Forums > Specific Focus > Home, Garden & Construction in Mexico

talosian

Aug 12, 2004, 7:41 AM

Post #1 of 15 (7568 views)

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Anyone here a (former) math major? HELP!

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I am redoing a solar heating system on my roof. I need to know the following:

Facts: I am using hose with a 1" outside diameter. I need to make a coil (side by side0 approximately 6' in diameter, 19' in curcumfrence with a center (open) hole of about 28". I liken the center open hold to the eye of a storm.

Question: How many liniel feet of hose do I need to make the coil?

Many thanks for serious responses.

Spock.
"When all logical explanations have failed, we must look to the illogical for the answer.

Rolly / Moderator

Aug 12, 2004, 7:57 AM

Post #2 of 15 (7560 views)

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Re: [talosian] Anyone here a (former) math major? HELP!

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Hi David,

If I understand your question correctly, you are making a coil of hose with 28 turns, each with a length of 19 feet. 28X19=532 feet. Mighty long and mighty heavy. How are you going to support this? It will be heavy when empty, and very heavy when full of water.

Rolly Pirate

Esteban

Aug 12, 2004, 8:52 AM

Post #3 of 15 (7547 views)

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Re: [talosian] Anyone here a (former) math major? HELP!

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since pi X diameter = circumfrence
use inches...you have the first coil = 228 inches
subtract the OD of the pipe (1 inch) from the diameter in inches and use the equation to figure the second coil. Keep doing that for succeeding coils till you have reached the 44th coil which will leave you 28 inches for your eye of the storm.

donwilliston

Aug 12, 2004, 8:58 AM

Post #4 of 15 (7547 views)

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Re: [talosian] Anyone here a (former) math major? HELP!

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Hi,

Puzzles are really neat things when you need an activity during the noonday sun, but your puzzle really stumped me.

Well, 500 feet of hose is not a terribly difficult calculation; but “Hose?”, not flexible copper pipe? And a coil rather than a snake-like flat pattern. A coil is great around a stove pipe on New Hampshire, but in California you may want a flat collector. Anyway, 500 feet of 1” OD hose will not have enough flow to do much heating.

Don’t get me wrong, I’m not busting you, I just can’t picture your system.

don

---
"It's good enough to be true" Gracie Maurahan 1970
---

tonyburton

Aug 12, 2004, 10:07 AM

Post #5 of 15 (7535 views)

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Re: [talosian] Anyone here a (former) math major? HELP!

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Assuming you mean a flat coiled hose with a hole in the middle, try the following (all measurements in inches).
Inner hole has radius of 14 inches.
Outermost coil has radius of 36 inches.
Difference = 22 inches - number of complete coils to complete the shape you describe.
The circumference of an "average" coil is closely approximate to the circumference of the coil that is located midway between the innermost coil (radius 14 inches) and outermost coil (radius 36 inches) - i.e. the coil that has a radius of 25 inches.
Circumference of this coil is 25 x 2 x pi = approx. 157 inches.
There are 22 coils in total, therefore lineal length of hose required = 22 x 157inches = 3454 inches or 288 feet.

(This post was edited by tonyburton on Aug 12, 2004, 11:06 AM)

Rolly / Moderator

Aug 12, 2004, 2:48 PM

Post #6 of 15 (7511 views)

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Re: [tonyburton] Anyone here a (former) math major? HELP!

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After reading these other posts, I realize that I had the wrong vision of your coil. Follow Tony's advice.

Rolly Pirate

kwkuster

Aug 12, 2004, 8:32 PM

Post #7 of 15 (7479 views)

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Re: [talosian] Anyone here a (former) math major? HELP!

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I don't feel like taxing my brain tonight but I think Tony proposed a linear solution to a non-linear problem. If Tony is sure, go for it - otherwise maybe we should go around again on this one

alex .

Aug 13, 2004, 8:04 AM

Post #8 of 15 (7457 views)

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Re: a round straight line with a hole in the middle

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or Archemedes Spiral. Yep, 22 turns is correct. Here is a calculator that you can use to tinker with the size of the hole, the outer diameter and the diameter of the hose;
http://www.classictesla.com/java/cst.html
Once you know the number of turns, then follow Tony's method of multiplying total number of turns by the length of the average turn.
Alex

(This post was edited by alex . on Aug 13, 2004, 8:05 AM)

kwkuster

Aug 13, 2004, 3:58 PM

Post #9 of 15 (7427 views)

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Re: [talosian] Anyone here a (former) math major? HELP!

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Thanks to the magic of excel, I spent two minutes making a spread sheet calculating the circumference of each spiral, added them up and got about the same answer as Tony did. The flaw in his logic, and mine, is that we have the solution for 22 concentric circles not a spiral. However the answer is a good enough estimate. Buy 10 or 20 feet extra anyway.

(This post was edited by kwkuster on Aug 13, 2004, 4:01 PM)

talosian

Aug 13, 2004, 9:06 PM

Post #10 of 15 (7407 views)

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MANY THANKS TO ALL

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Yes, Tony had the correct idea. I had one coil and it was about 285' and worked out to 20 rings with a slightly larger "eye." Now I will be getting about 1500' in 100 meter coils and putting it on my roof to replace the broken and cracked hose to get the solar heating system for the pool working. These things must only last 1-3 years in this sun and then they crack and fall apart but I'll see on this one.

Spock
"When all logical explanations have failed, we must look to the illogical for the answer.

tonyburton

Aug 14, 2004, 8:48 AM

Post #11 of 15 (7391 views)

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Re: [talosian] MANY THANKS TO ALL

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Glad we could help. When's the grand pool opening? We'll all try and be there!! Tony

Rolly / Moderator

Aug 14, 2004, 12:30 PM

Post #12 of 15 (7383 views)

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Re: [tonyburton] MANY THANKS TO ALL

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I'd like to have a pool party at my house. Everybody is invited. Be sure to bring your own shovel. Smile

Rolly

Esteban

Aug 14, 2004, 1:52 PM

Post #13 of 15 (7378 views)

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Re: [Rolly] MANY THANKS TO ALL

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You'll need some jackhammers too in that soil eh Rolly?

Rolly / Moderator

Aug 14, 2004, 3:07 PM

Post #14 of 15 (7377 views)

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Re: [Esteban] MANY THANKS TO ALL

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No jackhammers here. We sit on an antediluvian lake bed. Just solid dirt with almost no rocks here on the valley floor. Very different story in the near-by mountains -- stone quarries there. When we dug the various footings for the Las Casas project, I don't recall that we hit a single rock.

Rolly Pirate

Esteban

Aug 15, 2004, 12:05 PM

Post #15 of 15 (7351 views)

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Re: [Rolly] MANY THANKS TO ALL

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Sounds like good gardening possibilities!