Is it possible to make a flat straight leaf spring flexible and bend about an edge. Like a cantilever beam.
Sure, why not?
OK, here's what I want to do. In assembly, I have a rectangular flat spring steel fixed at one end. On the opposite end I push on it with a plunger (cylinder) to bend the spring steel into an arc. THe act of the plunger moves the spring steel. How do I make the spring steel flexible at a known length at the fixed end.
this kind of depends on what you're after. If it's just being able to see the thing flex, I don't think the functionality you want is available.
If you're intersted in analysing loads over a range, I would think you can create a simple mechanism and run it in BMX.
There is a fairly simple way of creating such a part; I have used this successfully in the past. If you sketch a short straight line for your fixed portion, then a 2-point spline tangent to the line and bending away from it for your flexible section, you can extrude and thicken this sketch to create a part like what you want. There are complicated ways you might control the length dimension of the flexible portion, but if you just create a construction circle through the end point and set its radius you will probably be close enough. Now to see your spring in the unbent condition, just change the "bend-away" dimension to zero. You can also use 3 or 4 point splines, arcs and conic sections to create similar geometry. In an assembly you can use various techniques available to make it "work"; perhaps the simplest is to create an assembly Relation that governs the flexible part dimension.