| From: Tom Vogl
Subject: Notes on J-comp adjustment Date: May 4, 2002 The other day, my J-comp went slack, that is it suddenly refused to pick up most of the harnesses it was supposed to. (I'm currently weaving 20/2 cotton at 36 epi across 44.5 inches.) To be didactic: Please remember the convention I use: The normal weaving position is the "South" end of the loom and the weaver looks 'North'. From that perspective, left is 'West' and right is 'East'. Since you will be often looking at the loom from the back end, compass directions are less confusing, especially for someone like me who has trouble telling left from right. When that happens, the first culprit to accost are the two cables that run up from the cross bar just beyond your right toe, over a vertical pulley and then horizontally across to the back of the tie-up unit. If they are too slack, shafts will not pick up; if they are too tight shafts that are not supposed to rise, do it anyhow. Remember that the west side of the tie-up unit controls the even shafts and the east side the odd shafts; also on the tie-up unit shafts go from south to north so that shaft 16 is at the north end of the tie-up unit on the west side. The idler pulleys for these two cables are on hinged aluminum supports pivoted on the aluminum channel that runs horizontally along the tie-up unit on each side. The tension on these two cables is adjusted by how far they are pushed out from the channel itself by the adjustment screw (secured by a locking nut). Note that there is a separate cable on each side, so that each side can be adjusted independently. What happened to my loom (a very rare occurrence according to Dale) is that one of the adjusting screws (the NW one) had slipped off the plastic block on which it usually rests. Replacing the 1 1/2" 10-24 screw by a 2" 10-24 allowed the screw to rest on the aluminum channel and permit the full range of adjustment. {Since I had noticed this problem at first, I spent a lot of time trying to make a tension adjustment by the other three adjusting screws and managed to thoroughly foul up the balance. Once the new screw was installed it was a matter of experimentation to restore the proper tension all around by observing which shafts went up when they should not have and vice versa as per the rules stated above. On a totally different adjustment subject, is how forcefully the right treadle moves forward at the top of its travel (to make contact with the microswitch bar sticking out from the front panel and that produces the signal that initiates shed change). The force to provide this Northward motion is provided by two springs that can be seen on either side of the tie-up unit. The springs are anchored at the North end of the tie-up unit by two long eyebolts whose lock nuts protrude at the rear of each side to the unit. Tightening the nuts (keep the tension equal on both sides) produces a stronger northward pull on the right treadle. I hope some of this helps someone, someday. Cheers, Tom. |