Sunday, July 29, 2018

DRS Spinning wheels revisited

Is it DRS? 
Spin and maintain treadle pace, then draft faster.  If the wheel sucks all the yarn into the orifice faster than it can insert twist to make a competent yarn, it is not DRS.  If you get slack, it is likely DRS. A DRS wheel will insert the same twist all the time, so the grist must be adapted to the twist setting on the wheel. If you can spin thick or thin, without changing whorls, it is not DRS. Thin yarns need a lot more twist than thick yarns. Woolen yarns need more twist than worsted yarns of the same grist to have the same strength.

edited for clarity 9/11/18 because I had been calculating whorl ratios, and was thinking of all rotation relative to the bobbin, and here, that was pure nonsense.

The basic text on DRS is Alden Amos’s Big Book of Handspinning. It is not very mathematical, but it works.  First, how much twist do you need to insert to make a competent yarn?  That is critical. See the  Big Blue Book page 383.  Then, assuming bobbin lead, what is the effective diameter of the spinning bobbin. (I make my bobbins so their diameter is ~3π” to save math.) Thus, 1 rotation of the flyer (relative to the bobbin) winds  3 inches onto to the spinning bobbin, and for my standard single at 9 tpi, the bobbin must rotate just over 27 times every time the flyer rotates 26 times relative to you.   That is, the flier must make ~96% of a rotation or 346.3 degrees every time the bobbin rotates once (360 degrees). Thus, the ratio of the bobbin whorl to the flyer whorl is 1:1.037. The bobbin whorls are about 50 mm in diameter (sometimes I fall off the English system) and the whorl for the flier is 51.85 mm in diameter.  For 12 tpi, (or second layer of 9 tpi on a bobbin with one layer of single on it) the bobbin must rotate 36 times while the flier rotates 35 times. Therefor the bobbin whorl/flyer whorl ratio is 1: 1.027. I have a groove for that!   As the effective diameter of the spinning bobbin increases, the bobbin whorl/flyer whorl ratio must change to keep the twist consistent. Thus, my flier whorls have 2 or 3 grooves on them and I change grooves as the bobbin fills and the effective diameter increases. I spin woolen at about 25% higher twist than worsted of the same grist (e.g., 5,600 ypp worsted is spun at  ~9 tpi and the woolen of that grist is spun at ~12 tpi). The 5 grams of a fine single in a hank does not change the bobbin diameter much, so the whorls for fines have only 1 groove in them. In fact, fines are spun on a smaller flyer/bobbin assembly based on bobbin whorls of 100 mm and flier whorl diameters of 101.2 mm as this makes the wood working easier.  That should all be clear as mud. 

The deal is that I spin my spinning bobbin at something over 3,000 rpm, and my flier at about over 2,845 rpm, and that is good because fliers have much more wind resistance so this system spins them slower. Spinning bobbin lead is much faster than spinning flier lead. With “yarn lock” systems (e.g., Scotch Tension, or Double Drive systems with slippage), you end up spinning your flier as fast as your bobbin most of the time, so you put a lot of effort into overcoming the wind resistance of your flier most of the time. I see trying to spin a flier at 3,000 rpm as being a lot of work, I am lazy, I do not work that hard. I do a little math, and save myself a lot of work.

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