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Discussion Starter #1
is there a math formula to calculate how much extra you need to add for a bend?i dont have the money for a program and i dont want to waste any tubing. i used to have a cheat sheet i made a few years ago but somehow i lost it.go figure.
 

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Discussion Starter #2
if anyone wants to run it thru their program i would greatly appreciate it! im making a bar for over the midplate. from end to end on the plate is 27.750". the one leg is 11" long followed by a 65degree bend up 11.250" followed by a 25 degree bend then 5.500" long down 25degrees. it is then 12" long followed by the other 65degree bend.finally its 11" long for the last leg.
 

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You will actually gain length with the bends. You should be able to add the lengths you have listed there and come up with an length, although I add a little bit extra and usually trim it off after the last bend. I have calcs. to figure the bend starting points, which also accounts for the gain. You'll need the tubing size, desired bend, and the centerline radius of the die you are using.
 

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Discussion Starter #5
c/m. 1.250 x .065 on a 4" radius
 

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I just calculate assuming the centerline of the tube does not change length, and follows the radius of the bend. For a given bend of A°, it is A*pi*R/180. So if it is a 4" radius bend, for say 70°, I assume the bend will use up 70*3.14159*4/180 = 4.89" of tube length.
 

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You need a piece of tubing at least 78.25 long. You will GAIN .558" for the 65 deg bend and .0284 for the 25 deg bend. Once you know where you want the center of a bend, mark it then subtract 2.83 for the 65 deg bend and .9034 for the 25deg. That will be your start of the bend mark. Now heres the tricky part. Once you have the center of your first bend, subtract the GAIN for that bend, then from this mark you measure out to the center of the next bend and repeat the process. You will end up with three marks for each bend, the bend center, the GAIN adjustment, and the bend start. Hope this helps! Its way easier than it sounds, I bought a JD2 bender and using this info bent a funny car cage the first shot! Good luck!
 

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You need a piece of tubing at least 78.25 long. You will GAIN .558" for the 65 deg bend and .0284 for the 25 deg bend. Once you know where you want the center of a bend, mark it then subtract 2.83 for the 65 deg bend and .9034 for the 25deg. That will be your start of the bend mark. Now heres the tricky part. Once you have the center of your first bend, subtract the GAIN for that bend, then from this mark you measure out to the center of the next bend and repeat the process. You will end up with three marks for each bend, the bend center, the GAIN adjustment, and the bend start. Hope this helps! Its way easier than it sounds, I bought a JD2 bender and using this info bent a funny car cage the first shot! Good luck!
WOW! If I could figure numbers like that.....I sure wouldn't be working on race cars.:)
 

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I wish I could say I did it on my own lol! I bought Bickles chassis books from another member on here and they have all the calculations and formulas. Made learning how to use my bender WAY easier!
 

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Nice
 

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i use this simple formula

od of die x 3.1416
divide answer by 360
this gives you the amount of material used per degree of bend .

12" (6"CLR die ) x 3.1416 = 37.6992"
37.6992 divided by 360 = 0.105"

0.105" x 45deg =4.712"
 

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i use this simple formula

od of die x 3.1416
divide answer by 360
this gives you the amount of material used per degree of bend .

12" (6"CLR die ) x 3.1416 = 37.6992"
37.6992 divided by 360 = 0.105"

0.105" x 45deg =4.712"
Yup, that's the same thing I use (just in a slightly different format). It has worked well for me on the one chassis I built.
 

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THUS

it is cheaper to throw away six inches of extra length ( drop off / cutoff) to make the bend length correct


than it is to throw away the whole length of tubing because you made a multiple bend error mistake.
 
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