Mariner's Astrolabe, full scale, AON

[AON]

Just opened this log.  Will start posting here once some items are organized.

 

I was reading about maps and charts and once again they alluded to navigators using special instruments.  After having researched how it was done with different instruments I decided to create a 3D model of a working mariners Astrolabe.

 

At this moment I am printing the last part... well my printer's doing the work... I'm outside basking in the summer sun ☀️. 

Edited July 28, 2022 by AON

[AON]

This figure was the basis of my model.  An astrolabe retrieved from a Spanish wreck.

[AON]

This is my 3D model (created in Fusion 360 - free hobbist version).

Front and back view.

 

There will be six printed parts and two copper wire pins.

The body, pointer, plug (on the post over the pointer), lower swivel joint, upper swivel ring, and a back ballast cover.

 

I need the ballast cover to cover the cavity I've created to place a number of coins to create ballast weight as the 3D printed version only weighs in at about about 173 grams.  My weight will be a number of 1 cent Canadian coins... not in use, not accepted as currency anymore.

[AON]

I use the free Ultimaker Cura version 4.13.1 to create my g-code to print.

I will post pics of the printed parts tomorrow.

I am using a PLA/wood filler filament.

It can be easily sanded with regular wood sand paper.

 

Here is the data I've collected so far.

 

    PART       EST`D          ACT.       WT.        LG.        COST
1. body       15h 3m          ????     127g     42.47m   $3.80
2. Pointer    2h 19m      2h 41m     20g       6.6m    $0.59
3. Plug            19m             22m      2g       0.79m  $0.07
4. Swivel         27m             34m      4g       1.23m   $0.11
5. Ring       1h 27m        1h 43m    12g       4.11m   $0.37
6. Cover       1h 15m       1h 18m      8g      2.71m   $0.24

Total                                              173g     57.91m    $5.18

 

[AON]

I should mention the costs are for material only, not electricity nor design time.

 

I also want to mention my adornments on the ballast face side.  I added the year in Roman numerals (2022) and the dots are not braille.  It is a star map of the Little Dipper with the north star and the Southern Cross and the three others used to find the south pole.

[AON]

My 3D printer is a JGAURORA A5 as seen below.

If interested you can google it and see the specs for the unit.

I have the option to connect it directly to my computer but I choose to use a Thumb Drive (USB Stick)

 

 

[AON]

My print settings are mostly default.

I change the wall thickness to 4 layers, and 20% infill (Grid pattern).

This means the inside is not hollow nor is it solid.  Saves on material, cost and time.

Print temperature is 210°C, bed temperature is 60°C.

I always use a build raft and reduce the margin to 10mm outside the object.

I use a raft because somehow that always sticks to the bed and the object always sticks to it.

If I don't use a raft a successful print is a complete gamble.

 

Here you can see the base printed, the raft is under it, on top of the glass bed.

You can also see the 20% infill.

At the top is a shamrock shaped outline.  It is filled with a "support" that I will remove when cleaning up. The support is what the top face prints over to close this rear access pocket.  This is where the coins will go.

 

Edited July 27, 2022 by AON

[AON]

Now I am anxiously awaiting it to complete the top layers and hub or spigot for the pointer.

Tomorrow I will clean it up with various sand papers, and check the fit of the pointer, lower swivel and ballast back cover plate.... and the coins.

I will slip a note on top of the coins for the person that some day might open it up.

Edited July 28, 2022 by AON

[druxey]

Hah! Another rabbit hole that you are going down, Alan. Next it will be a back staff, then an octant....

[AON]

more likely an early quadrant.

[AON]

The print finished after 17 hours and 5 minutes

So much for the 15hr 3min estimate.

Here you see the finish front.  Needs a bit of cleaning up.

Dimensions are body 6" diameter x 5/8" thick and 7" tall over the crown

Next is the back or rear that faced the raft and glass.  As this was hidden it could not be "ironed" as the front or top face was.

This will need a bit more sanding and cleaning.

And that is why I print four layers instead of two.

For those unfamiliar you can see the "supports" in the ballast coin cavity and on the crown.  As these were steps up in the build process those layers needed supports provided under them or the machine would have been printing in mid air!

Edited July 28, 2022 by AON

[AON]

Over the last two days I completed the clean up and dry fitting.  Yesterday morning I did a test with the epoxy on two rafts to make sure it didn't dissolve the PLA/wood fibre material.  Yesterday evening I glued the cover on the back and the hub or spigot back onto the face.

 

The hub broke off in cleaning and fitting parts.  As the hot printer nozzle lays and presses a layer of filament on top of a lower layer, the layer becomes a wee bit wider than one would hope for at mating surfaces, hole and hubs.  So holes need to be opened up, flashes cleaned off, and hubs need similar treatment.  I ended up with a slight interference fit between the pointer and hub, or so I thought, but turning the pointer might have twisted the hub a bit, weakening it.  When I attempted to disassemble them the hub snapped clean off.  I repaired this with a short piece of 1/4" wooden dowel and epoxy.  I put a groove down the length of the dowel and filed a couple shallow notches in the hub matching hole so when the epoxy set the spigot hub to base assembly cannot spin.

 

If I were making more of these there are a two things I'd change: Increase the fit tolerance for less cleanup and increase the embossed numbers to a bolder font.

 

Below is the result, dry fitted, in stages.

[AON]

All the parts cleaned up.

[AON]

The cavity filled with fifteen 1 cent pieces.  There is a penned note on a piece of folded paper below the coins.

[AON]

Cover fitted.  The gap will be filled with wood dough and will disappear when painted.

[AON]

The "fix" for the broken spigot or hub.

[AON]

Hub reinstalled over the dowel

[AON]

The pointer installed over the hub

[AON]

The retention plug cover installed over the pointer and the lower swivel and upper ring assembled (and pinned with copper wire).

[AON]

The complete assembly.  The lower ring is not pinned to the crown of the astrolabe base part.

[AON]

It has been taken apart and parts epoxied over night.

Now I will need to chose a suitable colour and get a can of Acrylic spray paint.

 

... and I worked on my Bellerophon upper deck gunports yesterday afternoon Druxey!  🙄

[DocRob]

I  just stumbled over this very interesting project of yours, the print looks great Alan
If you are looking for extremely good metallic colors, my weapon of choice since years is always AK's Extreme Metal range, at least if you consider airbrushing. They have all the important non ferrous metals in their range, like copper, brass and bronze. They have an extremely fine grain and airbrush un thinned perfectly. They are not suitable for brush painting though.
AK has also a range of metallic waxes, (True Metal) which can be brushed, applied with cotton swabs or cloth and they do look good and 'metallic' too

 

Here are some non ferrous examples of my Nautilus build with Extreme colors applied (bronze, brass and copper mainly, but also stainless steel and gun metal).
It's hard to show the shininess and metal likehood in the pics, but at least, I tried . I hope that helps a bit

 

 

 

 

Later in the build, I patinaed the whole sub with pastels and pigments, which came out satisfactory to my eye.

 

 

 

 

 

Cheers Rob

 

 

Edited July 30, 2022 by DocRob

[AON]

Good morning Rob.

Air brushing is another process I've not attempted.  You definitely have the talent for it.

Very realistic.

[DocRob]

Hello Alan, 
thank you for your kind words. One subcategory in plastic modelling is driving me mostly, it's replicating materials in different states of use and tear or in other words, how to let plastic look like metal, wood, cloth or whatever.
Airbrushing is not that hard to learn, especially not for gifted craftsmen, building wooden ships with great patience. It's a learning curve, but be prepared, it's about 80% masking, cleaning, preparing, mixing, testing, ... and only twenty percent of actual spraying maximum. It has a lot of advantages, even with wooden ships as I found out lately with my first build and spares you of garish rattle cans, which are smelling bad and mostly flooding the object way too much.
If an airbrush is not an option for you, the metal waxes might be one. You can apply them with cotton swabs and cloth without leaving brush marks. You find some videos on YouTube were they are presented with their pros and cons. The waxes are called True Metal Wax and are produced by AK. 

 

Cheers Rob

[AON]

I will be using Kingart Metallic Acrylic - Bronze - paint on my astrolabe

[AON]

My completed working mariner's astrolabe.

Painted and one coat of matte sealer.

 

The $0.15 ballast made a huge difference!

 

Edited August 1, 2022 by AON

[AON]

Had a nice sunny day yesterday so I tried out my astrolabe.

 

First I set my sundial onto a solid flat board, aligned it to magnetic north which for us is very close to true north and levelled the board.

 

 

Then I watched and watched and.....

Eventually at about 1:17 PM (DST) the shadow was straight under the pointer meaning the sun was pretty darn near directly over head.

I took a reading....   64°

subtract that from 90° gives me 26°

correct this for the tilt of the earth on 6 Aug 2022 (add 16.57°) gives me 42.57°N.... my latitude

 

well not quite.  According to GPS my Latitude is 43° 1' 12" N (43.02°)

 

That is about the accuracy of a mariner's astrolabe.

 

Now to figure my Longitude

 

If I had a clock set to UT or GMT I'd have read the time and it would have been about 5 hours and 17 minutes (5.2837 hours) difference from my reading of 1:17 PM (DST)

The earth rotates 15° per hour  so 5.2837 x 15 = 79.255°

According to GPS my longitude is 79° 15' 18"W or 79.255°

 

Edited August 7, 2022 by AON

[Canute]

Congratulations on your design and use of that astrolabe. Accuracy looks to be 5 miles. About par for using this system. 👍

 

Development of accurate chronometers was key to developing accurate celestial navigation systems. For the Northern Hemisphere, we had figured out latitude (at night anyway) by shooting Polaris. It's elevation is your latitude, no calculations. Time is critical for longitude calculations. I spent 6-7 years doing this stuff as an aerial navigator, using bubble sextants.

[AON]

Should also mention that if I used it at night, reading the elevation of the north star (Polaris) from the horizon I would not subtract the angle from 90° as it is exactly the latitude of my location.

 

I printed an early quadrant the other day.  Painted it yesterday, and with the temperature feeling like 39°C today I will likely finish it off and post some photos here to close this build off.

[AON]

Thanks Canute.

Seems our posting were at the same time!