Can't Figure Out How To Draw A Parametric Involute Curve for Cam Lever

[Anonymous]

So I'm trying to design a cam lever lifting mechanism for my workshop. I've got a sketch going with a known starting radius (starting position and distance) and the desired amount of lift (after a 90º rotation), I have these two set up so if I change the amount of desired lift the starting radius changes as well.  

I also have the start and stop points of the curve at 5º off-center from the pivot to give the cam a locking action.

What I'm trying to do, but can't for the life of me figure out how is to make a nice curve between the two points (see attached image) with a constant rise that is parametric, so if either of the radii change the curve will adapt. Maybe I'm just super bad at math, maybe this is impossible, or maybe I'm just missing something. 

Any and help is much appreciated!

[g-andresen]

Hi,

It would be helpful to know if it should be a curve of the type y=x^2.

günther

[Anonymous]

This thread might turn out to be an embarrassment for me, but my math skills are basic at best. So basic that I don't understand the clarification you've asked for 😞

[Anonymous]

All I know is when the cam is rotated 90º I need the workplace to be "pushed" by a specific distance. This I've modeled and figured out pretty easy, but I can't figure out how to make a nice curve between the two points.

[g-andresen]

Hi,

Please share the file and explain the movement.

File > export > save as f3d locally  > attach it to the next post.

günther

[davebYYPCU]

Change the connecting line to a 2 point Spline.

make the spline handles tangent to the horizontal and vertical elements of the block, Fusion will present the best fit curve for you, and it is adjustable if you change the tangent handle length.

More technical formulas would be beyond both of us.

Might help....

[Anonymous]

@g-andresen  Here's the file. 

One thought that's crossed my mind is maybe I'm just asking too much of the cam. Maybe 1.25" is just too much lift for a nice constant curve?

[Anonymous]

@davebYYPCU  that actually seems to give a pretty nice outcome. The only question then becomes the dimensions for the spline toggles 🤔

[davebYYPCU]

You didn't ask for horsepower efficiency on the shaft.

Try the ellipse, for constant pressure, your spline is not so far off.

Might help....

[etfrench]

Try a control point spline:

Change the shape in the User Parameters dialog.