DIY Moon Phase Dial

[Gina]

Found an offcut of half inch plywood in my pile of sundry timber in the shed and cut out a square for the back of the clock.

[happy-kat]

Ply is so much nicer than mdf

[Gina]

I refuse to touch MDF - horriblr stuff!!    Ply is nicer than OSB too   And this ply has some nice grain figuring too

[Gina]

Still running well and now completed several notches of the moon drive ratchet wheel   The mechanism appears to be working perfectly

I shall need to sort out slip rings for the power supply to the LED inside the moon globe.

[Gina]

Decided to run a test and see just how fast the clock could be driven   So I connected it to my W7 laptop and transferred the test sketch to that.  Gradually reduced the phase delay until the clock stopped when running off 12v.  Running fine at 3ms - stopped at 2.5ms so have it set to 3ms and a minute takes just under 12s - so that's just over 5x normal speed.  That's better than I thought since there's about a 2x gear reduction from motor to seconds shaft.  Motorised GMT to BST and back would take 5m which would be just about acceptable I think - particularly if I made it automatic at 2am when I'm usually asleep

[Stub Mandrel]

Won't the moon phase be (slightly) wrong when you the clock goes forwards in the spring? Running backwards in Autumn will advance the moon an extra hour as well, because the ratchet will still work. That's the moon phase going 2 hours fast a year. Acceptable or not?

[Stu]

Won't the moon phase be (slightly) wrong when you the clock goes forwards in the spring? Running backwards in Autumn will advance the moon an extra hour as well, because the ratchet will still work. That's the moon phase going 2 hours fast a year. Acceptable or not?

SSSHHHHH!

[Gina]

Been looining into powering the LED in the white side of the moon globe.  One connection can be the central shaft that is 6mm studding, the other will need a slip ring which could be underneath the moon spur gear with a spring contact on the frame.  The "stalk" of black ABS can be thicker to provide space for a hidden wire.

Two sketches showing slip ring and model for thicker "stalk" with hole for wire.

[Gina]

Won't the moon phase be (slightly) wrong when you the clock goes forwards in the spring? Running backwards in Autumn will advance the moon an extra hour as well, because the ratchet will still work. That's the moon phase going 2 hours fast a year. Acceptable or not?

If the ratchet did still work the error would be an hour in 28 days = 1 part in over 600 - less than moving your head from side to side   BUT in reality there wouldn't be an error from that cause because the movement would be too small to cause "ratcheting".  But there is an error in moon phase due to there being no movement for 6 hours while the paul is drawn back and double speed movement in the next 6 hours.  Also, for "nit pickers" the forward movement is sinusiodal rather than linear.  I'm not really bothered by a non-accumulating error of up to around 3° (6 hrs in 28 days)

[Gina]

Printed the new "stalk" and moon globe drive gear and fitted them together - nice tight fit   Taken the moon globe off the clock and got it apart to make use of the black hemisphere - I need to make a new white one and I'm printing that now.

[Stub Mandrel]

If the ratchet did still work the error would be an hour in 28 days = 1 part in over 600 - less than moving your head from side to side   BUT in reality there wouldn't be an error from that cause because the movement would be too small to cause "ratcheting".  But there is an error in moon phase due to there being no movement for 6 hours while the paul is drawn back and double speed movement in the next 6 hours.  Also, for "nit pickers" the forward movement is sinusiodal rather than linear.  I'm not really bothered by a non-accumulating error of up to around 3° (6 hrs in 28 days)

If Buzz Aldrin had taken that attitude he could have ended up landing in the wrong crater!

[Gina]

Ah but I'm not Buzz Aldrin and I'm not going to the moon   Chance of seeing it would be something...  So my moon dial globe will be just to remind me what it might look like if I were outside the earth's atmosphere

[Gina]

I think I've succeeded in printing a reasonable white hemisphere.  Here it is next to the gear and "stalk".  This is just by reflected light - I have yet to set up the LED and see how well it works with transmitted light.  I'm about to do that.

[Stu]

Looking good Gina.

Have you 3D printed some baubles for your tree this year? [emoji3][emoji3][emoji319][emoji319]

[Gina]

Thank you Stu   No I haven't - I'm not having a tree but I did consider printing baubles for other people

[Gina]

I printed the white hemisphere opposite way up from last time - works better

[Gina]

The LED has a narrow light spread so I need to add a diffuser - printing that now.

Here are some photos of the LED illuminated hemisphere.  LED pointing in different directions and finally with a piece of ABS over it to diffuse the light a bit.

[ChrisLX200]

You could have printed a textured Moon globe... or half of it anyway ;-)   http://www.thingiverse.com/thing:14011

ChrisH

[Gina]

That's a good idea - I'll look into that - thank you

The diffuser works but I think the white hemisphere shell wants to be thicker so that diffuses better.  Here are photos of the diffuser and with the white hemisphere on top.

[Gina]

Downloaded that moon "thing" but the problem is chopping off the part I don't want.  Tried importing one of the STL files into SketchUp but it wouldn't

[Gina]

I'm printing "moonshot.stl" to see what it's like - only needs 32g of filament.  I estimate that it's a bit smaller than my globe maybe something like 75mm diameter compared with 100mm for mine.  It would be nice to have a more moonlike globe.  Two optione to use this "thing" - paint half of it matt black or print a white and a black one and cut in half then join a white and a black hemisphere.  Anyway, I'll see what the print is like when it's finished (ETA an hour and a half).

[Gina]

Another possibility might be to have a fixed white moon globe and have a black hemispherical shield rotate around it.  An advantage would be that the LED would be fixed and not need a rotating connection to its power source.

[ChrisLX200]

Another possibility might be to have a fixed white moon globe and have a black hemispherical shield rotate around it.  An advantage would be that the LED would be fixed and not need a rotating connection to its power source.

That's good idea if you can do it :-)

ChrisH

[Gina]

I think I can - I'll sort out the details tomorrow - errrr... later today .

[ChrisLX200]

LOL! yes, I'm sat waiting for a new filament tube holder to finish printing, listening to the wind howling outside. I've had all sorts of problems printing with ABS but I think it is working now. I may attempt to machine the parts for an all-metal hot end which I think would help.

ChrisH