The design of a 8 day wall clock

In this project, I wanted to explore the possibility of making a longer running clock.

Basically start with a clock that can run for 4 days, then doublre the run time with a pulley

The elements of this mechnical clock

1. The motor

2. The escapement

3. The gears and layout

4. The frame and enclosure

This is the time where the clock will start to take shape

The Motor

The motor will be weight driven, 1 meter drop for 4 days, with a pulley to get 8 days

In this example, the idea is to buid a clock that has a 8 days run time

The pendulum will be about 1 meter long

It will have a 30 teeth escape wheel that will have one rotation per minute, that 1440 rotion in 24 hours

For 1 meter drop over 4 days, that is 250 mm per day

With a drum that has a diameter of 50 mm, and 1440 rotation of the escape wheel in 24 hours, 1440 * 1/900 = 1.6 rotation/ 24 hour.

ø50 mm x 3.14 x 1.6 = 251mm/day, 1004 mm in 4 days. and with a pulley, it will run for 8 days

The Escapement

The escapement will use a pin pallet anchor and a 30 theeth escape wheel

The base diameter of the escape wheel will be 60 mm, the openning of the anchor will be 66°, the distance anchor to escape wheel is 50.0824 mm

A prototype of this escapement showed that the force needed at the pallet to be around 2-3 grams on a 40 mm drum, that is 1.6 to 2.4 on 50mm drum

The Gears and Layout

It will use the layout 4 option

It will use a 1/5 x 1/5 x 1/6 x1/6 = 1/900 ratio from drum to escape wheel

The gear size will be module 1.6 for the first two reductions of 1/5, then module 1.2 for the last two 1/6 reductions. More on why in a gear chapter

With 1.6 to 2.4 gramms needed at the escapement, at the motor drum, the minimum needed will be 1.6 / 2.4 x 900 = 1440 to 2160 grams. more likely it will be at least double that, 2880 to 4320 grams, and with the pulley, one more time the double, 6 to 10 kg

From this, 2 thoughts:

It is worth spending time on designing and testing an efficient escapement

The frame and the gears will need to be strong enought to handle 5 to 10 kg at the motor/drum

Drum to escape wheel ratio: 1/6 x 1/6 x 1/5 x 1/5 = 1/900

There is a 1/60 ratio from the escape wheel to the "pick up" arbor with 3 gears, z = 20, z = 39 and z = 6

From there, 1/1 (39/39) ratio to the minute hand and 1/12 (6/72) ration to the hour hand

The Frames

Layout1

The design will need to fit in a 200/ 200 square

First test with all the gears in line in the diagonal of a 200/200 mm squarre, it could fit...barely!

Layout 2

All gears inline, with the escapement offset to the side. Could be in a squarre frame or even a round frame. That could work nicely!

Layout 3

One interesting option, the pendulumm can swing in the middle of the frames, with the escape wheel offset, the challenge is that the weight and pendulum are in the same plane

Frames V1

This one looks like a winner, round frame, weight in middle, pendulum slightly offset to the right and in front of weight

Layout 4: Master Sketch

This sketch is going to be used as a reference for the dimension of the frames

I will use the same sketch for gear placement in the assembly

A second sketch, base on this one will be used to place the hands and associated gears

First frame design

takes long to print

Rethink the design and gear ratio

bigger drum gear and new gear ratio

inline gears

The Pin Pallet Escapement

This escapement has a wheel diameter of 60 mm

It has a 1 second period, pendulum is about 1 meter long

Escape wheel has 30 teeth and will rotate once per minute

With 30 teeth, the angle between teeth is 12 degree

The opening of the anchor need to be: n teeth angle PLUS 1/2 teeth angle (n x 12 + 6)

Options are 90, 102, 114, 126... I went with 114, that is (9 x 12) + 6 = 114

With a 60 mm escape wheel , the design below gives me a distance of 55.08 between the escape wheel center and the pivot of the anchor

Design

Circle of 60 mm

Two radius lignes at 114 degree