Using Sketches to size Cylinders

Don't you love downloading your favorite pneumatic cylinder only to find out that the stroke is either too long or too short, or the cylinder runs into the rest of your assembly when it's fully extended?  With this method you can get the correct stroke length every time.

If you combine the previous methods I showed (vectors and moments) then you can even choose the correct bore size.  Of course you don't need any help with that, but in complex assemblies where the loads are critical this is a life saver.

1.  Pick your favorite pneumatic cylinder manufacturer.

2.  Browse their catalog for the cylinder you're looking for.

3.  Look for the dimensions "[some letter] + stroke".  This will give you the base cylinder length given some stroke.

4. Draw 3 lines, all co-linear to each other.

5. First line is going to be your base (I used 2.56 in the video).

6. Second line is going to be your stroke (this can be set to driven if you don't know what stroke you'll need).

7. Third line is your rod length + clevis pin center.

Once you have those three lines you know how long the cylinder is going be when it's completely retracted.  Now all you need to know is where the cylinder is going to be when it's extended.

8.  Draw another co-linear line connected to the end of your 3rd line.  Make this line equal to your stroke line.

9.  Draw two circles centered at the origin of your line quatro.

10. First circle will connect to the end of the rod+clevis line.

11. Second circle will connect to the end of the last line.

Now you know how your cylinder is going to travel anywhere w/in its stroke limit.

The second video shows a combination of things: a target to hit, a moment arm, and a cylinder that's moving the moment arm.  I could've added loads and how to solve for them, but the sketch would be too busy and too complicated for a simple tutorial.