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Unread 03-23-2011, 01:31 PM   #1
IrishCJ6
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Bend radius

Can anyone tell me what the calculation for working out the bend radius of a 2" steel tube, want to design something up in CAD

Thanks in advance

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Unread 03-23-2011, 04:31 PM   #2
jeepfreek383
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wouldnt the bend radius depend on the die your using maybe this will help or im just not sure what u mean

example (based on a 7" center line radius die for 2" tubing)
radius (clr) of bend 7.00"
degree of bend 90*


7.00 x 90 x .01745 = 10.9935 tube allowance for that bend

this works for any size tubing just change the centerline and degree
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Unread 03-26-2011, 07:40 PM   #3
dwilliams35
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Definitely depends on the die/roller: I guess theoretically you could get down to a 2" radius if you fold the ID to a straight 90.
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Unread 03-27-2011, 07:32 AM   #4
YJhobby
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It has a lot more to do with what material type, wall thickness, dia, etc... than the die you use.

As a design engineer, I can tell you there has to be a chart out there on the web that could help you. The ones I use are all proprietary, so I can't help ya there... But first you should know the answers to the following:

1) What type of steel are you using? Hot rolled? Some type of DOM? 4130?

2) What diameter? You specified 2"dia...

3) What wall thickness?

With those answered you'll be able to find a chart that list the smallest bend radius allowed for the specific material, wall thickness, and dia.

Most tubing benders have specific dies that meet practically all those criteria, but give a "generic" BR to all the tubes. For an optimally designed tube structure, the BR of each joint would be adjusted (larger or smaller) to meet maximum strength, weight savings, or some other desired parameter...

How are you planning on forming these bends? Odds are you will design to the "low-cost manufacture" design parameter, meaning all your bends will be one radius, so you only need to buy or use one die. Get the die that fits your tubing size, and makes a bend with a radius as big or larger than the chart-specified minimum.
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Unread 03-27-2011, 08:36 AM   #5
dwilliams35
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Quote:
Originally Posted by YJhobby View Post
It has a lot more to do with what material type, wall thickness, dia, etc... than the die you use.

As a design engineer, I can tell you there has to be a chart out there on the web that could help you. The ones I use are all proprietary, so I can't help ya there... But first you should know the answers to the following:

1) What type of steel are you using? Hot rolled? Some type of DOM? 4130?

2) What diameter? You specified 2"dia...

3) What wall thickness?

With those answered you'll be able to find a chart that list the smallest bend radius allowed for the specific material, wall thickness, and dia.

Most tubing benders have specific dies that meet practically all those criteria, but give a "generic" BR to all the tubes. For an optimally designed tube structure, the BR of each joint would be adjusted (larger or smaller) to meet maximum strength, weight savings, or some other desired parameter...

How are you planning on forming these bends? Odds are you will design to the "low-cost manufacture" design parameter, meaning all your bends will be one radius, so you only need to buy or use one die. Get the die that fits your tubing size, and makes a bend with a radius as big or larger than the chart-specified minimum.
I really don't think the question was "smallest bend radius allowed", it was quite simply what the bend radius was so he could work up a project: that being the case, the die is most definitely the most important part: the material will show you the limitations given that die, but you're going to have a heck of a time pulling off a 4" radius with an 8" die no matter what material you use.
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Unread 03-27-2011, 11:09 AM   #6
IrishCJ6
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Thanks for the replies, my main objective was to have a working design measured up prior to starting on the actual Jeep (less wasteage), for this to be somewhat correct I need to find what radius will be pulled especially at the likes of the 90deg bend on the top of the hoops, and say the bend at the windscreen, I will be using 2" seamless tube with a wall thickness of 2.5mm (sorry not sure of imperial equivalent) I haven't got the bender yet so not sure on die radius, the cage will be for a CJ6 jeep so if someone already has a good plan for either the front or rear hoop I would be much appreacitive.
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