Adjusting a Jack Loom
This page is copyright 1998
Joanne Hall, Elkhorn Mts Weaving Studio, Clancy, MT 59634
Used by permission of the author.
- Adjust treadle tie-ups.
- Tie up treadles to raise only one shaft.
- Add treadle springs.
- Adjust the height of the beater.
- Extend the back of the loom to increase the depth of the loom.
- Raise your back beam.
- Move your lease sticks.
- Adding weights to your shafts can be helpful.
- Add springs or bungie cords at the bottom of the shafts.
- Use a stretcher (temple) to solve some selvage tension problems.
- Remove the shuttlerace to develop a better rhythm.
- "Size" warps that may be "difficult."
- Weight the beater.
- Use a cushioning material to reduce noise.
The suggestions above are to be tried only after you know that you have put your loom together properly and that all parts are in good working order. Metal parts should not be dirty or rusty, the frame must be securely assembled and tight and all the wooden parts are smooth. Warps must always be centered; extra heddles if left on the shafts must be divided equally so that there is the same number of heddles on each side of the shaft. Heddles need to be put on properly, and use no more than 10 metal heddles per inch per shaft; more than this requires string heddles. Warp tension must be the same all across the warp. Contact the loom maker if you think there are problems with the loom. Most companies supply replacement parts even for discontinued looms.
1. Treadle tie ups may need to be adjusted to get a better shed if the top of the shed is uneven.
If part of the top shed is too high, determine which shaft is rising too high, untie the cord or the treadle attachment and make it longer. If the shaft is not rising high enough, shorten the tie. Check each treadle to make sure that all the shafts rise to the same height. If the lower part of the shed is not even, the problem must be solved with numbers 4 or 8. "The most objectionable feature of nearly all looms of this type is not so much the lower speed and therefore inferior performance, but the impossibility of adjusting the lower part of the shed." S. A. Zielinski vol.2 p.30
2. Tie up your treadles to raise only one shaft and treadle with both feet at once.
If you are working with a warp that doesn't want to separate when you press on the treadle, either because it is a fuzzy warp, or is sett very close as with double weave or warp faced weaving, you can try tying the treadles each to only one shaft. Then treadle one at a time, raising fewer warp threads with each foot. This would still be slow to weave and would interrupt your rhythm, It also takes longer to memorize the treadling sequence, so you might want to try some other adjustments first. For very difficult sheds, try using a batten to clear the shed and hold it open. Back to Top
3. Treadle springs can be added to keep the weight of the treadles from pulling on the lamms, which then push the shafts up
These springs are very easy to install at the ends of the treadles. You will need to add a rod to the back of the frame where the shafts are. From this rod you attack one spring for each treadle. These springs do not pull on the shafts and they are not attached to the shafts. They merely hold the treadles up so that the lamms do not have to hold them. Sometimes this is all that is needed to have a better shed. After you begin to weave, attach the springs which are needed to keep the shafts from rising when they are supposed to stay down. You may not need to attach all of them. These springs are standard equipment on Leclerc jack looms with more than four shafts.
4. Adjust the height of the beater.
On some looms the beater is made so that it is adjustable in height. On a counterbalance loom, the beater is positioned so that the warp threads pass through the center of the reed. On a jack loom the warp threads rest on the bottom of the reed. This is because the warp threads need to rest on the shuttlerace. Jack looms have shuttleraces because the weaving is done on a looser tension and the shuttlerace is needed to support the shuttle as it is thrown across the warp.
The lower part of a jack loom shed is sometimes not even, as the first shafts hold their warp threads lower than the other threads. You cannot see this as the beater corrects the difference. The bottom of the beater with its shuttle race is holding these threads up to the level of the other threads. The beater must be high enough to even out the bottom of the shed. If the beater is holding the warp threads too high, the resting shafts will rise. In this case the beater should be lowered. If the bottom of the shed is uneven and some threads do not lie on the shuttle race, raise the beater. If the beater is too high, the reed may be adding too much friction to warp threads. If you are working with fragile threads, you may want to lower the beater and place a smooth dowel under the warp threads directly behind the beater. It needs to be at a height which holds the warp threads just above the bottom of the beater. This will decrease the amount of friction put on the warp while beating.
"We shall risk here a statement that the reason why so little weaving with fine yarns, single linen, etc. is done in North America is that there are too many jack-type looms on this continent. S.A. Zielinski vol.2 p.30
You might also add foam rubber or a cushioning material under the first and second shafts, so that they rest a little higher than the other shafts. This will help to even the bottom on the shed so that you can lower the beater. "One of the most serious disadvantages to the push-up system is the wide gauge required.......well over 1/2" per shaft. A set of four shafts occupying a space of 61/2-7" is not uncommon." Fannin
5. Extend the back of the loom to increase the depth of the loom.
On some looms this can be done very easily by replacing only one part of the frame on each side of the loom. On other looms it may not be possible without major carpentry, but it is worth a try if your loom is only three feet deep. It is better if you can make it four feet deep, or even three and a half. Any extra depth that you can get will allow you to work with a tighter tension and will help to keep your shafts down."The frame should ordinarily be longer from front to back than from side to side, to provide ample weaving space. If the frame is very shallow it is impossible to weave more than an inch or two without releasing the tension and winding up the web, which is a nuisance. Also undue strain is put on the warp when the sheds are opened." Mary Atwater p.32
6. Raise your back beam
This can be helpful if you cannot make your loom deeper. It is easy to check to see if this will help by simply checking your tension. After beginning to weave, press down on a treadle and feel the tension on the top and the bottom of the shed. If the tension on the top of the shed feels tighter then the bottom, then loosen your tension. Add a stick onto the top of your back beam, retension your warp, and again check the tension on the top and bottom of the shed. If this makes the tension more even, tie the stick securely to keep it in place and continue to weave. You can try different thicknesses of wood, but be sure that the stick is very smooth. Many very old counterbalance looms had the back beam several inches higher than the breast beam for more comfortable weaving.
7. Move your lease sticks through the warp and if there aren't many twists leave them between the back beam and the warp beam.
Lease sticks are left in the warp near the back beam by many weavers. This makes it easier to repair broken threads but it also eliminates any twists in the warp, allowing the sheds to open more freely. But if your loom is not very deep, it will shorten the distance from the shafts to the back of the loom where the warp threads are together. It may help to remove them completely. If you have twists in your warp, insert the lease sticks periodically and wind your warp forward, carefully easing the sticks along to take out the twists. Then remove the sticks and rewind the warp onto the warp beam. You can try to place the lease sticks between the back beam and the warp beam, but if you have some twists in the warp, it may not work to leave them here. The next time you beam your warp, try to find some help so that you can beam with the least sticks left in the warp. Your helpers will hold the warp at tension and the lease sticks are eased along as you wind the warp on. You can also use a raddle with 1/4" spaces to prevent large groups of threads from twisting. Back to Top
8. Adding weights to your shafts can be helpful.
The added weight should be removable, as your next warp may not need the added weight, or it may be needed on a different shaft. This extra weight results in more difficult treadling, as you will be lifting more weight. Heavier shafts may also be more wearing on fragile warp threads.If you have extra metal heddles, you can put them on the shafts, an equal number on each side. You must put them on before you begin threading the loom, so you need to know which shafts will need the extra weight. This is easy on a balanced weave as you can put an equal number on each shaft. On an unbalanced weave, add them to the shafts which hold the most threads and are tied to the most treadles. If you need more weight, you can tie a metal rod onto the top of the shafts which need extra weight. These can be added even after you have begun to weave.
Another way to weight the shafts is to use an extra treadle. The treadle can have a weight added if the treadle is not heavy enough. Each shaft is attached directly to the treadle, which must be one of the center treadles. This treadle is not used for weaving, except to pull down a shaft if it doesn't fall all the way down. If your jacks are beneath your shafts this may not work. Please note that some jack looms like Macomber already have heavy shafts. Some loom makers sell weights to add to their shafts.
"Single tie-up jack-type if used at all, should have adjustable weights attached to each heddle-frame....the more heddles on a particular frame, the more weight." S.A. Zielinski vol. 2 p.13
9. Adding springs or bungie cords at the bottom of the shafts can help to hold them down.
If you have trouble with the first shaft on an unbalanced weave, this can be a good solution as sometimes the added weight on the shaft isn't enough. You can attach the spring just to the shaft which needs it. If your loom has jacks under the shafts, you may only be able to do this to the first or the last shaft. If the jacks are at the top of the loom, installing springs is very easy and they can then be removed when not needed. This is important since you will have to treadle against this spring, making the treadling harder for that shaft. AVL has a variation of this solution with springs."Power looms using a positive spring return for lowering the shafts do not have to be concerned with this (heavy treadling) because there is enough power available for overcoming the added resistance. On a foot-powered handloom, anything that makes the shedding motion heavy and slow to operate works against the weaver....Weights, therefore, seem to be the best solution where springs would render the harness motion too heavy to operate." Fannin p.80
"Use a double tie-up, i.e., tie a cord direct from the harness frame that you wish to remain full down to the treadle that is in the full down position. (When this treadle is then depressed, it will raise the frames you have normally tied up and also drive the additional tied harness frames down.). Use of any of the above procedures will cause the treadling action to be heavier and slower." Leclerc p.21
Schact looms have a version of this using a rubber band.
10. The use of a stretcher (temple) will solve some selvage tension problems and make beating easier.
Preventing draw-in by using a stretcher not only keeps your selvage warp threads from breaking, but allows you to beat in your weft without so much force. Without a stretcher you are beating against the drawn-in warp threads, which are holding the beater away from the fell line. This alone can solve some problems. Stretchers are recommended for all weaving except tapestry and some warp faced weaving.
11. Remove the shuttlerace if you want to develop a better rhythm.
If your shed is clear, you have heavy shafts and a fairly tight tension, try removing the shuttlerace. If it is an added part of the beater, simply remove the screws which hold it on. If it is a solid part of the beater, you would have to have a new piece made for the lower part of the beater. On one loom I simply turned it around, so that the shuttlerace was behind the beater.
12. Difficult warps can be sized.
With a warp that you know will be difficult to weave because it is fragile, fuzzy, or a hand spun yarn, try sizing the warp before it is beamed. Gelatin, hide glue, cooked flax seed or cooked cornstarch can be tried. If you have a warp which is already on the loom, you could try a soluble oil, spray starch, silicone spray, or Johnson & Johnson's No more Tangles. With linen, water is helpful.
13. Weight the beater.
When you want a tight beat, you can place a metal rod under the beater to add weight to the beater. This is usually not necessary if the suggestions above have been tried. It is more important to use a stretcher, for instance, than to weight the beater.
14. Placing foam rubber or a cushioning material under the shafts can help to reduce the noise.
While this can help, you have to recognize that jack looms are inherently noisy.
"The large number of moving parts contributes significantly to a high noise factor....the noise simply must be accepted as a part of the mechanism." Fannin p.83
" The noise of harnesses returning to their resting position can be quite an item if you do not have a loom room away from the rest of the household." Thorpe p.16
Copyright 1998, Joanne Hall, Elkhorn Mountains Weaving Studio. (jah@montana.com) Used by permission of the author. Citation sources.
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