Hints and tips for building Woodenclocks.

 Over the years that I have been designing and building woodenclocks, there are some techniques I have developed that either make my work easier or more accurate or both. Some of these I have added to the clock instructions so only get seen if you are building one of those clocks. This article then is an attempt to collect all of these Hints and Tips together in one place.

1) Starting with probably the most obvious one which addresses the problem of gears tending to stick at some point and stopping the clock from running. In the gear train itself one or more of the gears may not be meshing correctly there may be some interference between some of the gear teeth. You need to test each pair of gears in turn by mounting each meshing pair in the frames on their own and turning them by hand very slowly with little pressure. If any pair stick or interfere with the other you should mark the teeth that are affected and carry on until you have turned the large gear around completely then strip down and dress the teeth you have marked until they work together smoothly. Repeat this process so all the meshing pairs of gears are running freely.

It is not sufficient to test them when the gears are mounted in the clock and then left to run continuously with the weight in place as the free-running gears will easily override any slight interference whereas when the gears are running in the clock with the escapement in place they never run fast and so easily feel the effects of interference.

2) Concerning bearing Lubrication the type and viscosity of the lubrication in the “as shipped” bearing is highly significant and represents a considerable drag inside the bearing. I recommend that the grease or oil be soaked out with white spirit, I expect that the solvent leaves a thin residue of lubricant, but it would be wise to apply a little light Machine oil, like that used for Sewing machines or Clippers. The Bearing shown here is of the type termed Needle Roller Drawn Cup.

3) The DXF files supplied with each clock include all the parts that can be cut using the CNC router, they do not include those round items such as the turned parts cut from Doweling nor any pins or nuts and bolts, information on these parts is included in the Detail drawings supplied in PDF format. The parts themselves are laid out in single DXF files ready for you to extract and use in your CAM software. The profiles are shown on 6 separate layers, these being ‘Outside Cuts’ ‘Inside Cuts’ ‘Pockets’ and ‘Non-Cutting Profiles’  'V Cuts' and 'Black' The layers are colour coordinated as shown.  

4) Sometimes it is necessary to make the Pendulum Rod longer than the 700 mm or 1000 mm you were able to purchase. If this is the case you will need to cut down the second piece of tube to the additional length that you require. Now you need to make sure the cut ends are square so that when they are butted together there is no gap. A short length of steel pin Ø 4 mm is used to fit into the ends of the two pieces of tube to support and align them before glueing into place using a strong adhesive like Gorilla glue or Araldite, whilst the glue is setting hold the two tubes along their length to ensure they stay in line. Clean off the excess and wait for a couple of hours until it is dry before you use the new tube.

5) Recommended Ball bearing type is stainless steel with metal shields as these do not actually touch on the balls inside whereas the flexible seals can do. 
A typical designation would be:-
SMR84ZZ Ball Bearing - Ø4 x Ø8 x 3 mm
Or for a flanged version
SMF84ZZ Ball Bearing - Ø4 x Ø8 x 3 mm

6) I always use a Bow Line Knot on the end of the cord holding the driving weight of a clock, it is one of the most useful knots you can know. The Bowline forms a secure loop that will not jam and is easy to tie and untie. The Bowline is most commonly used for forming a fixed loop, large or small at the end of a line. Tried and tested over centuries, this knot is reliable, strong and stable. Even after severe tension is applied it is easy to untie.

7) Hand-finishing all the parts that you have cut can be a tedious process and can be difficult to achieve a consistent finish, especially in tight internal or external corners. To get over this I use Brass piloted router bits to do the bulk of the work, unlike the more usual large Ø12 mm bearing, these use a smaller Brass sleeve as a follower enabling you to get into much tighter places. I find it most useful when using plywood as well as improving the appearance it stops splintering of the top layer of ply or removing any evidence of already splintered.

8) I usually finish my clocks with a coat of Danish oil mixed 50/50 with white Spirit, the second coat at full strength, the second coat I try to stay clear of the faces of the teeth as the coating can take a day or two to dry out and remains a little soft until it is fully dry. I know that some builders like to apply a coat of very low viscosity super glue to the surface of the gear teeth, to give a very hard surface to the tooth surface before the final sanding and this certainly offers the opportunity to get a smooth hard-wearing finish. 

9) I like to make the Back Frame and the Frame Spacers as stiff as possible to avoid the clock distorting under the load applied by the driving weight. To ensure this I always fit the biggest Braces I can between Back Frame and the Frame Spacers and ensure everything is glued together. The front frame is held in place on the Frame spacers by two small Wedges. These have been designed to be an overly tight fit to account for variations in material thickness. To get them to fit properly so that they slide in easily to start with and then become tight when fully pushed in you will need to sand material off the back of the Wedges.

10) On some of my clocks, some shafts really need to have a head on the end to hold in place parts such as gears or ratchet and pawls. If making headed pins is not possible then other solutions have to be used. The pictures on the left show some of the parts that can be used. The best, because it has a head and an accurate shaft diameter is the clevis pin, which can be cut to length and used directly. Simile a round head Nail could be used but the shaft itself is not as smooth or accurate. A small Rod magnet with a diameter larger than the shaft can be simply stuck to the end of the shaft, as long as the shaft is not stainless steel. Last a small plastic washer with a hole slightly smaller than the shaft diameter and a slit through the side to allow it to flex, can be slipped onto the end of the shaft to form a head.

11) When cutting the profiles for parts that are to be fitted together then you are going to need to modify your profile cuts to overcome the problem of fitting square-cornered tabs into the round-cornered holes produced when the holes or slots are cut with a round router bit.

You can do this by modifying the fillet in the manner shown in the sketches to the left here, the holes use a ‘Dog Bone‘ type which has the fillet formed at a diagonal to the corner where the original square corner is cleared out by the fillet whose circular edge just clears the corner. On the external cuts, the fillet is formed with its radius centre on the original cut line, it can be done in either direction as shown in these examples but for preference, I would use the upper example as it doesn't weaken the tab.

12) In some of the simpler clocks no bearings used so the shafts run on the bare wood of the drilled hole. I had noticed when making Clock 21 that using a laser to cut out all the profiles and holes left a burnt surface on all the parts cut this way. This, of course, was carbon which just like Graphite is a lubricant, so as this simple clock design does not use actual bearings, I have attempted to simulate the Laser cutting process by Burning the hole surface with a red hot Ø3 mm rod.

The two photos shown here illustrate the process, the Ø3 mm Rod is held in the drill chuck and then heated to red heat with a blow torch, at which point the front frame with the Ø3 mm holes already drilled is placed on the baseboard below the glowing rod and then the rod slowly fed through the hole to burn its surface, and that's it. You now repeat the process for all the holes that will carry a rotating shaft in the front and back Frames.I have tried this on one of the clock prototype and it does seem to have some merit, I haven't tested it over a long period of time nor have I run comparison tests with an assembly with non-burnt holes but the results do seem encouraging so may be worth giving it a try.

13) You can make the weight from whatever you like, ideally, it should complement the aesthetic of the clock and not look bizarre or incongruous. I favour the brass weight but this is not always practicable and can be expensive. I have used a granite block in the past and more recently used a soft drink bottle or Can. To determine what size weight to use to drive the clock, I normally use a two-litre Coke bottle partly, filled with water to start, and add or remove water to get the clock running continuously. You would do this after assembling the clock and making sure everything is running freely and the escapement is set up correctly. Usually, a bit of back and forth here to adjust the escapement then adjust the weight. The Hanger adapter plate can be cut from 3 mm thick plastic or Plywood, get the DXF file by clicking on the illustration.