In another thread about autocovers.....
"Not sure without seeing it first hand but I believe something has to be installed out of square. Measure an x from end of track to end of track. Check width on both ends, check length of both tracks."
This was in response to my comment that the skew adjustment on my autocover has "hysteresis" and/or "backlash"; if I slide the adjustment plate about 1/4 inch, nothing might happen. Then I slide the plate another 1/4 inch, and it overshoots by 3 inches. Then I slide the plate the other way, and nothing happens. Etc. After a few months, the skew drifts a couple inches typically. I set it back to about 3 inches skew, which is about the best I seem to be able to do without opening and closing the cover several times (you can only slide the adjusting plate when the cover is closed), and I'm good for a few months. The manual seems to imply that 3 inches is okay and "within tolerance", but swimcmp and other pros think I can do better.
So I measured the X dimensions end-of-track to end-of-track and got 32 feet 10.5 inches one way and 32 feet 11 inches the other way. Both short track-to-track widths are the same, 15 feet 9 inches, and both track lengths are the same, 28 feet 11.5 inches. So, I think it's reasonably square.
Attached is a photo showing the 3 inches skew.
Any ideas? It kind of makes sense to me that things will always be a little off. The cover always closes perfectly, since it is closed by two ropes which pull it, and the rope length can be set accurately; unless the rope stretches, it will stay set. But it opens by a big drum rolling up the whole cover, and getting a precise setting with all the wrinkles and folds which are necessary because the cover has to be somewhat "oversized" to work properly, well, that really does seem difficult to me. I'm surprised I can even get it to within a few inches actually.