Irregular 4 bar lift

How do you calculate the arm lengths for a 4 bar lift so that it meets requirements such as max height and angle, or is trying various combinations of arm lengths the easiest way for it?

The mechanical device you are designing when you refer to “4 bar lift” is a linkage. If you search for “linkage design” you will find results as or more technical than you want, some of which (example)will have simulator software.

A 4 bar lift is very straightforward. The bottom arm will swing in an arc from the ground until it comes into contact with the top arm or some other physical impediment present within your build. You can keep the sides of the linkage parallel if the arms of each side are the same length, or make more complex movement by varying the lengths. Since vex parts so conveniently have holes all over the place, I would suggest mocking up some shapes by loosely connecting parts with long screws and nylocks (barely tightened, just so they don’t fall off.) Once you have seen how different pin points affect motion, the technical postings you search for on linkage design will be more useful.

calculations would save you time if you know what you’re looking for in a linkage system

For max height, add the height from the floor to your lowest bar to the height gained from the lowest linkage, minus the height due to the angle drop. To find the height from the lowest linkage, you would need trig identities (Most likely sine), and to find the angle drop, you would first need to find the angle.

For the angle, you’ll need to find where the two bars intersect by drawing imaginary extensions. You would probably then need to use law of cosines, knowing that the distance between the two intersections would be a fixed distance by whatever mounting bar you choose to have

Check this old thread. It has some nice things that will help you. There was another one I can’t find right now that talked about one of the Autodesk products for mobile devices.

https://vexforum.com/t/using-and-interrupt-with-an-if-statement/15624/1