greygoos wrote
Great find - thanks, it answers a lot of questions.
About the lift: I noticed in the video the guy (watch his feet and the trailer's rear height dip) entered the tailer to raise the top. As it rises, the light from the open rear door can be seen through the rising window but he can not be seen, so I figured he is somewhere in the front two thirds of the trailer or on the floor well below the window. It’s now clear he was near the center with the lead screw lift.
He speaks of the leadscrew inside a wooden tube and a cross brace. Several configurations may be possible, and at first I assumed he used the cross brace to distribute the upward lift among the center 3 roof ribs. But the photo suggests something else: the leadscrew penetrates the cross brace and the drill is hooked to the short non-threaded end.
If the brace is at the top, then the drill would be between the brace and the center peak of the ceiling, with the brace running parallel to (under) the center rib. If the brace is at the bottom, it probably spans the two bench seats and the drill is between the brace and the floor. In this case the brace is much shorter and there is probably more room for the drill, but it also reduces the extension of the lead screw (see below). Based on the photo, the brace seems to be rather short, so I suspect it spans the bench seats. In either case, the center rib carries the full load.
The important issue is that there is only a
single central support during erection and load on the leadscrew is compressive, unlike a scissor jack where it is in tension. I still worry about binding during erection of the top: what works well while “shiny and new” may become problematic as things age. A snag during erection could lead to bending of the compressed leadscrew and even minor bends prevent smooth screw rotation.
The room taken by the drill is important because it reduces the possible length of the screw, and the lift extension can never exceed the screw length. Although it is possible to avoid linear alignment of the drill and screw, it adds complexity. It is also important to have a minimum overlap between the screw and extension tube.
If all this works, then so should a pneumatic lifter, and it would not need the cross brace and all the space taken by the drill, so the extension could be larger (or the minimum piston overlap can be greater). But I doubt a DIY PVC lifter would weigh less than his 3KG (6.6 lbs), a rather remarkable achievement.
He spends a lot of time on the virtues of the curved fabric roof, but I have long been convinced that is what best fits the bill. This is one of the most interesting trailers I've seen in some time. And the WoodWidget site has other unusual bike & boat projects too.
Thanks again for the link, I need to read it again.