DIY Moon Phase Dial

[Gina]

Here's an exploded diagram of the gear train driving the moon phase globe.  It occurs to me that the rachet wheel could have 3 times as many teeth on it and do away with the 1:3 reduction gear.  3x14 = 42

[Gina]

42t rachet wheel and 32:45 gear ratio driving the globe.  Now just needs a cam and lever system to drive the rachet wheel from the hour shaft.

[Gina]

Moon drive redesigned to use gravity for the rachet paul (not shown).

[Gina]

Moon rachet wheel and drive gear.

[Garethr]

Gina,

Love these projects of yours.

I'm happy with a dial on a clock face as part of a set of three on a birthday present.

But nope not Gina.  

How the heck you work all these things out, let alone make them makes this forum worth its weight in gold!

Love it  (even though i'm only keeping up with about 50% of what you are describing and hoping to make into a working project)

Looking forward to purchasing the MK2 version. (at cost and shipping of course)    

Gareth  

[Gina]

Thank you very much Gareth

This is how I envisage this clock (rough diagram).

We now come to the Heath-Robinson part - levers and pauls

Here's a diagram of the mechanism.  The hour shaft (yellow) will have a cam (red) on it which moves a weighted lever (blue) back and forth.  This motion is converted to push-pull action and operates a paul (pink) which pushes the rachet wheel (light blue) one notch round twice a day.  Another paul (green) stops the rachet wheel going backwards when the drive paul is pulled back.

[Garethr]

Gina.

The prosecution rests its case.

My Lord let the defense approach the Jury

Gareth

[Gina]

You should see the mechanisms in "real" clocks - particularly of Victorian vintage.  And automata are real pieces of clever wheels, gear and levers.  I've always been fascinated by mechanisms like clocks and automata.

[Garethr]

Gina.

Iv'e seen them and that's why I have have so much respect for the project.

Gareth

Are we still on for the MK 2 Version  

I can hear the gentle tick tick from here

[saac]

I love your projects Gina you are an inspiration.  I hope you don't mind but I've shown a few of your projects with your 3D printer to our Craft and Design Department at School.  They recently acquired a 3D printer and are finding their way. I thought your work of how it can be used for real projects would help them along.  I wonder what you could achieve Gina if you had access to a fully kitted workshop - get buying those lottery tickets!  Good luck with this, it's going to be a real gem Gina.

ps, how about an orrery next!

Jim

[Starlight 1]

You should see the mechanisms in "real" clocks - particularly of Victorian vintage.  And automata are real pieces of clever wheels, gear and levers.  I've always been fascinated by mechanisms like clocks and automata.

I have 8 old clocks some with Moon , have them over 40 years and still going. all well over 100 years old.

[Gina]

Gina.

Iv'e seen them and that's why I have have so much respect for the project.

Gareth

Are we still on for the MK 2 Version  

I can hear the gentle tick tick from here

Thank you Gareth   I'm afraid the SGL rules don't allow discussion of sales etc. except that unwanted items may be sold or bought in the Classifieds section.  That's how I understand it.

[Gina]

I love your projects Gina you are an inspiration.  I hope you don't mind but I've shown a few of your projects with your 3D printer to our Craft and Design Department at School.  They recently acquired a 3D printer and are finding their way. I thought your work of how it can be used for real projects would help them along.  I wonder what you could achieve Gina if you had access to a fully kitted workshop - get buying those lottery tickets!  Good luck with this, it's going to be a real gem Gina.

ps, how about an orrery next!

Jim

Thank you Jim   I'm very happy for you to show my projects to the school and if my project threads on here can help others I'm delighted   I also try to be entertaining with my wacky projects.

An orrery?  Well, who knows - they are certainly fascinating.  You do realise you might have started something, don't you ?

[Gina]

Made the ratchet part too big on the rachet wheel - it came out twice as big as I had intended.  Here's a new design.

[Gina]

The UP printer has stopped working (again) and I'm not in the mood to fix it ATM.  My other 3D printers are also out of action ATM so 3D printing has come to a temporary halt.  That doesn't stop me continuing with the design though.

As a change from the moon globe end of the mechanism I think Ill look at the other end - the stepper motor drive.  I shall be using my favourite little geared stepper motor, the 28BYJ-48 which has 4096 steps per revolution.  I have all the details for an Arduino sketch to drive this via the standard driver module. 

Clock gear train starts off with the seconds shaft which rotates once per minute.  From the construxtion point of view it will be easier to use a pair of gears than to connect the motor directly to the shaft.  This also means I can choose the gear ratio.  To give the clock a suitable tick-tick sound the motor can be fed with a number of steps once a second.  A tick-tock sound could be created by alternating the number of pulses between two different values but I'll leave that - may do it later, get the clock working first

For a 1:1 gear ratio the drive would want to rotate 1/60th of a revolution per second this would require 4096/60 = 68.266667 pulses.  That's not possible.  For a 1:3 reduction gearing pulses per second = 4096/20 = 204.8.  Almost as bad A whole number is needed unless the number is split between two different values in a 2s cycle.  To get a whole number we need to put a 5 in the equation as well as a 3.  In other words 1:15 or 2:15 etc.  The larger gear needs a multiple of 15t.  60t with a diameter of 90mm would be suitable which gives mod 1.5 size teeth.  The small gear (motor pinion) could be 8t and with mod 1.5 the diameter will be 12mm.  This Is quite suitable and gives a gear ratio of 8:60 = 2:15  Number of pulses per second = (4096/60) x (60/8) = 4096/8 = 512.

Here's a screenshot of the motor pinion in SketchUp.

[Gina]

On second thoughts, this amount of gearing down only makes for more pulses per tick.  There is no problem with power, these little steppers are more powerful than they look.  A 16 or 32 tooth motor pinion would give 256 or 128 pulses per tick respectively.  Alternatively the larger gear could be 30t and the smaller 16t or for that matter the gears could provide a small step up of 30:32 (that's as near 1:1 as makes little difference).  Then just 64 pulses per tick would be required.  You could say that the gearing simply adjusts things to provide a whole number of pulses.

[Gina]

I've managed to get the UP printer working for short runs and have printed the rachet wheel and moon globe drive gear.

[Gina]

After looking at the main assembly of the clock I came up with a revised design for the moon phase levers.

[Stub Mandrel]

I would make the cam with an oversize hole and a nut to holds it in place. This will allow you to adjust its throw, and also to compensate for wear in the future. Ratchet and pawl setups can be very fussy. Make the other pawl's position adjustable too, if you can.

[Gina]

I don't think it's as critical as all that.  As long as the oscillating motion of the paul is between one and two times the ratchet tooth length, the ratchet wheel will be advanced by exactly 1/42nd of a revolution for each revolution of the hour shaft.  I could make the cam system very long lasting by adding a ball bearing to the cam - this is a frequently used system for cams in steam engines.  OTOH with just two revolutions per day I think a plastic cam and cam follower should last many years.  I could use nylon for reduced wear - I do have nylon filament for 3D printing which I can use in my RepRap style printers.

[Gina]

Circuit board.  At top is the time code receiver aerial, and to it's right the time code receiver PCB.  Below that is RTC module with backup battery then moving left, Arduino Nano and ULN2003AN stepper driver chip.

[Garethr]

Gina,

Sorry never meant to infringe the SGL rules.  Comments were always in jest and meant to encourage, sorry if it appeared any other way.

Where the heck do do you find the time to research these projects and work out whats required.

Gareth

[Gina]

No problem Gareth  

I'm retired and only have myself to cater for these days so plenty of spare time - though there are jobs I ought to do   After being a full time carer for several years I need to have things to fill my time.

[Garethr]

Gina.

Thanks

A comprehensive guide on how to image DSO's from just outside London and all its LP using a Skywatcher 200p on modded Eq5 mount then how too process the data would be most welcome next time you feel the need for a project.  (step by step of course).

Gareth  

[Gina]

Since I shall have more than one clock running off an Arduino I think it makes sense to have one "master" and drive the others as "slaves", then one time code receiver can keep all clocks synchronised to UTC.  I was thinking of running my day/date display off the same Arduino as the moon clock anyway.

One thing I have yet to work out is changing to/from BST (or Daylight Saving Time for our overseas readers).  Yep, that "pain" has reared it's ugly head yet again