Clock: escaping from reality

If all there were to a clock (wooden or otherwise) were a bunch of gears with a weight (or spring) attached, then it is probably pretty obvious that the falling weight would just unwind the gear train at the proper rate for whatever weight you put on it. Minus friction. So how does a clock keep time? It has to have an escape mechanism, clockspeak for a device that interrupts the weight on its Newton-ordained fall to the ground. The escape mechanism on a clock is usually, in a clock, based on a pendulum; since a pendulum of a given length gives you a very steady beat. But alas, there is friction. You can easily make a pendulum. Put a weight on the end of a rod. Put it in some sort of pivot. A nail, say. Push it. You will see that eventually the pendulum beats no more. Friction, you see. So there is another function the escape mechanism must perform. It has to give a bit of a kick to the pendulum, to counter-act the evil friction. Actually, friction can be a Good Thing (TM) else your car wouldn't stop when you hit the brakes, but in clocks we really, really, don't like it. Again in clockspeak, the bit of a kick is called impulsing the pendulum. Over the years, nay centuries, there have been numerous very clever humans who have designed escape mechanisms, as a Google search on "clock escape mechanisms" will convince you. Mine is what the designers of this clock deemed best, a "deadbeat escape mechanism". There are many others.

The basic escape mechanism consists of the anchor and the pallets.The anchor consists of a piece of wood. You can see the anchor very clearly in the pic above. It looks like an anchor! The pallets are pieces of brass. Resist wear, you see. It was fun making the pallets. I milled them on the lathe, but took no pictures because it was a very simple job. Then I filed to the required angles. Now I have to adjust them, but that will take time (it's a clock!) and I have postponed it. I moved on to that tedious job, the minute work as it is called. The thing is, the clock is set up (all those gears!) so the Center Wheel (one of the gears) revolves at 1/60 times a second, or in other words one minute. But there is an hour hand. It must go around the dial much slower than the minute hand. In fact it must go around 60 times slower. (assuming you have a 12-hour dial). More gears. That's what the minute work is for. Another gearbox. Now the wheels were cut out on a bandsaw by hand. Hardly precision work. Furthermore here are small imperfections caused by the fact that you did not drill the holes for the axles, or arbors, exactly where you should. So we have to depth the gears (wheels). In this clock, says Mr Wilding, this involves sanding off bits from the teeth until the gears spin freely. At first I tried sandpaper. Very slow. I spent three days depthing the wheels. Then I got smart. I rigged up my lathe with it Dremel milling jig, which I described elsewhere.

The Dremel has a router bit in it. With this baby I can take off as little as .01 cm (or .0005") at  one go from the wheel. (Not really. This is wood, not metal. Precision is futile). This speeded up the problem considerably. Couldn't have done this with the going train (the main gears) because the wheels are too big to "swing" on my little Taig. Later I got even smarter. But that's another post. Live and learn.

So just when you thought you were immune from clocks, I have to return to them. I warned you. Clocks are an obsession. Great thing to do in the winter, though. have had a snowstorm and there is a new 40 cm on the snowpole! 

The above picture shows the center wheel. Mr Wilding (whose instructions I am following)  would spell it "centre wheel. " Engineers would say "gear" but I too bow to clockspeak. After all it has been around since the 16th century, if not longer. The pic shows one end of the center wheel.  Mr Wilding put steel ends on his wheel axes. Sound idea. Cut down on friction. Almost any clock plan you will find on the Internet has solid steel arbors (axles). The other end of this arbor is a point. Here I am turning the point on my trusty Taig lathe. I have finally learned how to turn points. It requires a contraption called a compound slide in the US and a top-slide in the UK. No matter, same thing. I could have done it with a file, but the compound is much faster. Good practice, too. Voila the point being turned. By the way, the things we are turning are called pivots in clockspeak. Bearings from where I come from.

 In Mr Wildings's modifications, the points run in brass bushings. A bushing is just a piece of something (my case, brass. And by the way it is very difficult to find brass in Alaska. Not a material in great demand here) with a hole in it. No big deal. However, the bushings must be reamed out to a 60 degree point to accept the points. Further, the holes you drill must accept the bushings as a tight fit. In fact you should press the bushings in. I used my drill press as, well, a press. This means that you cannot trust the hole sizes on the drawings. On the balance, this is not a clock for the amateur.  As the British say, the words do not match the music. For Mr Wilding, who has built more clocks than I have passed power poles, this is no problem. I have had a few problems matching up the two. If only he had corrected the drawings!

 Above, I am using a 60 deg reamer to ream out the bushings. No major problem there. Next problem is pushing the bushings into the "plates" of the clock. The   plates  are the frame of the clock. If you happen to use Mr Wilding's instuctions you will have drillled undersize. For pressing I use my drill press and brute force. I was careful to drill the holes undersize. A nuisance when it is all done, because I work metric and all my stock is Imperial i.e. RGU, but it can be done.

Here I am pressing the bushings into their holes.I used a 60 deg point. These babies are not coming out with any ease. Good.

 

The next step is to assemble the clock. Again Mr Wilding fails me. The drawinngs all use numbers, but Mr Wilding uses names (third wheel, fourth wheel, etc.). I  really wish  he had corrected the drawings. No matter.  Let's start assembling this thing. First thing in is the  escape wheel:                     

 And next, the third and fourth wheels. Which are obscure numbered parts on the drawings. Grr. I wish Mr Wilding had supplied corrected drawings! No insult to Mr Wilding, but this is my first clock, and the words don't match the music.

Looks like a clock, does'nt it? But alas, there are trials yet left. Although we carefully "depthed" the wheels, the thing sticks. It does not run freely. Lots of reasons, but most likely, when we drilled the holes for the arbors, we did not do it quite right and there are some sticky spots on the wheels. Stay tuned. The wheels must spin freely or we are lost. So back to square here minus one. More to come.

I note that most modern clock plans specify steel arbors. Running on hardwood bearing holes. Probably cheating! But much easier for a good woodworker than the stuff I am going through. And all in RGU, too. Drill 17/128th of an inch. Why oh why RGU?

Winter Scenes

One of the greatest pleasures of the Alaska winter is skiing. I go out nearly every day. The weather has been clear, which means cold. Day breaks at -20C, but by noon it is above freezing, so out I go then. The snow has been beautiful. Long glides! Love it. I have beaten out a loop in the woods. Note the conspicous absence of straight lines. There are no straight lines in the woods. Too many things in the way. Deadfalls. Brush, early in the winter. You detour. The trail gets beaten out early in winter, after that I just follow it. So the loop never takes the same course each year. Also I have a tendency to turn left too much! Must have something with being left-handed. Furthermore there are no "landmarks" in the woods. When the sun is out you have a built-in compass, but sometimes the sun is shy. I could of course carry a compass with me; in fact my watch has one built-in. But then I'd have to take off my glove. A pain. So my trails will break a snake's back. There are no snakes in Alaska; we do have bears to make up for it.

It takes me about 45 minutes to complete the loop. First I warm up on my backyard oval. Then I do the loop. Takes about an hour. Great exercise. If my hands do not freeze. But a dear friend gave me some marvellous gloves, made in Norway by Swix, sold by L.L. Bean, a byword in Alaska. My hands have never been so warm. Thank you, Kathy.

After we have done the loop, the house is in sight and the track is clear. Oh happiness! We have worked out, we will soon be inside, and will get back to clockmaking. I bet you were glad to get a respite from clockmaking, too.

And now for a coda. Composed by Alaska Weather Enterprises. Performed by the Alaska Weather Machine. Yesterday was as clear as the photos above. This morning when I got up it was snowing. My official snowpole says +10 cm. as of 1400 local time. Of course, what the snowpole says bears no relation to what it may be elsewhere; John says there was all of 30 cm (a foot) of snow in the driveway;  He plowed the thing.  Now I realize that by some standards this ain't much. Thing about the Alaska snow is that it stays put, and this distinguishes it from, say, Syracuse NY where it can put down a meter in 24 hours. But it does not last. Ours does. All winter, in fact. Hmm. Today is the equinox, isn't it? Start of spring. Couldn't prove it by me. But if you don't like snow, you should not live in Alaska!  If you do, cross-country skiing is your friend.

There is a place called Cordova, AK. Gets four or more meters a year, and it never goes away. They have real problems. I consider my problems minor compared to theirs.

Clockwork

I am back to clockmaking. I have been running into problems. Mr John Wilding wrote the instructions. But the drawings that come with the instructions do not reflect the modifications. Mr Wilding, as I have said, has built more clocks than I have passed power poles. He modified the pivots. Engineers call these things "bearings". He used pointy steel ends for his axles, which in clockspeak are called arbors. These pointy things run in brass tubes pressed into the clock frame, or plates. . We made the plates in episode 0 of this saga. So I have to make the arbors first, drill them for the pointy ends (called pivots in clockspeak, got that? Even in Italian they are called pivots) and then make the brass tubes, called bushings and this is engineerspeak too, so I can deal with it. Unfortunately the drawings (plans if you prefer) do not reflect his mods. Mr Wilding's mods are really very good; they cut down on friction, the deadly enemy of accuracy on any clock, wooden or otherwise.

 I first made the "center wheel" arbor as it is called. It calls for a 12mm dowel and (actually 1/2") and I had no such animal. So I turned down a 3/4" dowel. This was a Good Idea (TM). No commercial dowel is either circular or straight. It is not even dimensionally correct. Above, I am center-drilling the arbor to put a pointy thing (pivot) through it. Now this is no mean feat on the Taig lathe. You must support the outboard end so that the arbor does not whip about. I used my home-built steady-rest, mentioned elsewhere. This required boring out the center hole on the steady-rest to 12 mm + which was a project all by itself.

Finally I had the hole drilled. Now for the pointy thing (pivot) itself. This is a piece of steel hardware store rod with a 60 degree point on it.

 This was a breeze. I have finally learned how to turn points on things. I still have to work on my finish. I suspect my carbide tools are finally wearing out.  I am supporting my pivot on a collet. I have but the standard set of collets for the Taig lathe. But when you can use then they are marvellous. No runout (off-center) at all, unlike a standard chuck. Plus they will not take your fingers off, unlike the standard Taig chucks.

This pivot goes into the bushing -- or as Mr Wilding calls it, a bush. So we have to turn a bush from brass. This involves (1) cutting the thing, with a hacksaw, from my priceless stock of brass that I found at Fastnall in Anchorage, (2) drilling it through, (3) cutting a taper same as the pivot and (4) cutting to length.

Above I am at the stage of cutting the 60 degree taper on the bushing. I am using a priceless 60 deg. countersink picked up at Lowe's. 'Twill do. The other end of the arbor is a plain old piece of steel. Hardware store! I gave it a skim on the lathe to true it up. When all this is done, we can shove the wheel onto the shaft. This particular wheel has no pinions attached, a blessing. It will drive the minute hand.

So there we are. In the meantime we have have had lots of fun (and a great deal of trouble) making the arbors for the gear train that gets you from the escape wheel to this particular wheel. But the clock is beginning to take shape.

I am not in the least ashamed of my efforts so far. As the British say, the Words of my tune do not match the Music. Mr Wilding's variations on the clock (all for the good) do not match his drawings. And so I have to stop and figure things out. Worse, Mr Wilding uses RGU all the time. I refuse to work in RGU so I have to stop and convert, almost all the time. Then I have to deal with the RGU feed on the Taig lathe, but that is simple;  at least it's decimal and not absurd fractions of an inch. Next episode will detail (I hope) the rest of the "going train" which is clockspeak for the gearing that gets you from the pendulum beat to the hands on the clock.

Ansd it's off to Nome!

Time for that great Alaskan institution, the Iditarod. Pictures from last weekend, to be sure. Should have posted earlier but as usual life got in the way.

For those of you who do not wish to bother to look up my previous posts, the Iditrod is a dog sled race. Anchorage to Nome, over 1600 Km, with a slight detrour between Wasilla and Willow. Not enough snow these days to go the whole way, 50Km or so, because Wasilla is an urban heat island these days.  By great good fortune the race passses less than 2 Km from home. n fact as the road goes it is exactly 2.7 Km or a mile and a bit. So there we were. We took hot drins, padding, and our warm clothing although the temeratures were extremely mild, freezing or so. When we got there,  we found the usual Alaska family festival atmosphere. People bring tents, food, barbecues, children, and snow machines. These are known as "snowmobiles" in other states. These are thousands of them. Well, quite a lot, anyway. We arrived with a certain amount of time on hand. The  trick is not to be too early. The race starts at 2PM. It will take them about 25 minutes to get to where we are.

Still it is a big thing when the first teams arrive. They are in strict start order at this point, chosen at random. They have a compact not to get ahead at this point. That can wait for Rainy Pass. Still it is very exciting when the first team appears.

It is kind of difficult to take photographs,. because the sun is shining. Good, yes? Not for photography. You can't see your viewscreen (it's digital, stupid) in the glare! So eventually the driver goes past.

And if you have a program you cheer the driver on by name. Go. Joe! Always some people who are prepared. I am not one of them. The start order is on the Internet. I should really print out the start order!

Fianlly the dogs recede into the distance. We are thrilled. I'd be a lot more thrilled if it weren't for all those snow machines, but then, I am atavistic.

And they are off to Nome. Woof! Love those dogs. They are happy. They are pulling. That is their job. True craftsmen, er, craftsdogs. They are doing their job, and doing it well. As we admire crafstmen, we should admire craftsdogs.
 

The depth of the wheel (and pinion)

Today I finished the last wheel and pinion set in what clockspeak calls the "going train." This is the gearbox that gives you the proper relationship between the beat of the pendulum and (for example) the second hand. It takes three wheel and pinion (big and little gears) to get away with this.  It might take more if your clock has an oddball pendulum. Traditionally we have the "great wheel" which in turn connects via pinion to the to the "center wheel" and so via pinion again to the "third wheel" and so up to the "escape wheel." These terms date from the 16th century or so. When you start reading clockmaking books, or even looking at the internet, the terms reoccur over and over. By constant reading these terms are second nature to me by now, but it sure wasn't so at the outset.

But one problem at a time. Today's problem is "depthing."  More clockspeak. That is you have to put the axles, which are called arbors, so that the gears mesh correctly. Not exactly CNC. They did this easily in the 16th century! In a wooden clock, the technique is different. The holes are specified the by the paper patterns. The gears, as they come off the bandsaw, are guaranteed not to mesh. We are talking of tolerances of less than 0.5 mm. I defy anyone, Superman excepted, to cut something on a bandsaw to within 0.5 mm. That is the width of a thin pencil lead. So the teeth jam. So you have to sand them down so that they do mesh properly.

There are many reasons gear teeth jam. But a really big one is that the teeth are not the same length.  So today, finally learning from experience, I built a jig to get the same length on all the teeth of my last wheel/pinion combo. I thank the collective Internet for this idea. I am not the first person to build a wooden clock.

Above is the jig. It is a piece of wood with a finishing nail driven through it. It is clamped to my table. It bears against a circular sanding disk that came with my $10 jigsaw. You rotate the wheel (or pinion) and eventually it will sand the wheels down so that the teeth are exactly (well, maybe 0.05mm) the same length. In a brass wheel clock, you turn it on a lathe until the wheels are at the final diameter. Much easier. Well, we have chosen a wooden clock as our first effort. So we must deal with it.

Amazingly when I tried this wheel/pinion combo there was only one tight spot. Another reason your wheel/pinion combo sticks is that the teeth are too fat. A bit of work with a fingernail file and she was done. I am now ready to try the arbor-making business. The arbors, or arbours if you prefer the traditional spelling, or even asses in Italian or ejes in Spanish, are the axles on which the gears all turn.

Clockmaking is an obsessive business. I must be obsessive. I am enjoying  it.  The first combo took me four days, or maybe even five. The next set went in three days. This one went in an hour.

The moral of the story is that if you can see a pen line on the pattern, you have not sanded enough!

Depthing the wheels

Once you have cut out your wheels (big gears) and pinions (little gears) the next step is to "depth" the wheels. This is clockmacker-speak for "getting the gears to mesh correctly." As cut and sanded, the wheels and pinions will almost certainly not mesh. Small errors in cutting the gears will magnify.

Now in a clock we have a huge gear reduction, possibly 3600 to one (that is the number of seconds in an hour). This huge reduction is accomplished in stages and that's why we have pinions and wheels. That is why a clock looks so complicated. Every wheel (lots of teeth) meshes with a much smaller pinion (few teeth). And we are dealing with wood, which even in its plywood incarnation is kind of recalcitrant. A clock put together in winter might not run in the summer because the change in humidity swells up the wood and the teeth jam. Brass is much more humidity-resistant and that's why we usually make wheels out of brass. We also make pinions out of steel.

But I am stuck with wood. I am not complaining! I chose the way myself. Now we have to live with it. Each wheel has a mating pinion. I'm following Mr Wilding's instructions and he as built an infinite number of clocks compared to me; this is my first clock. Anyway what Mr Wilding recommends I do.

So above I have very, very carefully drilled holes in the back "plate" (frame piece of the clock). The holes are just large enough to accomodate a finishing nail. I have cut off the head of the nail. And so begins a tedious odyssey. You spin say the pinion, the little gear at the top. At some point it will certainly jam. You look at it with a magnifying glass. If necessary with a jeweler's loupe. You determine what is wrong. In general if you can see ink lines in the gears it will jam. You carefully sand away these lines. It still may jam. You sand away some more. I use my swiss files and lady's fingernail abrasives, AKA nail files, very cheap. Let us be thankful for lady's long fingernails. So there we have one pair of wheel-pinions complete.

Very tedious. But watchmakers have the same problems, only at a much smaller scale. So I am grateful. I only have to  use a loupe occasionaly. I have a really nasty problem on the second wheel-pinion combo. Stay, as they say, tuned.