Shop Math

[Wood_workur]

Post an equation that would be useful in a wood shop.




GUARENTTED EASY way to draw a PERFECT elipse


My son learned this in math today, and I thought I would pass it on.

You all probably know the old trick to draw an elipse- a string and two nails. Now you can calculate the location of those two nails percisely. (the nails are located at the foci, just an fyi.)

First, draw perpendicular axies on you "elipse-to-be" (where they meet is the center)

Now, mark the extents of the elipse.

Then input your distances into this equation:

square-root( a^2[a is the distance from the center to the end of the short axis]- b^2[b is the distance from the center to the end of the long axis])=c [the distance from the center to each of ther foci, which are located on the long] axis.

Now, for the legnth of the string, tie a loop with a circompference that has a length of 2a+c, and slip it over the nails, and draw your elipse.

Now wasn't that easier than trial-and-error, and cheaper than one of those jigs at rockler.

[ted van halen]

Post an equation that would be useful in a wood shop.




GUARENTTED EASY way to draw a PERFECT elipse


My son learned this in math today, and I thought I would pass it on.

You all probably know the old trick to draw an elipse- a string and two nails. Now you can calculate the location of those two nails percisely. (the nails are located at the foci, just an fyi.)

First, draw perpendicular axies on you "elipse-to-be" (where they meet is the center)

Now, mark the extents of the elipse.

Then input your distances into this equation:

square-root( a^2[a is the distance from the center to the end of the short axis]- b^2[b is the distance from the center to the end of the long axis])=c [the distance from the center to each of ther foci, which are located on the long] axis.

Now, for the legnth of the string, tie a loop with a circompference that has a length of 2a+c, and slip it over the nails, and draw your elipse.

Now wasn't that easier than trial-and-error, and cheaper than one of those jigs at rockler.

NOOOOOOOO!!!!! Not the 10th grade geometry again. I thought I'd be done w/ that 20 yrs ago in mechanical drawing. If I need anything layed out precise now I just rely on my Unigraphics workstation at work. I do "occassionally" have to do some manual calculations but a TI-89 takes most of the pain out of that too.

[crokett]

Post an equation that would be useful in a wood shop.




GUARENTTED EASY way to draw a PERFECT elipse


My son learned this in math today, and I thought I would pass it on.

You all probably know the old trick to draw an elipse- a string and two nails. Now you can calculate the location of those two nails percisely. (the nails are located at the foci, just an fyi.)

First, draw perpendicular axies on you "elipse-to-be" (where they meet is the center)

Now, mark the extents of the elipse.

Then input your distances into this equation:

square-root( a^2[a is the distance from the center to the end of the short axis]- b^2[b is the distance from the center to the end of the long axis])=c [the distance from the center to each of ther foci, which are located on the long] axis.

Now, for the legnth of the string, tie a loop with a circompference that has a length of 2a+c, and slip it over the nails, and draw your elipse.

Now wasn't that easier than trial-and-error, and cheaper than one of those jigs at rockler.

crokett decides to never build a project that requires an elipse as he wonders what an extent is.

[Wood_workur]

1/2 the length of the elipse on each axis. It is where the elipse extends to.

And why are you talking about your self in the thir person?


This is hard to descrip without a pic. Maybe I have just encouraged more efficent designs (all square, no curves)...

[ted van halen]

... Maybe I have just encouraged more efficent designs (all square, no curves)...

I support the line as being the shortest distance between two points. Besides, I can't cut a straight line much less a straight curve(!)

[gsmittle]

I support the line as being the shortest distance between two points. Besides, I can't cut a straight line much less a straight curve(!)

Ummmm....Last I heard a curve wasn't straight... So what's the problem?

All this math makes my head hurt. I'm with the guys who only build rectilinear stuff....

g.

[jonathanb3478]

I do "occassionally" have to do some manual calculations but a TI-89 takes most of the pain out of that too.

My project is an elliptical speaker enclosure with one of the ends shaved off for a flat front baffle. I went to math.com and whipped out the trusty TI-85 from highschool. Wow, I forgot how much that li'l TI-85 can do

I now have a couple programs in it for calculating some of the elliptical features of my enclosure (thank God I did not loose its manual!).

[crokett]

1/2 the length of the elipse on each axis. It is where the elipse extends to.

And why are you talking about your self in the thir person?

Cause sometimes crokett feels like a nut...

I'm still gonna stay away from elipses

[wreckwriter]

This brings up a question: can anyone recommend a book which details basic shop math and construction techniques; what angle to use for various things, how to even space things, etc?

[bigsteel15]

This brings up a question: can anyone recommend a book which details basic shop math and construction techniques; what angle to use for various things, how to even space things, etc?

This one.
http://www.leevalley.com/wood/page.a...096,46109&ap=1

I think it's available almost everywhere.

[wreckwriter]

Thanks Brian.

[bfrikken]

crokett decides to never build a project that requires an elipse as he wonders what an extent is.

^^
LOL - very funny!

[drumpriest]

btw, evenly spacing things is fairly simple, just divide the length by the number of "things" plus on.

len / (things + 1)

I love my ti85, in college I wrote all kinds of programs for it, great machine. Now personally, when I need an elipse, I just draw one in my photo editor, print it out, and trace away. Same for most of my curved work, they are most bezier spline representations from my 3D modeller.

[vaking]

What is wrong with you people talking about curves not being straight. Everybody knows that a curve is a slightly bent straight line. It can't get simpler than that.

[Wood_workur]

What is wrong with you people talking about curves not being straight. Everybody knows that a curve is a slightly bent straight line. It can't get simpler than that.

Exaactly- "no- that is really part of the design- I told you the front would be curved" (looks at extreemly jagged table edge!