DTSFab.com (Desert, Trail and Sand)
The Machine Shop => Tools/Tips and Tricks => Topic started by: fabr on July 05, 2009, 05:05:10 PM
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What formula is there to determine a radius of an arc if you know the distance between the end points and the height of the arc at its' apex above a line connecting the end points?
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Square 1/2 of span.
Divide by rise.
Add rise.
Divide by 2.
;)
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or if you want that in its correct format.....
edge of the circle is b (at a 90 degree angle to a)
then (^2 equals "squared"):
(((a/2)^2)+(b^2))/2*b =radius
or half a squared plus b squared divided by 2 times b.
I think the degrees are (atan(a/2)/(r-b))*2
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WTF? is that oz speak? Seriously I didn't understand a bit of that. Thanx for the help but now I need a lot more help it seems.
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I knew there had to be a formula, but not knowing it this is how I would have figured it out before the days of Cad.
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Square 1/2 of span.
Divide by rise.
Add rise.
Divide by 2.
;)
so,if the span is24" with a 6" rise- we have 12" squared =144"/6=24+6/2=15" radius?
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Precisely. In fact I just used your figures and used a piece of cable to check it. It is indeed a 15" Rad. In fact to 'prove' the calc I just measured out your figs on a piece of paper and a piece of cord to check it......
(https://dtsfab.com/proxy.php?request=http%3A%2F%2Fi293.photobucket.com%2Falbums%2Fmm54%2Fartieonedge%2F06072009315.jpg&hash=e832ab7d9e9c1607c07c8a9a9fe0876e3d929082)
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WTF? is that oz speak? Seriously I didn't understand a bit of that. Thanx for the help but now I need a lot more help it seems.
Nah...Aus speak is much worse than that... just simple caclulus...... 8)
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Anybody want the calcs for determining just how many more cc's a rebore will gain? Thats easy too.... let me know if you want it... ;)
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I think Im a postwhore.... :-\
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Anybody want the calcs for determining just how many more cc's a rebore will gain? Thats easy too.... let me know if you want it... ;)
THAT I can do and YES you are a post whore.I should know one when I see one ya know!
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:-\ :'( I can reform.... with help an dcounselling....
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The formula....Who gives a shit. Cad will figure it for ya. ;D
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Precisely. In fact I just used your figures and used a piece of cable to check it. It is indeed a 15" Rad. In fact to 'prove' the calc I just measured out your figs on a piece of paper and a piece of cord to check it......
Oh the wit!!!
Fab it's called a Chord.
http://www.ajdesigner.com/phpcircle/circle_segment_chord_c.php (http://www.ajdesigner.com/phpcircle/circle_segment_chord_c.php) (first link off google)
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The formula....Who gives a shit. Cad will figure it for ya. ;D
On the down side, it'll make you look real stoopid when you can't explain "why it is so"?
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On the down side, it'll make you look real stoopid when you can't explain "why it is so"?
Something like the example, I don't care why it is, just that it is, I can draw it faster than I can work the math (which I really can't seem to grasp anyway), and I can now prove that it is by using the results CAD gave me and working backwards.
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Something like the example, I don't care why it is, just that it is, I can draw it faster than I can work the math (which I really can't seem to grasp anyway), and I can now prove that it is by using the results CAD gave me and working backwards.
Does one equal the other?
In maths, you can't "prove" anything without understanding it from first principles ;)
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Does one equal the other?
In maths, you can't "prove" anything without understanding it from first principles ;)
I'm gonna end your fishing trip right now.
I give up.
You do it how you want, I'm just gonna nod my head, then do it my way.
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I'm not fishing for anything - I'm refuting the premise "ignorance + CAD is a valid substitute for knowing"... its NOT.
Look at it like this: You don't know what you don't know, until you know it.
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and when the power supply is interupted during your long hot summer....do you stop buggy building because you cant calculate that problem?
Im not critising you (or anyone...cept prolly Fabr.... cause thats fun... mmm.... and Spec... and maybe Bug... maybe Eng to... perhaps the Yumster...oh it goes on..) but Trojans right (althoug a little outspoken as is his want...).
There is no substitute for knowing stuff.... it really does enrich your life.. (im being serious now)....
I used this line on Fabr a during one of our 'set to's' some time ago ...... there is none so blind as he who will NOT see.... you do things your way... whatever makes you happy.... ;)
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All this BS for a simple formula.LOL!!!!!!!! Thanks for the info guys.
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and when the power supply is interupted during your long hot summer....do you stop buggy building because you cant calculate that problem?
I do have books, but I am not going to open them till I have to. :-*
CAD is quick, easy, and doesn't make mistakes.
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I do all my math the old skool way ;D
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Yeah,I take off my shoes too.
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Don't take off your shoes in here unless your replacing them with hip waders. ;D
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All this BS for a simple formula.LOL!!!!!!!! Thanks for the info guys.
and you are surprised ??? ( I think not.... :D)....
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Don't take off your shoes in here unless your replacing them with hip waders. ;D
and a quick smite for you too mate.. ;D
Hip waders? Do you reckon the crap is flowin that deep?
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I do have books, but I am not going to open them till I have to. :-*
I'm sure you do. Will they be of any use when for the last 10 years they've been proppoing up the wonky table?
Ignorance is no crime.... but stupidity is ;)
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Yeah,I take off my shoes too.
jj:
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I'm sure you do. Will they be of any use when for the last 10 years they've been proppoing up the wonky table?
Ignorance is no crime.... but stupidity is ;)
Personally I see no ignorance or stupidity in using CAD to get the answer. I myself prefer to know how to do things several ways to get an answer. I mean I like using CAD but if the cad is not available then it's nice to know the math behind it also. If someone prefers one over the other I have no problem with that either. Using cad is not stupid. Nor ignorant. I WAS ignorant of the formula but not stupid enough to not ask for it.
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I wasn't implying stupidity. I meant ignorance is not stupidity. beter?
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Me better now and I agree completely. ;D ;D