Help calculating piston rod angle

[David Manley]

I can't quite figure out how to calculate the angle and vertical distance of a piston rod on a rotated crankshaft, specifically using LDCad's Selection Info tool. Here's a diagram:


So the crankshaft has been rotated -49.5 degrees. The piston rod (A-B) will move up the Y-axis, but I don't know that distance (it's slightly less than the current Y distance between A and C). Also, point B will remain at its current X position but point A will rotate around point B to connect with the axle at point C. The angle of that rotation is the second thing I don't know.

No doubt this has been tackled many times before, but I'd like to know the precise way to figure it out (rather than downloading an already finished model). It's either slightly more difficult, or vastly simpler than I realize.   (And I do know about the piston placement script in LDCad, but AFAIK it doesn't recognize these old-style piston parts or brick-built cylinders.)

Again, the two values I need to find are:

• The distance to move the piston rod along the Y-axis, and
  
• The angle to rotate point A around point B so that it connects with axle C
  

There is a feature in LDCad which may help you do this automatically. See the following image:



If you select the three points you are interested in, then right mouse click a part, the "Selection" menu pops up. At the bottom of the menu, there is a menu item "Selection info". Click it and a number of options are shown. For example, to get the angles shown in my diagram, I have "Show Info" set to yes, "Show distance" set to no and "Show angles" set to yes.

Try this and see if you can get the information you are looking for.

Regards,

David