Angle Question

[Lonnie in Orlando]

Hi guys,

Can you show me how to compute the angle where two faces of a pyramid meet. My old trig days seem to have failed me. I'm stumped.

Given - -
A pyramid with a square base and isosceles triangle sides.

Find - -
The angle where two sides meet.

Thanks for your help,

- Lonnie

[gjat]

You take a baramoter, break it into 3 pieces that are propotionally sized to the sides of the pyramid, then take a compass to measure the angle where the two sides meet and divide by two.


Or you take a barometer and give it to an Egyptian engineer as payment to figure out your angles and lengths.

Quite elementary.

[cabinetman]

Calculating angles of a pyramid.
.

[Mr__Bill]

Do you want the angle as if you measured it on the outside of the pyramid? Or do you want the setup on a compound miter saw of how to cut the two angles when you are building your pyramid and must make the miter joint at an angle too?

If it's the first, then not having a barometer, I use a protractor thingy that has arms and many scales. I hold it to the pyramid and then look at all the scales to see which is about what I thought the angle was and use that answer.

If the second, then kick my self for loosing the chart I got way back when in shop class that gave you the miter setups for such a cut. It's the same as the cut for crown molding when it starts down the stairs (or up). As for the trig., it's been so long that I tend to forget that you can figure things like that out mathematically.

Here is a handy dandy chart that just might help. I think I'll print it out and stick it with my miter saw and then forget where it is....

Hope this at least doesn't confuse too much.

Bill
if I knew where I was going I sure wouldn't be here....

[pelligrini]

I draw it in Autocad.
It's done on a computer, so is that considered computing?

[gsmittle]

You take a baramoter, break it into 3 pieces that are propotionally sized to the sides of the pyramid, then take a compass to measure the angle where the two sides meet and divide by two.


Or you take a barometer and give it to an Egyptian engineer as payment to figure out your angles and lengths.

Quite elementary.

Nicely said, Herr Bohr, nicely said!

g.

[Lonnie in Orlando]

Thanks for your help. I don't think the formulas and charts work for my project. I don't work with bevel/miter combinations, such as for crown molding, so I'm a little dense. I finally figured out a formula that seems to work and put it and other variables into an Excel spread sheet.

FYI - I'm designing a lamp shade similar to this one ...


So I'm looking for the outside angle where two sides meet.

I cut this test piece today. This is a 120* outside bevel. The bottom rail of the shade would meet it at 55*. Results in a square shade.

BTW ... what the heck is a "baramoter"?

Thanks again,

- Lonnie

[LCHIEN]

"Barometer" reference refers to this recent post - apparently you can measure anything with a barometer.

http://www.bt3central.com/showthread...ight=barometer