What Pendulum Works with a 241-840 at 75cm?

Is There a Specific Pendulum Required for the 241-840 at 75cm?

One of the most common questions we receive at Clockworks is: “I have a Hermle 241-840 movement with a 75cm stamp. I’m using the Mechanical Westminster Vienna Clock Kit—but I don’t know which pendulum to use. So what should I choose?”

Indeed, this is a great question, and the answer is both straightforward and crucial for accurate timekeeping. Therefore, in this article, we will guide you step-by-step through understanding the 75cm pendulum length, how it affects performance, and exactly which pendulum you should use with the Mechanical Westminster Vienna Clock Kit from Clockworks.

Order the full kit here:

Mechanical Westminster Vienna Clock Kit – Clockworks.com

Understanding the 241-840 Movement and 75cm Stamp

Specifically, the Hermle 241-840 is a German-made mechanical movement commonly used in wall clocks. Especially in traditional Vienna regulator-style cases. This movement features:

• Westminster chime on the quarter-hour
• Hour strike on the hour
• Spring-driven power
• Center and chime arbor shafts for hands
• A rear pendulum post for mounting the pendulum assembly

The “75cm” stamped on the movement refers to the pendulum length, but not in total inches or centimeters from the hand shaft to the tip of the pendulum. Instead, this measurement refers to the effective pendulum length—which includes the leader, suspension spring, and the center of mass of the pendulum bob.

In short, the 75cm stamp guides you to use a pendulum system that keeps the movement running at its correct beat rate and time.

What Pendulum Works with the 241-840 at 75cm?

Clockworks recommends using a wood stick pendulum with a round bob for the 241-840 when paired with the Mechanical Westminster Vienna Clock Kit. Because this is the most historically appropriate and acoustically balanced setup for Vienna regulator clocks.

For a 75cm length requirement, the recommended pendulum includes:

• Suspension spring (typically 3/4″ long)
• Pendulum leader (usually around 4.5″ long for this model)
• Pendulum rod with hook
• Brass or brass-finish round bob, usually 4 1/2″ to 6″ in diameter

Clockworks sells pendulums specifically tuned for this setup. So you don’t need to do any manual measuring or guesswork—just order the 75cm-rated pendulum matched for the 241-840.

Why the Right Pendulum Matters

Choosing the correct pendulum length ensures your clock:

• Keeps accurate time
• Chimes correctly on the quarter-hour
• Avoids overpowering or stalling the escapement
• Retains its authentic Vienna-style appearance

If you install a pendulum that’s too short, the clock will run too fast. Also, if the pendulum is too long, it will run too slow—or may not tick properly at all.

This is why selecting a pre-matched 75cm pendulum built for the Hermle 241-840 movement is critical.

How to Install the Pendulum Correctly

Follow these steps to install your pendulum on the 241-840 movement:

1. Install the suspension spring onto the post at the top rear of the movement.
2. Hang the leader from the bottom of the suspension spring.
3. Attach the pendulum hook to the slot or hole on the bottom of the leader.
4. Test the tick-tock rhythm and adjust the beat using the crutch adjustment if needed.
5. Level the clock case to ensure proper swing.
6. Use the rating nut at the bottom of the pendulum to fine-tune the speed.

You’ll find these instructions included in every Mechanical Westminster Vienna Clock Kit ordered from Clockworks.

Can I Upgrade or Replace the Pendulum Later?

Yes. You can replace or upgrade the pendulum at any time, as long as you maintain the correct 75cm length. However, you might consider a replacement if:

• The bob is dented or tarnished
• You want a different aesthetic
• The rod becomes warped or cracked
• You’re restoring a clock and want a vintage look

Clockworks keeps replacement pendulums in stock, and our team can cut one to your exact needs.

Final Thoughts

If you’re working with the Mechanical Westminster Vienna Clock Kit featuring a Hermle 241-840 movement stamped at 75cm, you’ll need a 75cm stick-style pendulum with a round bob, precisely matched to that movement’s specifications. Clockworks makes it easy by providing the correct pendulum along with the compatible leader, suspension spring, and expert guidance to help you complete your Vienna-style clock with confidence.

Order the correct pendulum now at Clockworks.com — just search for Pendulum for Hermle 241-840 (75cm).

For help with compatibility or installation, email us at clockworks@clockworks.com. Our experienced team is ready to assist.

Updated on: 29/09/2025