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Information Please!

From The American Horologist magazine, May 1946

Information Please!
Directed by 
W. H. Samelius, Chairman
Science of Horology and Technical Board


ERS: What is elapsed time and what is a dead beat escapement?

Answer. Webster defines "elapse" slip or glide away. Special instruments were made for. the armed forces to show elapsed time. The timepiece has the conventional 24 hour dial with hour minute and second hand. A small dial showing hours and minutes is placed midway from the center of the large dial and the outer diameter of dial.

The hour and minute hand for this smaller dial, or elapsed time dial are controlled by a start, stop and flyback mechanism, similar to the mechanism as we find in the timer watch. When the elapsed time is to be read, the hour and minute hand are on the zero point.

Pressing a button connects the elapsed time train with the regular train, thus setting the hands in motion. Pressing the button again disconnects the elapsed train from the regular train and locks the hands from further motion. Thus, the hours and minutes read from the elapsed time dial is the time accumulated from the starting of the mechanism to the stopping, or the time accumulated from any given point to destination. After reading "elapsed time" the button is pressed once more when the hour and minute hand return to zero position. All this takes place without interfering with the mean time train, or the mean time as shown on the large dial.

The deadbeat escapement was invented by George Graham at the beginning of the 18th Century. It has proved to be very satisfactory for seconds beat clocks such as regulators or clocks employing long pendulums. The deadbeat escapement is designed to give the pendulum a very short arc, around two or three degrees. A short arc of two or three degrees is advantageous in eliminating the circular error that occurs in pendulums taking greater arcs. The escape wheel has pointed teeth, the points leaning forward about 10 degrees. The locking faces of the pallet are ground concentric to pallet the arbor, so when the tooth comes to rest on the locking face of the pallet, the tooth will remain as the pallet or locking face swings into the wheel. The only resistance we have is the pressure of the tooth against the pallet which is constant regardless of the amount of slide or run. There is very little oil adhesion. Usually the dead beat escapement has 30 teeth where the seconds beat pendulum is employed and the pallet embraces 8 teeth. The object of leaning the teeth forward 10 degrees is so the very tip of the tooth rides the face of the pallet, eliminating oil adhesion and I friction.

AK: I hear about hairspring collets poised and also that roller tables are poised. Is someone spoofing me?

Answer: No, no one is "spoofing" you. The practice of poising hairspring collet and rollers has been carried on for many years, especially in the high grade watches. Ordinarily, the roller and roller jewel are attached to the balance wheel when the poising operation is being performed. This is putting the balance in static poise. After placing the hairspring on the balance and putting the balance into motion, we then enter into dynamic poise and even though the balance and roller may appear to be statically poised, it can still be dynamically out of poise for that reason you will find the hairspring collet having been poised by cutting away one side and drilling holes into it so the mass of weight when put into motion will be in dynamic poise. Perhaps you have heard· or know that an automobile engine or some of the running wheels will start vibrating at certain speeds. That is because the weight is not equally distributed dynamically.

HSW: Please explain the difference or meaning of undersprung spring and the oversprung hairspring.

Answer: In the earliest watches, the hairspring was attached to the balance staff under the balance wheel so it vibrated between the balance and the lower plate. This method was more or less conventional in our earliest verge watches and continued with many of the English watches and even some of our early American watches were Undersprung in this manner.

The oversprung spring is the conventional spring as we have it today, the hairspring being attached over the balance and between the balance bridge, which is a great deal more convenient when adjusting.

OP: I lost a cannon pinion for an antique watch and am at a loss to know how many leaves the cannon pinion should hawe so the hands will register properly. There are 40 teeth in the hour wheel, 30 minute wheel teeth and ten leaves in the minute pinion.

Answer. Assuming you have a 12 hour dial, the formula for finding the number of leaves in the cannon pinion will be: Multiply the number of teeth in the hour wheel by number of teeth in the minute wheel. Then multiply the number of leaves in the minute pinion by 12. Dividing the results of teeth x teeth.

(30 x 30) / (10 x 12) = 10

number of leaves for missing pinion.
Proof:


(10 x 10) / (30 x 40) = 12

or 12 revolutions for cannon pinion to one. revolution of hour wheel.

TBT: I have a French clock with cylinder escapement. I removed the escape wheel from the pinion in order to polish the pivots, somehow I lost the escape wheel. What I want to know is how many teeth it had, and how can I select the proper size 1

Answer: Generally speaking all cylinder escapements have 15 teeth. When selecting the size of escape wheel, place the escape wheel directly over the escape pivot hole so the hole in the wheel and jewel hole coincide. Then select a wheel large enough so when the tooth is passing by the balance pivot hole, the pivot hole in the' jewel will be half way up the incline of the tooth. In other words, half the impulse angle of the escape tooth should be inside the hole and the other half outside. You will find on all cylinder escapements, means for adjusting. The balance bridge is attached to a lower bridge or chariot. This chariot is attached to the lower side of the plate, having a lower balance hole jewel. By loosening this chariot, both the chariot and balance bridge can be moved forward or backward from the escape wheel so proper impulses and a safe drop lock can be acquired. The escape wheel tooth must drop on the outside of the cylinder safely close to the impulse edge. In other words, the cylinder escapement has drop, lock and slide similar to the lever escapement.

DL: I would like to know how to true a mainspring barrel.

Answer: The writer assumes the barrel is out of flat causing it to rub the center wheel or bind between the plates. It is possible that you did not replace the barrel cover to its fixed position, as in many hand made watches the parts are marked for location, that is, the cover and the barrel are marked with dots so when the cover is replaced these dots must n be opposite each other. Sometimes they are called locating marks. If this is not your trouble, more than likely the cover has been damaged and needs repairing. To repair the cover and get the barrel to run true in the flat, the following procedure will be helpful.

First see that the cover snaps safely into place. If not, you may have to undercut the snap edge of the barrel and possibly stretch the cover by lightly hammering the cover along its edge on the underside. This operation must be carefully and slowly done so as not to overdo it. When the cover has been prepared, then open the hole in the center a liberal amount and fit in a blind bushing or solid plug. Next, cement the barrel to a cement chuck that runs perfectly true in the flat and center the barrel hole so it runs perfectly true in the round. Snap the cover to its proper position, drill and bore a hole through the bushing to fit the barrel arbor. If this is carefully carried out, the barrel will run perfectly true in the flat once more. If you have a slide rest, you may use that with a boring tool which is more convenient and safer to use than trying to bore the hole in the cover by hand. 








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