Friday, January 14, 2011

Virtues of Scotch Tension

Previously, I noted that Double Drive (DD) spinning wheels can go faster because they have two drive bands to transmit that power from the drive wheel to the flier assemble. However, you may not really need to go that fast.

If you do not have a real need for speed, “Do you want a DD spinning wheel?” I suggest, not likely.

With DD wheel, the ratio between differential rotation speed (DRS) strongly affects the kind of yarn that you spin. A set DRS can help you spin a very consistent yarn if you are working with the same kind of wool and want to spin miles and miles of the same kind of yarn (production spinning).

On the other hand, if you to work with different kinds of fibers/wools, or you want to spin a different kind of yarn, with a DD wheel you need to change the DRS. This means changing your bobbin or changing your flier whorl or both. If you want to spin different yarns with a DD wheel you need a whole set of bobbins and flier whorls.

Now, some of this can be done by working with a partially filled bobbin to fine tune DRS, and some can be done by adjusting belt tension. However, these steps only take you so far. If you do not have a bobbin/flier whorl combination to give you the DRS that you need for the yarn that you want to spin, you are going to have to fight your wheel for every inch of that yarn that you produce. This takes away from the joy of spinning. This is one reason that people have different DD wheels. Each has a (set of) different DRS, and thus different yarns that they spin easily.

DD wheels come with a very limited selection of bobbin/flier whorl combinations that allow the easy spinning of a very limited number of different yarns. If you have an Ashford Traddy with a (Fast) DD kit, you will find it easy to spin lace singles at about 5,000 ypp. However, spinning 11,200 ypp singles leads to cuss words that cannot be said in public – until you get the right whorl (custom made), and then it goes like butter on warm toast. (Oh, yes, it can be done, but it is not as easy as it is when you have the bobbin/flier whorl combination to produce the correct DRS for that yarn.) If you want to spin 22,400 ypp singles (easily), then you need a different (custom) bobbin/flier whorl combination. Thus, if I want to spin a new kind of yarn, I start by going into the shop and turning a new spinning bobbin that gives me the correct DRS for the yarn that I want to spin. And, when I am spinning ST, I put a lot of yarn on my spinning bobbin. When I am spinning DD, I stop and wind off frequently, because as the bobbin fills, my DRS changes.

Scotch tension (ST) on the other hand will allow you to produce almost any yarn that you want from almost any wool. Small changes in drafting technique, or treadle rate or brake tension are all that is required to easily produce a wide variety of yarns. Thus, Scotch tension is better for people that want to work with a variety of different wools/fibers to produce a variety of different yarns. The downside of ST is that it has lower limits on speed and it is harder to produce a very consistent yarn.

The virtues of DD are ease of producing a consistent yarn very rapidly. The vices of DD are the extreme difficulty of producing yarns for which you do not have an appropriate bobbin/flier combination to produce the correct DRS, and the difficulty of obtaining appropriate bobbin/flier combinations for specialty or unique yarns (particularly for old wheels.)


AN said...

I'm sorry, but I have to disagree, I can spin any weight yarn with any tpi I want on my DD wheel, with absolute ease.

I would query your setup, drive band, smoothness of whorl/bobbin grooves, tension, ratios. The fact that you have altered your setup from the design adds to this more likely being the issue.

Have you tried DD on other wheels?

=Tamar said...

You make your own bobbins to spec. I am not a spinner, but even I can tell you just made a million women jealous.

Aaron said...

Yes,I have tried other wheels. And, yes I can spin the stuff that most modern spinners spin on any of those wheels in their standard configuration, but each has a sweet spot, such that it produces certain yarns more easily than other yarns. However, if I want to spin 30,000 ypp wool yarns on those wheels, I need to get the DRS correct.

My epiphany came while spinning some 11,200 ypp singles from poorly carded roving. It kept breaking off. I went out to the shop and turned another bobbin that brought my differential rotation speed (DRS) down. There was a dramatic reduction in the required effort to spin. All of sudden, I did not have to resist take up at all (and my single did not break off.) Suddenly, a whole range of finer spinning opened up.

I took this lesson and applied it to spinning other grists. The effort required to spin particular grists plummeted, while the consistency of my spinning improved. My 5,600 ypp singles now go like “butter on hot toast”, whereas before they just went like “butter on toast”.

Toast with butter is good, but hot toast with butter is better. said...

I'm interested in finding someone who makes or supplies gansey needles. Can you help me?

Aaron said...

I am going put stuff back up in my Esty store - Right after Stitches West.

Aaron said...

Dear AN,
I hit a bit of a milestone the other day, spinning Romney at 166 wpi. That comes out to about 28,000 ypp or 50 hanks per pound. Now this is a nice kid Romney with a spin count of ~52. So, I am not all the way to spinning the spin count of the wools that I work with, but I am getting very close. Can you come that close to spinning the spin count of the wools that you work with?

Last week I made a 1.05 DRS bobbin, and after Stitches, I will make another try for the 170 wpi that I can indeed spin the spin count of the wool I work with.

Tools matter!

Anonymous said...

thanks for this nice post 111213

Anonymous said...

thanks for this tips

Victoria said...

How do you calculate your DRS and bobbin size? I'd like to get some idea of it, since I don't have any space for woodworking tools of my own, so I'd have to order them as needed, or take considerable trouble finding someone who can, since I no longer live close to someone I know who has such tools and curiosity. That way, I could calculate what ratio I need, then what size bobbins I need, then could go about getting them made. There's no way I could just pop into the garage, you know? (I live in a small apartment.) Thanks.