Frustum Pyramid

[Scrutch]

If I take the square root of this guy I get 325, which is the number I'm looking for. This make sense to you...?

Ok, I'm a mess this afternoon...went for a walk and things seem to be much better now...I think. Started all over on the formula and keyed it in very slowly while paying attention. Even though there is no excuse for user errors like this I would still like to say "Sorry Coach... :?

When I use the negative 1/3 as a multiplier just like I was shown, instead of just the 1/3 the result returned becomes positive...Duhh! As for wondering about using the square root of the result, I kind of forgot that we were solving for Area...Duhhh!

Thanks a lot for the coaching and hand holding. This is going to save me a lot of time on my drawings. I'll let you know on the results of the other three formulas but I haven't seen anything very promising yet. About now I'm wishing I had paid a lot more attention in math class. :roll:

 

[Scrutch]

Word of Warning: I do not know that #3 on my list will always be the correct answer. You may have to take some steps to ensure you have the right one. For one thing, I think you need to do #3 AND #4 and see which is greater, unless someone is kind enough to demonstrate how we might be able to tell. I'm pretty sure #3 is greater, but I haven't actually sat down to work it out. As for #1 and #2, one may also need to calculate those and see that they simply give the wrong volume - then discard them as possibilities. So, you can get the right answer by chekcing in pairs. Try #1 or #2, if you get the wrong volume, then #3 or #4 is the correct answer. If you get the right volume, then #1 or #2 is the right answer. Once you know which pair has the right answer, pick the greater of the two. It's not trivial, but it can be done.

Ok, I've got the math working in AutoCAD and can give you the results of the tests...#3 returns the Area of B1(large base) and #4 returns the Area of B2(small base). #'s 1 and 2 do not match anything I'm looking for...#1 is the fat side of 200' larger than B1 should be and #2 is the fat side of 13' larger than B2 should be.
I've only checked this on a half dozen structures but it appears that it is doing exactly what I want. As soon as I get the structure programmed to read the formula I'll be able to easily check several hundred of these guys very quickly. This is going to be Great for my production drawing time. Thanks is not enough but it comes from way down. Thanks tk...

PnS...Would you be willing to walk me through the other half of my problem? I need to know how big to build the embankment given the volume that comes from the retention pit. These would be isosceles trapezoids with the corners trimed at a 45dg angle...inside and outside. The givens would be the inside toe perimeter, height of embankment, slope of embankment and the volume. So the only variable we would have to adjust with would be the width of the flat portion on the top of the embankment.

 

[tkhunny]

Yikes! Maybe I'm just not in the mood, this afternoon. Can you provide a picture with labeled parts? The enbankment goes ALL the way around?

Obviously, we know already the inside measurements at ground level. They match the sides of the pit, no?

 

[Scrutch]

Yikes! Maybe I'm just not in the mood, this afternoon. Can you provide a picture with labeled parts? The enbankment goes ALL the way around?

Yikes is close...some other descriptors comes to my mind but then I haven't a clue as to what's involved here. Might be able to use some of the formula from before for this or not, I certainly don't know. Pictures are a problem for me as I haven't any place to post them and the forum won't let me post an image from my hard drive... PM maybe...? This doesn't have to be done this afternoon...I wouldn't say "no rush" but it can wait for a bit.

Obviously, we know already the inside measurements at ground level. The match the sides of the pit, no?

Right on...' Most ' of the time the slope is the same as the pit and it's just an extension above ground from the pit walls. Some times they want to use a different slope for the embankment but it's rare. Thanks for the response and if you feel up to the task sometime in the near future just give me a ping. I'd like to thank you for the help on the pit guy, I can NOW draw one of these things in about 20seconds and most of that time is from entering the data into the dialog box. :lol: