i need a hinge

[bigdogrod]

that's funny, i made a lowrider with a tilt and spin bed a long time ago, but never had it dance.

i looked for a linkage designer app and found a couple online, but they were hard to get working right. i may just have to start to experiment with some styrene

[dremu]

Originally Posted by bigdogrod

i may just have to start to experiment with some styrene

Honestly, this may be your best bet -- or do the Cardboard Aided Design thing as a starter. A few thumbtacks as rotation points and you're golden.

I suspect you're looking for like a Z-shaped double hinge, common on lift crane mechanisms. The challenging part is that the two sides are often asymmetrical, like one part of the "Z" is shorter than the other. I generally do all my stuff up in CAD (the computer kind, not the cardboard kind) before moving to the physical world, but the geometry there gets really painful really quick. Stupid irregular triangles and Laws Of Cosines, ugh.

Anyway, this example isn't quite the same, it only has a single hinge point, but you can see how the cylinder drives a set of levers, not a fixed point on the arm to the right. Those levers have to be precisely sized; too long and the cylinder won't push enough, but too short and you won't get enough travel.

I ended up doing trial and error until to make it work =))

https://youtu.be/Up3gK26ORb0

Here's another one I did which is Z-shaped, two hinges, but the two sides (red and darker blue "cylinders") are symmetrical. I could not for the life of me figure out how to have one shorter than the other and still work, when the center bar (lighter blue) is of fixed length and at a fixed position.





Food for thought, anyway, maybe that helps?

-- A