technical question about pop-top canopy scissor lifts

hmmm, ok, so they twist... im really surprised about that but that may explain why on a lot of poptops ive seen have a very slight twist can be seen in a corner. I've often wondered why they couldnt get it spot-on.

Im really surprised about it 'cause i thought the scissor lifts where designed to lift up straight, using optimum materials to retain horizontal and vertical stoutness..

I have two scissor lifts, one for each side.

Ozhum, you mention "so that way the whole top isn't trying to be twisted and goes straight up"...
I get the directional set-up you described but i dont understand why. What's wrong with each side pushing in the same direction, they are only sliding along the rails with most of thier energy going up. Are you saying they have to be opposed because it would overstrain the sock one end

huge thanks for posting.....

If I read it correctly, you have a square/rectangle with a scissor lift in the middle of each side.

When erected most of the force will be vertical, however there will also be a horizontal force component. Unless these 4 forces are exactly equal, you could end up with a twist or diamond.

Rosco is right, that was how it was explained to me when I built the poptop for the Oka by both the bods that made the vinyl skirt and caravans.
You can make the poptop so that it only has two scissor lifts, four and other combinations, they can also go the in same and opposing directions, all depends on weight, size and the height the top goes up.
The problem is that you have a large "flat" roof supported by the scissor lifts, the vinyl skirt is just there to keep the weather out it has virtually no structural affect other than sometimes limiting upward travel.
The scissors are not rigid as there is no precise mounting at either top or bottom and they can and do twist themselves, the spring tension is stopping a lot of the movement and that combined with the skirt remaining under tension at the point where the scissors can no longer lift due to the weight is what you want as the roof reaches its travel limit so that it doesn't move and creak due to vehicle movement or wind affect.
I've seen poptops where the are only two scissors, one on each side and they were slightly off centre to the top and each other which effectively cancelled the end/sideways push. It was also on a small very light van roof without solar and even interior lights on the roof section.
Landcoaster, from memory when I built my poptop the Breha scissors were good for just under 700mm lift and the bods that made the skirt suggested 500mm as a good height to make the skirt with those scissors.

thank-you again for your posts Peter, it has helped me appreciate the task..