Showing posts with label spindle physics. Show all posts
Showing posts with label spindle physics. Show all posts

Friday, November 15, 2013

More on Twisty Sticks

A twisty stick is a piece of wire 8-12" long with a hook at one end.  The Scandinavians make, big, tapered, wooden ones, but I am interested in the British tradition.

They were used for grading wool in the time of Chaucer, and it makes sense to me that a spinning tool was used to determine how fine a wool can be spun.  Anyway, Chaucer was hundreds of years after great wheels had been introduced for the fast spinning of woolen yarn, so twisty sticks are likely an old and deep tradition.

Alden Amos uses 1/8" wire and gives directions with drawings for making them in his Big Book of Handspinning. He likes them, and considers them an essential tool - the kind of thing that spinning guilds should make for every member as guild projects.  I like 2 mm steel wire and make them a bit longer (10.5" over all).  Mine weigh about 5 grams, and I use them for yarn grists that I would use a 5 gram spindle with whorl, e.g. ~30,000 ypp.  An iron hook from cheap, soft iron wire bound into the split end of a dogwood twig with a bit of linen thread and some glue makes a 2 gram twisty stick.  It works. With  half an inch of iron wire, linen thread, hide glue, and a sharp flake of chert, an iron age spinner could make one in a few minutes. It has about the same size shaft as AA's twisty sticks so it will be about as fast, but it only uses half an inch of thin iron wire. This gives us an idea as to why they are called "sticks".  A twisty stick is a drop spindle with a hook, but no whorl, and is often made entirely of metal.

I find that I can do a thigh roll with the twisty stick with one hand do a long draw draft with the other hand and quickly have a good make of yarn. The draft and the thigh roll can occur at the same time.  Then, I can drop the drafting hand, and the return thigh roll will wind on the yarn. The wind on is backwards.  There is almost no wasted motion.  Where a little more twist is required,  the twisty stick can be given an extra shove and released for a moment at the end of the forward thigh roll. Then the twisty stick will deliver a surge of twist to the yarn. The process is very fast. It is not something I have seen any other modern spinner do. It is not in the literature.  This is very odd.  The copp is built to wind off as an end feed package.

However, I do not know how to spin worsted with a twisty stick. So what I produce on twisty sticks are "weaving quality" woolen yarns. The quality would improve if I would practice. The problem is that even the best twisty stick is not as fast as my AA modified wheel, so my tendency is to spin any yarn on my wheel.   Thus, I am not likely to put the required practice time into twisty stick spinning, and I will not achieve and maintain professional competency with the tool.

Still, I have no doubt that Iron Age Brits used this method to produce woolen cloth for export.  I would not be surprised to discover that this was the "rolling on the thigh" method described for Bronze Age Greeks.  It is a concept that would allow a textile professional to produce less expensive woolen cloth.

The wire gets brittle and breaks. What the archaeologist would find a few hundred years later is a small piece of wire.  Any archaeologist ever see anything like that in a Bronze Age or Iron Age site?  Any chance that such an artifact has been found and incorrectly identified?

We have not really thought about hand spinning with a spindle on an industrial scale (e.g., ship-loads of cloth) for a long time.  Linen and hemp need a spindle with whorl because the long fibers and low twist per inch require slow insertion of twist. Thus, we see the spindles with whorls in the Egyptian drawings. Silk also has very low tpi, and want slow insertion of twist. Spinning worsted wool requires a whorl because both hands need to be free to draft, and therefore spindles for worsted spinning need whorls to store momentum and gradually transfer the twist to the yarn over a period of time . This is what we see depicted on Greek urns. Weaving wants worsted warp, so wool cloth production always set a demand for worsted thread, and we find  lots of whorls in every hand spinning culture.

However, woolen and cotton spinning just want lots of twist insertion. Woolen and cotton can absorb twist very rapidly. Drafting can be with one hand, so one hand can keep the spindle turning at a very high speed. If one hand is devoted to tending the spindle, there is no need to store momentum.  One can get the highest rotation speeds and therefore the fastest yarn production from a spindle with no whorl.  The spindle can be spun up very fast, and  all the twist energy transferred to the yarn almost instantly, rather than momentum stored in the whorl.  Over all, the process can be much  faster than modern spindle spinners using whorls think is possible.

This can be seen by the fact that the basic unit of woolen production was a hank of 1,600 yards, while the basic unit of worsted production was a hank of only 560 yards.  Yes, I think that in a world where all spinning was done by hand with a spindle, a yard of worsted was worth 3 yards of woolen. Wool yield, wool preparation, and spinning effort are all factors, but I would also say that in a given time, a woolen spinner would be expected to spin ~3 times the yardage of a worsted spinner.  We do not see this today because both woolen and worsted spinners use spindles with whorls that all rotate at the same slow speed.  Thus, woolen spinners spin at the speed of worsted spinners.   And the goal is better yarn, rather than  faster yarn.

Victorian ladies looked at the depiction of Egyptian linen spinners, Greek and Roman worsted spinners, and decided that all spindles need whorls.  Modern spinners (after 1960) took this as the wisdom of the ages. They felt that spindles needed whorls - everybody knows that, why would they stop and test this bit of folk wisdom? They did not think about spinning faster by using a spindle without a whorl.  They were spinning for a hobby, they did not care how fast they could spin.  In fact, showing off how fine and fast one can spin is considered rude.  When hobby spinners want to spin woolen faster they use a great wheel or charkha.   

I think spindles for worsted spinning need much higher moments of inertia than spindles for woolen spinning.  I find it amusing that this difference does not show up in the spindle market place.  It does not matter to me because I make my own spindles, and mostly I spin with my wheel.  

The above will raise some hackles  Any hand spinner that can sit down and spin wool at its spin count (http://en.wikipedia.org/wiki/Spinning_count) is very welcome to tell me that I am full of shit.  Any person that cannot hand spin wool at its spin count should be polite.  

Thursday, April 05, 2012

Understand the Spindle! part 2

In Part I, I mentioned mass that is farther from the center of rotation slows the rotation of the spindle.  This is a dramatic effect.  Suppose you have a spindle with a 12 gram whorl in the shape of a flat disk. If that whorl is 1 inch in diameter, then the speed will be X for one "flick" that gives the spindle rotation.  If the spindle is made with a thinner whorl, then a 2 inch diameter whorl, still weighted at 12 grams, have a speed of X/8.  If the spindle is made still thinner so that it has to be 3 inches across to weight 12 grams, then the speed will be X/27.  That is, a spindle with a 1 inch whorl will spin 27 times faster than a spindle with a 3 inch whorl when they both carry the same rotation energy.  When spinning yarns of the same grist, the spindle with the 3" whorl will deliver its energy to the yarn much more slowly and be much more suited to spinning thicker yarns that require much less twist per inch.  The 3" whorl also has a longer lever arm and thus can deliver more torque.  Thicker yarn requires more torque to insert  twist into the yarn.  Thus, large whorls are better suited to spinning thicker yarns and small diameter wholes are better suited to spinning finner singles.

Cupped and rim weighted whorls, where even more of the weight of the whorl is farther from the axis of rotation result in even slower spindle rotation. This is not bad if you are learing to draft, but it is no good if you want to spin a lot of fine yarn, fast. The classic example is the CD spindle  (http://danielson.laurentian.ca/qualityoflife/Fulltext/Textiles/Making_a_cd_drop_spindle.htm ).  These are spindle with wide, thin whorls that spin slowly for a long time.  The classic Russian supported spindle (http://askthebellwether.blogspot.com/2007/08/how-do-you-spin-on-russian-spindle.html) has its whorl very thick and close to the axis of rotation.  As I look around, the Russian support spindle and the Tahkli are the most comon fast spindles around.  However, it was not always so. 

We find large numbers of small "whorl beads" at sites around the world. see http://www.philamuseum.org/collections/permanent/139611.html , http://www.metmuseum.org/collections/search-the-collections/140002024 , http://antiquegreeks.info/?s=Bead+Spindle&c=37906 , http://www.stringpage.com/viking/spindles.html , and  http://www.woolery.com/store/pc/Medieval-Spindles-c281.htm .  Were these really used for spinning or were they just decorative beads?  Using metal machine nuts of size and weight similar to those described on the Viking page, I have made spindles that spin fine threads fast. To modern spinners that are accustomed to spinning with modern spindles that spin slowly, these spindles with small whorl beads spin disconcertingly fast.  Unlike the supported Russian and Tahkli spindles that are spun up with a flick, these top and bottom whorl spindles that I have been making can be spun up with thigh rolls and 2-handed tosses to truely high speeds.  Speeds that spindles with mass on a longer leverarm cannot match.

Nobody using a modern Peruvian spindle such as (http://abbysyarns.com/2011/02/peruvian-spindles-my-spindles) can spin that fast, because their spindles are have evolved by tradition to spin slower, with more torque to spin the coarse singles being produced for local utilitarian consumption.  In fact, there are modern Peruvian spinners that use metal machine nuts as spindle whorls. These spinners do spin fine threads fast, they just have not gotten as much publicity.

I do not want a spindle that spins for a long time.  When spinning fine threads (e.g., 100 wpi and much finer) , I want a spindle that transfers its energy to the thread  -- very rapidly.  That means, the spindle is spinning fast.  When my spinlde is inserting twist rapidly, it is putting energy into the thread and that loss of that energy will slow the spindle down rapidly. Thinking that a spindle can insert twist and keep on spinning is like believing in perpetual motion machines. Spindles store energy, they do not create energy.  A spindle that spins for a long time means that it is not transfering its energy to the thread.  A spindle that spins for a long time means that it is spinning slowly, transfering its energy to the thread slowly, and it is inserting twist slowly.  I am not saying that this is bad. It is necessary for thick yarns and for spinners that are slow drafters.  I am saying that traditional spinners used spindles that made spinning the kind of yarn that they wanted to spin easier and faster.  However, today we have a lot of spindles for spinning all kinds of yarns thrown on to the market, and they are not labeled as to what kind of yarn they were designed to spin.  Moreover, modern spinning teachers do not explain in any kind of  detail WHY such and such a spindle is better for a particular project.

Wednesday, April 04, 2012

Understand the Spindle!

What could there be to understanding a simple spindle??? What could I say, that other spinning teachers have not already said?  This post is not about basic spinning with a spindle, it is about becoming a very good spindle spinner, quickly!

Spinning is about inserting twist into a fibers.  Twist is energy.  Inserting twist is physics. A full understanding of spinning includes understanding the physics of the situation well enough to understand why different kinds spindles are better for different kinds of projects.  Understaning the physics of spindles will help you choose more functional spindles and help you match the project to the spindle.  The right spindle for the project will help you spin faster.  The right spindle for the project will help you spin finer.  The right spindle for the project will help you avoid overspin!  (I am not kidding!)  The right spindle will help you spin thicker. 

Physics gives us a model so that we can understand what kind of spindles will work better for different kinds of yarns.  This means that we do not have to experience every kind of spindle before we can pick the right spindle to spin the knid of yarn that we wish to produce as the next project.  This makes learning to spin easier, faster, and cheaper.  That is, we do not have to have spun with (own) all kinds spindles to know what spindle is right for the yarn that we want to produce.  It takes much of the trial and error out of becoming a very good spindle spinner.

There are a lot different ways to "spin-up" your spindle.  Supported spindles want to be "spun-up" one way and top whorl drop spindles want to be spun-up in other ways.  Read "Amos" and  talk to your spinning teachers.  Learn all the ways that your spindles can be spun up.

For a particular spinner at a particular time, a specific spin-up technique will impart a certain amount of energy into the spindle. For now, I am going to call this a "flick", however the energy is delivered to the spindle. That energy will be expressed as rotation, or angular velocity. The speed of rotation will depend on the energy the spinner is able to deliever, the total mass of the spindle, and the distribution of the mass with respect to the axis of rotation.

If the spindle is light in weight (low mass) the spindle will spin faster.  If the spindle is heavier, the spindle will spin slower. A flick will cause a supported Russian spindle made from the the local (Russian) pine to spin faster than the replica turned from maple, because the pine spindle is lighter than the maple spindle of the same dimentions. On the otherhand, each spindle contains one flick of energy and will insert the same total number of  twists into a thread of the same fiber and grist.  However the pine spindle is rotating faster and thus will deliver its twist faster, so that the spinner will need to draft faster when using the lighter pine spindle.  The  maple spindle will spin slower so the spinner has more time to draft.  The faster drafter will have to wait for the slower maple spindle to deliver the twist required to hold the thread together.  Where the form factor is the same, the lighter spindle will spin faster (given the same flick).  However, the recreational spinner may (very likely) prefer the slower pace of the slightly heavier spindle.  Or, a "Russian" spindle turned from basswood, will spin faster than one made from Russian pine because the basswood spindle will be ligher than the pine spindle.

For two spindles of the same mass, the spindle with more of its mass farther from the axis of rotation will spin slower when given one flick of energy.  Again the total energy available to insert twist is the same in both spindles.  However, the spindle with its mass closer the its axis of rotation (e.g., Russian spindle) will spin faster than a spindle with (some of) its mass farther from its axis of rotation (e.g., a "CD spindle").  Thus, the Russian spindle is more suited to fine grists that require 30 tpi to hold together and the CD spindle is more suited to grists that will hold together with only 4 tpi.  Because the Russian spindle is spinning fast, it will deliver its energy and slow down rapidly.  Spinning at ~500 rpm the Russian spindle will deliver the twist for 16 inches of thread  (at 30 tpi) in about one minute and come to a rest.  In contrast, the CD spindle may only be spinning at 50 rpm so that it takes 10 minutes to deliver its energy.  Thus, it takes the CD spindle a very long time to twist a fine thread, so people do not use CD spindles for fine spinning, they use them for thicker yarns that require less twist to hold together.  These thicker yarns develop more twist rigidity and take more energy to twist, so that for the yarns that CD spindles are used to spin, CD spindles slow down and stop in much less than 10 minutes.   However, given the same kind of "flick" a CD spindle and a Russian spindle of the same total mass carry the same energy, but they rotate at different speeds.