You also need to consider the amount of force it will take to close the lid from it's fully open position.

Absolutely, but that will involve picking one of the mounting positions that will allow the spring to collapse and let the lid close completely.

<sigh>

My diagram shows the lid fully opened at an angle you define via slider. The length of the spring at this point is its full extension.

It also shows the lid fully closed. It shows the length of the spring at this point. If you move the mount points to places that makes the length of the spring in the closed position shorter than its minimum length, it indicates this by turning the lines red.

Hmm. Maybe I didn't notice there was a slider to control the lid angle... Let me take a look at it again.

EDIT: Ok, there it is. Never mind then about my previous posts. Seems like your ggb setup can do what I was talking about. I missed the slide to the left of point "A" the last time I looked at it.

Now I just have to play around and then multiply out the ratios to calculate real-world dimensions. I'll give it a first shot later tonight I hope - I'm probably going to spend most of the day outside today since the weather is amazing right now.

Is there a way to tie the sliders on the right to corresponding lines in the layout? For instance, can we have the sliders e and s limit the line BC1? There are certain situations with invalid values that do turn the lines red, but it's currently possible to cause BC1 to go outside limits without it turning red.

Is there a way to have the limits actually restrict movement? For example, stopping the angle change on A when the line hits either extension or compression limit? I don't know anything at all about this software...

Why is it that when I move B around, the lid mount point figures change? And they also change when I slide "I" even though B doesn't move when I do that? And both lid mount values change when I slide "I" even though I'd only expect the "up" to change, since visually that's all that's happening in the layout.

Is it possible to eliminate the C'1 point and associated lines? I can't see a need for them - unless they're of course used to help calculate the other stuff. It seems that the current dimensions to include some inch lengths, so it would be ideal if I could slide back the lid mounting point along the lid line - while keeping the lid line its current length. That would go a long way to help me wrap my brain around the way the layout works.

I also don't understand the value for "Spring closed Length" it seems to increase as the spring line decreases in size.

BC₁ shows spring with the lid fully opened. It is always the maximum length of the spring. All of the other real-world dimensions are based off of this. As such, it is impossible for it to be "out of limits". There are some absurd locations for it, but it is impossible for it to be out of limits, as it is a constant.

I don't believe that there is any way to prevent you from moving a point outside bounds. Well, there is (the point with the vectors is required to be on the circle with center A and radius AC, for example), but I can't think of a way to do it in this case.

AC and AC' describe the edge of the lid. Chances are that the place you're mounting the spring to the lid is not on the same plane as the edge of the lid; that is, that the lid is really a shallow box and not just a flat piece of wood. C₁ and C'₁ are points that take into account how far into the lid box you'll be mounting the spring. If you really will be mounting it flush with the edge, move the l slider to zero, which will make the sub-1 points coexist with their masters.

Um…. As you move the box end of the spring closer to or further from the hinge point, the lid end also has to move. Imagine a non-compressible rod. If you have the lid propped open and you held the rod in the same location as if it were a spring and then you moved the rod further into the box, the end of the rod at the lid would move closer to the hinge.

I understand the movement of a fixed rod. But in the layout nothing is visually changing except the point I'm moving, while the numbers all change.

I see now that C' is for the lid closed, so I better understand how it all works. It's just very difficult for me to do what I need to do with the setup. Wile moving point B around there's no way to keep BC1 at a fixed length - am I guessing that as long as it's 1.0 then it represents 100% length? However, if so, I don't know why it doesn't go red when moving above 1.0

What I was describing was having only the single line representing the spring and to see it closed you'd change the angle of A. In other words, it would be more like a simulation of the real product rather than plotting simultaneously both open and closed.

While it's true that the top mounting point will be set in (or upward) of the edge of the top, the location along the edge of the top, represented by the distance from A to C also needs to change. Having a slider for that or simply being able to move the point would be very useful. The lines currently represented by AC and AC' could be replaced by ASomethingelse and ASomethingelse' with the current C points sitting on that line.

Yes, true. As you move things around, the scale changes.


I don't know; are you? If you are, you're guessing wrong. BC₁ is, again, ***ALWAYS*** the length of the extended spring.


Which is less useful than what I've provided you, unless you really have a burning desire to move mount points, then check the open setting, then move it to closed and check the closed setting.


And it does, depending on the length of the extended spring and location of B. If you want it to be a particular length, just move B until it reports being that length.

If you want to be fancy, you could then define a circle with center on C₁ that passes through B and then modify B to be required to be on that circle. (That's a circular definition, though, so you'll be required to create some sort of intermediary object before you modify B.) This will prevent the scale from changing.

I've got the lifts in what I think may be the perfect spot now. Without upholstery they're powerful enough to lift open the top by themselves. However, once I put one of my sofa cushions on it, it stays down. The actual upholstery on the final product will be pretty much the same materials, only about 50% more of them. That should allow for a fairly light lifting action without any accidental lift-offs.

Needless to say, there was quite a bit of trial and error involved. Oh, and "by feel," the difference between 1 and 2 lifts (in use) is dramatic.