It allows some measure of irregular drafting without affecting the quality of yarn making. Some treadle wheels can handle this well, but others do not. With Double Banded spinning wheels, the person normally needs to maintain an exact feed and drafting rate, relevant to the treadling rate, to obtain a perfectly even yarn.
The single banded machines are more flexible, as the free turning part can be braked to run at different speeds to create many varied and different ratios . There is two types of single banded spinning wheels, depending on which part has the brake. The Irish Brake system has a free turning flyer with a cord acting as a brake, The Scotch Tension system has a cord restricting the free turning bobbin and acts as a brake. These 2 systems are often referred to as bobbin led, or flyer led (leading, meaning the driven part).
The scotch tension (flyer led) has a friction brake cord in a groove at the end of the bobbin. This is tensioned to create a drag in the wooden groove. This is quite a good system, although the tension cord needs to be pulled tighter frequently , to make the bobbin slow down, to keep the ratio the same. This is due to the growing diameter of the filling of the bobbin, which gathers in faster as the filled diameter increases. You still need to keep a consistent feed rate in drafting, to match the flyer speed. With the bobbin being braked, the yarn ratio to the flyer is set.
The speed of the flyer, determines the pull in rate. With the driven flyer, (flyer driven, as above), the speed of fibre drafting must match the speed of the flyer, otherwise unevenness of the yarn will occur. For most experienced people, this is quite acceptable, changing and matching both speeds, as they do their spinning.
The Irish brake design is the most versatile and the most variable. This is because it is largely self regulating, with no constant changing of the bobbin brake, as the bobbin fills, as occurs with the Scotch Tension system. (flyer driven). Also there is no need to match drafting rates from your fingers, to the speed of a driven flyer, again as happens with the flyer driven spinner. The Irish brake system is the same system as used in modern mills today. The only variation is, that they have their bobbins mounted vertical, instead of horizontal. The Irish Brake system (bobbin driven), can alter the type of yarn by three methods. 1. Alter the speed of the driven bobbin. This affects the twist rate only 2. Alter the natural speed of the free turning flyer by the tension device, by setting the brake tension. This alters the draw in rate. (creating a more or less flow of yarn to the gathering bobbin) 3. Alter the hold-back against the spinner pulling in, when drafting the fibre. (i.e. feed in slower, or faster against the pull.}
Consider this scenario:- The bobbin is running quite quickly, pulling in the yarn, across the free turning flyer. If you hold back against this effect, the flyer will increase in speed to match the bobbin speed, because the yarn is travelling over it. (It will overcome any tension effect placed upon it by the brake cord.) With the bobbin and flyer now running at the same pace, no yarn can gather on the centre of the bobbin. You can keep holding the yarn in one place for a couple of minutes if you wanted, and the yarn would not break. The twist effect will continue and the yarn will curl up. This is due to the yarn being at right angles across the flyer to the turning bobbin. This additional twist can be dissipated in a long draw from the fingers, when you are ready. The effect is to self regulate the excess twist. Obviously holding onto the yarn in the same spot for a couple of minutes would be excessive, but it illustrates the function. If irregular drafting is happening, because of difficult fibre, the flyer will change speed to suit whatever is happening in your hands, and any unevenness of the twist, will self regulate between the point of loading on the bobbin and the pinch fingers.
Out of the three designs - i.e. double banded, scotch tension and Irish brake design, the Irish Brake is the most versatile and easiest to get good results, even with irregular drafting.
It is important to know, that on any spinning wheel design that it is the flyer speed that determines the pull in rate. However on a bobbin driven machine, it works in the opposite way, in regard to the flyer speed. Normally on a scotch tension, or the double banded designs, the faster the flyer goes, the more pull in. On a bobbin led design the slower the flyer goes, the more pull in, because there is more of a direct flow of the yarn, to the driven bobbin. The slower flyer in this case, allows for a faster loading onto the bobbin, which is running at a set speed.
Now that the polymer flyer bearings are fitted instead of leather, on all Roberta electronic spinners. (all Roberta's since 1993). The spinning of cotton, or even very short fibre, can now be handled with ease. The adjustment on the tension cord of the flyer, can now be altered, to affect the draw in rate, from a light pull in, to a heavy pull in rate. If the flyer is lubricated well, and is absolutely free turning, a very light pull in would happen. (i.e. with no brake tension being applied.) In this situation you can regulate the draw in rate from almost nothing, right up to as strong as you wish, by just applying the tension cord. Once set, it stays like that for days of use.
The improved version of the Roberta electronic spinner with its polymer type flyer bearing supports, now replaces the traditional leather. This has overcome the negative feature of the leather bearings on older Roberta spinners that gives a strong pull, often due to poor lubrication. Now people who spin, can obtain all of the advantages of the bobbin driven design in the Roberta electronic spinner, and being able to start off with a light pull in, right up to any pull in rate desired, for the drafting rate wanted. Coupled with this, you can alter the bobbin speed (controlling the twist rate only), to whatever is wanted.
The Roberta electronic spinner is now the most versatile spinner ever created. You can design any type of yarn, out of any kind of fibre, and spin it with ease. There are no restrictions to making anything you want to dream up. No changing flyers or bobbins, or any other thing, is required to get this versatility.
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