Ask Madelyn: Having Trouble with Sheds

My weaving group suggested I write and ask you about a problem I am having. I have a 4-shaft Nilus Leclerc loom. My current warp is 23″ wide and I am having trouble with the sheds. They are so narrow that I have to work to get the shuttle through them. Some are better than others.

Cords attached to lammas

Cords attached to lamms

Any suggestions?

Thank you in advance,


Hi Janice!

On most jack looms, treadles are hinged at the front of the loom. To open a shed, each treadle is attached to wooden pieces under the shafts, sometimes called lamms. These pieces are pulled down when the treadle is depressed. At the same time, pivoting jacks placed between the lamms and the shafts are pulled down on one end and therefore raised on the other end to push the shafts up. The shafts will go up just about the same distance that the treadle moves down.

Cords shortened on two treadles

Cords shortened on two treadles

Therefore, to increase shed size by making shafts go farther up, the treadle needs to go farther down. Shafts can only rise as far as warp tension will allow, but usually the obstacle to a decent shed size is the movement of the treadle. On your loom, you can shorten the looped cord that attaches the treadle to the lamm. That will raise the treadle and give it more room to move the jacks and therefore the shafts. For looms with eight shafts or more, sometimes it is important to make the cords to the back shafts shorter than the cords to the front shafts. The back shafts have to move up more than the front shafts since they are farther from the fell of the cloth.


P.S. Janice shortened the cords (shown here on the first two treadles) and shed size was much improved.

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Posted September 4, 2015. Updated January 8, 2018.

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