Restoring A Bulle Clock A practical Guide

1 Restoring A Bulle ClockA practical GuidePeter J SmithPage 2 Restoring a Bulle ClockCopyright 2005 Peter J SmithSection 1 Bulle Clock PrinciplesPage 3 Restoring a Bulle ClockCopyright 2005 Peter J Smith1. Bulle Clock PrincipleThe principle involved in the Bulle Clock isvery simple. Consider the large curvedmagnet on the base of the Clock . This isnormally magnetised with 3 poles. Yes I do mean 3poles. North at the ends and South in the middle. Infact it does not matter whether it was the other wayround South North South. It would only mean switch-ing the battery terminal the other way round. Now, asyou probably remember from your school days, if youpass a current though a long coil of wire you wouldinvoke a magnetic poles would depend on which way you con-nected the battery.

2 If you were therefore to suspendthis coil of wire on the end of a rod so that it encasedthe bar magnet but did not touch it then you have thepotential for the magnet to attract one end of the coilto one of it s poles. So if you were able to switch thecurrent on and off at specific points in the swing cycleyou would in fact start an oscillation of the coil firstbeing attracted to a pole and then when the current isdisengaged the pendulum would fall back to rest. Butit s inertia would carry it in the opposite direction pastit s resting you keep switching the current on at the rightpoint then the amplitude would increase until theforce of gravity would match the attraction of themagnet and the pendulum settled into a consistentamplitude of swing. Perfect for a can experiment with this yourself by hand.

3 Before the movement is replaced connect the negativeside as normal to the frame and also wire the looppast the suspension to the pendulum rod. Then youcan tap the silver contact pin on the pendulum with awire connected to the positive terminal of the the connection at the bottom of the swing whenthe pendulum is swinging to the right. Disconnectbefore it reaches maximum amplitude. If your timingis good and your reflexes are accurate then the pendu-lum, will gain in amplitude and it will be quite easy tomaintain now all the Bulle has to do is two a switching mechanism and interpret thependulum swing into displayable time. The move-ment sub assembly does this by providing a forkmechanism for the pendulum contact pin and a trainof gears to drive the hands. The fork has a silvercontact on one side and a fibre contact of the the pendulum swings the contact pin willconnect with one side or other of the fork dependingon which way it is swinging at the time.

4 If it is thesilver side then the circuit is completed with thebattery and the coil performs its duty and interactswith the pendulum as we discussed. On the way backit leaves the fork in its rightmost position and crossesto the left side where it engages with the this being a terrible conductor does not allowa circuit to be completed and therefore provides nocurrent for the coil and the pendulum swings undis-turbed. Meanwhile a pawl which is attached to theother end of the fork arbour is also pushed backwardsand forwards with each swing of the pendulum. Onswinging to the right the pendulum forces the pawl toengage with a ratchet wheel which then moves oneratchet tooth to the right where it it stopped fromreturning by a second pawl. The pendulum thenswings back to the left and the first pawl slides backover another tooth but does not drag it back.

5 Theprocess repeats when the pendulum then swings tothe actual wiring for this complete cycle of eventsis therefore simple. The negative terminal needs to bepermanently connected to one side of the coil whilethe positive side needs to be connected intermittentlyvia the fork and contact SideSo from the negative terminal on the battery in thebase of the Clock the black wire should connect toanywhere on the column of the Clock . Nothing assophisticated as this was available to the earlier mod-els though. The whole column was, in effect, thenegative side of the is normally one of the three or four screwsthat hold the column to the base. Later clocks con-tinue the wire up the tube and exit from the hole onthe side of the smaller column tube that holds themovement sub assembly.

6 From here it passes to anarm at the top of the is then connected to the pendulum via acoiled hair spring (photo 1/1).Because the suspensionunit separated the pendulum from the column via twoPage 4 Restoring a Bulle ClockCopyright 2005 Peter J Smithpieces of non conductive silk there needs to be amethod of jumping the 1/1 This is achieved by connecting a long loop of silvercoated wire from the top suspension nut and bolt to thelower nut and bolt. The lower connection was some-times made via a small screw attached just underneaththe suspension bolt (photo 1/2)Photo 1/2 The negative side now could travel all the waydown the iron rod to the first of two wire connectionsthat attached the one would not normally be seen as it wasinside the coil cover. As the iron pendulum rod wasbolted to the cover all that was needed was to wrap afew loops of the coil wire around the end cap spacertube which was then pulled up tight to the coil coverby the thread on the end of the iron pendulum rod.

7 Thecurrent could then flow around the coil and out theother side must now be insulated completely fromthe cover and any other part of the frame. So it startsit s journey back to the positive side of the battery bylooping though an insulating waxed material tube thatpassed though the brass coil cover and up to the thinbrass rod that traveled up the back of the iron pendu-lum rod but still insulated from it. This rod must nottouch the pendulum at any point so it also is pusheddown into the same wax jacket. The top end of thebrass rod terminates in a small bracket in which isembedded the silver contact 1/3 This bracket must also be completely insulatedfrom the iron pendulum rod. It does this by using afibre sleeve that completely encompasses the ironpendulum rod before being clamped tight by a silver pin is therefore the end of the line for ourwandering negative SideNow for the positive side.

8 This starts fromthe battery up via the red wire through thecolumn to appear at the small hole on theside of the smaller top column. It must be completelyinsulated from the column. It then travels a shortdistance in the open air to a nut on the back of themovement. The movement itself is insulated from therest of the Clock by fibre washers that are positionedPage 5 Restoring a Bulle ClockCopyright 2005 Peter J Smithin front and behind the movement at the two pointswhere it is bolted to the frame. If these fibre washerare missing then the Clock ain t gonna work. As thefork is part of the movement it becomes the closestpositive point to the negative silver contact 1/4So if the pendulum swings to the right the pin willcontact the fork and the circuit is made thereby pass-ing a current through the coil and inducing a magneticfield that drives the Clock .

9 It does this at the lower endby passing (still in its wax jacket), through a brass lugthat protrudes backwards from the top of the brass coilcover. It then attaches to the brass vertical rod via twonuts and washers between which the wire is clamped.