How much Gross Grain is left on the roll

[nacra533]

For the DIY or gear maker, it's nice to know how much gross grain, or tape, or whatever else is left on a roll, without unwinding it. I found these two formulas online and they agree with each other. I have not measured them, but they agreed with what was printed on one of my rolls of grossgrain.

L=pi*(r2^2 - r1^2)/t where

L= length of tape remaining in inches
pi=3.14
r2 = outer radius of roll in inches
r1 = radius of the cardboard core in inches (typically about .072")
t = thickness of the grossgrain in inches (typically about .0165")

Another one using diameters is:

L=pi*N*(D+d)/2 where

pi=3.14
N=(D-d)/2*t
D= outer diameter of roll in inches
d= diameter of cardboard core in inches (typically 1.45")

I use the formula in excel and enter the diameters and thickness and let Excel do the rest. I convert the the total length measurement to feet and yards. Actually having the measurement in feet is more beneficial to me making gear.

[GrizzlyAdams]

For the DIY or gear maker, it's nice to know how much gross grain, or tape, or whatever else is left on a roll, without unwinding it. I found these two formulas online and they agree with each other. I have not measured them, but they agreed with what was printed on one of my rolls of grossgrain.

L=pi*(r2^2 - r1^2)/t where

L= length of tape remaining in inches
pi=3.14
r2 = outer radius of roll in inches
r1 = radius of the cardboard core in inches (typically about .072")
t = thickness of the grossgrain in inches (typically about .0165")

Another one using diameters is:

L=pi*N*(D+d)/2 where

pi=3.14
N=(D-d)/2*t
D= outer diameter of roll in inches
d= diameter of cardboard core in inches (typically 1.45")

I use the formula in excel and enter the diameters and thickness and let Excel do the rest. I convert the the total length measurement to feet and yards. Actually having the measurement in feet is more beneficial to me making gear.

The first is intuitive---the area of a ring with given inner and outer radii, divided by the thickness. An approximation to what happens when the tape wraps around itself, but seemingly fine if t is small relative to (r2-r1). The second says exactly the same thing, but it seems odd to me to create D^2 - d^2 by the product (D-d)*(D+d) and then get rid of the extra 2 from D^2 = (2r)^2 with two separate divisions by 2. Huh.

[Shug]

I love when ya'll talk and type like that!!!!!
Shug.... Math Dolt

[Old River Rat]

I would just have to keep track of how much I have used from the roll. Or unroll it and measure.

[Syb]

I have absolutely no idea what Nacra and Grizz are talking about

Syb

[lonetracker]

not enough

[rjcress]

Uh...
was any of that in English?

It must be, I recognized the word DIY.

[nacra533]

The first is intuitive---the area of a ring with given inner and outer radii, divided by the thickness. An approximation to what happens when the tape wraps around itself, but seemingly fine if t is small relative to (r2-r1). The second says exactly the same thing, but it seems odd to me to create D^2 - d^2 by the product (D-d)*(D+d) and then get rid of the extra 2 from D^2 = (2r)^2 with two separate divisions by 2. Huh.

I thought the second one was more clutzy as well, although they give exactly the same result. When I punched it in to Ecxel, I used the fmla with the radius, then immediately miscalculated because I entered diameter. I changed my input to diamter and divided it by 2.

Here is one
http://answers.yahoo.com/question/in...9131009AALIEzO

Here is the other.
http://www.newton.dep.anl.gov/askasc.../math99015.htm

[GrizzlyAdams]

I thought the second one was more clutzy as well, although they give exactly the same result. When I punched it in to Ecxel, I used the fmla with the radius, then immediately miscalculated because I entered diameter. I changed my input to diamter and divided it by 2.

Here is one
http://answers.yahoo.com/question/in...9131009AALIEzO

Here is the other.
http://www.newton.dep.anl.gov/askasc.../math99015.htm

yeah. The intuitive one comes from the hoi polli on the Internet, and the clutzy one from Argonne National Laboratories. Your tax dollars at work

[WV]

Dutch and I divided a large amount of amsteel by weighing it. (I weighed it and gave Dutch half; he hasn't complained yet.) You could do the same thing with gross grain. Might even be easier, since it's probably not wound on a core.