Thanks Nomadcat.
Let's see, work on the van this past weekend or head to the woods?
Woods win.
Sofa-bed continued:
After having completed building the lifting mechanism I bolted it to the Seat Platform.
I need to make a way to attach the top of the actuator to the Back Platform. Since I had moved the Center Support the attachment point would now be on one of the side panels so I wanted to do a little reinforcing first. Cut a small plywood panel that fits tightly into the Back Platform recess.
Then glue (Mmmmm - wooden toaster pastry) -
and screw into place.
Because of the way the sofa-bed operates the top of the actuator can't be rigidly attached. It has to be allowed some movement. After some testing and a couple prototypes-
I came up with this design.
The bolt has a 1/4" diameter and I need it to be able to slide within a slot on the aluminum bracket. To create the slot I drilled a series of 1/4" holes taking great care to keep the holes in a straight line. Then used a hand file to smooth down the ridges left from the holes. Again being careful not to enlarge the slot but keep it at 1/4". The advantage of using aluminum to make the bracket is it's a lot easier to drill and file than a similar sized piece of steel would be.
As the sofa-bed converts from bed to sofa I'll explain how the bolt moves in the bracket slot.
The sofa-bed is in the bed position. The Back Platform is lying flat. The lifting actuator is completely "closed" or un-extended.
The transitioning begins. The actuator has just started to extend. Notice the change in position of the bolt head.
The top of the actuator post has made contact with the bottom of the Back Platform. This contact is how the lifting force from the actuator will be transferred to the Back Platform. The purpose of the bracket is to guide the top of the actuator post and keep it in place. I'm using the base of the bracket to help spread the lifting force.
Here the actuator has extended to the end of it's stroke and raised the Back Platform as high as it can. Due to the pivoting of the of the actuator post edge against the bracket as the angle of the Back Platform increases the bolt has moved downward slightly in the slot.
Even though the actuator has raised the Back Platform has high as it can the platform is still not in it's final position.
At this point the second actuator is activated. It moves the two hinged platforms backwards and brings the Back Platform against the end support blocks.
As the second actuator continues to operate it causes the Back Platform to slide up the end support blocks increasing it's angle . When the second actuator stops moving the Back Platform will be positioned so it's angle matches that of the end support block.
While the angle of the Back Platform was being increase the bolt through the end of the lifting actuator was sliding downward in the bracket slot.
Figuring out the whole system of getting the lifting actuator to get the Seat Platform most of the way up then having the end support blocks lift it the rest of the way while not binding up on the lifting actuator was a major challenge. I'm sure it looks fairly straight forward here but it sure wasn't in my head.
In this picture you can see the pencil marks and screw holes from some of the different designs I tried before creating this one.
continued -
Linear Mode
