Most mechanical clocks have an hour hand concentric with the minute hand with the hour hand making one full turn every twelve hours. The special set of wheels off the centre arbour is called the motion works. Attached to the centre arbour is the minute hand. The hour pipe fits over the centre arbour and to it is attached the hour hand. This set of gears, called the motion works, is driven by the time train and powered by a spring or a weight.
I am working on a movement made by the Sessions Clock Co. It is from a model called the Grand Assortment probably made sometime before 1920. This is Grand Assortment #1 in a series of three.
The case is in rough shape and certainly needs some tender loving care. I thought my major challenge was putting life back into a tired case (another story) but it appears the movement needs resuscitation as well.
Adjusting the time on the clock is a challenge because the minute hand is very stiff and takes some effort to move it. Something is amiss with the motion works, the time train itself or both.
I initially cleaned the movement, checked for wear and determined that the little wear I observed should not be enough to affect the running of the clock.
I reassembled the movement and while on the test stand the problem reoccurred, a minute hand that was just as stiff to move as before and after a few hours, the movement simply stopped. I later discovered that the homemade click spring on the time side had unhooked and caught on the second wheel.
I am not an expert on the meshing depth of gear teeth but I suspect that there is enough wear in the motion works and the time train to prevent the gear teeth from engaging smoothly with the contact point of the next gear, the lantern pinion. The combination of wear in several locations might produce the stiff centre arbour condition. Based on this theory I went ahead with bushing work.
This time I was somewhat more discerning concerning potential wear points and yes, a more careful inspection revealed there was likely enough wear to affect the running of the clock. I began with new bushings on the escape wheel rear plate and third and fourth wheels on the time side and finally the second wheel back plate for a total of 4 bushings on the time side; nothing on the strike side. It looked fine.
The main wheel arbours on this movement aren’t interchangeable. It is easy to confuse the two. After reassembling the movement I noticed that the plate did not go all the way down on the strike side. I compared the two arbours and the time side arbour is narrower at the top. Swapping them back to where they belonged fixed it.
Setting up the strike side correctly on the first go-around is probably more luck than skill but this time there was no additional fiddling with the correct position of the warning wheel which is just below the fly.
I did not completely eliminate the stiff centre arbor but it is improved and the clock is running well. If I have to take it apart a third time I will check for a bent arbour in the train or the center arbour itself or a bent pivot.
Now to address a pretty sad-looking case.