melpaul2002

I have a roll of tape that is 50 meters long and 0.5mm thick.

I need to make a new roll that has an outside dimension of 800mm and an inside dimension of 700mm.

How many meters / rolls will it take to create the bigger roll and what is the formula.

Ralf

Shall the forum do your homework you miserable little cheater?

melpaul2002

not exactly home work ! but yes please.

Regards

dnb

Never been one for doing other people's homework...

Work out the area of the side of the roll of tape.

((800/2)^2 * pi)-((700/2)^2 * pi)

Now equate that to the area of tape. so the above expression = X mm of tape multiplied by 0.5mm.

Be careful with the units

Hope this is right. Been a long tome since I've done any maths

[Edited by dnb - 9/9/2002 7:57:33 PM]

[Edited by dnb - 9/9/2002 11:21:07 PM]

[Edited by dnb - 9/9/2002 11:36:38 PM]

Ralf

What is the diameter of the old tape roll?

Ralf

better try ((800-700)/0,5)*((700+800)/2)*pi

Ralf

Erm, dnb, it's not right.

And it can hardly be longer ago than my math courses.

Now come to the board, wipe away the wrong formula and write it again correctly.


Ralf

melpaul2002

Now you have both lost me with the equations, its actually for a product I want to make at work.

The final thought is to get an accurate cost for something.

each small roll 5.5mm wide x 0.5mm thick x 50 meters costs $0.785

If I knew how to work out the Sq Inch cost I could calculate the final cost.

OD in Inches Divided by 2 X itself x 3.142 memory +

ID -------------------------"-------------- memory -

Memory recall = Total number of SQ Inches required.

So the price per Sq Inch is..................

Ralf

Well, if the roll consist of 200 layers of tape (200*0,5=100 just as OD - ID; 800-700=100) with an average diameter of 750mm (as in (700+800)/2).

The formula for the circumference is diameter*pi

Multiply this with the number of mean layers

750mm * 200 * pi = 471.238,898mm = 471,239m

Pretty big roll of tape

Its cost would be: 0,785/50 = 0,0157 $/m multiplied with 471,239 m = 7,39845 $(Dollar?!)

You owe me a roll of tape, nah make that a beer!


Ralf

Clarebabes

That's an accountant for you!

Ralf

Hi Clare, indeed counting the days 'till ring time

Oh, I have a notion you husband inquires about a TVR, oops.


Ralf

melpaul2002

Ralf, you are very clever, Are you saying the roll will have 200 layers knowing what the other dims are ? or is this just an example.

surely to make the bigger roll will not take 431,000 meters, maybe 431 would be more like it !

Yr helps appreciated.

Ralf

The roll will have 200 layers as one layer is 0,5 mm thick. 200 of them will bring the inner diameter of 700mm to 800mm (700 + (200*0,5) = 800)which are your requested dimensions.

Now you have the smallest diameter measuring 700mm * pi. The next layer would measure 700,5mm * pi, the next 701 * pi and so on another 198 times until 799,5 * pi and 800 * pi.

In this case, to save you the maths, you can assume that in the middle the circumference is 750 * pi and as the mean of all 200 layers you may replace all the 7xx,x measures with it. (Allowed here because the formula is simply 'diameter * pi' without any ^2 or so)

So you have 200 layers of tape at a medium diameter of 750mm (=0,750m).

This gives you 200* 0,75m *3,14 = 471 meters and 23 cm and 8 mm and a bit more.

Hope that helps



Ralf

dnb

with copy and paste things sometimes goes astray...

Happy now?

dnb

Can you stop hitting me now please?

Ralf

OK, OK



feel better now?

er, you male or female?

dnb

male.

I should be more careful with cut and pasting formulas. Oh well...


Was I right in assumuing the 50m * 0.5mm was the length and thickness of the unrolled tape?

Ralf

Yes.

Would you accept a padding on the shoulder instead of above smileys?

Yes? Oh, fine.


Ralf