Sunday, September 11, 2011

Selvedges and Pi

When weaving the lace shawl I noticed that the selvedge threads were considerably tighter than the rest of the warp. I couldn't work out why and assumed I must have done something silly when lacing on. With the shawl off the loom and having been allowed to relax and with a bit of pulling and stretching it seems to be OK.


I retied the warp with particular care to make sure that all of the ends were under equal tension. After about nine inches of weaving the same thing happened again - a tightening of the selvedges. The picture on the left shows how the warp is curving up at the selvedge. I looked at everything again, inspected my draft and then felt very silly when I realised the cause.

 In balancing the disposition of the warp on the sectional warp beam warp I had beamed the warp so that I had the selvedges [four threads on each side] in their own section. These threads had more space so the warp did not wind up to the same diameter as all the other sections. This can be seen in the picture on the right.

As we all know, C/D =  Pi, so the two selvedge sections that I measured as having a diameter of 5.9 cm has a circumference of 18.535 cm whereas the other sections with a diameter of 6.4 cm has a circumference of 20.106. What this means that for every 8 inches of warp released from the back beam only about 7.3 of the selvedge threads were being released. It soon mounts up!

It is all corrected now, the selvedge threads are off the warp beam and dangling at the back appropriately weighted. I now know that I should not have sections with less than the standard epi in them. This means a better balancing of the pattern repeat with the epi. If I need extra threads they must either be beamed separately [or dangled down the back] or I could fill the whole section anyway and just use the threads that I need.

Tuesday, September 6, 2011

Lace and Overshot

In chapter 12 of "... 8 Shaft Patterns by Carol Strickler..."  is #488 which is described as  being "Diamond in lace and overshot from Manual of Swedish Handweaving..."  It caught my eye because the threading is very similar to that in my Ultimate threading that I have been getting so excited about in previous posts. I now know that what I have "discovered" is just an extension of multishaft overshot but I hadn't realised that so much could be done with it.[http://gangewifre.blogspot.com/2011/07/ultimate-threading.html].

The draft is shown below slightly modified [the lilac one] and the two in black and white are some extensions of the idea to 20 shafts.

Having just finished weaving the Lace Shawl I wove a bit of a sample of this lace/overshot draft. Lace seems to work best on slightly less than the plain weave sett and overshot [IMHO] works better on something slightly tighter so it will be interesting to see how this turns out when I get it washed. I suspect that it will be a little bit too sleazy - no matter as the plan for this warp is that it gets progressively close in sett so I will weave a progression of samplers.
                                               
     

Sunday, September 4, 2011

Lace Shawl

I have threaded the loom  [AVL WDL] with my Ultimate Threading and the first cab of the rank is a lace shawl. The yarn is Bendigo 2 ply set at 13.5 epi and all is going well. Shaft 24 has finally given up the ghost [the wire from the shaft to the dobby is kinked and will not engage consistently with the electromagnet) but it was no matter as I was just using the shaft for the selvedge so I was able to switch to another one.



I am using live weight tension on the warp beam at the back of the loom. I have kept  the AVL brake cord, I have just detached it from the loom frame and attached 10lbs as the main weight and  x2 1lb sinker as the counter weight.

   

 Because I have had problems with the ratchet and pawl on the front sandpaper beam I have put on a similar live weight tension system at the front of the loom which pulls in the opposite direction. I adjust the weights so that the warp can be advanced with the lightest of touches on the ratchet leaver. In practise this means that I advance the warp much more often than I used to.

Before stumbling on this system I advanced the warp whenever I moved the temple, about every 2". Now I move it forward about every half inch - there are no ratchets engaged or disengaged in the process so everything is very smooth. Too much weight and the warp will advance just from the pressure of the beater; I tried this as a means of advancing the warp but I could not get a consistent beat. The front beam has 2 lbs pulling the warp forward - I suppose the difference needed is due to the friction of the yarn on the back beam heddles and reed.

The diagram shows the principal