First, this post is based entirely on the assumption that your
system is a standard
counterweight system, either single or double
purchase.
Second, as others have already pointed out the probable problem, I have tried to show the ways to search out and pin
point it.
You have already narrowed the problem down quite a
bit, in that you say it is only
in one point in the travel of the
line set, and after pulled through, runs fine. You did not mention any other symptoms such as the
batten jumping or the
purchase line "
whipping or jerking". This alone virtually eliminates any of the blocks in the
system as the primary cause of the problem. That leaves the items that pass a specific
point or cycle only once during the travel.
That means the probable problem is with (in no particular order):
1.
Purchase line.
2. Individual lift lines.
3. Guide
system:
.....a.
Wire guides
.....b. T
track or J
track guides.
My first thought is, as others have already pointed out, the guides. And, it is highly improbable that your
system is a
wire guide. A
node or tape or contamination on a
wire guide would tend to create a sudden "bump-jerk" in the
system, and often the problem will be scrapped away by the
arbor after a while, at the same time completely wasting any
grommet or plastic guide eyelet in the
arbor. A
lift line with something on it would exhibit the same tendency but would not be self clearing. If a
lift line were the culprit, it would be because of a hard kink or a bird's nest. However I don't think it is a
lift line as it would tend to make the
batten "dance" as one
line grabs and the others run free, a rather noticeable action. A
purchase line has only 3 points of contact that could cause the problem, the
head block and
tension block which you said you've checked, and the rope lock. You also indicated you did a thorough check of the
purchase line, removing
spike tape and such ( Please folks, use ribbon or similar, NOT tape ) so it is an unlikely cause.
Now we're at the most likely cause, a
track that is bent, bowed or deformed. This will squeeze or bind the guide shoe as the
arbor passes and then run free when it has passed. Run the
arbor and observe where it is in the
track when the "stick" happens. Check the
track in that area for loose wall anchors, loose, bent or broken knee braces, loose or missing bolts between the wall and knees and
track. check in a wide circle as this kind of problem can often exhibit itself away from the actual cause.
Without an on site inspection I can't be sure, but from the symptoms described, this would seem to be the most likely cause of the problem.
Hope this helps.
