Order your copy of Warping Your Loom & Tying On New Warps HERE
Introduction:
The chapter is comprehensive, but I want to give a glance at what is there. Much more information is required to fully understand how various looms work and are adjusted. This is just a short introduction.
Part 2: Preview of How Looms Work
These looms have shafts that only move up when treadles are pressed. The top of the shed is made by lifting shafts and the bottom of the shed is where the warp threads rest and remain unmoved. Any number of shafts can be lifted: from on to all-but-one, making this loom favorite of American weavers because of this flexibility.
Often, but not always, the mechanism for lifting the shafts is a “jack”—a lever with a pivot in the middle. The levers work like a balance scale in that when one side of the lever (jack) is pulled down by a treadle, the other end goes up and lifts or pushes the shafts upward. Jacks can be under the shafts or above them. Usually there are two jacks for each shaft, one at each end.
A few looms are made so the shafts go down when the treadles are pressed. The weight of the foot on the treadles keeps the bottom of the shed flat. I’ve only seen one sinking shaft loom: it was my first loom, and it was homemade.
When shafts on counterbalance looms are tied to a treadle, the shafts go down when the treadle is pressed and the untreadled shafts automatically go up like a balance scale.
There are rollers, pulley, or short bars called horses that are attached so every shaft has a balancing shaft. The action is like a balance scale in that what goes down with the treadle forces a matching set of shafts to rise. Only the shafts that are to be lowered are attached to the treadles.
The weight of the foot on the treadle keeps the bottom of the shed down and forces the top of the shed to stay up. With gravity working on your side to lower the shafts and with the counterbalance action, the shafts can be very lightweight, and you can weave faster and easier. If the loom is deep enough it can make large, clean sheds with the warp under high tension.
Countermarch systems vary but all of the systems are designed so the shafts are both raised and lowered. The shafts work independently rather than being connected to each other like in counterbalance looms. Between the shafts and the treadles there are two sets of lams, which are levers or bars. The upper set of lams is usually shorter and the lower set of lams, longer.
Most countermarch systems have above each shaft a jack or a pair of jacks (levers with pivots in the middle). When one end of the jack is pulled down, the other end goes up.
The lower set of lams is attached to the jacks overhead, and the upper set of lams is directly attached to the bottoms of the shafts. Think “Long lams lift; short lams sink”
The sheds are made by tying up the treadles so all the shafts that are to be lifted are connected to the lower set of lams, and all the shafts that are to sink are tied to the upper set of lams.
Usually, the lams pivot at the side of the loom (like railroad gates); however, some countermarch systems are designed with lams that are not attached to the side of the loom.
Thank you for providing thos information. It was so helpful in identifying the different loom types. The drawings are the best. Thank you to the artist.