thenotched end of the leverwill be in' a posit ion tomove the 3 I -da y monthwheel forwa rd one tooth.This will occur on thenight of the 30th of the month as the detentis finishing its travelling to the right. Onthe det ent being released by the pin in the 24­hour wheel it . will return to its normal positionand in so doin g carry the 31-day month forwardone more tooth and thus bring the date to thefirst of the ne xt month.

For the month of February containing 28 days ,the pin on the lower end of the bell crank leverwill have fallen into one of the deepest slots andthe upper end of the bell crank lever will be atits lowest position on the night of the 28th andits notched end will then advance the 31-daymonth wheel three teeth as the detent travelsto the right; on being released again it will stillmove the 31-day month wheel one tooth forwardon its return journey to the left and bring the dateto the first of the next month.

For L eap Year the same action takes place,

180

AUGU ST 9, 1951

but as the slot in the four-year cam is made slightlyshallower, the notch in the bell crank lever willonly advance the ]I-day month two teeth as thedetent makes its excursion to the right, and on itsreturn journey to the left the 31-day month wheelwill again be advanced one tooth. The pin inthe bell crank lever will slide out of the shallowslots of the four-year cam wheel quite easily. The

Fig . E

bottom sides of the slots are .sloped away forthis purpose. In the case of the deep slots, thisis not so easy owing tothe angular movement ofthe cam wheel, but in order to accomplish this,there is a shaped finger fitted to the axis of theyear wheel and turning with it. The extremityof the finger will pick out the pin and prevent it,for a time, re-entering the slot again until thefour-year cam has moved on sufficiently for theslot to be out of reach of the pin . As a furtherpr ecaution to prevent the pin entering thesedeep slots again after it has done its work, thereare shutt ers fitted and pivoted on small shoulderedscrews. These automatically open and shut bytheir own weight according to their position asthe cam wheel rotates. These are not shown inthe drawing but can be seen in the photographs.

The next item made was the square dia l whichwas a fairly straight-forward job. T he raised

THE MODEL ENGINEER AUGUST 9, 1951

S ide view, looking from right

chapter ring was engraved but' the lettering in thefour smaller dials was painted on, the idea beingto have these engraved professionally aft er theclock had been exhibited.

Cutting the circular openings for the smalldials in the back plate of the dial was an int erest­ing job. The writer obtained a tool used by plum-

bers for cut ting holes in wat er cisterns, and byaltering the shape of the cutter it was possibleto produce a nice chamfered edge to the circularopenings. The tool was fitted to the carpenter'sbrace and by op erating this very slowly a niceclean result was obtained with no chatter marks,and very little after- tr eatment was required.

181

THE MODEL ENGINEER AUGUST 9. 1951

@

@

~

.~----.:::::::;:::===:::::::~ Ill:;

~[Dlr ~[;j '

10,' !"£p

Time was now getting on and a start on theclock case was made during the Easter week-end.The trunk of the case was made detachable from 'the base as the writer found it much easierto construct this type of case in two sections . '

One axiom that is necessary with woodworkis that -all the tools must be kept in the sharpestpossible condition. .

The case was finished towards the end of Mayand by June rst the movement was set in the caseand the job considered finished. The clock was

182

set going and behaved very well and was leftalone until Sunday, August 6th, -1950, when itwas taken down and the various parts packed upfor the journey to the "M.E." Exhibition.The case just before packing was given the once­over with beeswax and turps.

On the eventful Tuesday afternoon of August 8thit was all packed into a Morris 8, the writer nurs­ing the movement on his lap all the way to theHorticultural Hall -so as to avoid disturbing thecalendar work -of the movement.