Yes it does - that would be helpful.
Here is my coil :
N = 11
t = 0.125" (3.175mm)
w = 3" (76.2mm)
spacers = 0.125" (3.175mm)
IR = 1.75" (44.5mm)
OR = 3.87" (98.4mm)
Thanks y'all
Ok, I've posted the formula(s) over on ABSE.
I notice an inconsistency with your measurements. Imagine starting at the
inner radius and moving outward. You should pass through 11 strips of .125
thickness and 9 insulating spaces of .125 thickness. This adds up to 2.625
inches, which when added to the inner radius of 1.75 inches should give an outer
radius of 4.375 inches, not 3.87 inches.
Or, working backwards, if you have an outer radius of 3.87 and an inner radius
of 1.75, this gives a winding depth of 2.12. Subtracting the total thickness of
11 strips of .125 gives a remainder of .745 to be divided into 10 insulating
spaces of .0745, not .125. I used .0745 in the example calculation, so the
winding pitch (distance from center-to-center of two adjacent turns) is .0745 +
..125 = .1995" = .50673 cm.
A subtlety in the use of these formulas is that when there is insulating space
between the turns (denote each space by d), you must imagine an insulating space
d/2 on the inside of the inner radius, and d/2 on the outside of the outer
radius. So if you measure the inner radius (call it r1') right up against the
copper and the outer radius (call it r2') similarly, the "true" inner radius to
be used in an inductance formula would be r1 = r1'- d/2 and the "true" outer
radius would be r2 = r2'+ d/2. But notice that the average radius, a, is the
same whether calculated as (r1 + r2)/2 or (r1' + r2')/2. Since the formulas I
posted don't explicitly use r1 and r2, you can use r1' and r2' to calculate the
variable a.
But the winding depth c must be calculated as r2 - r1, not r2' - r1'. Another
way to do it which always avoids errors is to measure the pitch (p) of the
winding and calculate winding depth c as n * p.