On setting and adjusting Ithaca Calendar Clock Movements

by John C. Losch

There are actually several models of Ithaca Calendar Clock movements, but the majority, found in at least three sizes I am aware of, operate nearly the same way. I have a large early one which seems to not correct for leap year, but most do. Some have sheet brass frames, but nearly all are assembled on a cast iron frame, with early ones using an iron base and sheet brass posts.

Although the instructions which came with the clock are helpful when setting a clock which has been allowed to run down, they are of little help to a repairman faced with mis-adjusted linkage, or damaged parts. Some "Farmer's Clock" models have a wire loop at the top of the case to pull up for setting, but most models require either turning the clock hands the requisite number of days, or reaching inside the movement to make major correction of the setting. Examine the movement and it becomes evident the operation of the calendar mechanism relies solely on the falling of a loosely fitted assembly of levers dropping off a snail-shaped cam driven by the clock movement. Obviously the cam raises the lever assembly, and at midnight, when the clock is set and adjusted correctly, the lever suddenly falls off the cam at the back of the clock movement.

At about half the length of the lever assembly, the single rod falling off the clock cam is divided into two levers with adjusting nuts controlling the distance each of the individual rods falls as the assembly works at midnight. To coordinate these rods, if one system works but the other doesn't, begin by disconnecting the one which works the 'name of the day' drum at the left as one faces the front of the movement.

Now, with the clock set at midnight, so there is the maximum travel of the lever at the clock movement, adjust the nut that is lifted until raising and dropping the clock lever will make the shaft that carries the 'day number' hand ( the calendar center shaft) advance the hand one space or notch at a time. This may require lowering the nut beneath the connecting brass piece. The pawl that pushes the shaft clockwise should move just a little beyond where it will drop into a slot when the lever and rod fall.

After confirming that repeated careful lifting and dropping of the lever makes the hand on the center shaft advance every time it should, move the bottom nut towards the one at the top of the lifting rod until there is a distance a little less than twice the thickness of the brass piece between the two nuts. These nuts should not move easily, and after all adjustments have been completed, and there is no doubt the device is working reliably, it is practical to put a drop of blue Loctite #242 on the nuts to prevent them from turning. Blue Loctite, for threads, is not as permanent as Loctite #609, the one Bill Smith recommends for making lantern pinions. Follow adjustment of the numerical day rod, the one just done, by doing the same thing with the one that advances the day name drum. When both rods work dependably with activation of the rod at the top of the movement, it is possible to give attention to the Month drum. This drum is advanced when a rod running the length of the calendar movement, pivoted at the left of the movement, is raised by a brass wire riding another snail cam. This one is attached to the center shaft so it raises and drops the month rod once each complete revolution. Unless there has been some mishandling of the calendar mechanism, this rod requires no adjustment. In the unlikely event that it does not sufficiently raise the pawl so it is engaged to advance the month drum, a small adjustment can be made by bending the wire that rides the center shaft cam. Be VERY sure a change is needed before attempting to make one.

Up to now, all of the mechanism is rather self explanatory if it is examined carefully as it is operated. Essentially each device, the center shaft, and both drums, depend on a pawl which pushes square toothed disks forward. To make this work the advancing pawl lifts a detent up at the same time it pushes the disk forward one space. There is also a second pawl in the drive assembly, intended to prevent the shaft or drum from moving backwards. Each holds the shaft and drums in place as the levers and rods are slowly raised for the next cycle.

The most complicated part of the Ithaca calendar system is the sliding step device that allows the center shaft to advance two spaces when going from the end of thirty day month to the first of the next month. There is a further complication for February, which has 28 days three out of every four years. Adding to the complication is leap year, when there is an additional day in February.

At the left end of the month disk there is a variously stepped cam which pushes on a brass wire mounted to ride against that cam. (My job now becomes more difficult since I do not have an example in front of me. The mechanism I have is a very early one with an entirely different system for adjusting month lengths.) I think that wire is mounted to a separate cast iron post, but where it is attached is incidental.

In turn, the brass wire riding on the disk on the month drum reaches toward the stepped plate referred to earlier, and attached to the 31 square-toothed wheel which turns the center shaft. The stepped plate slides back and forth, influenced by the position of the wire reaching toward it. The wire actually positions the stepped plate so that it will hold up the detent for the 31t wheel until the driving pawl has been able to carry the wheel two or more spaces farther than is usual for a 31 day month. It too is self explanatory, if one will study its action. Also mounted on a post beside the disk on the month drum is a small disk wheel with four deep notches. That wheel, actually a cam, is actuated once a year by a pin located on the end of the month drum. The wire that shifts the step plate on the center wheel fits freely in each of those slots. Once a year that disk begins to move in anticipation of the end of February. The wire is lifted out of the deep slot by the disk on the month drum as the small disk starts turning. The wire is then left resting on the spot between the deep slots. The wire is also pushed so far forward that it makes the step plate move farther than usual. The effect is that the drive pawl pushes the center wheel three extra spaces during that cycle, so the hand has jumped from 28 to 1 on March first.

Then comes leap year. Of the four positions on the little disk mounted near the month drum, one is deeper, and therefore obviously different from the other three. That is the position for the brass wire to occupy at the end of February in leap year. Because the brass wire intrudes less against the step plate on the center wheel, the center wheel is only made to advance two spaces, and that will not occur until the hand has pointed to 29.

Setting the clock for leap year first requires knowing when that takes place. By gently pushing the brass wire resting in the deep slot of the small disk forward, the disk can be advanced until its action will correspond to the anticipated leap year. Remember that disk will be advanced once each year, but I am sorry to say, I can't tell you whether that happens just before or after February. You can determine that by turning the month drum and observing when it happens relative to the display at the front of the drum.

By lifting the detents of the center shaft, the day drum and the month drum, each part can be moved individually, so that they can be set to correspond to the calendar on the wall. After that is done, make the leap year setting being careful not to disturb or change other settings.

All of this verbiage is of little value if the mechanism is defective. Except for some judicious dusting, there should be nothing in need of repair on an Ithaca calendar mechanism. Dream on. If nothing else were wrong, nearly everyone of these devices will have some problem with loose paper strips on the drums. The drums shrink, the glue yields (better than tearing the paper), so the loose paper is in danger of getting torn, if that has not already happened.

I do not accept responsibility to advise on this problem. I have done several things I regret, ranging from trying to re-glue the paper in spots, to slipping strips of thin foam sheeting under the paper to compensate for shrinkage of the drum. These clocks are of increasing value and rarity, and I would myself like to know what experts in this area recommend. Beyond the inescapable risks that come from handling the drums with their paper, on these mechanisms, there are times when some drastic repairs are needed. First, Ithaca calendars were never intended to be oiled. Sadly, many have been. Facing those conditions, there is little choice but to try to remove gummed oil. On a good day, it can be washed out with a highly volatile petroleum solvent, or one of the approved non-inflammable substitutes. (A few months ago I made the mistake of suggesting tri-chlorethylene which is a known carcinogin. There are replacements, but I do not know their names.)

Acetone is not a good solvent for cleaning if the finish on the metal is still in tact under the oil and grease. Those parts were lacquered, and acetone will flush off the lacquer if used for this purpose. If the parts of brass attached to the drums are so badly gummed and sticky they do not respond to solvent flushing, it will be necessary to perform major surgery. Bad scene, but is becomes necessary to actually remove the brass from the wood drums. It is held in place with brads. Note the position of parts before pulling things to pieces, then start levering the brass away from the drums with discreet pressure, until it is possible to grasp the heads of the brads with pliers to pull them out.

From this point, serious cleaning, polishing, and metal finishing are appropriate. That it too involved a digression for this text. There are other repairs. Only once have I seen an Ithaca mechanism which could be classified as legitimately worn. Evidently it had worked most of its life, and had so much side play in some of the brass rivets holding and aligning pawls and levers, that I had to make corrections. I made and fitted new rivets where there would be an improvement.

Make sure that the drums and center shaft are adjusted with no more end-play than necessary for freedom. There are adjustable screw-bearings for this purpose. The rugged cast-iron frames do not change much with temperature, so it is possible to make close adjustments without risk of future binding. Most of the brass wire used in parts of the mechanism are hard drawn spring wire, so adjustments should be gentle, and avoiding sharp bends to avoid fracture.

As with the paper, and the finish on the brass parts, I would try to preserve the original paint on the frame whenever possible. That paint seems to be shellac based, and is vulnerable to even soap and water. ( Shellac paint was rapid-drying, and it is likely, especially on earlier models, that the brass was shellac coated as well.) The best treatment in most cases is to wash the frame lightly with water if it is gunky, then give it a moderate coat of raw linseed oil. This takes about a week to harden. I prefer raw oil because it drys slowly and penetrates the paint and bare pores on cast iron, thus retarding rust. Boiled oil is similar to varnish, so varnish would be just as good if speed is of the essence.

I am sure I have overlooked numerous problems, potential as well as common. Unfortunately I did not have one of the most common types of these mechanisms to look at as I wrote these notes. I think I could be more specific if I re-did them with an example for reference. I would welcome additional and corrective information on this subject.

Personally, I have always admired Ithaca Calendar clocks as an ingenious solution to a complex practical problem. They are actually another example of mechanical computers, and "cheap" as they may be from a construction point of view, I consider them another important step in American mass production. Think about whether that term means, "production of MASSive quantities," or production for the masses." In Rome, I suppose, there is yet another meaning.

So much for what I can think of on this subject at the moment. I hope it helps. Jcl.

John C. Losch
Holliston, Mass.


© John.C. Losch, Reproduction without permission prohibited , except for personal use.

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