More Compound Pendulum Physics as related to Escapement Efficiency

 A builder asks:  I want to pick your brain about pendulums. I'm thinking of Organic and Flight. Organic is perfection, the way you dropped the center of gravity and curled the pendulum around. I understand the bob at the top to adjust the timing and how critical the weight is.

Then I moved to Flight. When you sit down to design that pendulum, other than cutting out a trial pendulum and weighing it, how else can you begin to predict how much that pendulum will weigh, and therefore work? Or do you just empirically keep working at it until it does?

I see that you keep the center of gravity low, by expanding the lower pendulum leg from the pivot point.

 I know the length of the pendulum with the Bob creates the 2-second cycle.

Thanks, 

Eric

More Compound Pendulum Physics as related to Escapement Efficiency

The mass of a well balanced horizontal pendulum is, within reason, almost irrelevant if one keeps in mind that it is easier to push a child on a swing than an elephant.  Moving the mass of the horizontal pendulum is the job of the clock's drive weight, gear train, and an especially important consideration is the efficiency of the escapement itself.  

Take for example the SwingTime (or Mantis or Flight) and Organic, all of which have compound pendulums.  The SwingTime (or Mantis or Flight) clockworks cannot be driven by hanging drive weights using the usual one inch diameter drive pulley barrel.  There is simply not enough torque produced from the pulley barrel's 1/2 inch of leverage to be transmitted through the gears into that inefficient escapement to run the clock.  SwingTime requires that it be driven by a motor arm transmitting its torque through the large center wheel...and it must be a relatively large center wheel diameter, too, to create a large enough lever.  I tried running a clock with SwingTime's escapement with a smaller diameter center wheel and even after adding significant additional weight onto the motor arm, it still did not have enough torque to run that particular clock.  A long lever is required.

The picture above shows what kind of lever one might need to move an elephant.

On the other hand the Organic has a very efficient escapement and using this extended lever motor arm on the already large diameter center wheel almost overpowers that clock design.  Organic is almost unstoppable.  I have to stick a pencil in the gears to keep it from starting on its own.

So the mass of a horizontal pendulum, again within reason, is more a consideration of the type of gear train and escapement that one uses to drive the pendulum.

Once a horizontal pendulum, of pretty much any reasonable mass, is perfectly balanced, it takes very little force to keep it in motion once set into motion.  (Organic is so efficient that it doesn't even need to be set into motion ~ it starts itself.).

The beat or timing of the pendulum is created by the relative masses above and below the horizontal pendulum and their location relative to the pivot point.  Those are the upper and lower bobs, one of which is fixed and the other adjustable, depending upon the clock's particular design.  SwingTime, Organic and Flight all have adjustable upper bobs and fixed lower bobs.  Mantis has a fixed upper bob (the antennae) and an adjustable lower bob.

You may enjoy going back and reading my Pendulum Physics blog post on compound balance pendulums of 09 04 2022.  The above information is explained again in that Blog post somewhat differently than I have explained here.  https://claytonboyer.blogspot.com/search/label/Pendulum

So why do I design with the inefficient escapement of the SwingTime, Mantis and Flight?  Because I love seeing that excessively huge, beautiful pendulum swing that it produces.  The escapements inefficiency imparts a magnificently exaggerated movement to the pendulum.  Anyone who has stood in front of Mantis or Flight knows how relaxing and mesmerizing that huge, slow pendulum swing can be, and what a delight it is to watch each of these mechanisms displaying their dramatically exaggerated pendulum kinetic joy.

Celebrating Simplicity's 20th Birthday

Since our Simplicity has run now for over twenty years, just for fun I calculated the number of times Simplicity has swung its pendulum in those two decades. I was amazed to find that this clock has ticked and tocked over 315 million times! That is a number that is almost too large to comprehend, and yet our Simplicity happily continues on with its daily duties without complaint.

Our Simplicity is as happy today as that day, twenty years ago, when I gave its pendulum the gentle push that stated this amazing journey. And, look closely at the picture, you'll see that our Simplicity shows no wear at all! But best of all, this clock has been completely trouble-free all that time. I don't recall my wonderful Simplicity ever giving me a single problem. I just wind it, and it runs. Looking at its wear patterns, I would estimate that it probably has another two or three hundred years before it begins to show any signs of its age. I'll check it in a couple hundred years and keep you posted.

 For its first few years that Simplicity kept me company out in my shop where its beautiful song would be the first thing to greet me in the morning when I opened the shop doors. But out there with the constant Hawaiian trade winds to contend with, it would also be exposed to salty humidity and be constantly accumulating dust and, of course, be routinely covered in sawdust from my other woodworking activities. With that accumulation of humidity, salt, sawdust, at certain point, it would eventually stop ticking. I felt sorry for it. Having to put up with all that humidity, dirt and dust, must have been a challenge, however it never really complained. And the fix was so simple! With a few blasts of compressed air that beautiful Simplicity was ready to go out dancing once again.

Today that same Simplicity is featured as our living room clock, where it shares the opposite side of our fireplace mantle with the Zinnia. Simplicity and Zinnia make spectacularly beautiful fireplace finials.

Simplicity is the second clock that visitors see when they come into our home. The first clock visitors see is the Arts&Crafts in the foyer. The A&C is an electromagnetically impulsed clockworks. All of these mechanisms are such a delight!

As you probably have read in the Instructions sent with your plans, it is best to stop the pendulum each time that the clock is going to be rewound. This helps preserve the delicate pendulum, pallet adjustment. Then, once the clock is rewound, the pendulum can be restarted. After ten or eleven years of stopping that pendulum every time I rewound the Simplicity, I wanted to create a way to rewind the clock without having to stop and start the pendulum, and yet still allow the clock to maintaining the proper pendulum/pallet adjustment. My idea was to create a maintaining power arm that could be temporarily added to the large center wheel during the rewinding process...and it works beautifully! That Maintaining Power Arm now rests, along with the Speed-O-Key, on the shelf behind the Simplicity's center wheel. But I still have the original Simplicity key on display because it is such a beautiful showpiece of wood art.

If you have the Simplicity plans and would like to make a Maintaining Power Arm for your clock, simply email me a request and I'll be happy to send you the pdf.

I hope that you choose to build a Simplicity. I also hope that you enjoy living with your clock the next twenty or...maybe three hundred years.

After decades of building lamps, chairs, tables, bowls, cabinets, kitchen items, kinetic sculptures, automata, etc. I am convinced that these clocks are absolutely the VERY BEST way to spend time in the shop. I hope that you think so, too.

Robot Design

Builder Steve asks Clayton, "I’m intrigued to know how you design these robots. Do you use Meccano to test out varying options?"

Clayton answers: 
I've never had a Meccano set, but I think having one would have been a boon to my creativity.

I design in my head, then I draw, and test, and test, and test, draw some more and re-test.  Eventually I either give up, or have a success.

You can see one of my failures below.  Cracks me up every time I watch it.  Virtually nothing is successful the first time.

Creating an Accurate Escape Wheel

If your accuracy at the scroll saw happens to be a bit lacking, here are four steps to help you create a wheel with a high degree of accuracy. 

I chose the escape wheel for this demonstration because the escape wheel has the most exacting requirements of any of the clock's train of wheels.  However, these four steps can also be successfully applied when creating any of the clock's other wheels.

The parts shown in green on each picture are the parts to be cut or sanded at that particular step.

Whirly in Color!

 

Master Gear Wizologist Ken Duffy created a wonderfully customized and multi-colored version of the Whirly. Ken not only added delightful colors, but he also created a third way to power the Whirly. The original Whirly is powered by either a drive weight or by a constant force spring. Ken has powered his colorful Whirly with an intermittent motorized rewind.

For those of you that have already purchased the Whirly plans, or new plan purchasers that find Ken's customizing concepts interesting, contact Clayton. Links and motor arm information to upgrade your Whirly are available upon request.

(AH) Alignment Hole Click Gear

Steve asks Clayton: 

I've noticed on the Swing Time plans the notation "AH", which I hadn't seen on other plans I bought before.

Maybe I missed it, but what does "AH" stand for?

Thanks

Steve 

Aloha Steve, when parts need to be reinforced during gluing, or need to be aligned in a specific orientation, I will add alignment holes (AH) notations to the plans to be sure that the parts are aligned correctly.

In the SwingTime plans that you are working on, the parts of the Daisy Dial Train need to be aligned correctly to get the hour and minute hand assembly to work properly.  

The Daisy itself has an up and a down.  The cleft in the Daisy needs to be positioned UP, and the rounded bulb placed at the bottom.  The exact alignment can be achieved between the Daisy and its Support by inserting a short length of rod into the alignment holes during gluing.  These rods can be left in place, or they can be removed after the glue has dried.  In this case the choice of leaving the alignment rods in place or removing them is up to the builder.

Also in addition to positioning the Daisy on its Support, the Tri needs to be positioned correctly on the Daisy's Hour Hand so that the the Hour Hand is pointing in the proper direction to show the correct time once assembled.

For both of these situations exact alignment is produced using the Alignment Holes (AH) provided in the various parts.

There is another situation in which alignment of other parts, such as gears, is critical.  For example, in the Genesis plans there is a "wheel set" (a pinion and a large gear) that need to be aligned during assembly.  Alignment holes in those parts show the builder how to achieve the correct alignment of the teeth of these gears that will allow the clock to show us the correct time.  

Other times you might see Alignment Holes in the Click Gear and its Support in the rewind system of the clock.  In this case we Do Not want to remove the alignment rods after the glue has dried between the parts.  The alignment rods in this situation allows for a stronger joint between the parts than what is provided by just the glue.  The reason for this additional strengthening of that glue joint is that the Click Gear must support the entire drive weight of the clock.  We certainly don't want the Click Gear breaking loose from its Support.  Leaving the alignment rods in place allows for a bit more insurance against separation of that glue joint, and helping to prevent the drive weight crashing to the floor.  "Drive Weight Crash (DWC) Prevention" is also why I recommend using only the highest quality plywood when creating the Click Gear and Clicks.

BTW...once the Click Gear is glued and pinned to its Support or Pulley, I also add a coating of cyanoacrylate glue (CA or Super Glue) to the tooth surfaces of my Click Gear ~ just for a little more insurance against Drive Weight Crash.  That additional procedure of adding the CA may be overkill, but I'm superstitious.  (I've also learned to stop listening to the voices that come out of the electrical box in the attic storage room)

In over twenty years of creating these wonderful mechanisms I have only had one DWC...and if you've ever had one, you know that one DWC is one to many.  So using high quality ply to make the Click Gear and Clicks, and the addition of the support pins to assist holding the rewind system's glue joints together, will help to avoid the dreaded Midnight Crash Syndrome.  

I hope you are enjoying your build and please send pictures when you get your SwingTime completed.  

Aloha.  Clayton

Help! My Clock Runs too Slow (or too Fast)

 FOR A CLOCK THAT RUNS TOO SLOW...(but also be sure to read over the section below on "For a clock that runs too fast"). 

If you have recently finished your clock and put it into beat and it's running too slowly - I recommend you do nothing for four to six weeks. 

Some time ago I got an email from a builder whose Simplicity ran too slowly at first, he cut off the pendulum...only it was too soon.  When his clock eventually found its beat, it then ran too fast.  I recommend waiting a few weeks before shortening a pendulum shaft because it is much easier to cut off a pendulum than to add to it. 

Some clocks need to run a while before they find their "beat".  It is best to simply watch a new clock for a few weeks.  Stand back and enjoy viewing its motion, and congratulate yourself for getting a chunk of wood to move.  Just enjoy the movement. 

If your clock still runs too slowly after it has run for a few weeks, then you can begin to shorten the pendulum's shaft a little at a time, until you get your clock running at the perfect beat. 

But even before cutting off the pendulum, I would recommend that you read over the "Depthing" procedure in my Troubleshooting Blog posts and in my FAQ's, and follow those instructions.  Depthing will help to free up any residual internal friction in your clock and possibly make it run more freely.  The links to my Blog and FAQ's is at the bottom of my main page. 

You can also add just a slight bit of paraffin to the tooth contact surfaces where the pinion and wheel teeth touch.  Add just a very slight amount - because too much paraffin can clog the dedendum and make the clock stop.  Candle wax works okay, but I like to use a color coordinated Crayon.  Crayon paraffin is softer than candle wax, and that sharp point makes getting between the teeth much simpler. 

You can also remove the pallets, wind your clock, and let the gears run free.  When the wheels stop, rewind the clock and let it run free again a few times.  Things get spinning pretty fast!  But sometimes this helps to "break in" the mechanism more quickly. 

If/when you have done all of the above suggestions and your clock is still running too slowly with the bob all the way up as high as it will go on the pendulum; to determine how much of the pendulum to cut off you can measure the threaded rod sticking out the bottom of the bob, and remove about half that length from the pendulum's shaft...but be sure to wait a few weeks before cutting the pendulum to give your clock time to 'break in' and find its beat. 

FOR A CLOCK THAT RUNS TOO FAST...(but also read "For a clock that runs too slow" above.) 

If you have just put your clock into beat, leave all alone and just enjoy the movement for four to six weeks.  Some clocks run fast, others too slowly when first put into beat and they require a "break in" period to find their beat.  I recommend during this time to just stand proudly in front of your clock and pat yourself on the back for doing such a good job of getting a chunk of wood to move. 

After the break in period if your clock is still running too fast (and it depends upon how fast) two things may be happening.  If your clock is gaining minutes a day, you can try to simply make the bob heavier, and/or lengthen the pendulum by a few inches.  If your clock is gaining hours a day, something is probably slipping inside the clock's train and you'll need to investigate further to find the broken, unglued, or unrestrained part. 

Certain escapements, like the Graham, are not very sensitive to drive weight, but others, like the grasshoppers and the "walking" on the HO, and the verge and foliot on the Wee Willie and Horologium are quite sensitive to drive weight.  If your clock is running fast, try to decrease the amount of drive weight.  Also read the section on "Depthing" on my site in my FAQ's and the four informative Troubleshooting posts in my Blog.  The links to these can be found at the bottom of my main page. 

As I mentioned, if you just put your clock into beat, it is best to not do anything for a few weeks except enjoy the movement.  After that time you'll want to check the bob weight by adding fish weights evenly on each side of the bob, and/or increase the pendulum's length depending upon how fast the clock is running. 

Take a look at my Attempt for an easy way to add length to a pendulum. 

Also, you'll want to do all of this where the clock will actually be permanently mounted.  It's weird, but sometimes just moving the clock from the shop to the house can cause the clock to run faster or slower (I have no explanation as to why, but it has happened a few times to my own clocks). 

Enjoy! 

Aloha.  Clayton