Automatic Warp Tension

Why Dynamic Trumps Static Every Time.

Over the years, weavers have purchased AVLs for a wide variety of reasons and purposes. Some invested in their AVLs for the need for increased speed. Others liked a specific AVL Only feature like the Automatic Cloth Advance. But invariably, when long time AVL users are asked what part of their looms was ultimately most satisfying, they invariably settle on one answer: Automatic Warp Tension.

Unlike other looms that use static systems to lock in their tension, AVL looms have a dynamic system that makes adjustments with each beat. A few words of explanation will help make this clear.

Other looms use a ratchet and pawls to make sure that the back beam will not move. With each succeeding pick, the tension on the warp increases. It keeps increasing until it’s either too tight to continue or the fell-line has advanced to a point where the shuttle no longer fits. At this point the weaver pushes down on a foot brake to release the back beam and it does just that – in some cases with a big “ker-chunk.” Next, the weaver cranks up the tension to get it back to where it was before, each time using his or her hand to “test” the tension. If one was to measure the resulting tension on the finished fabric then a graph of it would look like a saw tooth: rising, rising, rising and then a 90 degree drop back hopefully to ground zero and up again. The result in some cases might be fine, but in others (particularly with unforgiving fibers like silk or linen) it might be a rippled fabric.

AVL looms, on the other hand, set the warp tension at the warp beam. Jim Ahrens’ system adapted from Luther Hooper’s 1910 classic Hand-Loom Weaving (see image at left) and others use a simple mechanical principle: a lever arm with a weight. The farther the weight slides out the more tension. Once the tension is set, it generally never needs to be reset or readjusted. It always stays the same. If one were to graph the tension on the fabric coming off an AVL then it would look flat like a mountain lake at sunset. The resulting fabric should reflect the even tension by lying flat and smooth.

Best of all, the AVL Automatic Warp Tensioning is remarkably easy to use. After all there’s no re-setting, no re-adjusting. There’s no foot brake, just a simple system making dynamic adjustments with every beat.