I’m ditching my strategy of using futon hinges. While I expect they would have worked fine, using them would have cost me some space lengthwise on the whole platform, and considering space is at a premium in a van… I’m going back to my previous plan to employ linear actuators. Unfortunately, this will be more expensive and more complex.
The main issue with using linear actuators is puzzling out both how large units to get, as far as stroke distance, and then where exactly to mount them on both ends, to get the desired result. I’m sure is software out there that folks use for this sort of thing, but I certainly don’t know what tools exist, nor do I have easy access to them, so I decided to go a more primitive route using graph paper, a pen and a pair of scissors.
It’s a good thing I decided to go this route. Yesterday I had done some simple mental calculations and decided “I need 20″ actuators to get this to work”, and then hopped on Amazon, did some poking-around, and ordered a pair of 20″ units. It wasn’t until later in the evening, when I decided to cut out some strips of paper to the proper relative sizes and start trying to puzzle out mount points, that I realized; the 20″ figure is the stroke length, i.e. the difference in length of the whole unit between fully withdrawn and fully extended, and did not account for the length of the housing! A 20″ unit was more like 40″ extended. Waaaaay too long! Fortunately I was able to cancel that order quick enough.
So, now it’s on to figuring out just what size unit would work. And I got pretty lucky; I thought to myself “let’s see what a 12″ stroke unit would look like”. And now that I know to account for it, I hunted down a suitable looking unit, made note of both the housing and stroke lengths, clipped out strips of graph paper to match the size of my movable bed platform piece (25″) and the actuator (16.8″ closed, 28.8″ extended), marked everything up, and laid them out on a scaled-out diagram on a sheet of graph paper.
Aaaaaaand… amazingly, I seem to have nailed it in one try! Mounting the actuator extended end about 11″ from the rear end (14″ from the hinge pivot point), and the base end on a support 15″ down from the base of the platform, appears to work. Obviously the actual mount points will need to be puzzled out in the real world, but the diagram shows that it’s very close.
So, I placed another order for a pair of 12″ actuators, a rocker switch that can be pushed in either direction to control the movement of the actuators, and a pair of cigarette-lighter plugs to wire up to get power to the whole thing. (I’ve no portable battery bank or anything of the sort, so when I need power, I’m going to have to pull my truck up next to it and use the cig-lighter plugs in that. Clunky, but it works.)
Everything arrives in a couple of days.