|Modern Times Clock|
(just some eye candy unrelated to this post)
Berry writes: I have everything completed now on the clock but having issues (I bet you hate letters like this). The motor drives the Center Wheel just fine. The Third Wheel and Escape Wheel and Pallet chug along day and night. It looks great. Unfortunately the Minute and Hour hands don't keep the time. I marked the Center Arbor Tube and Hour Arbor Tube with a spot of ink at the top. After one hour they were at the 9 o'clock position. Fifteen minutes later they're both back at 12.
Residual internal friction is the bane of our wooden clock movements. Friction can happen in a variety of places, and that’s why I always recommend Depthing as we build to help find and eliminate as much internal friction as possible before the assembly is completed.
The Depthing process takes time, but it also saves time at the end in trying to find hidden friction points. Once the Depthing of all the pieces is complete, it almost assures that the clock should run well once the pendulum is put into motion.
Depthing is a simple process of testing one wheel with its pinion using the clock frame these two gears will be running in. Depthing is testing ONE wheel and ONE pinion...not the whole train of gears at one time.
Removing wood from the back of the toot allows the spacing of the front of the teeth to remain constant while at the same time opening up the space between the teeth enough for proper clearance.
A clock wheel travels only in one direction, and with only one wheel and one pinion in the clock’s frame it gives us the opportunity to first visualize the direction that the wheel will be turning in the clock, and to decide which side of the teeth is the contact side.
With one wheel and one pinion being tested inside the reassembled frame we are also simultaneously testing other parts, like the Frame’s arbor holes and the arbor’s spacers, and this allows us to make sure that these parts are not causing the increased internal friction.
If the spacers are causing internal friction they can be filed or sanded slightly to allow freedom of motion of the two arbors. There should be about 1/16” (1.5mm) of end play (front to back movement) in each arbor.
Bill C asks: How do you time the escape wheel and the pallet to the crutch and pendulum bob? This would help me set the pallet on the escape wheel and to know if the pendulum bob should be plum to vertical level. Thanks for your help.
Aloha Bill, you are correct, the three components, pallets, escape wheel and pendulum, all need to be adjusted to each other to have the clock run correctly.
First start with rounding and balancing the wheel, and then go to setting the pallets to the escape wheel. You'll find how to manually check the function of your pallets and escape wheel in the FAQ section of my site. Links to this, and more, are at the bottom of my main page.
Once you have a round escape wheel and have tested that the pallets work around it a full 360* (I usually go around multiple times just to be sure), then you can set the pendulum to the pallets so that you get a good, strong, even tick-tock.
You mention a vertical, plumb pendulum rod...that's not the way pallets are set, however I can give you a little hint to what it should look like...with the pendulum stopped, one of the escape teeth should be resting about halfway up the pallet face. I stopped my Simplicity this morning to take this picture for you.
When you move the pendulum to free the escape tooth, the other escape tooth should come into contact with the other pallet face in about the same location when the pendulum is at rest. On a round escape wheel with nicely made pallets, the tooth should be at rest in about the same position on this second pallet face as on the first pallet face.
Rounding the escape wheel to its center arbor is important. I mount my escape wheel on a board with an upright rod in the wheel's center hole and clamp that to my sander. Find the lowest tooth on the escape wheel and turn the wheel so all the teeth are sanded to that height. Or, better yet, if you have left the paper pattern on the escape wheel, turn the escape wheel, sanding around the wheel so that the black line on the pattern just barely disappears. Now we know that all the teeth are the same height with respect to the center arbor hole.
Balancing the wheels is important also, and a balanced wheel is most important at the escape wheel. Stick a rod in the arbor hole of the wheel assembly and the low side is the heavy side. Lighten it by drilling or sanding away some of the back of the wheel, or adjusting the size of the wheel's cut out design by sanding some away.
The photo I'm including I have named "Simplicity after 15 years". My Simplicity is actually older than that but I've lost track. In addition to the pallet/tooth positioning, what I also wanted you to notice in this picture is the amount of wear on the pallets and escape wheel teeth after the clock has been running consistently, every day for more than 15 years. Take a close look...that's right...none!
I was just sitting here thinking...Simplicity ticks once per second, or 3600 times an hour, times 24 hour, times 365 days a year for 15 years - that is well over 473 million ticks and tocks. No sign of wear, and never a problem...wow!
Pretty amazing. I have a Big Smile on my face right now! That Simplicity looks like it should still have another two or three centuries of good running left in it.
I hope you love your clock just as much.
Enjoy! Aloha. Clayton
Answer to question 1) The length of the run time depends on a number of things, but the main factor in determining run time is the number of winds of the spring. The Neg'ator springs I recommend will give a run time of about 40 minutes. Other constant force springs may be used, however their length is usually much shorter (for example; 22" or 560mm versus 106" or 2690mm) and will give a proportionally shorter run time. (using these spring examples means a difference between an 8 minute of run time and the 40 minutes).
We have also found that the Zinnia run time can be dramatically increased by eliminating the grease from the bearings. For our light duty kinetic sculpture purposes the grease inside the bearings actually increases the internal friction and can cause shortened run times.
By soaking the bearings overnight in mineral spirits and washing out the grease we've been able to double (in some cases) the run time of the Zinnia.
I do recommend adding a drop of clock or light oil back into the bearings...but I think this may be mainly superstition as there is probably still sufficient lubrication for our purposes.
Answer to question 2) The wheels of the Zinnia are first balanced and then unbalanced with the unbalancing weights that are attached behind the wheels. Recommending that the wheels be balanced first allows me to specify in the Zinnia plans which arms are the best for the placement of the imbalancing weights.
Balancing is not particularly critical as the unbalancing weights can be placed on different arms to get the sculpture to run. However, I build my plans primarily for the beginner, and I must make sure that if my instructions are followed the chances of success are going to be good.
Experienced builders could (possibly) disregard my instructions and still make the sculpture work...so..."critical"...no, but recommended. Enjoy!