Posted on Leave a comment

Ouroboros – part II

At its simplest: A circle is a … closed curve that divides [a] plane into two regions: an interior and an exterior. But it is so much more than that. One of the more marvelous properties of the circle is that, by definition, all radii are perpendicular to the circumference. Though seemly obvious, this has the convenient side-effect of transferring pressure, which acts outwards equally (i.e. along all the radii simultaneously) over the surface area of its containing vessel, into two force vectors that are perpendicular to each radius and tangent to the circle at all points around the circumference. The net result is that the pressure is converted into pure tension: rather than bending, the circular ring just wants to get bigger, elongating the material. Because this happens to be the way in which metal is the strongest, it is also the most efficient way in which to use it, requiring the least amount of material to contain a given pressure. Which is, of course, the reason that pipes and other pressure vessels are round (or, more ideally, spherical, but don’t get me started on spheres).

In the interim, I caused the translocation of a low-quality 1″ bearing from its previous resting place to my doorstep in exchange for a small amount of the most widely-known social construct most often referred to as money. And I made a plan.

The shaft is made from the same cold-rolled steel stock that the lever handles were machined from.

The crown gears have grooved hubs so that they can be keyed to their shafts but I had no key stock on hand. I cut some out of a piece of scrap – which was only somewhat quicker than going all the way to the specialty hardware store – who may or may not have had any (“Did you say ‘metric’ key stock?”).

Milling the slot in the shaft is a lot easier than cutting the groove in the hubs 🙂

Ah yes. I love it when things fit first time.

The other motivation for using the big cast iron face plate from the lathe is that has the same mounting system as all the other lathe chucks. So rather than mounting the face plate directly to the shaft, I am making a back or adapter plate from some mic6 aluminum (that has been patiently and unknowingly waiting for this day) so that all the other chucks will fit the turn-table.

Test fitting the back plate to the shaft.

Things are coming together.

Now we just need a nice neat control system, which I absolutely promise to clean up and put in a proper box very very soon.

But for now, I can’t wait to give it a test drive.

And so we return to where we started; It always comes back around. Ouroboros: the snake that eats its tail.

Posted on Leave a comment

Ouroboros – part I

Ouroboros – It always comes back around – part I

The Early alchemical ouroboros illustration with the words ἓν τὸ πᾶν (“The All is One”) from the work of Cleopatra the Alchemist in MS Marciana gr. Z. 299. (10th Century) – 1
It always comes back around – Michael Kiwanuka

Ouroboros: the snake eating its tail signifying infinity and the eternal renewal. Across cultures and throughout recorded history, the circle has always been associated with perfection and the divine. Euclidean geometry, the intersection of Platonist thought (the theory that ideas have an independent, “perfect” existence outside of the physical world) with logic (a process of systematized reasoning where each thought is linked to the next in a chain of validity) could be considered to be the headwater of the river of technological progress. From Euclid’s circle comes the wheel, the foundation of machinery, from the wheel comes the gear and from gear it is just a short leap of imagination to the steam train and its aesthetic and cultural off-shoot (and, many would maintain, the logical endpoint of progress): the espresso machine. Today’s post is all about round things (not run-on sentences, just read it again, it makes sense)…

… specifically, turning this lot of rotational miscellany into a welding turn table. The large wheel is a faceplate that has been languishing in a cabinet under my lathe since I bought it ten years ago. It still has the original grease/ear wax stuff from the factory on it so obviously the previous owner also found it useful. The blue cast iron bracket thingy used to serve as the lower bearing mount and hand crank for raising and lowering the head of the mill before it was converted to CNC. The shaft and the crown gears were also parts from the hand crank.

The casting from the mill is not particularly high quality and needs to be cleaned up and properly squared before it can be used. The surface above the bearing mount pocket wasn’t a precision surface in the original design and therefore wasn’t machined – which is fair enough. The little bits cast iron and grit that aren’t actually attached to the casting because it wasn’t even sand-blasted, a bit less so…

After the cleanup, I add a trio of tapped holes to attach a retaining ring to keep the bearing in place. This could also be done more simply with an internal cir-clip, but I don’t have any on hand, nor do I have convenient tooling to cut the internal groove.

I’m making the retaining ring itself from a piece a (presumably cold-rolled) steel from the scrap bin. This came from a completely weird and baffling machine that I bought surplus just for the nice black anodized aluminum base plate that became my primary work surface (you may recognize it as a backdrop in quite a few photos). I have absolutely no idea what it was for (miniature seismic simulations??) but it came with all sorts of esoteric bearings, pulleys, springs and custom fittings. This piece is part of a matched pair of beautiful adjustable counterweights. Apologies to the designer and fabricator of this beautifully made mystery device, but I’m cutting it up.

Sizing the internal bore and the external diameters to their required dimensions on the lathe.

The finished retaining ring – the pair of slightly larger holes were from the original part. Presumably they are threaded to receive the divining rod attachments.

Now we need some structure to attach everything to. I don’t have anything nearly big enough for this on hand and it really should be made from steel, but the size requirements and the stock available means that these heavy aluminum angles are going to have to do.

The new welder makes welding aluminum really, really easy by comparison with the old machine. I haven’t investigated the science behind the ‘why’, but the AC balance setting allows the arc to “clean” the metal, removing the surface aluminum oxide in front of the weld. Magic. Suffice it to say that if I can put that bead down, anyone can weld aluminum.

The two sides are notched and spacers are added to make room for the bearing mount.

More to come….

.

1 – By Unknown – Chrysopoea of Cleopatra (Codex Marcianus graecus 299 fol. 188v), Public Domain, https://commons.wikimedia.org/w/index.php?curid=36915535

Posted on 2 Comments

What’s in a name?

So, what’s with the name? Lapera means the pear in Italian. It is a nod, of course, to the origins of these fabulous beasts as well as being the name of my existing design company: Pear.

To inaugurate my new home I decided to do something a little special: a coffee machine needs a name, and the name goes on the badge!

We start with a few iddy-biddy single-flute bits and a stack of aluminum blanks.

And a clean vise – you have to maintain your vises in order to maintain your vices. I really should be out-sourcing this part because there are more efficient ways to make it, but, for the first batch at least, these are gonna get made in-house.

A mist setup on the mill keeps the cutter clear of chips. Which isn’t a big deal for the large bit used for the clearing, but is vital for the smallest one which is less than a 1/16″.

The milling path generated by the CAM software is highly satisfying.

Initial machining is done.

Lots and lots of cleaning comes next: rinsing, ultrasonic de-greasing, chemical etch, more rinsing, baking to bring any residual oils to the surface, solvent bath and yet more rinsing.

I borrowed these guns from a friend who “doesn’t miss powder coating”. I completely agree – this process is a hassle to do for large or numerous parts unless you have a really good setup and do it all the time. The guns are fascinating, for a number of reasons, not least of which being that they are the first and only ‘product’ that I have used that is almost entirely manufactured with a plain-old PLA 3D printer.

The powder coat itself looks like pretty dull stuff.

But it sure shines up nice after a quick trip through the oven.

After a quick sanding to reveal the bare metal, a little bit of a trim and a clear coat, the badges are ready to join the fleet.