Math problem (excel formula)

[ebea]

Hi all! Are there out in the Forum, one or other person, with good math understanding? I need some help, to find a way to calculate an outer measure (outer to outer of the bend), on a pipe which are bended 2 times, in an angle on 180 degrees on each, and to make a formula in Excel, for this!
I can best illustrate it, with a drawing. I have uploaded the drawing on Dropbox, as I cannot post attachments here!
I know D = Total lenght of the pipe
I know A = inner diameter of the bend
I know B = gap on the pipe
I need to find C

https://www.dropbox.com/s/32b8iv2ze5mw29k/pipe-bend.png?dl=0

Thanks

 

[Sam_ExcelVault]

I feel that the formula part might be relatively simple once the math problem has been solved!

Is the total length of the pipe ‘D’ the inner or outer length?

Also, do you have example numbers for the known lengths that we can use?

 

[jtakw]

Hi,

I also need to know the Thickness or overall diameter of the Pipe itself, do you have that?

 

[ebea]

Hi, and thanks for reply! Let me put in some measurements, to make it maybe a bit easier.
D is the total lenght (outer), and can be as example = 166 mm (small measurements)
The pipe thickness can be 6 mm
But the A, B, D is measurements which can be changed in cells, which holds these numbers. I need to end up with a calculation in a cell, where the result C is shown up. It's for calculation of the outer lenght on a Antenna Dipol (yagi antenna).

I hope this help.

 

[ebea]

Hi, and thanks for you'r reply! Look into my answer in #4 . I hope it cover what was missing in original question

 

[jtakw]

Hi, and thanks for reply! Let me put in some measurements, to make it maybe a bit easier.
D is the total lenght (outer), and can be as example = 166 mm (small measurements)
The pipe thickness can be 6 mm
But the A, B, D is measurements which can be changed in cells, which holds these numbers. I need to end up with a calculation in a cell, where the result C is shown up. It's for calculation of the outer lenght on a Antenna Dipol (yagi antenna).

I hope this help.

Hi,

This should be accurate to the extend that the Bends at both ends are perfect Half Circles, if not, at least this should get you started on building the logic for a formula:

Book1
	A	B	C	D	E
1	Inner Bend Diameter	Gap Length		Total Length	Pipe Thickness(Diameter)
2	15	10	30.177	166	6
Sheet21

Cell Formulas
Range	Formula
C2	=(D2+B2-2*PI()*(A2+E2*2))/2+A2+E2*2

A B D and E2 are user input values.

 

[ebea]

#6 - Thanks you jtakw - But something is not correctly, as the result can't be so! If I try to make a calculation with you'r formula, and take a "real" example, with a lenght (actually it's a wave length, determined from a frequenzy). The higher Frequenzy, the shorter the length will be. But the Bend will still be nearly the same, and also the Pipe thickness!

Length = 166 mm
Inner bend = 25 mm
Gap = 15 mm
Pipe thickness = 6 mm
It gives a result with you'r formula, on 11.3 - But the result should be close to 65.0 in this case

 

[jtakw]

Sorry, I used the diameter rather than the radius in my formula, this one is corrected:

Book1
	A	B	C	D	E
1	Inner Bend Diameter	Gap Length		Total Length	Pipe Thickness(Diameter)
2	25	15	69.38054	166	6
Sheet21

Cell Formulas
Range	Formula
C2	=(D2+B2-2*PI()*(A2/2+E2))/2+A2+E2*2

 

[ebea]

Thank you, jtakw - it was a great help - I could'n "crack the Nut"

 

[jtakw]

You're welcome.