Need to measure some cylindrical storage tanks for their diameter

[DrPizza]

Go to a hardware store. Get a couple of pieces of 1/2" CPVC and a union (to make it long enough). Get a couple 3/4" CPVC T's. They'll slide over the 1/2", but will be a little tight. Make a giant caliper this way. Hold one end on the edge of the tank. Slide it across the tank - the widest point of the tank (diameter) will push the other tee out the farthest. Climb down, measure. No math involved (since you can't do it the simple way of measuring the circumference.)

 

[Howard]

Go to a hardware store. Get a couple of pieces of 1/2" CPVC and a union (to make it long enough). Get a couple 3/4" CPVC T's. They'll slide over the 1/2", but will be a little tight. Make a giant caliper this way. Hold one end on the edge of the tank. Slide it across the tank - the widest point of the tank (diameter) will push the other tee out the farthest. Climb down, measure. No math involved (since you can't do it the simple way of measuring the circumference.)

Doctor, you are a miracle worker.

 

[Squisher]

How accurate do you have to be? Plus or minus an inch? Plus or minus a foot?

The reason I asked this is if you only have to get the dimension within a foot you could probably could make a number of big radius gauges. You might be able to be even more accurate than I think.

They sell an Arc Master Radius Gauge ($120)

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=120374788669

 

[zinfamous]

Sub it out to someone in India

best answer.

 

[edro]

Wrap a rope around the tank.
Tape it as you go, keep it taught.
Divide length of rope by 3.141.

 

[Squisher]

Doctor, you are a miracle worker.

If Doc's idea would work because you have access from above you could make yourself a crude set of dividers out of some 1/4" hardboard too.

 

[her209]

Step 1: Wait until sun comes out.
Step 2 Measure width of the shadow cast.

FUCKING WIN!!!

 

[gorcorps]

Go to a hardware store. Get a couple of pieces of 1/2" CPVC and a union (to make it long enough). Get a couple 3/4" CPVC T's. They'll slide over the 1/2", but will be a little tight. Make a giant caliper this way. Hold one end on the edge of the tank. Slide it across the tank - the widest point of the tank (diameter) will push the other tee out the farthest. Climb down, measure. No math involved (since you can't do it the simple way of measuring the circumference.)

We need a MacGyver smiley

 

[lord_emperor]

Step 1: Wait until sun comes out.
Step 2 Measure width of the shadow cast.

FUCKING WIN!!!

You could accomplish this at night with a flood light and some math too.

 

[biostud]

why do you need to know the diameter?

 

[Miramonti]

Use a paperclip.

 

[endervalentine]

hahah, sweet, got a new interview question now

 

[3chordcharlie]

You could accomplish this at night with a flood light and some math too.

But then you coudn't use a sextant.

 

[ElFenix]

We need a MacGyver smiley

no bubblegum wrapper involved

 

[ArJuN]

Measure its shadow and divide by the hour. Simple.

 

[Howard]

why do you need to know the diameter?

Relocating the tanks into "holes".

 

[Throckmorton]

Measure its shadow and divide by the hour. Simple.

The width of the shadow is always going to match the width of the tank, regardless of the time of day

 

[IronWing]

Use the measuring tool in GoogleEarth.

 

[Howard]

Use the measuring tool in GoogleEarth.

Indoors

 

[IronWing]

Two measuring tapes and two 2x4s or other long straight things (pipe, rod, etc) of equal length both longer than diameter of tank.

Lay the rods on opposite sides of the tank such that each rod touches the tank wall. Run a measuring tape from the end of one rod to the end of the other. Repeat with second tape on other ends of rods. You will have sort of formed a rectangle. Adjust the angles of the rods with respect to each other until the two tapes show the same distance, making sure the angle between the tapes and rods are 90 degrees. The measurement given on the tapes is the diameter.

 

[ussfletcher]

You know.. you could just estimate.. make a line on the floor with chalk about even with both sides and measure across.. D:

 

[Howard]

You know.. you could just estimate.. make a line on the floor with chalk about even with both sides and measure across.. D:

Hmm... two spirit levels could get me pretty damn close.

EDIT: Or plumb bobs. Can I do it with three, so that it doesn't matter if I've got diametrically opposed points or not? Is it possible to calculate the diameter of a circle given a triangle whose points all lie on the circle?

 

[DrPizza]

Hmm... two spirit levels could get me pretty damn close.

EDIT: Or plumb bobs. Can I do it with three, so that it doesn't matter if I've got diametrically opposed points or not? Is it possible to calculate the diameter of a circle given a triangle whose points all lie on the circle?

Yes. The point where the perpendicular bisectors of the sides of the triangles meet is the center of the circle. (Circumcenter.)

 

[Howard]

Yes. The point where the perpendicular bisectors of the sides of the triangles meet is the center of the circle. (Circumcenter.)

I think they teach you this stuff in high school so you can forget it later... thanks!

 

[Skyclad1uhm1]

Mail Mythbusters that according to your colleagues it cannot be measured in a conventional way.