3/1 Broken Twill with Alternately S/Z Threaded Tablets

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A while ago I was working on a twill belt and the edges of tablets kept getting caught on each other. I basically use a two-pack method where I separate the tablets into a pack of those that turn forwards and a pack of those that turn backwards, then after turning them all together I shuffle them back into one pack for the next pick. This may seem like a lot of shuffling and moving, but with a bit of practice it turns into quite a fast weaving technique.

The main drawback is that since twill is usually woven with all tablets threaded in the same direction, some tablets inevitably catch the edges of others when shuffling them together. This is rather tiresome since those tablets have to be individually wiggled back into position, and after a while I began to think about how easily the tablets slide together when weaving alternately S/Z threaded doubleface. The two methods are closely related, and intuitively it seemed to me that there should be no reason why twill could not be woven with alternately S/Z threaded tablets as well.

So I considered that given two setups, one with all S-threaded tablets (A) and another with alternately S/Z threaded tablets (B), what are the structural differences? If we use identical turning sequences, logically the only difference is that in B every second cord will have a twist opposite to that in A. Using the basic turning sequence for twill, this is the result we get:
A: All Tablets S-Threaded, S-Twill B: Tablets Alternately S/Z-Threaded, Z-Twill
Structure
Turning Sequence
Structure
Turning Sequence

Surprise! Sample B turns out to be a perfectly good band with a Z-twill structure.

However, let's consider what we need to do to get an exact duplicate of A. All we have done in B is change the threading direction of every second tablet, and consequently the twist of every second cord is the reverse of what it is in A. To duplicate A we therefore have to change the twist back again, and this is accomplished quite simply by inverting the turning direction of the Z-threaded tablets. If we apply this to B, we get sample C:
C: Tablets Alternately S/Z-Threaded, S-Twill
Structure
Turning Sequence

This principle also holds true for a pattern with long floats, no matter where they are placed. As a simple example, let's take a plain lozenge and look at the results below:
D: All Tablets S-Threaded E: Tablets Alternately S/Z-Threaded
Block Pattern
Turning Sequence
Structure
Block Pattern
Turning Sequence
Structure

No changes in the design are necessary; all long floats can remain exactly where they are and only the turning sequence is different. The two examples will result in identical bands, both pattern-wise and structurally.

There are two significant advantages to this method. Firstly, it is easy to alternate between twill and doubleturn doubleface; we only need to idle the appropriate tablets at the right time and the switch is accomplished. Secondly, and to my mind more important to most weavers, is that the tablets slide together very easily and without catching on each other when they are alternately S/Z threaded.

As to disadvantages, well, I have tried to find some, but so far I have not come across any. The examples I have woven with this method were much more pleasant to do than on an all S-threaded band, and turned out exactly the same.


A Tip for GTT Users
Changing from an all S-threaded pattern to an alternately S/Z-threaded pattern in GTT is extremely easy. Just follow these two steps:
1. Click on the button to set the threading of all tablets to alternate S/Z. This has two effects in the Real Image display: the background changes from S to Z twill, and there are lots of spiky edges.
2. Change the Background Twill option from S-twill to Z-twill. In combination with S/Z threaded tablets this will restore the original appearance.


Occasionally maintained by Eckhard Gartz.
Last modified 9/6/2005.