Hi,

I've decided to build my own CB loom with the option to eventually turn it into a CM loom. I've been searching all over the web for info about loom design and am missing one piece of information that seems fairly crucial to the proper function of any loom.

For a given distance from breast beam to back beam, the open weaving distance, where should the first shaft be placed - the shaft closest to the breast beam? I've been looking at various photos and it seems variable. Some looms look like the first shaft is placed in the middle between the two beams with all the other shafts - 8 to 10 in the back half of the open warp. Others look like the last shaft - #8, is in the middle of the open warp distance and the rest of the shafts lie between the middle of the warp and the breast beam.

Any opinions on which is the best placement of that first shaft?

Thanks,

Ed

Comments

Fri, 10/18/2013 - 23:34

ReedGuy

Some floor looms have more depth, that is why some harnasses (all the shafts) look to be in the middle. The important thing is to be able to reach the beater comfortably when seated, as well as the treadles. You also want to be able to weave as much area as you can comfortably reach. So don't limit this distance to 10 inches, when you can reach 22 from the breast beam to a hanging beater positioned closest to the harnass. The harnass is usually within a couple inches of the beater when hung from the furthest position from the weaver on the castle of the loom. Your shed opening changes constantly from the first weft shot, until such point the shuttle will not pass freely. Then the warp is advanced forward and retensioned. Often an over head beater pivots at notches in the castle that allow the beater to be positioned closer to the harnass as the weave progresses. There could be 3,4 ,5 positions or whatever. The more depth the loom is, the better the shed. Six feet from breast to back breams is better than 3.5'. Remember though, where this loom is going to be set up. You need some space. ;)

Fri, 10/18/2013 - 22:57

Telemorris

Thanks ReedGuy. I'm currently looking at 22" from the breast beam to the beater (I've got long arms). That keeps me about 2" or 3" away from the breast beam so I'm not touching the cloth. Should I design this so I sit right up against the breast beam and get that much more weaving space?

If I do that, I really do need to push the first harness back in order to make room for both the cloth beam and my knees.

So many interrelated measurements. I'm having fun figuring this all out.

Fri, 10/18/2013 - 23:53

ReedGuy

A little space does not hurt, never know who might inherit that loom. ;) Don't forget the beem above the cloth roller, some call the knee beem. The cloth comes off the breast beam and down to the knee beam before being wound on the cloth roller. It is directly above the cloth roller. On my floor loom there is 20" from the front of the breast beam to the beater bar where your hand rests, measured on the top corner of it facing the harnass. This is with the beater positioned closest to the harnass in the notches up on the castle. The breast beam is at least 32", maybe as much as 36", from the floor to the top of it.

When you get that loom built, don't forget a good bench. One that is not a tipping hazard. ;)

Sat, 10/19/2013 - 00:19

Telemorris

Not to worry about the bench. I'm very fond of Walt Turpening's bench design and plan to make one for myself.

ReedGuy, how close to the breast beam do you sit? Are you saying "A little space does not hurt..." because I'm making a loom that will only fit a very tall person and need to make it possible for someone smaller to eventually work this loom? How tall are you?

I do plan to use a knee beam in this loom. I'm more concerned about where the cloth beam is located though. Too close to the front of the loom and my knees will be bumping that beam.

Sat, 10/19/2013 - 00:48

sandra.eberhar…

Make your loom fit you.  Some looms are more adaptable to different size people than others are, but nothing beats a loom that fits you.  My favorite loom was made by an excellent carpenter to a traditional "barn frame" pattern for a person who was just my size.  Being able to make it to fit you is a treasure, especially if you are quite tall or short.  As long as you are going to all the effort to make it, make it for you.

Sat, 10/19/2013 - 00:59

sandra.eberhar…

Many looms are attempts to put as much as possible in a compact package.  When you do this, the placement of the shafts gets odd.  Most of my looms are large; at least 5' deep; and the shafts are located closer to the front of the loom because there is room to put them there and alow enough room to form cloth.  I have a loom that you can put the shafts closer or further from the breast beam.  The instructions say that you will get a cleaner shed with the shafts closer, but treadling will be harder.  Generally, the closer the 1st shaft is to the beater, the larger the shed will be.  Depending on how you design your loom, you may be able to play with it.  If you make a European style loom with gallows instead of a castle, you can move things forward and backward until it works well.

Sat, 10/19/2013 - 09:51

kerstinfroberg

A standard feature on Swedish looms is a "fabric protector", a (removable) slat that slots into the front upright, in front of the breast beam. This allows the weaver to sit as near as possible.

This pic is lifted from an ad, because it makes the protector slat easily visible:

Sat, 10/19/2013 - 10:36

ReedGuy

Kerstin, that looks like a good idea for a cloth protector.

Something to keep in mind when designing for your reach of the beater when seated behind the breast beam, is that the beater will most often be pushed away from you a little beyond where it would naturally fall at rest, when the loom is warped. You may need that extra couple inches when throwing the shuttle. So don't design it so that your left barely reaching with your finger tips. That will not be comfortable weaving. You also want to be weaving so that your elbows aren't colliding with the breast beam. You want to make cloth, not fight battles with the loom. ;)

I am 5-11" tall.

My bench build is on here, as well as my loom. I made the bench so it rocks and can be taken apart by removing wooden pins. It also adjusts height.

I'm very happy with my loom. I may make one more accessory some day, and that is a supplemental warp roller and beam. :)

Sat, 10/19/2013 - 19:59

Telemorris

Thanks Reedguy. I'm not sure I understand what you're saying about the beater being pushed back further. Do you mean that the process of opening the shed causes the beater to pull away from the breast beam so you have to reach farther to catch the beater? I'm planning a gallows style of frame which will allow me to move the beater closer to or further away from the breast beam. I like the gallows design because it gives me some flexibility to change distances as needed, within reason. I'm drawing this out in my drafting program, starting with measurements based on Walt Turpening's bench design criteria and adding other dimensions like my reach from front of shoulder to first knuckle and distance from belly button to end of knee. I totally agree that I don't want to fight my loom. No sense in my knees running into the cloth beam when it's full. I do plan to design the height of the breast beam and my bench so that my elbows are about 2" above the breast beam. And I'm planning the treadle height to allow my knee to be 2-3 inches below my hip when my foot is on top of a treadle. Hope that makes sense.
Sat, 10/19/2013 - 22:13

ReedGuy

No, the beater will often need to be pushed a little beyond rest position before throwing the shuttle. This is mostly at times when the weaving progresses and the shed opening becomes restrictive, before adjusting the beater position toward the harnass or advancing the warp. Pushing the beater back toward the harnass a little gains some shed space for the shuttle.

Sun, 10/20/2013 - 22:58

sandra.eberhar…

A hanging beater will often hang somewhat forward, giving you more space between the beater and first shaft than you would like.  Depending on how the beater is constructed, it can hang vertically or slant forward.  People who have a forward slanted beater may push the beater away from them with each pic to get the beater closer to the shaft for a better shed.  I have  a loom that, like Reed Guy, I push the  beater back when the fell is getting close to the beater.  This loom has a verical hanging beater.  I also have a loom that the beater hanges several inches forward of vertical. Instead of pushing it back each time, I attached bungee cord to hold it back.  I found the constant push-back clumsy and time consuming.  I can't move the beater back because it's already against the box sitting on the gallows that holds the parallel countermarch pulleys.

Mon, 10/21/2013 - 08:49

ReedGuy

I have a wide shuttle race on mine for a fly shuttle, so mine actually leans backward, because of the race shifting the centre of gravity (more weight on the front), but I do push back sometimes as the shed closes.

So some beaters lean back anyway. ;)

Depending on how your beater is constructed, and your beater bar is forward at rest, and you have a top bar that slides up and down the uprights (pegged in the uprights), you can reverse the pivots and probably find that the beater now leans back. I don't know if that would interfere with movement up top on some looms. If the beater pivots are mounted on the top bar on the face of it and not under it, this works. Otherwise no difference.

See how mine leans backward?

 

Wed, 10/23/2013 - 16:56

Telemorris

A related question: What are the dimensions of the shaft sticks themselves given a 36" width to the reed? Are they 3/8" thick by, say 1" tall?

Also, what is the distance on a CM or CB loom from one shaft to the next on center? I'm wondering how much clearance is needed between shafts. This also has a bearing on the width of lamms and upper CM balance bars.

Wed, 10/23/2013 - 18:12

kerstinfroberg

The first picture is of my AVL shafts, the second of my CM shafts (bought from Öxabäck, even though the loom is an antique)

As I'm metric, I'm not intuitive with imperial, but I think the width comes to slightly over 5/16" and the height to about 1 5/16" (this for the Öxabäck ones; the AVL ones are slightly different)

Both pictures are of shafts on loom - that is, they hang very near each other, regardless of loom type. I don't have pictures of a CB loom, but given the "looser" tie-up, they are likely to get slightly more apart.

Wed, 10/23/2013 - 18:52

Telemorris

Thank you Kerstin!

That helps me a great deal. Can I assume that the upper jacks and lamms are the same width?

And yes, your conversion from metric to imperial is fine. I also work in metric.

Wed, 10/23/2013 - 20:39

kerstinfroberg

About the CM: I bought the whole package of upper CM jacks(?) from Öxabäck, to put on my antique. It worked well with the (old) parts I had - but as I didn't have enough (original) shaft bars, after a while I decided to get a whole "package" of new shafts, too. I haven't measured the lamms, but as the loom works well I assume they are (about) the same dimensions.

I can take measures tomorrow, both of lamm width and height measurements. Anyway, as my loom is home made (or at least "no name"), I'm sure measurements are not *that* critical. For "function" at least - some ppl are very interested in "looks", but to my mind, how a loom helps me weave is more interesting than how it looks at rest... (YMMV, I'm sure :-)

(read the story of my loom here )

Wed, 10/23/2013 - 21:34

ReedGuy

Yeah, I beleive the jacks are as thick as the lamms or very close. Mine are, and my loom is also home made. :)

Thu, 10/24/2013 - 15:31

kerstinfroberg

Perhaps these measurements can be compared to ReedGuy's - he made the whole loom, and therefore mad all parts to correspond/"suit" each other. My loom had been rebuilt, changed, re-fitted over (probably) >100 yrs - I've had it for >30 yrs myself, also changing, re-fitting... as needed.

Anyway.

The lamms (which came with the loom) are 15 mm wide (as opposed to the Öxabäck shafts/CM jacks, which are 8 mm). The space for mounting the lamms is 31 cm, which tallies with the fact that the loom has 20 treadles. I did not get more than 18 long lamms and 17 short when I bought it - so when I got the new CM "top piece" I was content with just 16 shafts.

The "lamm attachment piece" has 3 holes; I use the two upper ones which are 32 and 50 cm from the floor. (It can happen that the lamms "tangle", but it doesn't happen often enough to be a problem; if I use the lower hole for the long lamms they interfere with the treadles, which *is* a problem.) The clearance between the upper lamms and the bottom of the shaft bars is 19 cm, and it looks like I'm using the 27 cm heddles (which apparently are only 26,8 cm)

The knee beam is directly over the cloth beam; measurement from front of front upright to center of these beams is 37 cm. (forgot to measure beam diameter, at a guess it is something like 12-13 cm)

I have used this loom with everything from 4 shafts up to 16; with everything from 2 treadles to 20; with warp lengths from 1 m (not a very good idea) up to 35 metres.

Sometimes the shafts fall a bit when the pin is taken out, sometimes they do not. As the shed is easily adjusted to function well, the "fall" has never bothere me.

(I have a "ready-made" Glimåkra too, but it is in pieces and I have an injured wrist, so I can't compare measurements right now)

 

ETA: after I read Joannes comment below on breast beam height - mine is 81 cm/32"

Thu, 10/24/2013 - 15:00

Joanne Hall

Since you are tall, you probably are planning on a high breast beam height.  If you plan to make it a countermarch, it will need to be at least 36 inches tall, especially if you are making a wide loom.

As Kerstin said, the shafts are thin and close together when you have more of them.  And the treadles are close together if you have more of them. The treadles can be make narrow, with a taller thickness to maintain the weight.  Glimakra does this on the looms with more shafts and treadles, so that the treadles can be closer together.

Sometimes the lower lamms are taller and/or thicker as well as longer so that they can balance the weight of the shafts.

Joanne

Thu, 10/24/2013 - 19:17

Telemorris

Thank you Kerstin and Joanne! I can't thank you enough for the very helpful information.

 

I'm designing this loom to be able to start as a CB but with the flexibility to move to CM later. The gallows structure will make that possible. I'm somewhat limited in space in my studio/office so the current plan is to start with a 40"/1 meter wide weaving width (depends on whether I get greedy or not). I like the traditional wedge system for holding the loom together because I could make the loom wider in the future if there's a need. Distance between the breast beam and the back beam will be between 40"/100cm and 48"/122cm. I may be crazy to make the loom that big given the space available but I could cut the beams down to make the loom narrower if necessary.

 

Joanne, yes, I do plan on a 38"/96.5cm breast beam height. I haven't figured out yet whether I need it to be higher or not. Much depends on how close I can set the treadles before my foot interferes with the treadles on either side of the one I'm depressing. Any suggestions?

 

I'm attaching the current drawing - just a sketch really - of my plans for the loom. It includes a stick figure of myself sitting at the loom with accurate measurements for my personal dimensions which helps with knowing how far apart to make various parts of the loom.

 

<edit> I forgot to add that the two "hands" in blue show my hand and forearm at elbow height, the other shows my reach from shoulder to first knuckle on my hand. This drawing shows my elbow at 2.75"/7cm above the breast beam. I also have my knee 3"/7.6cm below my seat height so I'm not lifting my leg too high (advice from Walter Turpening though he didn't specify a distance). Shed opening is shown at 4" which means a drop of 2" at the attachment point at the treadle. I know the shed doesn't need to be that large, but I though it best to allow for a larger shed just in case.

 

I still don't know how much distance to allow for cloth thickness around the cloth beam at the end of a longer warp. I want to keep my knees from running into the cloth. Should I push the cloth beam back a few more inches?

 

Hope all of this makes sense! </edit>

 

Loom drawing

Thu, 10/24/2013 - 18:51

jander14indoor (not verified)

Based on addmittedly limited experience, but analytical outlook of an engineer, be aware of the comments about weight and balance of the shafts/lamms/treadles as a system.

On a counterbalance loom you primarily need consistent part weights (all lamms the same, all shafts the same, all treadles the same across the loom) since the shafts and lamms generally are used in matched sets on either side of the pulley, balance comes automatically.

On my countermarch (and I suspect all countermarch looms based on Joanne's comment) the balance is between the shafts, lamms and treadles as a bunch.  And leverage becomes important.  Example, on one of my shafts, it just wouldn't move properly until I added weight to the lamm that pulled the shaft down.  I could add less weight by locating it at the end of the lamm.

 

My experience anyway.

Jeff Anderson

Livonia, MI

Thu, 10/24/2013 - 22:44

ReedGuy

Yes, you do need to balance the lamms, shafts and treadles. And as Joanne said about the lamms, the lower lamms are a bit beafier and longer than the upper ones. Think of the upper lamms and the shafts (work with gravity) as a counter weight against the lower lamms (work against gravity). This is how I designed mine and it worked perfectly. When I pull the locking pin in the jack frame, the shafts stay stationary. I have not yet had a tie-up that this was not the case. There are often fine adjustments of the cords, once you get started weaving. That is because of individual cord length adjustments between treadle and lamms. That is normal.

Thu, 10/24/2013 - 22:54

Telemorris

Thanks Reedguy. Your comments sound almost as if the weight of the shafts and the upper lamms need to equal the weight of the lower lamms I know there's some offset in the calculation involved since one end of both the upper and lower lamms is held stationary, but is that the basic equation of it?

Fri, 10/25/2013 - 06:58

ReedGuy

The lower lamms should be slightly heavier.

And as Joanne said, and after thinking about it some, loom height is good. Often folks are finding they need to raise their looms to get more clearance. My breast beam is 36", and as I recall now, that was a minimum suggested by Joanne from an older thread from 3 years ago. Joanne is the expert on these looms, not I. ;)

Fri, 10/25/2013 - 07:13

Joanne Hall

From this diagram, I can't tell if it is in scale, but it looks like the beater sides are not very long.  You will get a longer sweep of the beater and need to advance less often if you make the beater tall.  With a bb height of 38 inches, you may want the loom frame to be taller.  Or, at least the beater cradle should hold the beater taller.

You may want to lower the horizontal beam of the side frames.  This will lower the knee beam, but will allow the shafts to sink without hitting the side frame.  The shaft bars are usually a few inches longer than the weaving width.

Joanne

Fri, 10/25/2013 - 07:16

Joanne Hall

If you can find a Swedish loom near you that you can visit and measure, that would be helpful.  You would benefit from centuries of loom design. There is a lot that goes into a loom and it is hard to think of everything.

Joanne

Fri, 10/25/2013 - 10:57

ReedGuy

Heddle length will also determine how much the shafts move. The length of the heddle from the eye to the bottom of the upper shaft bar for instance. The shaft bars can only travel up or down (maximum) until they hit the warp. So if you have 11" inch heddles, the shafts can only move 5.5", less the width of the shaft bars, from rest position.

Everything is interdependent.

Wed, 07/01/2015 - 15:03

efdesign98

I have noticed that the reed height/shed height is an interesting factor in the design.  The reed height has to be greater than or equal to half the heddle height  to get a full shed opening.  Slightly greater would be better, but it would cost more.  This choice has to be made carefully as well.

I've been studying this old loom I've bought with the notion of creating a short-ish counter shed loom, but given the information here, I will either have to give up that idea or modify it significantly

Sat, 07/04/2015 - 17:43

kerstinfroberg

High sheds seem to be a modern idea - in my survey of old Swedish wooden reeds (I measured some 60-70 reeds, in total), the shortest one was 5,5 cm (between the frames), then tallest is slightly under 8 cm.

When I went to weaving school the standard measure was 10 cm, but nowadays it seems that 12,5 is the new standard. My AVL loom does not accomodate reeds shorter than 5" -  but, all the same, the AVL has a shorter (lower?) shed than does my old CM with a 10 cm reed... which means that, if I want to use my "ordinary" Swe hand shuttles, I have to be careful not to load them as full as I can when used on the old CM.

So, I think one question would be: do you really need very tall sheds?

Wed, 07/08/2015 - 21:59

efdesign98

I think it depends on the size of your weft, the volume of weft you want on the shuttle which in turn defines the size of the shuttle, and the frequency with which you have to "splice" the warp.

We've been making rugs from old blue-jeans using ski style shuttles that tend to be taller than others.  This in turn gives us more wraps on the shuttle, etc.  It is possible that as we get used to it that we can deal with a shorter shed, but laziness and inexperience seem to indicate a need for a taller shed.

As I've been studying this loom, I see that the shed is opening more on the order of 8-10cm rather than the 12,5cm that is indicated by the height of the heddles.  I've recently adjusted the brake system and the two main beams, so maybe with a bit more tweaking of the lift mechanisms, I'll get the taller shed I'm looking for.

It is all an experiment!

Thank you for including the links.  I just downloaded both books and look forward to reading them.