Can anybody calculate, this odd size gas tank, volume.

In my coupe, plan on making a tank, that fits perfectly behind the seat and gives me maximum trunk space.
How much gas will this thing hold??????

36" wide, 18" tall, 16" deep with a angeled back.

Thanks, Chris
Here is a little sketch, I made.

 

About 33.7 gallons

 

Figure the volume in cubic inches and devide by 231 = gallons.

You may have to guess at that angled part....

 

Great, thanks.

 

That's it! I came up with 33.66

 

Or think of it as $143 a fill up

 

(corrected 7/24/08......formulas were right but I had punched in the wrong numbers)

I broke down the problem this way:

1) isolate a rectangular section L=18" W=8" H=36"
2) volume of the rectangular section is L*W*H=5184 in^3
3) convert to gal => 5184 / 231 = 22.44 gal
4) remaining right-triangle prism with Base=8" Height=18" and L=36"
5) volume of the prism is 1/2*B*H*L = 2592 in^3 = 11.22 gal
6) summing the two parts 22.44 + 11.22 = 33.66 gal

quite a bit of fuel.

=Chad J.

 

Bigger than your bladder, thats all that matters anyway right???

 

Briggs is on the right track, but he's made a basic math error. His treatment of the isolated rectangular box is good. But he divides the entire "prism" as he calls it by 2, when only the base x height needs that function, then you multiply that by the length. In other words:

8 x 18 x 36 = 5184 cu in
8 x 18/2 x 36 = 2592 cu in

5184
2592 added together equals 7776 cu in. times .00433 (conversion factor from cu in to gal) equals 33.6701 Gallons as noted in one of the first answers.

and I told my math teacher I'd never need this stuff...

dj

 

If you put two of them togeather wouldn't it be 24 X 18 X 36? Then you just do the math and divide by two?

 

I got the same... 33.66gal

 

I guess I'm mathmatically lazy. I'd build it, seal it, fill it with water, then start filling 5-gallon buckets with the water and see how many I filled.

 

Hey, dont make it so easy, some if these math whiz's are trying to impress us!

 

There's a formula for odd shapes, but there's a slight amount of approxiamating involved. But, I come up with about 31. I'm a lousy guesser

 

I actually need that in "Imperial Gallons" not US gallons
Just kidding, thanks for the info, I even got Groucho to use his calculator.

 

Now I feel mathematically fucking stupid.

 

Looking back, Rich Fox had the best answer.

 

Overtons might have a ready made tank in that size? www.overtons.com


Hmm, just looked, they dropped the one I was thinking of and the prices went up in the last year or so!

 

I am a math teacher and these calculations are correct. Propwash, you get an A+. If you want Imperial gallons it would be 28.03 Imperial Gallons.

 

Thomas Eddison hired a fresh collage grad . He gave him a light bulb glass fixture and said tell me the volume of it.
This young man did all the math and spent quite alot of time to come up with a number. It was wrong Eddison said fill it with water and pore it into a graduated container. I like simple

 

For a simple shape like that,there should be no guessing involved.

 

I hear ya! I almost always have to stop for a piss sooner than I need to stop for fuel.

 

Thats alot of fuel.... remember with that many gallons its gonna weigh alot... so spring it correctly too!!! My tank is small but hangs off the back half and surprizingly lowers the car alittle filled compaired to empty... but maybe thats cuase I have so few leafs in the rear

 

It is about 33.7gal. But before you start cutting metal, I think that 19-1/4" actually needs to be closer to 19.7" if you want the opposite side to have 2 right angles.

 

My sixth graders learn this one.... you essentially turn the thing into a rectangle.

Formula for area of a trapezoid = (b1 + b2 / 2) x height


Take the top and the bottom measurements, add them together, and then divide by 2.
In this case, 8 + 16 = 24... Divide 24 / 2 = 12

So now, take the simple volume formula L x W x H (12 x 18 x 36) = 7776 cubic inches

Divide 7776 / 231 = 33.66 gallons

 

33.67 gallons?!?!?!? What are you building a cross country runner??? If you only got 15 mpg you would have more than a 500 mile range. That's like ten hours of driving.

A quick google says gasoline weighs 5.8 to 6.5 lbs per gallion. That's a load of ~195-220 lbs in fuel. You might want to design the fuel tank to sit low in the car to help handling when loaded. If it's mounted high it'll have a negitive effect when full.

 

I stand corrected with my previous numbers. I edited the post....my formulas were correct but I had punched in the wrong numbers. Either way - I made the wrong answer. 33.67 it is.

As my undergrad professor used to say to a class I took on static structures, "You build bridge. Bridge fall down. NO PARTIAL CREDIT!"

 

20.91-ish

Add the top and bottom, 5.25 and 10.25, then divide by 2, 7.75

Add the front and back, 14 and 15, divide by 2, 14.5

7.75 X 14.5 X 43 = 4832.125

Divide that by 231 = 20.91

 

33.7 Gal If you haven't already I would be puttin in some kind of baffles to stop the motion of the fuel , not to mention the noise right behind you

 

Here's one I drew up a few month ago for my One Eyed Roadster. It's in DWG format. If someone can convert it to PDF, it would be helpful. Other wise you will need autoCad to see it...
It's pretty much the same design as the one shown above, just a little smaller.. El Gringo is going to build it for me...