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I was of the opinion that the oval tank held 10 gallons of fuel, but I just ran the tank size through my calculator and it shows it should hold

8.8 gallons. Do my calculations hold up or did I miss something?

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The 1922 and 1924 owner's manuals both say ten gallons.

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it is difficult to mathematically figure the content of an oval tank. If you average the height and depth you will not get it right,.

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8.8 or 9 sounds about right.

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Easy way to tell is fill it completely, take two 5 gallon containers to drain into, and see if it fills them both.

You can see the fuel easily through the filler opening so you don't over flow it if it doesn't hold exactly 10 gallons. I do know the round one does.

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I went out and checked the dimensions on my roadster tank and ran it them through my calculator again and it does come out at 8.8 gallons.

I was building some fuel gauges and was using one of those old dip sticks to get an idea of how tall the thing had to be, but everything was way off.

Out of curiosity I compared a few of the dipsticks I have and there are no two of them the same. Am not sure where they came up with the gallons per inch on them.

Well, I guess we know now!

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The gas gauge stick that Macs sells is graduated to ten gallons for the round tank but only nine for the oval tank, even though there is room on the stick for ten gallons and beyond.

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I think my stick also goes to 9 for the oval. Any more then that there is no room for expansion and a lot just sloshes out the vent hole.

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Service bulletin for July 15th 1920 gives the gallons in graduated measurements for the Square, Round and Oval tanks. All 3 tanks are shown up to 9 Gals ea.

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My stick shows a 10 gallon mark for ovals but when you put it in the tank the 10 is sticking out, the 9 gallon mark would be very full.

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I have a question (again). I always thought the oval tanks measured 10" high by unknown because I don't have one but more than 10" wide by 28" long since the round tanks are 10" dia. X 28" long. I've always thought this because why else would Henry (the other one) have bothered to change the tank design if not to increase capacity?

A round tank calculates out to 9.52 gallons. If my assumptions on the size of an oval tank are correct wouldn't that mean an oval tank has a capacity of something more than 9.52 gallons since the area of the oval cross section is more than the 10" diameter round tank cross section?

I suppose one obvious answer is that I'm wrong about the oval tank size, but if that's so why were they changed?

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I understand the reason for the oval tank was to lower the seat.

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I measured my oval tank to be 8.00 x 12.00 by 27.50 inches. It is my understanding that the tanks used on the Canadian cars were calibrated for imperial gallons so they were a different size.

Too blasted cold to go out to the barn and measure a few more so I will just make the assumption that they are the same as this one. Do those measurements sound good to you guys?

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My understanding is the same as Steve's -- the tank was reshaped to lower the seat. The oval tanks are wider and about two inches less tall than the round ones. I have a hundred or so vintage wooden gas gauges, and virtually all of them indicate 10 gallons for round tanks, and 9 gallons for oval tanks and '26-7 tanks.

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Thanks guys! I now know that my assumption about the oval tanks being 10" tall was wrong. I guess lowering the seat didn't occur to me because I have an early TT so it just didn't seem to make sense, but it does now.

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I can't help myself, they hold 8 Imperial Gallons! Heh, heh...

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I can't help myself, they hold 8 Imperial Gallons! Heh, heh...

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I've always understood it that the ovals held 9.5 gallons...but hey if it's got 1/2 more...woohoo, that's win win, lol.

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area of an ellipse (oval) is Pi * a * b where a is the semi- major axis (half the long axis) and b is the semi- minor axis (half the short axis)

therefore given measurements from above major of 12" and minor of 8"

Pi * 6 * 4 = 75.39822369 square inches.

then given tank length of 28" ?

we get 2111.150263 cubic inches.

given 231 cubic inches in a gallon

we get approximately 9.14 gallons.

given a tank length of 27.5 inches we come up with approximately 8.98 gallons.

Have never measured my oval tank so I took measurements from above, but if a person could make them full they would be 9.14 or 8.98 gal. depending on actual length. Given we would never fill them full we will not reach 9 gallons in the tank.

oz

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I checked mine with water and it was 10 gallons. Now doing the math of volumes/weights, the math says 10.7 in gasoline.

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volumes and weights would be difficult because pounds per gallon will change with expansion.

at 72 degrees F gas weighs 6.25 lbs/gallon

above 72 6.25 lbs would be more than a gallon

bellow 72 6.25 lbs would be less than a gallon.

given Gas expansion is minor I don't think we could get 10 gallons to expand to 10.7 gallons it would take a 1000 degree temp change. yikes.

therefore after all the googling and math, I think the measurements of the tank I used must be off, or there must be some variation in tank sizes.

oz

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oops extra zero

10 gal. expanded to 10.7 gal. would take 100 degree temp change.

oz

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If anyone is interested, here are the inch-gal calculations for the oval tank.

1 gal = 1.340 inches 1 5/16

2 gal = 2.195 inches 2 3/16

3 gal = 2.950 inches 2 15/16

4 gal = 3.666 inches 3 11/16

5 gal = 4.360 inches 4 3/8

6 gal = 5.070 inches 5 1/16

7 gal = 5.820 inches 5 13/16

8 gal = 6.660 inches 6 5/8

9 gal = 7.900 inches 8 inches

10 gal is on the ground under the car

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Larry;

The on the ground part, I found that out!