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

Relative Seasonal Stability of Various Woods used for Pendulums

Question from reader:  How accurate is your Number Six Clock?

My Number Six clock is quite accurate.  It is usually nearly spot on, but sometimes can run within about a minute or two a day depending on ambient atmospheric changes.

If you maintain a constant heat and humidity in your home, a pendulum clock will maintain better accuracy.  If your home has huge heat and cooling swings, or huge changes from humid to dry air, then any pendulum clock will also show less accuracy, this even includes clocks with metal pendulums.

The pendulum is the timing unit of any clock. A clock's accuracy is determined by the pendulum, and not by the gears.  However, the stability of the material used for the pendulum can affect the clocks accuracy.

A very stable wood used for a pendulum shaft is going to be a more accurate pendulum than a wood that changes a lot with changes in the ambient heat and humidity.  So if accuracy is top of mind, we would like to know the "Relative Seasonal Stability" of the woods we choose for our pendulum.

The way the wood is cut from the tree also has an effect on the stability of the final pendulum.

There are three ways wood is cut from a log; 1) Flatsawn (AKA Plain Sawn), 2) Riftsawn & 3) Quartersawn.  The stability of the final product from those cuts is also in that same order.

Flatsawn (the kind of wood that most of us have readily available) has the least stability to changes in heat and humidity.  Riftsawn is quite stable and can give better results when used as a pendulum, but the very most stable cut of wood is the Quartersawn.  Here is a picture that describes the three different ways wood is cut from a log.

With that being said, even Flat or Plain Sawn wood make excellent pendulums because the grain of the wood is almost assuredly going vertically throughout the entire length of the pendulum.  Flat or Plain Sawn wood has about the same stability to atmospheric changes as a solid metal rod.

Flat or Plain Sawn wood make excellent pendulums, and except for some plywood pendulums, Flat Sawn wood is generally the only type that I ever use on any of my clocks.

Here is a chart that shows the relative stability of wood by species and cut.  Since most of use can only get (or afford) Plain/Flat Sawn wood, compare the examples of White Oak (9.1) and and Honduras Mahogany (4.1).  The Flatsawn Mahogany has more than twice the Relative Seasonal Stability of the Oak.

So according to this chart if you had a choice of Oak or Mahogany, and you were shooting for the best accuracy from your pendulum, you would absolutely prefer your pendulum being made from a close grained wood such as Mahogany.

Graham Escapement with Pendulum Adjustments

Builder Joe has a question about Graham escapements:

I have another question regarding my pendulum slowly stopping.  In your FAQ (on our website):

"Now when you get to the escape wheel, put the wheel in with the pallet arbor.  When the pallets are in proper position, gently restrain the pallets with your finger on the arbor.  Now turn the escape wheel.  It should first push one of the pallets out of the way, and this will cause the other pallet to come into contact with another escape wheel tooth.  Keep turning the escape wheel and the pallets should gently rock back and forth."

Should the pendulum be on it?  I have tried without the pendulum, but I can’t get the pallets to keep rocking.

Thanks again, Joe

Clayton answers:

The entry in the FAQ's describes a manual test of a Graham escapement.  It is a check designed to let you determine if the pallets and escape teeth interact correctly all the way around the escape wheel.  

However, what is described there is only a manual test.  Once the pendulum and the drive weights are added and the clock is put into motion, we introduce inertia that will cause the pallets and escape wheel to interact differently than described in that manual test.  In a working clock the pendulum's inertia will move the pallets further than will happen during the manual test described in the FAQ's.  The drive weights will cause the escape wheel to move faster than it does during the manual test.

Slowly moving the escape wheel by hand, and restricting the pallet arbor, should give your Graham pallets a nice rocking movement as the escape teeth move gently from one pallet face to the next pallet face.  Manually restricting the pallet arbor as described in the FAQ's, the pallet arms should not be involved.  

But when the weights and pendulum are added and the pallet arbor free to move, as in a fully functioning clock, more movement is introduced into the mechanism and the pallets are not now stopped by the their faces, but instead are stopped by the side of the pallet's arm.

The FAQ check is a manual check of the escapement.  It is something you can do to test function while the clock is being assembled and laying on its back on your workbench.

However, the actual movement of a fully functional escapement with drive weights and pendulum will be different.

Here is how a fully functioning Graham escapement works...

The pallets are first stopped by the side of the pallet arm.  The escape wheel is held completely still by the side of the pallet arm until the pendulum has completed its motion and reversed its direction.  Then the escape tooth is released from the pallet's arm and the tooth slides across the pallet's face - giving impulse to the pendulum, and simultaneously causing the next pallet arm to enter between the teeth, which puts the opposite pallet arm in the way of the escape tooth on the other side of the escape wheel.

With an understanding of the step-by-step motion of a Graham escapement explained, in the video below we can actually see it all happening.

If your pendulum is slowly coming to a stop, there are a few issues that need to be addressed.

First, do you have enough drive weight to power your clock?  Every clock is different and will have its own minimal drive weight requirement.  Check out my Blog post on Drive Weight for a way to determine just how much drive weight your specific clock actually needs. (link to my blog is at the bottom of the main page)

But what if you find that your clock needs excessive drive weight to power it?

If your clock is in need of excessive drive weight, the second issue to be addressed is the depthing of each wheel set in the clock's train.  This Depthing procedure is described in detail in the Troubleshooting section of my Blog 

The third issue to be addressed is a test specifically for the action of the pendulum/pallets and crutch.  For this test you will want to remove the escape wheel from the system as we will only be testing the pendulum/pallets/crutch assembly, and all of their associated arbors, and spacers.  

With the escape wheel removed from the system, but with all of the parts of the pendulum, pallets and crutch still working together, pull the pendulum's bob about three or four inches to one side and let it go.

The pendulum/pallet/crutch assembly should continue to rock for at least 60 seconds before stopping.  And 90 seconds is even better.

If your pendulum does not continue to oscillate for at least 60 seconds, we need to find out why.  We need to find what is restricting the movement of the system.

One of the most common reasons is that the groove that the knife edge of the pendulum pivot sits in has been carved too deeply.  That groove should be about 1/32" (.75mm) deep.  A too-deep groove will add excessive friction to the knife edge of the pendulum and restrict its freedom of motion. (this does not apply to the clock designs using bearing packs)

Another area that should be checked is the interaction of the crutch pin and crutch.  

If the crutch pin fits too tightly into the slot in the crutch, the binding friction will stop the clock.  

If the crutch pin fits too sloppily into the slot in the crutch, the impulse from the pallets will not be transferred to the pendulum, and the clock will stop.

The crutch pin should fit in the crutch slot and be free, but not sloppy.  As a measuring tool, you should just be able to slip the corner of a sheet of paper between the crutch pin and the side of the crutch slot.