Mechanical Movements

Clock pendulum components description

Description of the clock pendulum parts and components. Please use this as a glossary of the parts to a clock pendulum assembly.

The clock pendulum

A clock pendulum includes the bottom rating nut and threads, the pendulum bob, and top hook. These items are removable on wood stick pendulums only. Lyre metal clock pendulums do not have the ability to come apart.

Clock pendulum leader

A leader is the part the pendulum hangs onto when it is installed on the clock. It the in turn hooks to the suspension spring on the very top of the pendulum assembly. Pendulum leaders vary depending on the manufacturer of the clock movement. They can also vary in length as well as style.

Suspension spring description

The clock pendulum suspension spring is the short spring steel part on the vary top of the pendulum assembly. Its purpose is to suspend the leader and pendulum in the air. Its steel spring like strips flex to let the pendulum swing back and forth with ease and momentum.

Replacing Lost Pendulum Parts

Replacing a lost pendulum part from its assembly is more complicated than just matching up a broken part. It is required to narrow down the part needed by a different method.

The lost pendulum

A clock pendulum that is missing can be replaced by first identifying the movement manufacturer. This is can be done by getting the movement numbers off of the back plate of the movement itself. This cannot be done with the manual that came with the clock or stickers off of the wood clock case. After getting the numbers off of the movement it can be matched up on this page to know who made the movement. With the movement maker known it is time to proceed to the information at this pendulum page.

Lost pendulum leader

A leader is the part that hooks to the suspension spring on the top and the pendulum hangs on the bottom. If this part is missing it is best to identify who made the movement as described above. After knowing who made the leader it can be matched up with the leaders offered. Upon knowing who who made the movement the leader possibility's are narrowed down considerably. At this time a visual of the pendulum hook style, the crutch on the back of the movement, and the suspension hook can be compared. Compare the components of the clock to the options in that manufacturer category and it will figured out the best one.

The lost suspension spring

First know that style A is the very most common suspension spring style in existence. Check the top of the pendulum leader and if there is a double hook on the end it will be style A required for the clock. Suspension A3 for large grandfather units, A2 for grandmother and wall clocks, and A1 for mantle clocks.

The mechanical clock pendulum length

A pendulum clock without a pendulum is a shame for sure. Getting the correct pendulum does take some diving into the clock world. If you have no idea what pendulum it would take, this is a basic guide. This is a basic guide to narrow it down to the best pendulum for your clock. This will cover most situations, without special equipment to figure out the length.

The movement CM or PL stamp

On the back plate of the clock movement usually, there are some numbers and or letters for identification. There maybe an indication of how long the pendulum should be in the mix of these numbers. It may say CM or PL and this stands for centimeters or pendulum length. This would be the length where it should keep approximate time. This is measured in a few different ways usually dependent on country of origin.

German made movements

Most mechanical German made clock movements are easy to figure out the pendulum length. The numbers will let us know or the clearly indicated CM or PL number will be stamped. If it is German, keep in mind the CM length is not the actual pendulum length. German units measure this length from the top of the clock movement, and this includes the three components of the pendulum all in one length, in centimeters. This length will include the pendulum itself, the leader that it hooks to, and the suspension spring on the top that the leader hooks on to, all in one CM measurement. CM stands for centimeters and PL stands for pendulum length.

If no stamp try to convert

With no pendulum length stamped into the movement some added steps are involved. The numbers on the back plate will cross reference to the pendulum length required. The first step is to identify the manufacturer of the clock movement by using the movement numbers. The movement numbers indicate who actually manufactured the movement. Various clock retailers may have have their name stamped onto it, but the numbers are always true to the manufacturer.

Converting numbers to CM length

Some movements do not have an indication of the pendulum length on the back plate. The unit will have a number that would need to be found on this website first to find out what the correct CM length is for it.

Converted number example

Let's say that the movement has no CM stamp on the movement and only shows the number UW32319. Go to the identification page to look at the movement number examples. In this example, we see that it is a Urgos. Now it is possible to go to the Urgos page and find the number to see what the pendulum length is. In this example, the pendulum length would be 80cm, representing the full length with the size of the bob factored in.

German grandfather movements

Almost all grandfather clock movements are going to be German if made after 1950. The first thing we need to do is get the numbers off of the back plate of the movement. This is the only way, and we can't cheat by looking at the paperwork or clock case. It has to come right off the back of the clockworks. The manual and the sticker on the case is of no use to get the pendulum.

American clocks

The American mechanical clock movement manufacturers referred to the pendulum length as a "drop". The drop is the length of the pendulum from the hand shaft all the way down to the bottom of the pendulum rating nut threads. It is a different way of measuring the pendulum length then the German made way. Both ways are based on the smallest bob diameter bob. If the bob is larger or heavier, the length would be longer than what is stamped.

No luck

If everything fails for one reason or another, the best chance for a pendulum is the wood stick style. This is the only style of pendulum that can be easily modified because you can chop it. These types of clocks are usually antiques, or of Asian origin, and information such as pendulum length is simply not available. Sometimes it takes a good guess on where the manufacturer intended to have the bob sit.

To do it this way, you only need a pendulum with a stick that is way too long to begin with. Chop it, try it, chop it, try it. Each time your slow, cut an inch and half off of the sticks length and hang it back on. It will only take a couple of times, and if you start way too long you can always go shorter.

Clock makers method

There is another way, its called setting the beat rate. This is a more involved way and usually just done by clock makers. It involves a beat detecting device that counts out the beats per hour, or the beats per minute. To do this, first you would need to know what the beat rate is supposed to be for that particular movement, and then keep adjusting the pendulum length until you have it keeping time. There are cell phone apps out there these days that will tell you the beat rate and the cell phone will listen and tell you if the clock will keep time with that pendulum. You go longer or shorter until your phone says the beat rate is set.

Contacting us for help

Please email the movement numbers from the back plate, and explain what part is needed. The email address to send this information is [email protected] Pictures are welcomed but not required. If emailing pictures please include the back side of the clock movement where the markings are.

Timing a mechanical pendulum clock

Timing the clock is all about the overall pendulum length and rarely has anything to do with the movement itself. Mechanical clock is easy to time providing you have the correct pendulum. When the pendulum is correct for that particular movement it will hang on the leader and keep approximate time. The fine timing can be done only with the pendulum adjustment located at the very bottom. At the bottom of the bob is some adjustment threads and a nut. To turn the nut one way raises the bob and the other lowers it. A shorter pendulum will make the clock run faster. A longer pendulum makes the clock run slower.

Fine timing the clock

If the clock is timing slow, raise the pendulum bob by turning the nut at the bottom of the bob. If the clock is fast, do the same but raise the clock's pendulum bob instead. One full turn is somewhere around 1-2 minutes a day faster or slower.

If there is no more adjustment

If the bob is all the way up and its still too slow or fast, you can shorten either the pendulum or the leader it hangs on to correct.

A lyre pendulum that does not keep time with the bob all the way adjusted will need its length altered. The overall length can be altered by the pendulum itself or the leader it hangs onto. The leader is about 5 to 7 inches long and engages with the crutch on back of the movement. The leader is the part that the pendulum top hooks on to. It is possible to shorten or lengthen the pendulum leader to put the clock in time range with some solder if needed. 1 3/4 inches is a good measurement to make one of these longer or shorter as needed, as this is the length of the threads at the bottom of the bob. So it will give you a full timing adjustment range all over again and you can go up or down as needed.

German pendulum length CM stamp

The pendulum length is considered overall and not just the pendulum. For example if the clock says 94cm on the back of it, this is the way the Germans measure there pendulum lengths from the top of the movement and all the way down. This will include the suspension spring way up top, the pendulum leader or guide you can call it, and also the pendulum from tip to tip all with a 4 1/2 inch bob diameter. Of course the larger the bob, the longer it will be beyond that 94cm measurement.

Used to keep time, now does not

If the clock kept time in the past but now does not, it means a worn gear. The escape wheel is worn and it is advancing more than one tooth at a time. The escape wheel alone would be hard to find, and hard to replace both. The entire movement would be disassembled to replace this worn escape wheel if there is another one found that will work. The cost of having this done would be the same price as a new movement. There is no such thing as having a repair on a clock movement being better than a new movement. The price would be about the same for a complete overhaul or a brand new one. First see if the clock movement is in production and available new. We do this by getting the numbers off of the back plate of the movement itself, right off of the brass. The email address is [email protected] and we will check availability and quote for the new one. If the movement is not in production anymore, then a repair is the only option.

Mechanical Pendulum Clock Timing Issues - Conclusion

Fine timing of the clock is easy as you can see. If the clock kept time in the past and now too fast, its time for a new movement and has nothing to do with the pendulum. A worn escape wheel is most likely the cause and a new unit would be less cost then a repair.