Cubic inch question

[firerod]

I have a Ford 8ba that has been bored .040 over and has a Merc. crank. What cubic inch does this come out to? Thank you and sorry for my ignorance.

[tubman]

261.8 (let's call it a 262).

[V8COOPMAN]

Originally Posted by tubman

261.8 (let's call it a 262).

That tubman sure knows how to punch a calculator....on the money! DD

[tubman]

Originally Posted by V8COOPMAN

That tubman sure knows how to punch a calculator....on the money! DD

Yeah, but I didn't have to look up the mathematical formula required. When I was in college taking physics, calculating devices (slide rules in my day) were OK during tests. They were checking your knowledge of Physics, not your math abilities.

[V8COOPMAN]

Originally Posted by tubman

Yeah, but I didn't lave to look up the mathematical formula required. When I was in college taking physics, calculating devices (slide rules in my day) were OK during tests. They were checking your knowledge of Physics, not your math abilities.

I've known that formula (by heart) since junior high. And I do it the ".7854" way. DD

[terry]

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Okay, I'm game. What does that fraction represent. Never did that well in physics. Terry

[leon bee]

So is my .080 over gonna be 269?

[cadillac512]

268.33


(pi X bore radius squared x stroke x 8)

[leon bee]

Thanks cad, guess I better say 268.

[firerod]

Thanks, that's what I came up with but was told it was wrong.

[V8COOPMAN]

Originally Posted by terry

Okay, I'm game. What does that fraction represent. Never did that well in physics. Terry

Hey Terry....

OK, "0.7854" is a function of pi, accurate to at least four decimal places.

0.7854 = 3.1416/4 or (3.1416 divided by 4).

Example: Bore X Bore X Stroke X .7854 X 8 (cyls.) = Cu. In.

Your FIRST Example:

Bore = 3.1875 + 0.040 = 3.2275

Stroke = 4.0

Constant = .7854

Number of Cylinders = 8
__________________________________

So: 3.2275 X 3.2275 X 4 X 0.7854 X 8 = 261.80224

[frnkeore]

I do it slightly different.

I punch in the bore (3.2275), then I hit the squared button (² ), after that, I multiple by .7854, then times stroke (4) and finally, times 8 = 261.80225148

Darn, I got a different answer, what happened

One of the nice things about using .7854, is that on number pads, it is the top, left hand corner keys. Makes it a little easier for me.

[leon bee]

It would take me 10 years to understand why you square the bore measurement.

[Mart]

You square it because you want the area of the cylinder.

Area of a circle is Pi r squared.

Because we know the bore rather than the radius, we have to use the alternative formula that uses the diameter.

Area of a circle is pi d squared all over 4. (over = divided by)

Volume of one cylinder of a stock 239 for example is:

3.1875 * 3.1875 * 3.1416 / 4 Which equals 7.9798. Unit is square inches.

Volume of a cylinder = area * length.

So 7.9798 * 3.75 = 29.9242. Now the unit is cubic inches. So just shy of 30 cu in.

Volume of the engine is volume of one cylinder times the number of cylinders.

So 29.9242 * 8 = 239.3936

Rounded to 239 for ease of reference.

I used a known engine because we are already familiar with the answer.

In the examples above the shortcut is to use pi/4. 3.1416/4 = .7854.

The above formulae are completely universal and by using centimeters the volume in cc can be calculated.

Mart.

[terry]

thanks, fellas. Terry

[ford38v8]

In my dotage now, my sliderule days are long forgotten, but you can do more today with a $6.99 drugstore calculator than the best sliderule ever made.
My old sliderule was never much good for making straight lines anyway, with that bumpy thingy right there in the middle.
I will say though, I had a round one once that helped me earn free pizza in my sports car rally days. (Back in the day, you'd have to tell them if you didn't want anchovies.)
Come to think of it, I guess I could have used my sliderule to determine how much beer was in a "'Yard of Beer' Stein".

[DavidG]

Mart,


With respect, if we know the bore diameter, we automatically know the radius as it is one half of the diameter.

[adileo]

Who says one only remembers 5 minutes of what they learned in 5 years of college?

You guys have proved them wrong��

[ford38v8]

Originally Posted by adileo

Who says one only remembers 5 minutes of what they learned in 5 years of college?

You guys have proved them wrong��

Aw, I retain very fond memories of a few 5 minute sessions in college!

[Randy in ca]

Originally Posted by adileo

Who says one only remembers 5 minutes of what they learned in 5 years of college?

You guys have proved them wrong��

Determining the area of a circle is taught about grade 6 or 7.

[DavidG]

Some learned it as 2piR squared and others as Dpi squared; either way the answer comes out the same.

[V8COOPMAN]

Originally Posted by DavidG

Some learned it as 2piR squared and others as Dpi squared; either way the answer comes out the same.

David.....Believe me, I KNOW how smart you are. There's no disputing that fact..........PERIOD! But respectfully, "2piR squared" ain't gonna cut it. You've given me cause to take aspirin already trying to make YOUR formula work. So.....I believe you meant "pi(r)squared", or pi(r)(r). No?

And "D pi squared" doesn't seem to work, either. And Sir....I blow it every now and then, too! DD

[JayChicago]

I think David just made a mistake by including the words “squared”. Circumference of a circle is 2PiR or Dpi. But neither is squared.

[DavidG]

Caught me guys! Man, getting old ain't no fun. Actually the two are equal, but you're right, not for the purpose at hand.

[tomcarman]

At the risk of offending some. A hillbilly decided to go to college to study math. He comes home on holiday. Ma asks what he learned in math. He says; "Ma, I learned Pi r squared". Ma says; "No no son, Pie are round".

[GB SISSON]

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Originally Posted by tomcarman

At the risk of offending some. A hillbilly decided to go to college to study math. He comes home on holiday. Ma asks what he learned in math. He says; "Ma, I learned Pi r squared". Ma says; "No no son, Pie are round".

... And cornbread r squared"

[tomcarman]

Originally Posted by GB SISSON

... And cornbread r squared"

What if it were a cornbread muffin?

[tomcarman]

As long as we're on the subject of "corny".
Ma does a little studying of her own. She asks; Alright son, what is 2 Pi R? The son thinks a minute and replies; "Why Ma, 2 Pie are better than 1".

[Frank Miller]

the .785 method is not so much a function of Pi but it is in lieu of Pi when plugging the diameter into a formula. For example if the diameter is 4 you readily know the radius is 2. But if the diameter is 3.187 you might not readily see that divided by 2. Because you are squaring the diameter you need to divide Pi by 4 or 2 squared.

[V8COOPMAN]

Originally Posted by Frank Miller

the .785 method is not so much a function of Pi but it is in lieu of Pi when plugging the diameter into a formula. For example if the diameter is 4 you readily know the radius is 2. But if the diameter is 3.187 you might not readily see that divided by 2. Because you are squaring the diameter you need to divide Pi by 4 or 2 squared.

Hmmm...! Not so much a function of pi...? OK then, but ".7854" does just happen to be the quotient when performing the "function" of ascertaining what 1/4 of 3.1416 might be, or more simplistically....3.1416 divided by 4! I'm not sure that I understand what is in question here.

If I simply punch "3.187² X 4 X .7854 X 8 =" into the calculator (it took me about 6 seconds to perform), I don't have to worry about finding radii or any other details. That simple ".7854" becomes an integral part of THIS formula. This seems (to me) to be a lot simpler than having to first determine the figures necessary to extrapolate for the formula "πr²". And THAT only yields the area of the circle. Now, ya still have to figure-in the height for the volume, and then multiply by the number of cylinders. "My" way takes care of "pi", and ALL of that other superfluous BS....just to figure out how big your flattie (or your Chevy, etc.) is.

"Bore X bore X stroke X .7854 X 8 =" .....easy, peasy! DD

[Mart]

Understanding how the .7854 was arrived at and knowing how it is calculated from first principles is the most important thing.

[V8COOPMAN]

Originally Posted by Mart

Understanding how the .7854 was arrived at and knowing how it is calculated from first principles is the most important thing.

I UNDERSTAND where it came from. The best part is that it works oh so well, EVEN for those folks that MIGHT NOT understand the "whys". DD

[PeteVS]

Originally Posted by adileo

Who says one only remembers 5 minutes of what they learned in 5 years of college?

https://www.youtube.com/watch?v=kO8x8eoU3L4

Oh, and if you divide cubic inches by 61, you get liters so you can live in the modern world...

[tubman]

I just usually divide by 60 to get litres; it's easier to do quickly in your head. Close counts in hand grenades, horseshoes, and now, engine displacement.

[Frank Miller]

Originally Posted by V8COOPMAN

Hmmm...! Not so much a function of pi...? OK then, but ".7854" does just happen to be the quotient when performing the "function" of ascertaining what 1/4 of 3.1416 might be, or more simplistically....3.1416 divided by 4! I'm not sure that I understand what is in question here.

If I simply punch "3.187² X 4 X .7854 X 8 =" into the calculator (it took me about 6 seconds to perform), I don't have to worry about finding radii or any other details. That simple ".7854" becomes an integral part of THIS formula. This seems (to me) to be a lot simpler than having to first determine the figures necessary to extrapolate for the formula "πr²". And THAT only yields the area of the circle. Now, ya still have to figure-in the height for the volume, and then multiply by the number of cylinders. "My" way takes care of "pi", and ALL of that other superfluous BS....just to figure out how big your flattie (or your Chevy, etc.) is.

"Bore X bore X stroke X .7854 X 8 =" .....easy, peasy! DD

You're still using Pi. You've just simplified the formula. Pi is the function as it relates to the circle.

[glennpm]

"The number π (/paɪ/) is a mathematical constant. It is defined as the ratio of a circle's circumference to its diameter, and it also has various equivalent definitions. It appears in many formulas in all areas of mathematics and physics. It is approximately equal to 3.14159. It has been represented by the Greek letter "π" since the mid-18th century, and is spelled out as "pi". It is also referred to as Archimedes' constant.[1][2][3]"


From https://en.wikipedia.org/wiki/Pi which also has a neat graphic.

[V8COOPMAN]

Originally Posted by Frank Miller

You're still using Pi. You've just simplified the formula. Pi is the function as it relates to the circle.

No kidding?

Did I not mention something about "pi" back in post #11? I'm not understanding the overall point that you're trying to make here! DD

[Phil Gillespie]

i am enjoying the Maths update lessons it sure takes me back.
Was there also a recent movie out called " The Life if PI".
I still enjoy doing mental numbers in the head to keep brain active.
Phil NZ

[GB SISSON]

I am in awe of the math skills shown here. I once trimmed out the interior of a house that had two round turrets. Watching my progress , our high school's math teacher, who had taken a painting job for the summer, asked me if I would be willing to come to the high school on career day in the fall and talk to the students about how I use math in my job. Well about mid September he called me and outlined what I'd need to discuss in my 45 minutes. Yikes! all I could think of was the strings and nails and routers bolted to long plywood strips that I used instead of math. I ended up declining his offer, as I had spent a career teaching myself how to do my work without using math. Sometimes we can work around our shortfalls on a relatively simple task and get by. Just don't ask me to offset grind your merc crank to 4 1/8". I could not begin to understand the math involved!

[Mart]

"Just don't ask me to offset grind your merc crank to 4 1/8"

If you can do that with a router and string I'd like to see it.

[old Tom]

Originally Posted by tomcarman

At the risk of offending some. A hillbilly decided to go to college to study math. He comes home on holiday. Ma asks what he learned in math. He says; "Ma, I learned Pi r squared". Ma says; "No no son, Pie are round".

corn bread r square

[GB SISSON]

Originally Posted by Mart

"Just don't ask me to offset grind your merc crank to 4 1/8"

If you can do that with a router and string I'd like to see it.

C'mon Mart.... That takes two strings and an angle grinder. Can someone show me the cubic inch displacement of my stationary engine? One cylinder, 6" bore, 12" stroke.

[Mart]

Yeah. I'll walk you through it.

bore * bore * pi /4 *stroke*no of cylinders

6*6 = 36
36* 3.1416 = 113.0976

113.0976/4 = 28.2744

28.2744 *12 =

339.2928 * 1 = 339.2928

So your single cylinder motor is 339.3 cu in.

[Mart]

Duplicate.

[GB SISSON]

Thank you very much Mart! The brass tag on it states that it produces 8 hp at 300 rpm. I run it at 75 rpm.

[ford38v8]

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Originally Posted by GB SISSON

Thank you very much Mart! The brass tag on it states that it produces 8 hp at 300 rpm. I run it at 75 rpm.

I was thinking hit and miss till you said that.

[GB SISSON]

Originally Posted by ford38v8

I was thinking hit and miss till you said that.

https://www.youtube.com/watch?v=ot5EaCZk5vo
Hit n Miss I did a lot of tuning to get it this slow. It was given to me because it was stuck and the head was missing so I freed it and made a wood pattern for the head and had it cast. In 1989.

[flatford8]

You could’ve been getting a load of laundry done while you were there.......I think watching and listening to one of those motors is to me, the most relaxing thing.....kinda like watching cows graze and chickens peck the dirt.....that’s quite a collection you have Gary!!!!.....Mark

[GB SISSON]

The big stover is mine and I have a 3hp as well as some old air cooled stuff. I sold the gas powered maytag washer. About 5 of us set up in that area every year for the last 34 years at Lynden Wa, in August. I feel smarter now that I understand that formula. Thanks

[V8COOPMAN]

Originally Posted by GB SISSON

I feel smarter now that I understand that formula. Thanks

In your case: 6 X 6 X 12 X .7854 = 339.2928

DD

[GB SISSON]

Originally Posted by V8COOPMAN

In your case: 6 X 6 X 12 X .7854 = 339.2928

DD

Wow! Too easy! I'm starting to like this math thing.