Rotola: The Crank and the Bow

When I originally started this project, I had some fantasies about creating my own YouTube channel to document my musical inventions and their progress; it didn't take much experience, though, to conclude that videography entailed much more work than I wanted to do.  Still, I wanted to share my ideas and efforts with whomever might be interested (there are a surprising number of makers of unconventional instruments out there, if widely scattered), thus my decision to include the rotola on my blog.  

However, even doing this has been more of a challenge than I expected, largely because I find it very difficult to manage the split-focus required to maintain a record of my process while I am in that process.  (I increasingly admire the folks who can maintain a video log of their work as they go; indeed, those that share about it say they actually have to focus on making a video first, then on its content.)  So, you may notice that, as my posts have progressed, they have become not only more patchy in their content, but also more retrospective.  I will complete my sharing of the balance of this instrument making project, but in the future, it might make more sense for me simply to post when I have completed a thing; I just can't keep proper track of all of it.  

So, with all that said, here are bits of what I did to make the crank and the bow.  

My initial visualization for the crank was for a relatively straightforward handle attached to a ring that clamped to the axle with a knob at the other end to hold while turning.  I played with several designs for this and all of them either didn't look very good (one of which was vaguely obscene) or weren't sufficiently robust.  After some time, I was struck with the idea that the crank didn't have to be a handle, but could be wheel-like, which solved the problem of robustness and opened new approaches for design.  I came up with several designs I liked, but they were either too difficult to fabricate or did not match the overall look of the instrument.  I finally settled on one that echoed design aspects of the stand:  

The handle would be located near the rim between the cutouts (darkened areas).  I liked this one a lot -- until it struck me that the cutouts looked a little too much like a certain famous cartoon mouse.  I solved that problem by addressing another one:  I hoped to make the cutouts exclusively with drill bits (as opposed to having to hand-draw individual curves)?  You can see the solution in the next pic below.  

To create the crank, I first built a jig that kept the disc blank centered so that, after roughly cutting it out on the bandsaw, I could use the the oscillating belt sander to get the outside edge concentric with the axle hole.  I then mounted the jig and disc on the drill press, where, guided by a printout spray-glued to the disc, I used two different sized Forstner bits to make the cutouts.  

I wanted a chamfer on the inside edges to add interest and make the wheel look thinner.  Here is a shot of that work in progress.  

Workholding took some time to figure out, but, more importantly, I had never done that kind of free-hand, curved chamfering, so I picked which side would be the (less visible) inside and did that one first.  The piece of walnut I was using was pretty brittle and splintery, making it especially challenging for a beginner.  I'm very glad I started with the mostly hidden face, as there was not only workholding and carving techniques to sort out, but also learning which tool to use, how to hold it, and keeping it sharp.  (I ended up mostly using a sloyd knife.)  While the outside came out better, it's still best not to look to closely at it.  

The end result.  The two small dots next to the axle are bamboo pins; I wanted to keep the crank removable, but my local big box store did not have small enough brass screws, so I used some shish-kabob skewers to make a friction fit.  It has worked fairly well so far.  

The bow presented some unique problems.  First, because I wanted it to wrap around the instrument and contact as many strings as possible, it necessarily would not be structured as bows typically are, placing tension on the horsehair to keep it taught.  Instead, it needed to act more as a frame, anchoring the ends of the horsehair strands such that they could stretch around the instrument and press against the strings as they rotated through their arc of travel.  This meant that the horsehair could not be attached to the bow (frame) as it might normally be, using the tension of the hair against the bow to keep it in place.  I would have to come up with some system that both held the hair securely while allowing it to be removed and changed when it wore out, yet do so independently of the degree of tension on the hair at any given time (which would hang loose when not being used).  I had some ideas for how to do this, but testing them would not be possible until after the second problem was solved.  

That second problem was that, in order for the bow maximally to wrap the horsehair around the instrument, it would have to be semicircular.  This presented strength issues, as there is no single cut possible from straight-grained wood in which the grain would follow the shape of the bow closely enough to prevent weak sections across the grain (this problem is called grain runout).  My first solution to this was to glue together three pieces of wood, in this case walnut, to make an arc blank such that the grain more or less followed the curve of the bow; thus no part of the bow would have significant grain runout.  I managed to get two pix of this attempt:

Here you can see the three pieces being butt-jointed together (just glued with no special joinery) to create the blank from which the bow will be cut; the cardboard template is in the foreground.  

This rather blurry shot is the best image I have of the almost-finished bow (it's from the background of another pic).  It has yet to have the attachment points for the horsehair cut into it, but it is otherwise complete.  If you look closely, you can see the joints where the grain direction changes between sections.  

The problem with this design is that, although it is unlikely to break due to grain runout, it actually did break several times -- under embarrassingly little stress -- at the joints, because butt-joints, especially with such thin wood, tend to be fairly weak.  Additionally, I had trouble clamping them properly, which undermined the strength of the glue.  A better solution would have been to have some sort of floating tenon connecting the sections, like splines or small dowels; these could even have been decorative, using a contrasting light-colored wood.  However, for whatever reason (I think I was just impatient and in denial), I did not take the time to do that.  After the sickening sound of the last snapped joint, I threw my hands up and started over with a different approach:  steam bending.  

I liked the walnut from the first iteration, as it would contrast nicely against the spruce of the soundboard, but none of the walnut I had was sufficiently straight-grained for steam bending and I was getting impatient:  by the time I had reached this stage, the rest of the instrument was completed and I wanted to get this project, beloved and exciting as it was, off my bench.  So I let go of my dreams of color contrasts and grabbed a chunk of ash from which I had cut the axle and drew a new design for the bow.  

Sadly, this is yet another bit of the build from which I have only sporadic images, so description will have to do for much of its explication.  Given that eliminating grain runout was now the goal (the bent wood approach would allow it, where butt-jointing only minimized it), I selected the most straight-grained section of ash I could identify and drew a pattern that allowed for continuous grain along the entire length of the bow, all the way through the handle.  After a few iterations, I had one that succeeded at this, looked good, and also took advantage of the curve of the handle to minimize the stress of the bend, which was tight (less than a 4" radius, as you'll see labeled in the next pic).  I milled a blank 10mm thick and then cut the pattern such that the "stick" of the bow would be 10mm square in cross-section.  I then chamfered all four edges of this to make an octagonal cross-section; I wanted to leave the final rounding until after the steaming so that I might have a little extra wood to work with if there were any splits from the bending (this turned out to be a good idea).  

Here is a shot of the bow in the bending frame ("r=95mm" refers to the radius of the form around which it is clamped).  

Here, I've begun to round off the handle-end of the bow, but you can still see the octagonal cross-section of the stick.  

This shows the slot cut into the end of the stick that is intended to keep the horsehair from spreading out too much.  You can also see that the stick is rounded now and the end has been cut in a curved slant.  Eventually, I drilled a small hole roughly perpendicular to this curve and drove a short brass rod through it such that the rod extended a few mm out the other side (opposite the camera view); to this the horsehair was anchored and tied off after a few wraps around the stick.  

Here is the slot at the end of the handle into which the other end of the horsehair would be set.  Once the hair was pulled into it, a shim of walnut was forced in behind, keeping the hair in place; the shim, being a press-fit, can be removed when it is time to change the hair.  

Here is a shot of the shim blank, prior to being inserted and flush sanded to the ash handle.  

Finally, here is the completed bow, finished with shellac, hair installed, and in position against the instrument's strings.  The design ultimately was very satisfactory, allowing good sensitivity in pressure and movement along the strings, important factors affecting the instrument's timbre, while being firm, robust, and fairly easy to hold.  Although small changes might be appropriate for different sized instruments, I expect future iterations of the rotola bow will closely resemble this.  

That concludes my posts about the fabrication of the rotola!  It was a long project and the most complex and challenging I've done so far, but very educational and rewarding.  My final post on the rotola will cover setting the instrument up, small tweaks, and end results.  

The Numinous Atheist

"I took the lamp and, leaving the zone of everyday occupations and relationships where everything seems clear, I went down into my inmost self, to the deep abyss whence I feel dimly that my power of action emanates. But as I moved further and further away from the conventional certainties by which social life is superficially illuminated, I became aware that I was losing contact with myself. At each step of the descent a new person was disclosed within me of whose name I was no longer sure, and who no longer obeyed me. And when I had to stop my exploration because the path faded from beneath my steps, I found a bottomless abyss at my feet, and out of it came — arising I know not from where — the current which I dare to call my life."

-- Pierre Tielhard de Ghardin, The Divine Milieu, Part Two, 2. The Passivities of Growth and the Two Hands of God, pg. 77

I recently reread Bless Me, Ultima by Rudolfo Anaya.  It's even more wondrous and amazing than I remember from when it was a middle-school reading assignment.  The main character, Antonio, a seven-year-old boy growing up in southeast New Mexico during World War II, struggles to reconcile the divergent ways of understanding the world that are pressed on him by his elders with those he discovers on his own.  Mystical, magical, horrifying, and inspiring, his experiences are grist for the mill of his young mind sorting the paradoxes of being human.  The story resonates with me because Antonio's confusion and drive to understand his world describe my own lifelong experience of wonder, fear, and hunger for certainty.  

Some of my earliest memories of my childhood are of moments of what I now call the numinous:  standing on the brick porch entry of my family's Upper Michigan Air Force Base quadruplex apartment -- as mundane a place as any -- and having an intense experience of being ready to die, expecting to be "taken up," even spreading my arms and looking skyward toward ascension.  I was probably four.  At age 10, playing in a stream in the North Carolina backyard of my best friend Beth, I remember a certainty that there was something magical about the place, that we were part of and witness to something bigger than us, something immense and incomprehensible.  As a young man watching the sunrise and writing in my journal as I dangled my legs off the edge of a lava flow atop Albuquerque's West Mesa, I surprised a wandering coyote who didn't see me sitting there until he was just a few dozen yards away; the moments we gazed at each other before he trotted off felt both matter-of-fact and transcendent, a magical space that would endure in my mind for the rest of my life, yet passed as quickly as a sandgrain meteor.  These, for me, are incontrovertible experiences of the numinous.  

Today, I hunger for that numinosity as much as I did as a child and youth, but an entire other self has developed, too.  My father had no room for mysticism, disdaining anything that smacked of magic or even the impractical, so I was taught early on that such ideas were for fools and, thus, if I wished to be anything other than a fool, I needed to eject these notions at their first showing.  Was it provable?  Demonstrable?  Repeatable?  If so, it might have merit; beyond that, it belonged in the trash bin of the gullible.  My father was not harsh, but he had a way of conveying disappointment that made clear my childhood fascination with ESP and spells and hexes was worthy of shame.  The most devastating blow to my obsession came in sixth grade, when a group of classmates conspired to convince me that one of them was brilliantly clairvoyant and the teacher, rather than interrupt their cruel joke and admonish the conspirators, simply rolled her eyes at me and let them play it out until I was utterly humiliated.  After that, I basically exiled my numinous and mystical self.  

Instead, I came to worship the empirical.  Without knowing it for what it was at the time, I took up the skeptics' great question:  how can we know what we know?  What can we learn with our imperfect and incomplete senses?  How can we augment our senses or account for their imperfections?  Given that, even with such augmentations or accounting, we nonetheless process all information with limited minds, how can we know if there is even anything "out there?"  Am I the only being in the world, the rest an illusion (the solipsist's conclusion)?  This makes no intuitive sense, but then can I trust my intuition?  

After years of such wandering, rejecting the numinous yet being unsatisfied with the empirical alone, my undergraduate studies in epistemology and skepticism helped me find a happy, workable (while still imperfect) solution:  there is a world "out there" and, although we cannot know it perfectly, we can know enough about it to operate effectively in it.  Indeed, there are ways that we can work to make our knowledge ever less imperfect and these ways are called science.  

Today, I am a trained scientist, an empiricist, materialist, and practical skeptic.  I do not believe in the existence of god(s), the spirit or soul, nor, by extension, ghosts (spirits with no body) or zombies (bodies with no spirits) and their ilk.  At the same time, it feels wrong to invalidate and shame others who do believe.  Moreover, how do I reconcile my own experiences of the numinous?  Again, my father, unwittingly perhaps, pointed me in a useful direction:  wonder.  As an engineer and a true geek's geek, my father had that childlike, "gee-whiz" excitement when it came to the sciences he studied and the gadgets he built.  His commitment to the empirical was not absent of wonder and, indeed, wonder drove all of his passions, whether flying airplanes, studying advanced mathematics, building race cars or personal computers (before they were a thing), or touring the Great Parks of North America in a 1961 Greyhound bus he converted himself.  Perhaps wonder is sibling to the numinous.  

Even after being shamed and argued into rejecting the mystical, I never stopped having mystical experiences.  In my late 20s, after I broke up with a woman I thought was my One Great Chance at True Love, I spent a (completely sober) day and night filled with music and visions, following a call that ultimately led me crashing nude into midnight ocean waves on an empty city beach, feeling that an old skin was being beaten off of me.  In my late 30s, following the birth of my daughter, I went through a period of introspection and transformation that changed the course of my life, a deep dive into religion and art that ultimately led me to becoming a psychologist.  Change and clarity arising from I know not where have punctuated my life, leaving me convinced in the moment that I am a mere vessel or conduit for some greater power.  

In studying the human brain, I've come to understand that such incongruous experiences have their origins in the fact that the conscious mind is but the thinnest of veneers over the vastness of the psyche:  the consciousness that the brain produces is but a fraction of its output and its greatest products appear to be outside conscious reach -- perception, identity, meaning, even decision-making.  Thus, what some people call God or spirit -- the experiences I call numinous -- likely, in my empirical cosmology, arise from these deep workings of the mind and brain.  Yet, that explanation of their origin does not make them less wondrous -- or numinous.  

Now as ever, I strive to stay in touch with the numinous in my life.  The breathtaking spectacle of the sugar maple in my autumnal backyard, the shivering insight that melts from a patient's face down through their body, the bottomless space beyond the planets on a moonless night, the derealized moment when a tarot card reveals its meaning, the joy and wonder in the eyes of loved ones, the sudden Knowing of a personal Truth, all these are part of it.  The numinous is a human birthright, from wherever it springs.  Christianity, Judaism, Islam, Buddhism, Taoism, Paganism, Wicca, spirituality, science, all of these are ways of explaining the how of our experience, but the what cannot be denied.  

I honor your numinosity as I honor my own and I wish for all humans to be in touch with theirs, however that may occur.  

Rotola: The Bridges and the Stand

 In my last post about the rotola focusing on the construction of the nut, I included an overview of basic string instrument construction; for review:  

In this post, I'll focus first on the other end of the resonating part of the string, the bridge, and then on something unique to the rotola, the stand on which the instrument rotates.  

The rotola has 16 strings and each string has its own bridge.  Here's a drawing of the bridges' front and side views:

They are not big, about 18mm high and maybe 6mm thick at the base and ~1.5mm at the top.  I decided to make them out of purpleheart, of which I have a large chunk.  I like the wood a lot, although I don't often use it, as it's really difficult to work with due to its extreme hardness and density; however, those same properties make it good for this application.  Additionally, while I have some hard maple, which is a more typical wood for string instrument bridges (particularly the violin and viol families), I wanted something that would contrast visually with the spruce of the soundboards.  

Fabricating these would be a challenge:  I needed to make at least 16 of them (spares would be nice, too) and they needed to be uniform and precise (note the curved base that fits exactly on the soundboard), plus, being small, they are hard to hang onto while working.  After much thought, I figured a way to make them from a long strip as a starting blank.  I could plane the strip at an angle along one face, then, supporting the planed side to keep the centerline correct, plane the same angle along the other face.  Next, I would mark out the width of the bases using a pair of dividers and then sand the correct radius between those marks.  Finally, I could saw out the rough triangles and clean up the sides using sandpaper on glass and file the notches for each bridge's string.  This more or less went to plan, although I mades some mistakes while working it out and had to start over.  

Here are some views of the process:

The purpleheart blank after it was cut, milled, and planed to size as precisely as I could make it.  

Two views of the jig I built to run the blank through the surface planer:  

For the second run (which I neglected to photograph), I had a shim with same angle as the cut, so the second side would be held at the same angle as the first going through the planer.  (For my first attempt at this, I used a hand plane and struggled to get the angles correct and consistent; the above success was due to having purchased a surface planer.) 

This is the setup I used to cut the radii into what would become the bases of the bridges.  The wheel is cut from 1 1/2" MDF (actually two 3/4" pieces glued together, leftovers from another project); I cut it initially on the bandsaw and then rounded it against the oscillating belt sander by rotating it on a fixed dowel inserted into the center hole.  I then stuck 120 grit sandpaper to the edge using spray adhesive.  I was able to raise the work surface by cutting some 1/8" plywood to fit around the disk and clamping it to the drill press table; this prevented leaving a ledge of unsanded wood where the bridge blank might slip under the spinning disk.  The setup worked fairly well, being only a bit off of parallel to the table.  

Here you can see the scallops made with the sanding disk.  

Next step was to cut the bridges out, which I did using this jig (left) and a pull saw.  The vertical piece of the jig had a magnet embedded in it to keep the saw at the correct angles (defining the side of the trapezoid and keeping the edge square to the centerline).  This also worked fairly well and you can see some of the cut bridges in the cup at center, but, unfortunately, I seem to have neglected to get any close-up pix of the finished bridges; you'll see later how they fit onto the instrument.  

Next, I went to work on the stand for the instrument.  As it is intended to be played by a single person, cranking with one hand and bowing with the other, it needs to be supported at the axle ends so that the pins and bridges have clearance from the stand, but not so high as to raise the business side -- the strings rotating across the top -- inconveniently high.  The simplest design would be some basic yokes at the ends and a plain platform spanning between them; however, I wanted the stand to be a part of the presentation and be attractive enough to compliment the instrument.  

I started out by hand milling down a large piece of fairly warped but beautifully figured walnut given to me by a friend.  This was before getting either a jointer or a surface planer and became an exercise in confronting my amateurism, ending with turning most of a 6/4 piece of wood into sawdust or shavings; you can see the resulting piece in the middle of the bench, below -- it's less than 5/8" thick.  

The two square pieces with holes drilled in the center will be the end supports.  These were resawn from 3/4" pre-milled stock and so was much less disastrous.  

I spent quite a bit of time experimenting with different designs before settling on these profiles.  

After routing roundovers on the stand's components, I rabbet-jointed them together with glue; I did not want any hardware or dowels showing.  Next, I cut two knees for each end to add strength to the joints.  

Here you can see the knees being glued in place.  

In the end, the joints were plenty strong enough and I am very pleased with the overall appearance of the stand.  

Notice that the left-hand end of the stand, for the nut-end of the rotola and over which the bow will rest, has a longer squared end than the right (below).  This is because, at the time, I was still considering anchoring the bow at the left end and making a hinge so that the bow -- and presumably some weight -- could rest on the string and not require a player to manipulate it; the hinge would connect to the stand somewhere along that straight edge.  I have since changed my mind on that bow design, but I still like the asymmetry.  

The right-hand end of the stand.  

Again, I neglected to photograph the finishing process, but the results will be seen in later posts when the instrument is fully assembled; it looks pretty good.  

Next post I will cover the fabrication of the crank and the bow -- and then it will be done!