Toy Piano Counterbalance Loom 1: It Works in Theory
traditional counterbalance loom
Early in my study of Kashmir shawl weaving, I built a small portable loom to weave samples of the shawl motifs I reconstructed, and to demonstrate the twill-tapestry weaving process. I was fortunate to be able to get these results using rigid heddles and a wide colour range of appropriately-sized tapestry yarns I already possessed. But I noticed that some weavers looking at the loom could not accept that the 2/2 twill weave-structure I could obtain using only 3 rigid heddles (raised or lowered as needed in relation to a 4th static set of warp threads), was the same as the traditional weave-structure they obtained using a 4-shaft counterbalance loom. Another distraction was the relatively coarse fabric I produced, 20 e.p.i., compared with their extremely fine threads traditionally used at 80 e.p.i.
I resolved that an improved loom for demonstration purposes had to be more recognizeably the same as the traditional loom, and that heddles sized for finer threads would allow me to re-create more extensive designs with scale and texture more like the original.
I set about trying to imagine how to incorporate in a portable loom, the appearance and mechanical advantages of a counterbalance harness that usually takes the form of a structure of cords and rollers or pulleys from which the shafts are suspended. Like any table-top loom where the treadling is accomplished with fingers instead of feet, it was easy enough to raise two shafts and lower the other two to obtain a shed-opening without any interconnecting mechanism. As each 2 shafts are lowered by treadling, to have the alternate shafts rise mechanically would be more reassuring and logical for the weaver, more recognizeable and convincing for the observer.
Initially I replaced the system of overhead cords and rollers with an arrangement of levers and pivots located under the shafts, but then wrestled with the objection that it would add too much to the height and wasted empty space within my portable loom. The breakthrough idea was that the arrangement of levers could occupy a little space within the sides of the shafts and pull up, rather than push up, the rising shafts as the lowering shafts are pushed down.
I built a two-dimensional model representing a view of one side of the loom from within the frame of the shafts. I found that it moved as predicted with no unexpected friction or binding, and working with the model allowed me to observe the limiting factors of its geometry and make adjustments to try to obtain the biggest consistent shed-openings. Work is proceeding on a three-dimensional prototype before I can really assess the advantage of having this mechanism installed on both sides of the loom, and whether the transverse portions of the shafts will interfere with it.
peter harris, tapestryweaver 