Jovilabe

.

"Chas fecit" would be usual

MichaelG.

Some of my shop work lately could be inscribed

"Jeff fecit purgamen"

I am impressed at your rate of progress. I am still flapping about trying to fabricate a back-plate for my collet chuck!

I look forward to seeing the assembled machine.

James

Don't trust any claims I make to being educated:

Latin is a language,
As dead as dead can be.
It killed the ancient Romans,
and now it's killing me.

Caveat emptor,

Dave

I'm just a humble botanist with access to Google Translate

But Michael got you there.

Neil

.

If that was supposed to be a cheap 'dig', Neil ... let me assure you that I have studied enough clocks etc. to know that one, without recourse to Google Translate.

MichaelG.

?

No I just mean I didn't have to tell him as you had. Even I knew that one without electronic assistance!

Rather than diving in with the big top plate, I thought I'd refresh my etching skills on a smaller sample - a circular calendar disk that will support the 'earth' and perhaps a small sun globe. This will fit on the mechanism that operates the pointer that shows where Jupiter is in the sky. As it will rotate once a year, it seems daft not to enhance it this way. So, a 60mm disk with twelve months around the outside then a ring with the four seasons (offset by 22 degrees to start them at the solstice/equinoxes, none of the 1 March nionsense). In the middle a nice mediaeval sun swiped off the net.

First exposure was too long and the developer too strong. A few tweaks, a recoat with resist and it looked OK after a test etch, so taped all the bare brass up and into the ferric... can take four hours or more and the ferric is getting tired. I will pull it out later and finish off tomorrow. Fresh ferric has been ordered but I think I may need fresh resist spray too.

The challenge for the big wheel is that the artwork will be over two sheets that will need perfect register. I will also have to expose in sunlight as far too big for the box - or maybe support it six inches or more above the box and have an extended exposure time.

Well, this is the result. The outer circle is 60mm across, the lettering is 1.5mm high.

Now the dilemma, do I accept an 'antiqued' finish of strive for a flawless etch that I am almost certain to be unable to achieve?

Neil,

Looks good to me.

May I ask how you transferred the image to the metal prior to etching? I have done a little etching with ferric chloride, ironing on a laser-printed image. My difficulty was getting the image to come off cleanly.

Regards,

James.

Thanks James,

I spray the brass with etch-resist, then laser print a negative image onto transparency film (inkjet film works too) and then expose it with my PCB light box. I use dilute sodium hydroxide to develop the resist and etch in ferric chloride.

Neil

Neil,

Thank you.

James.

This brass polishing is getting to me. Nearly all done, but the 60-t gears are particularly exposed and have no bosses (the 12-t gears are a push fit in them). Despite neatly parting them, any pause has left a ring that needs sanding out, most were OK a couple of sides took a bit of doing and one was awful. I have blood running from my right hand ring finger from pressing sharp gears down onto the wet and dry.

I will leave the fine grit and polish for tomorrow.

Bad news, I discovered three more gears will give me a 0.03% accurate lunar phase dial, and it fills the empty space on the big dial, but one is an idler so only two lots of gear cutting.

Caesar aderat forte

Brurtus adsum iam

Caesar sic in omnibus

Brutus sic in tram

All genuine Latin words, but of course it doesn't mean anything, but it kept us amused as schoolboys 50+ years ago

I'm getting a bit nervous, that I've bitten off more than I can chew.

Adding 15 more gears will give me four sub dials underneath the Jovilabe proper Jupiter rotation, lunar phase, sidereal time and UTC all to high levels of accuracy.

The down side is (1) will the torque required burst it? and (2) this is about twice as complex as the Antikythera mechanism... gulp!

Test polish for the sidereal dial, to go in the right-hand position (actually bottom of the dial as I have rotated the inner part 90 degrees).

Neil

Neil, if at the end it doesn't work all you need to do is crush it flat and throw it in the sea somewhere coral will grow over it. Then in 2000 years or so when archeologists find it they will get headaches trying to figure out what it is and how it is supposed to work. Make sure that you engrave your name on it so that you will forever be recorded in history.

By the way it is a great piece of work.

Edited By norman valentine on 26/10/2016 16:27:00

Thanks Norman, here's the moon phase dial:

The uneveness is down to the etch, not bad painting (for once!) the black is actually several layers of black sharpie then a windsor and newton gloss spray for all surfaces including metal. Works much better and smoother than cellulose and removable with white spirit.

Neil

Edited By Neil Wyatt on 26/10/2016 17:30:26

Phew!

26, 28, 29 (x2), 30 (x3), 33, 57, 59, and 48-T gears cut today and last night.

All that's left is 45-T and a bunch of 12-T that I can cut as a 'stick'.

But drinking a Cab Sauv for South Africa ('The Cheetah Reserve', far too nice and smooth for its price, and better than the Aussie CS that preceded it I'm afraid. So not a good idea to cut any more gears tonight

I can then finalise all the gear spacings on the bottom plate and redraw the top plate to suit actual, not theoretical locations.

Th washers came too, seem to be good quality that i can use straight from the packet. As hoped the M3 washers are an easy fit on 1/8", in fact slightly more clearance than expected (which is good). Thinking I need some graphite as dry lube will be best for something with parts that rotate as slowly as once every eleven.8 years...

Neil

I've only just been pointed in the direction of this forum and your thread. I'm really impressed work your gear work for this project of yours - a jovilabe makes a nice change from a traditional orrery - and from an historical point of view until the invention of accurate sea going clocks by the great Mr Harrison in the mid 1700's knowing the exact position of the moons around Venus was the only way of pinpointing your longitude as you sailed around the world - not an ideal navigational solution, but it worked!
Anyhow, apart from telling you how good this is looking so far I just wanted to defend the honour of the Antikythera Mechanism that you mention a couple of times - I'm not sure how much complexity your machine will have eventually, but the Antikythera really is a complex old beasty. It has several differential drives with pin and slot gearing, bits spinning within other bits, retrograde motion outputs for the five naked eye visible planets (pointers change direction from forwards to backwards and vice versa), accurate eclipse prediction capabilities, moon phase indicator, and of course there are the two big spiral slotted date dials.
I know all this as I've just spent the past two years or so building one... out of wood... Sorry, unfortunately I don't yet have a lathe in my life, or the skill to use one.
Anyhow, there are a few photo links below to show you what I've come up with - and so far it works beautifully... I just hope that my luck holds until the end.
There is still a fair bit to do before it's finished, but the mechanism itself is all done. The most difficult task will be calibrating it.
Keep up the great work, I shall be watching with interest and wishing that I had your fabrication skills!
 

Edited By JasonB on 11/12/2016 20:58:43