Bluebunny wrote:OP827 wrote: I have sketched it here in case you are not familiar with that mechanism.
Thanks for the thinks everyone! Other than the weight of the lifting aid, I'm getting confidence that the system will work OK (and yes, the beauty of it is that it assists EVENLY at each rear corner. I'll think about the straps, I worry a little about them walking on the pulleys.
And OP; awesome sketch; thanks for your thoughtful effort! I like the contrast between our sketching abilities
Yes, I would want to have such even lift with this two points design to avoid jamming. Now, I did not do webbing lift myself (steel cables only), but it should work. I personally don't like torsion spring idea as I see it as something that complicates things and make it more dangerous due to stored energy. With your light roof it would be an overkill. Garage doors are much heavier than your roof. You can also install a long shaft made from electric conduit for example, along the back with two points in each corner and have no issue with either ark or diameter increase (twice as less), let me know if you want another option sketch. the crank will then be located on the side. And you need a thin webbing as the load as small, it is not a car seat belts size(6000lbs load rating), something much narrower, smaller and thinner than that. Look at the load rating. I like nylon belts idea as they would be mush less noise comparing to cable and steel pulleys. Once stretched they should work evenly. You could also use Dyneema which is comparable to steel cable for elasticity and strength, but plastic flexible rope or webbing, but that is expensive and not really needed for this application. Also you can make pulleys with positive side flanges to ensure the webbing belt stays on the pulley. What is needed is a stopper that will lock the shaft at any given moment to prevent unwinding, similar to what is done on manual utility winch. I feel that the force to rotate the handle will be small and most likely does not need any power, torsion, or gas strut assist. This is based on my experience with my build. Let me know what you think. You right, you can incorporate the lifting system later, just keep in mind where you potentially route it so you can later drill slots and put a cover etc.. Sorry for the long post, but I thought it was useful to discuss the options.