snipped-for-privacy@yahoo.com wrote in news: snipped-for-privacy@z14g2000cwz.googlegroups.com:
In the days before computers and fancy stuff, we used nails, sheet metal or thin wood. Layout the points of the peaks and valleys (or wave points if you prefer) and spot a 4d nail at the point. Take the sheet metal (
1" wide x 20 - 24 ga. ) and weave it through the nails. Trace the pattern and now you know the rest of the story.
Make a template. Lay out a grid. Use a spreadsheet to plot points. Use a French curve to connect the dots. Read up on how to use a French curve.
State of the art as long as you don't compare it to Inventor, Alibre, Solidworks, Solidedge, Catia, Mastercam, Surfcam, ect, ect. AutoCAD survives for two reasons, name and the fact that a great many people don't need the power and flexibility that other programs provide. In the industry I'm in, aerospace, AutoCAD has long been a has-been. Seen from time to time but generally only in low level support roles.
You've had all sorts of answers for how to do this with various computer programs (or a pocket calculator), but here's another way that doesn't involve anything but a compass, straightedge and protractor, and you can lay it out directly on the board:
1.) Draw a horizontal line down the middle of where you want to put the sine curve, with the ends aligned with where you want the ends of the curve to go. Call this the "center line" 2.) Make marks (call them "section marks") to divide this line into equally-spaced sections, one section for each up-and-down-and-back-up of the sine curve that you want. Mark off divisions of each of the sections into 16ths. 3.) Set the compass to draw circles with a diameter equal to the height of the sine curve that you want to draw. Draw a half-circle centered at each end of the center line, so it looks sort of like a C at the right end and a reverse-C at the left end, and the center line goes from the center of one half-circle to the center of the other. 4.) With the protractor, mark off angles on each half circle, at every 45-degree point, and every 22.5-degree point between these. 5.) Draw lines parallel to the center line by connecting the tops and bottoms of the half-circles, and each corresponding pair of angle-marks. 6.) Go back to the marks you made in step 2. Starting at the left-hand end of the center line, draw a line perpendicular to the center line that goes all the way up to the top line. Put a dot where it crosses the top line. (You don't actually need to draw the perpendicular line; just draw the dot. But it's easier to explain if I say to draw the line.) 7.) Go to the right along the center line. For the next mark, draw another perpendicular line and dot, but put the dot where it crosses the second line from the top. For the next one, draw the dot on the third line, then the fourth, and so on. When you get to the bottom, start going back up. If you've counted right, you should get back to the top line when you get to the first section-mark. Keep going until you get to the other end. 8.) Connect the dots. If you're not good at sketching smooth lines, use a french curve or something.Obviously, the division into 16ths and the angles I picked are somewhat arbitrary -- just so long as you divide the sections on the center-line into twice as many divisions as you divide the half-circles into, it will work out. If you're using drafting triangles instead of a protractor, 12ths and marks at 30-degrees and 60-degrees will work well. Or, if you're good at sketching with only a few dots (I'm not), just make marks at 45 degrees and divide it into 8ths.
Is that clear enough, or should I do up some sketches and post them?
- Brooks
you could use something like this:
| you could use something like this: | |
-- Morris Dovey DeSoto Solar DeSoto, Iowa USA
well thats helpful
That's a pretty good idea. Plotting points, but no need to calculate their values.
Josh
if you enter the co-ors in the size you need
File, Print, select extents, deselect scaled to fit
do a FULL preview to not only see the outline of the objects, but the actual innards. Select each time. Multi-preview before printing.
if it takes up the whole page, but in the wrong direction, change the rotation 90. Thats for scaled to fit. origin is if it is offset, integral with the other print settings required = to center it, for instance
Your welcome.
LOL. Well if it is there why not use it. ;~)
I cheated once. Took a coffee can lid and made a hole very near the outside edge for a pencil.
Put a straight edge at the bottom where the sine wave was to go and rolled the lid across the straight edge, marking the plywood.
The cutting and sanding were much, much more of a problem than the layout. I gave up after a few attempts, because even the smallest error is noticeable be everyone. Just a guess but the wine rack mentioned by OP might hide small errors in the sine wave due to other objects which would draw the eye.
Phil
{snip}
When I need to make a curved cut in a piece of wood, I make a pattern from 1/4" hardboard and pattern-route it. Hardboard is easy to cut and sand smooth and if you make a mistake or cut a little too deep, you can fill/repair it with a little 5 minute epoxy and file it smooth.
Once the pattern is perfect and smooth with the curve I want, I attach it to the wood and route it. The end result is wonderful and perfect the *first* time with very little sanding.
Plus, in some of my woodworking I often make many of the same items, several at a time over a period of time. The pattern allows to me to make perfect pieces time after time and very quickly.
Joe Barta
[snip]
That's what I was going to suggest. It's easy, and you can easily scale the sine curve as large or small as you like by choosing an appropriately-sized circle. Since all that's required is a compass and straightedge you don't even have to leave the shop.
If this thread is about making support cutouts for wine bottles, I believe you should be talking ellipses or parabolas, not sine curves. Much simpler formulas too. Bugs
Well, thanks everybody for the replies. Apparently there are about 15 ways to skin this particular push stick.
-Phil Crow
That's a cycloid, not a sine. Still far and away the easiest is to use a graphing program like Graphmatica [download from archives.math.utk.edu ...it's awesome and free.] Type in y=sin(x) ENTER, and you then print from there or copy/paste into a word processor. Less than a minute if you have both programs up and running.
It can be done by hand, it can be approximated by hand. ifthat's good enough then that's the best way, but most people don't have a clue on how to do that.
Now, let's empty this can of worms and get on with it.
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