How is the mechanism for a slide out different then one for a pop top? Other then having to carry the weight it would appear to be similar. Keep in mind I am a newbie here.
I do not think anyone has answered your question here, so I wanted to give you a few thoughts that I have gleaned from others who have built various lifting roves.
Fist the difference in the Soft Sides, vs the Hard Sides, is massive!
Many of the shells built on here are of such a light weight composite that I think the weight difference would be negligible. This can not, however, be said for the lifting mechanisms.
I will focus on just three specific camper builds so you can go and read the threads and learn for yourself how they dealt with their specific issues. Just click on their names to take you to their particular threads...
MHISCOX has taken an XV-JP earthroamer, and made the top (with hinge on the rear) that was meant to fold out into a bed/awing setup, and made it lift only high enough to make a triangle shaped roof. As I recall this was a difficult build in many ways because of the hard roof, and he has soft sides.
Westyys has also built his hard sided lift roof. Same issues as Mhiscox, only harder because he had to lift the entire roof.
and
John Lovett has built his soft sided lifting roof on here.
Mhiscox had to time his roof just right, so that the two hydraulic lifting mechanisms would lift simultaneously thus insuring that the roof would go up to equal heights, and not put any strain on the hinge in the rear of the roof. This takes some time, effort, and a fair bit of arithmatic to be able to work it all out.
Westyys had to do the same as mhiscox only he had to do it for all four corners. Keeping in mind the other obvious difficulties, one important thing weather you use air, mechanical, or hydraulic, you need to remember that each of the four lifting devices will be a different distance from the lift mechanism, and therefore will require different timing to be able to allow you to lift the roof without causing any of the obvious concerns, such as cracking, scraping, gouging the sides of the camper, and possibly even causing the roof to be wedged up there so that you can neither raise nor lower the roof.
Ok, so, John Lovett: In reading his set up he found it really rather easy to do. There is an option, if you look at the FWC's style lifting roof, to raise the roof manually, John did a scissor lift on either side. I believe you just have to unlatch the roof and push up... or you can go with a mechanical lifting mechanism. If you plan to load up your roof this would obviously be the way to go, but things get more tricky and certain engineering will be required as seen in the other two trucks, but not as much. Now the FWC I have climbed into, and they have a very simple system. Basically the use two massive U shaped bars that are connected to one another, on each end of the rig. One U shape reaches to the roof, the other to the stationary sides, and as I said they are joined in the middle. This allows you to simply press the two U's toward the side walls and thus lift the roof. The bonus is that with a cloth side you can do that one end at a time, and you need not worry about the strain it will put on your cloth. This would obviously be impossible with hard sides. With the mechanical/air/hydro you can still lift a soft sided roof, and you do not have to have them perfectly timed, because you can allow for some warping of the roof while it is in transition, so long as it is correct when it is either in the fully raised or fully lowered positions.
I should add that the scissor system would likely lift the roof fairly evenly also, and with little effort because it would mainly be spring driven thus the same size springs should raise it up the at the same time...ish.
Well... I hope that was not too long winded, and I hope it makes some sense for you in your build efforts!