Lay out a sine curve?

The plans give a link to the pattern that they used

Frank

D'oh! Must have missed that on the read-through. Boy, is my face red.

However, the question remains--what if I wanted a curve with a different amplitude or wavelength? This template idea crossed my mind, but how to generate such a curve? Can Autocad do it? I've just received a copy of Autocad 2005, but really don't have much clue as to how to actually use it. I've bought the "for dummies" book, but haven't sat down and dug in yet.

At any rate, thanks, Frank.

Well, you could do what they suggest in the plans:

"You can use the pattern that we used by printing it out and transferring it to the wood in succession until you have the desired number of holes."

| Frank Ketchum wrote: ||| || || The plans give a link to the pattern that they used || ||

Phil...

I use DesignCAD and found that the "curve" (connect-the-dots with a smooth line) function will provide a close approximation when sufficiently many points are provided. I ended up writing a macro to produce a half-cycle cosine curve given the two end points (This gave me the ability to make smooth transitions between two horizontal lines, which was what I really wanted.)

If you'd like, I can produce a full-cycle sine/cosine curve and attempt to export as a dwg or dxf file...

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA

For future reference, if you want a real sine curve, and not an approximation [within the bounds of the tools and shaky hands] use a math program like Graphmatica, then copy/paste into a word processor or image editor for printing to the scale you want/need.

Graphmatica is shareware, but free for those who can't afford it [so just use it if you can't.] PhotoFiltre , or "The Gimp" are freeware image editors. OpenOffice is a great free office suite with a wordprocessor and spreadsheet and much more.

If you do it intelligently, you can do it to suit your project scale. One hint: in Graphmatica type in y = sin(x) for the unit sine curve, and you might want to change the default colours to black and white. You can change the equation if you want varied results; something like y = 3sin(x) or y = sin(3x) or whatever. You likely don't need that though.

Or, any basic trig text shows how to draw it from the unit circle.

this one. I do appreciate the effort, though. I guess my post was more in the spirit of knowing how for the next time, rather than having a "canned" curve to use.

Writing macros, huh? Is that a hard thing to do? I can barely draw a straight line with Autocad, so I guess macros are not in my immediate future, but it's good to know that when I get there, there's a utility that will help me out for the next time.

'Preciate the feedback.

-Phil Crow

You could make a somewhat complicated jig to do it, but it's probably a lot easier to just plot points. First, pick your wavelength (horizontal distance from peak to peak or trough to trough). Let's say it's 6", which is pretty close to what they used in their pattern. We'll call that "L". Then pick your amplitude. That's the height of the waves from the midpoint. In their example, I think the pattern is about 2 1/2" from peak to trough, which means that it's 1 1/4" to the midpoint. So the amplitude is 1.25; we'll call that "A". Then you simply take a piece of graph paper, plug in the formula for a sine wave into a calculator or into a spreadsheet, like Excel, and start plotting points. It's definitely easier on Excel, because you can do it once, and just copy and paste a bunch of times to get the rest of the points. The formula is y = A*sin(2*pi*x/L). If you're calculator is in degree mode, rather than radian mode, the 2*pi simply becomes 360. Just plug in values for x, and plot the corresponding value of y on a sheet of graph paper.

As I said, it's easier in Excel. Here's how you'd do it:

(1) Open up a blank worksheet. (2) In the first cell (A1), put your desired wavelength (e.g. 6). (3) In cell B1, put in your desired amplitude (e.g. 1.25). (4) In cell A3, put in this formula: =(ROW()-3)*$A$1/24 (5) In cell B3, put in this formula: =$B$1*COS(2*PI()*A3/$A$1) (6) Select cells A3 and B3 and copy them to the clipboard (7) Select a block of cells from A4 to B27 and paste from the clipboard (8) Select all cells (ctrl-a), then format cells (ctrl-1). Select the "Number" tab, and force the category to be "Number" with 3 decimal places.

The results should be as follows:

0.000 1.250

At this point, the first column is a list of x-values ranging from 0 to

You may notice that I chose to use cosine, rather than sine, in my formula. Either one will give you the same shape in the end, but a cosine curve will start and end at a peak, whereas a sine would start and end at the midpoint.

Josh

Thanks, Josh. Scuse me, I've got a spreadsheet to build.

-Phil Crow

Sure, most CAD packages can do curve fitting or there not very much "CAD." I do it in turbocad. However, historically the problem with Autocad is that its more of a workbench. Its a corporate product and lots of the nifty features come in add-ons that you also have to pay for. But this particular feature should be built in. It may not be tweakable by the parameters you wish to tweak, but it can be done.

Draw, Point, Multiple Point, enter co-ordinates of one point (x,y) and press enter, repeat for all points

Draw, Spline, select all then points you made

To make sure your cursor knows how to find these co-ord points you created. (They will appear as dots), go to

Tools, Object Snap settings, select nearest, under running object snap settings.

I always go to Tools, Object Snap settings, and check endpoint and intersection. In combination with the pick box size it tells the software what to do. Actually just to make changes. Many things like this can be saved.

press F2 to see the commands/ review the co-ords you entered. F2 again to close the window

You could plot points on paper for 0 to 90 degrees, connect the dots with a french curve, cut it out and use it as a template, flipping it from right-to-left and upside down as needed.

Get Mastering Autocad by George O'mura. Autocad 2005 is a state of the art cad program. You need a good source of info. You probably can find a lisp routine using Google that will draw it. I suspect Mathcad could draw it.

As I thought, the link will lead you to a free lisp routine.

What's the chances of someone throwing his wine rack up on comparator and measuring the frequency and amplitude of it. The man said he had AutoCAD. Those curves can be drawn in about a minute. Close enough for a wine rack.

You're kidding, right?

You can lay out a curve like this in Autocad just fine though, in Turbocad, you can edit the shape in ways Autocad can't.

Why go to that much trouble entering coordinates? DDE/Direct Distance Entry would be much simpler and faster

Nope, not kidding. Been using it for 25 years, make my living with it. I have a legal seat on my home computer. I know what it can do.