I have an index to all the woodenclocks on the website but it has no images of the clocks only the most salient features being mentioned to aid you in choosing what to look at first. So the following is a list of all the woodenclocks listed visually to make your choice easier.
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.
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.
You are probably aware of these terms in reference to setting up your CAM program when deciding which is going to be the best direction to follow to get your part's cleanest and most accurate finish.
The main difference between climb and conventional cutting is how the cutter bites into the material.
A conventional cut deflects the bit, causing it to dig in and produce a rougher surface, whilst a climb cut pushes the bit away leaving a smoother finish. Because of this when cutting Hardwoods it is generally believed that the best finish will be achieved using a climb cut for the gear teeth on the gears of the clock.
A simple visual check of any off-cut you have made will quickly tell you whether your set-up is correct, if the off-cut is cleaner than your part you have it the wrong way round.
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I would personally always use the Climb cut for all but the last layer where I swap to a single pass with a Conventional cut. This for me gives the best tool usage and the cleanest and most accurate finish.
It should always be remembered when setting up for cutting that you need to change the direction of cut when you move from cutting an Outside profile to cutting an Inside profile. As the cutter only spins in one direction all the time changing to an inside cut always necessitates the cutting direction is reversed.
The illustration below is taken from the Vetric Cut2D worksheet for one of my clocks. This shows all of the parts for a clock laid out on a single sheet ready for cutting. All outside cuts are shown in Blue and all inside cuts are in green along with other colours and layers for non-cutting items like text.
The Frames and Dial of any clock can be pretty large and therefore not able to be fitted to the Work Table or Bed in one piece. In these circumstances, you will need to cut the part into two or three pieces to enable them to fit. Simple glueing the parts together may well not be enough to ensure that the part is strong enough to function or indeed be accurate enough for the clock parts to be fitted. The following is a guide to a few of the ways to achieve a positive result.
Using CAD
The primary making method for the clock parts is CNC machining and the approach is to split the large part into several smaller parts using your 3D CAD software. I use Solidworks but any of the Free or Paid for CAD programs will be suitable for this task.
The first step shown above is to use sketch lines to show where the cut needs to be made. My preference in this is to use sketch boxes the size of the cutting table to establish the position for the cuts and then if necessary attach new planes vertical to the cut lines to guide the cut command that follows.
A simple Butt joint simply will not be good enough to withstand the loads applied to the Frame structure by the Driving weight, so there are several options you can use to reinforce the joint before glueing together. The first method shown above requires you to drill 2 holes into each side of the joint and fit steel pins to strengthen the joint. Great care is needed here to ensure accuracy in aligning the holes to each other, if in doubt use one of the following methods instead. In fact, this method is more appropriate if you are 3D printing the parts as it will be easier to accurately produce the holes.
The second method is to glue together the two parts but add a strengthening strip to the backside to reinforce the joint as shown above. Positioning this may be tricky as it may interfere with the gear train on the inside so it may have to be located externally and therefore visible if it is at the front of the clock.
Finally instead of a simple split line, a Lap joint may be more appropriate, with no extra steel pins required and no problem interfering with internal gears. It is produced using a Z cut across the frame as shown in the first picture above and the larger glue surface provides both the strength and accuracy needed for the joint.
Using a 3D Printer slicer
If you own a 3D printer, and you are going to be producing the parts for your clock on this you will have some other options to choose from. You can still use your CAD program to make the changes and output the STL files from there.
The alternative is to start with the STL files provided and make your changes in your Printers slicer program or if that's not possible then one of the later model Slicer programs can provide output suitable to your printer. I have used the Prusa Slicer 2 for this article as it seemed a little easier than some of the alternatives.
To see more details in the screenshots below, click on them.
Start by using The File menu at the top left to Import your file to the printer bed, it should adutomatically lay it in the centre as shown here. If it's not green then click on it. You can start making changes to the set-up now, you can change the material you're going to use and change the actual printer you are using. The changes to the position of the part on the bed can be made in the boxes highlighted at the bottom RH corner.
Normally when using a Slicer to split your part you will be splitting it at the surface of the bed, so we need to orientate the part so the split line is on the bed and to do this we need to rotate the part by 90 degrees. Click on the Rotate symbol indicated to open the screen shown above. To make sure you get the correct readings for position and rotation in the Box at the bottom right change the coordinates to Local.
Now grab the red handle and pull down, a box appears indicating the angular movement, keep pulling till it reaches 90 degrees, if it's difficult to get it exact slide the handle towards the centre and it will lock on 90. Alternatively, type in 90 degrees into the Rotation coordinates as shown.
Now click on the Split or Cut symbol on the left to bring up the little Box and select the top option only now click on Cut.
Now type in 270 degrees to lay the part back down on its back. That's the first half done so you can now go back to the Files menu and Export the file as a new STL file.
Now you have selected the bottom half of the dial to split and bring onto the top of the bed. Now repeat the steps from before to lay it flat and then export the Bottom half of the dial.
Other methods
There are a lot of alternative slicers that can be used for this task, an internet search for 'split an STL file' will supply you with many alternatives. However, a better alternative may be 'Meshmixer' it has a fairly straightforward Splitting function they call Plane Cut but will also repair any damage to the model that has occurred as well. This latter function can be useful on its own if you get a model that is damaged.
From a personal viewpoint I would always prefer to split parts in a CAD program I find it easier that way and in the main causing less damage to the part as it is always best to be using STP files for this task rather than using the STL files.
Spreadsheet to calculate the length of clock pendulums
If you have decided to design and build your own wooden clock then the following charts should give you some idea of how to tackle the tricky mathematical bits that are needed to make sure that the clock can run accurately throughout the day. Some of my earlier posts should have introduced you to some of these formulae that are used in this process. The idea here though is that we try to automate the process using Excel to do the heavy lifting and at the same time give you the opportunity to try out different combinations needed to me the constraints of the design you have in your head.
I have always used a modified version of the standard gear tooth profile so as to give me more clearance between teeth and a bit more leeway when cutting the teeth by hand or on a scroll saw. The most important thing with regards to tooth profile is consistency in the pitching of the teeth. The charts below reflect this and the details are given for both the large gear and the Pinions in the most used tooth sizes.
This is probably the simplest of the charts as it simply calculates the distance between the two mating gears by adding the two Pitch Circle Diameters (Ø50 mm in this case) together and dividing by 2. If you experience difficulty with distortion of the gears that causes problems with assembly then you might want to increase this by 0.5 mm.
I have included STP or STEP files with most of the clocks that you can purchase as these files provide you with exact 3-D models of the clock that you can use in your 3D CAD program to modify any of the parts.
That is useful if you own and use 3D CAD software but if you don't then the files can be used in conjunction with an STP file viewer program to provide you with a great deal of extra information about the parts of the clock and the way that they fit together.
There is a considerable number of these available on the internet, some free and some not so much. I have only looked at the free ones as, to be honest, you should be able to get all you need from them. The programs fall into two groups, On-line where you upload the files you want to view and PC or mobile Android or iOS based.
What I was looking for in a viewer was first and foremost how easy and intuitive it was to use and manipulate the parts or assemblies when loaded. Secondly was whether it would produce a list of parts in an assembly and whether it would highlight a part within an assembly when clicked either in the model or the parts list. This is important as it is sometimes difficult to find parts and identify them when you click on either the part or the part in the list.
Starting with the Online STP viewer my clear favourite here is the viewer from Autodesk, simply called the Autodesk Viewer which will open over 80 file types including STP, STL and Solidworks, etc.
Once you have registered and signed in, use the Model Browser to find the part of the assembly you want to view. once loaded as shown below the assembly can be opened up in the Model browser where you can click on individual parts or groups to make them either visible or invisible. It would benefit you at this stage to either read the instructions or set up some of the settings, I advise you to do
this as it makes it easier, later on, to manipulate the model and interrogate it for more information on the parts.
Now you are ready to use the viewer, one of the rather nice things you can do with the loaded assembly is to explode so that the parts can be more easily identified, this is simple simply click on the Explode symbol at the bottom and then slid the blue ball to the right to see all the parts fly apart.
To see individual parts without the clutter of the other parts around it simply click on the part in the parts list and the other parts disappear, to bring them back right-click on the same part and click on the Show all message to bring them back. finally, on this I would recommend you go into Configuration - Display settings and turn off 'Ghost hidden objects' as this makes the visible part more difficult to see clearly.
This next one can be downloaded to run on your PC or Mobile no Online option here. This is similar in many ways to the Autodesk Viewer but can load Solidworks files as well if you need that functionality. It is also slightly faster to load larger files as there is no internet connection needed.
Exploding of the assemblies is also similar to the Autodesk Viewer. Not much to choose between these first two and may come down to a preference for either PC or Online-based.
CAD assistant has similar functionality to the above and is either PC or mobile-based which may well be useful to iPad owners. It lacks the ability to explode assemblies but does have the functionality to change or add colour to a part which may well be the function that you are looking for.
I found it slightly more difficult to use than the others but to be fair that may be just me and certainly the ability to add colour could well make it worth looking at. If you click on the image below you should be able to download the STP files for this project.
So those are the ones that I consider worth using when you are trying to find more information about the wooden clock design you are going to build. Each has there merits and no reason for you not to try each one before you decide.
Some time ago I published a couple of posts about the clocks Pendulum, firstly a Simple Pendulum and then another post about the more complex Compound pendulum.
This time however it's time to look at the construction of the Pendulum and how it interacts with the rest of the clock. The following are all based on the construction of the simple Pendulum but they can also be read as applying to the Compound pendulum as well.
Moving to the Bottom of the Pendulum there are quite a few variations on the construction that I have developed over the years. The first of these shown here to the left is the use of an adjusting nut. You can see that at the very bottom of the wooden rod the material has changed to Brass and a threaded section added to the end. The Pendulum Bob is slid onto the bottom of the pendulum and then followed by an adjusting nut, the effective length of the pendulum can now be adjusted by turning the nut so that it moves upward to make the clock run quicker or downwards to make it slower. The reasoning behind these adjustments is discussed in the earlier article on the Simple Pendulum. The use of the adjusting nut makes it a lot easier to accurately adjust the rate of the clock because very small movements can be accurately made to the effective length of the pendulum. The disadvantage is that the construction is more difficult because of the joining of the two parts of the Rod together although drilling the ends of the parts and pinning them together can make it easier.
I have not mentioned the shape of the pendulum Bob but to all intents and purposes it doesn't matter as you can have any shape you like. I generally either use a Brass rod cut to a length, the same as in the illustration above showing the back of the clock. Alternatly a disc shape like shown above left.
Moving on, the first of the alternative methods of constructing the Pendulum Bob is shown below. This method requires that a rectangular slot is cut through the centre of the Bob and then a Lock component fitted into it. This Lock component has a hole at its inner end that is slightly offset from the centre of the Pendulum Rod passing through it. The outside end of the Lock is shaped like a bow, so by pressing in the centre of the bow the hole in the other end can be aligned with the Pendulum Rod to allow it to pass through. When pressure is released from the bow the hole is pulled against the rod locking it in place. In this way, the Bob can be slid up or down by pressing the bow as you move the Bob. Adjustment is not so accurate as with the threaded nut but it is easier to construct and gives a lot more adjustment movement. The weights added to this Pendulum Bob design give the Pendulum a little more momentum to overcome any small glitches in the gear train driving the movement of the clock.
