# how to choose the right spring/pendulum mechanism for a 400 day clock?

#### jess_tab

##### New User
Hello,
My team has been tasked with building an anniversary clock from scratch for a school project. I am working on the pendulum weight/spring thickness but I have no prior experience with clocks. Please can someone explain how I should go about picking the right spring and pendulum, factors I should consider, calculations, etc. ?
• Unclear as to how escapement attaches to pendulum
• Nivarox is the material of the suspension spring
• 8 BPM has been proposed
• The clock should fit in no more than a 1 ft by 1 ft by 2ft space
• weigh no more than 50lbs.
• powered fully mechanically.
Any help would be appreciated. Thank you

Last edited:

#### etmb61

NAWCC Member
Hello,
My team has been tasked with building an anniversary clock from scratch for a school project. I am working on the pendulum weight/spring thickness but I have no prior experience with clocks. Please can someone explain how I should go about picking the right spring and pendulum, factors I should consider, calculations, etc. ?
• Unclear as to how escapement attaches to pendulum
• Nivarox is the material of the suspension spring
• 8 BPM has been proposed
• The clock should fit in no more than a 1 ft by 1 ft by 2ft space
• weigh no more than 50lbs.
• powered fully mechanically.
Any help would be appreciated. Thank you

Hi,

Is your team tasked to design a long running torsion clock or to replicate an existing design?

Eric

#### jess_tab

##### New User
We have been tasked to design a long running torsion clock

#### etmb61

NAWCC Member
We have been tasked to design a long running torsion clock

Wonderful!

To start with, your 8 BPM specification is a design constraint that will force other decisions. You need to design a train that will turn the minute hand once per hour for as long as the clock needs to run on your power source. Your BPM will be determined by where in the train you place the escapement and the number of teeth in the wheels and pinions.

A torsion pendulum is usually connected to the escapement by some sort of fork and lever or fork and roller arrangement. Typically a fork clamped to the pendulum spring receives a slight twist from a lever attached to the escapement during each half cycle. The escapement needs to be operated by the fork without impeding the fork's movement. So a very light touch. The escapement needs to have enough power to impart the twist to the spring for the duration of the clock's run time.

The most challenging part will be the escapement. Lots of different methods have been tried over the years. The most common is the dead beat type. I've always fancied a pin-wheel escapement might work for a torsion clock.

Good luck!

Eric

#### jess_tab

##### New User
Thank you!

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