|
Sponsored Links (Register now to hide all advertisements) |
|
|
Thread Tools | Display Modes |
11-18-2020, 07:06 PM | #21 |
Senior Member
Join Date: May 2010
Location: southeastern Michigan
Posts: 10,101
|
Re: Cubic inch question
Some learned it as 2piR squared and others as Dpi squared; either way the answer comes out the same.
|
11-18-2020, 08:34 PM | #22 | |
Senior Member
Join Date: May 2010
Location: East Shore of LAKE HOUSTON
Posts: 11,108
|
Re: Cubic inch question
Quote:
And "D pi squared" doesn't seem to work, either. And Sir....I blow it every now and then, too! DD |
|
Sponsored Links (Register now to hide all advertisements) |
|
11-18-2020, 09:00 PM | #23 |
Senior Member
Join Date: Jan 2019
Location: Chicago
Posts: 731
|
Re: Cubic inch question
I think David just made a mistake by including the words “squared”. Circumference of a circle is 2PiR or Dpi. But neither is squared.
Last edited by JayChicago; 11-18-2020 at 09:33 PM. |
11-18-2020, 09:44 PM | #24 |
Senior Member
Join Date: May 2010
Location: southeastern Michigan
Posts: 10,101
|
Re: Cubic inch question
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.
|
11-18-2020, 11:48 PM | #25 |
Senior Member
Join Date: Feb 2017
Location: Rochester Wa
Posts: 574
|
Re: Cubic inch question
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".
|
11-19-2020, 12:01 AM | #26 | |
Senior Member
Join Date: Jan 2014
Location: Orcas Island Washington
Posts: 4,926
|
Re: Cubic inch question
Sponsored Links (Register now to hide all advertisements)
Quote:
... And cornbread r squared"
__________________
Owner/Operator of 'Jailbar Ranch' on the side of Mt. Pickett. Current stable consists of 1946 1/2 ton pickup turned woodie wagon with FH V8, 1947 Tonner Pickup (red) mostly stock with exception of a cummins 6at turbo diesel, 1946 Tonner Pickup (green) with 226 cu in 6 cyl flathead, 1979 Toyota landcruiser wagon, completely encased in 1947 Ford Jailbar sheet metal. Ok, cornbinder rear fenders..... 'Rusty ol' floorboards, hot on their feet' (Alan Jackson) |
|
11-19-2020, 12:18 AM | #27 |
Senior Member
Join Date: Feb 2017
Location: Rochester Wa
Posts: 574
|
Re: Cubic inch question
|
11-19-2020, 12:23 AM | #28 |
Senior Member
Join Date: Feb 2017
Location: Rochester Wa
Posts: 574
|
Re: Cubic inch question
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". |
11-19-2020, 09:46 AM | #29 |
Senior Member
Join Date: May 2010
Location: Auburn, MA
Posts: 2,106
|
Re: Cubic inch question
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.
__________________
“The technique of infamy is to start two lies at once and get people arguing heatedly over which is true.” ~ Ezra Pound |
11-19-2020, 05:35 PM | #30 | |
Senior Member
Join Date: May 2010
Location: East Shore of LAKE HOUSTON
Posts: 11,108
|
Re: Cubic inch question
Quote:
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 |
|
11-19-2020, 07:16 PM | #31 |
Senior Member
Join Date: May 2010
Location: Solihull, England.
Posts: 8,749
|
Re: Cubic inch question
Understanding how the .7854 was arrived at and knowing how it is calculated from first principles is the most important thing.
|
11-19-2020, 08:59 PM | #32 |
Senior Member
Join Date: May 2010
Location: East Shore of LAKE HOUSTON
Posts: 11,108
|
Re: Cubic inch question
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
|
11-19-2020, 11:14 PM | #33 | |
Senior Member
Join Date: May 2010
Location: FP, NJ
Posts: 2,770
|
Re: Cubic inch question
Quote:
Oh, and if you divide cubic inches by 61, you get liters so you can live in the modern world...
__________________
Don't never get rid of nuthin! |
|
11-20-2020, 07:50 AM | #34 |
Senior Member
Join Date: Dec 2013
Location: Minnesota, Florida Keys
Posts: 10,312
|
Re: Cubic inch question
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.
|
11-20-2020, 07:56 AM | #35 | |
Senior Member
Join Date: May 2010
Location: Auburn, MA
Posts: 2,106
|
Re: Cubic inch question
Quote:
__________________
“The technique of infamy is to start two lies at once and get people arguing heatedly over which is true.” ~ Ezra Pound |
|
11-20-2020, 11:21 AM | #36 |
Senior Member
Join Date: Sep 2014
Location: Wiscasset, Maine
Posts: 1,981
|
Re: Cubic inch question
"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. |
11-20-2020, 06:37 PM | #37 | |
Senior Member
Join Date: May 2010
Location: East Shore of LAKE HOUSTON
Posts: 11,108
|
Re: Cubic inch question
Quote:
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 |
|
11-20-2020, 06:50 PM | #38 |
Senior Member
Join Date: Sep 2011
Location: Christchurch New Zealand
Posts: 1,611
|
Re: Cubic inch question
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 |
11-20-2020, 07:56 PM | #39 |
Senior Member
Join Date: Jan 2014
Location: Orcas Island Washington
Posts: 4,926
|
Re: Cubic inch question
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!
__________________
Owner/Operator of 'Jailbar Ranch' on the side of Mt. Pickett. Current stable consists of 1946 1/2 ton pickup turned woodie wagon with FH V8, 1947 Tonner Pickup (red) mostly stock with exception of a cummins 6at turbo diesel, 1946 Tonner Pickup (green) with 226 cu in 6 cyl flathead, 1979 Toyota landcruiser wagon, completely encased in 1947 Ford Jailbar sheet metal. Ok, cornbinder rear fenders..... 'Rusty ol' floorboards, hot on their feet' (Alan Jackson) Last edited by GB SISSON; 11-21-2020 at 07:20 AM. |
11-21-2020, 05:25 AM | #40 |
Senior Member
Join Date: May 2010
Location: Solihull, England.
Posts: 8,749
|
Re: Cubic inch question
"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. |
|
|
Sponsored Links (Register now to hide all advertisements) |
|