Desk Clock Project

[Steve CrowParticipant @stevecrow46066]

It’s too hot and sticky for the workshop today so I thought I’d post this. I’ve been meaning to get around to it.

I wanted to make a clock of my own design during my retirement. I had a good idea of what I wanted – a desk/table clock with a few complications.

This is the general layout-

Central hour, minute and local solar noon hands. There’s a moonphase at the top and annual calendar at the bottom. Sunrise on the left and sunset on the right. The sunrise/sunset quadrants can be manually set, from the back of the clock, for GMT and BST.

The dial section will be in a glass and clear acrylic case and the whole thing supported on a gimbal arrangement.

Here are some drawings. For scale, the dial is 150mm diameter.

The movement lives in the cylinder at the back and drives the wheel train via a shaft that turns every 12 hours.

The whole design is inspired by Jodrell Bank radio telescope which I used to pass a lot as a kid.

Steve

 

[Steve CrowParticipant @stevecrow46066]

It soon became apparent that I wouldn’t be able to find enough information to make a manual movement suitable for this purpose. I have no horological training and have never attempted anything of this sort before.

I wanted to get on with it anyway so I went for a modular design with a high torque quartz movement. If I find out how to design a mechanical movement in the future, I can swap them over.

I hope the quartz confession does not alienate any purists!

[Steve CrowParticipant @stevecrow46066]

This is the wheel train-

It is driven by the hour hand shaft from the movement. The motion work is in green, lunar train in blue and annual train in brown. Black digits are tooth numbers and pink are theoretical depthing dimensions.

All gearing throughout the clock is Mod 0.3 involute.

The reason for the long gear train for the moonphase is not a case of chasing accuracy. It’s because I’ve tried to balance the length and shape with the annual train for a symmetrical effect. Note that both train terminate on the same size wheel – 73 teeth.

Steve

[Steve CrowParticipant @stevecrow46066]

And here is where I am so far-

I’ve made and tested nearly all the mechanical parts. I need to make a return spring for the sunrise cam follower and a few bits and pieces before installing the sunset side.

Steve

[Steve CrowParticipant @stevecrow46066]

The GMT/BST selector spring. Tension can be adjusted for a satifying click.

 

All pivots run in ballrace bearings at both ends mounted in bronze bushings (chatons?). The cam follower run in bearings too. They must be over 30 in the clock, I’ve not really counted.

 

And a side view with moonphase on the right.

 

And with the dial. Apologies for photo quality.

Steve

 

 

 

 

[John HaineParticipant @johnhaine32865]

Very nice Steve!  I was meaning to ask how you computed and formed the cams?

At the opposite end of complexity, a friend has a clock he bought in Belgium.  Two large hands, over 30cm long, freely pivoted on the top of a stalk about 50cm tall that sits on a table.  At the short end of each hand is a “blob” that contains a concealed quartz movement, each hand being weighted so that they perfectly balance.  Each quartz movement drives an eccentric weight, one from the hour shaft and the other from the minute.  As these slowly rotate they cause the hands to rotate too to show the time.  You can give either or both hands a twirl at any time and it will settle back showing the right time.

[Steve CrowParticipant @stevecrow46066]

With glass, bezel and case.

[John Haine]

On John Haine Said:

Very nice Steve!  I was meaning to ask how you computed and formed the cams?

At the opposite end of complexity, a friend has a clock he bought in Belgium.  Two large hands, over 30cm long, freely pivoted on the top of a stalk about 50cm tall that sits on a table.  At the short end of each hand is a “blob” that contains a concealed quartz movement, each hand being weighted so that they perfectly balance.  Each quartz movement drives an eccentric weight, one from the hour shaft and the other from the minute.  As these slowly rotate they cause the hands to rotate too to show the time.  You can give either or both hands a twirl at any time and it will settle back showing the right time.

Hi John, that is a very interesting concept.

As far as the cams go, here is how I plotted the EoT cam. The numbers on the perimeter are the EoT deviation, offset to take into account of the follower position relative to the dial. The others were done in a similar manner.

 

Once I was happy with the plot, they were printed to size for stencils and filing guides. I also made some circular calibration gauges as all 3 cams have the same “zero” or index diameter, if that makes sense.

Stencils are stuck to 2mm brass sheet and very lightly prick-punched a tad over size. Cut out with piercing saw then file to shape before facing and turning to profile. The cams themselves are 0.8mm thick and the boss is 1.8mm.

After that, They are tested on the clock using temporary hands with light filing to get things right.

Then they are crossed out.

Steve

 

 

 

 

 

[duncan webster 1Participant @duncanwebster1]

All far too clever for me, I think I’ll take up knitting, or wait for the MMEX where the club stands (best bit) have stuff to which I can aspire.

[Colin DParticipant @colind]

Wow !  That is beautiful work, and what a novel and interesting design  !

I’m more than impressed by that.

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