Tube Bending

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rudog
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Re: Tube Bending

Post by rudog » Sat Dec 03, 2011 5:40 pm

Thanx, Jim. I've got Gary's CD and the pdf files. (thanx, Gary. They are a big help.) It's come to my understanding that the dies themselves are not a round, but, rather an elliptical profile to prevent flattening.

I've been searching the net all day for specifics and even the Balleigh guru doesn't know the formula for how much ellipse is recommended. I know the follower die gets the ellipse. I'm not sure about the former die.

I can't find an affordable 9" slug. I've redesigned to use 2"x2" bar stock 6" long. It's what I got. Conveniently, that will allow a 60deg bend. The largest bend I need is 55deg for the goose neck. As soon as I can get a handle on this profile, I'll be cutting, welding and turning.

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Re: Tube Bending

Post by hansgoudzwaard » Sat Dec 03, 2011 6:07 pm

*elliptical*...I had no idea. I need to check my CD when I get back. Although , it won't make any difference at this point.

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rudog
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Re: Tube Bending

Post by rudog » Sat Dec 03, 2011 6:45 pm

hansgoudzwaard wrote:*elliptical*...I had no idea. I need to check my CD when I get back. Although , it won't make any difference at this point.
It will to me Hans. This information is not on the CD. Yes, the shape of the forming die is round, but, where the tube is round, it should mate into an elliptical seat on the follower die. Gary's plans show a round seat. Perhaps, I'm overthinking again.

Found this http://www.jalopyjournal.com/forum/show ... ?p=6965503
ellipse.JPG
ellipse.JPG (13.24 KiB) Viewed 1200 times

hansgoudzwaard
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SELF INTRODUCTION: I was on the last board as bonustoolkit. I have changed that to my given name.
I started a project build there " File and Fit." I paln to continue that when I go back home in Dec. 2011. I first joined the board when Gary W had it in the year 2005. That was the time I really gained an interest in building chops. I have a long way to go, compared to some here.

Re: Tube Bending

Post by hansgoudzwaard » Sat Dec 03, 2011 7:17 pm

*Perhaps, I'm overthinking again*.....I would not count it out. The frames bent on home benders on past CHB boards did not mention flattening , deforming, that I recall.

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rudog
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Location: Texoma

Re: Tube Bending

Post by rudog » Sat Dec 03, 2011 8:36 pm

That's good information. Flattening of a bend gets worse with thinner wall thickness. If it's good for worse case, it may be usefull for best case, but as you suggest, may not be necessary. Thanx.

I'll start making my dies. If all works , I'll post the results.

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Re: Tube Bending

Post by gww25 » Sat Dec 03, 2011 8:54 pm

The elliptical shape of the follower may actually be a clycloid or whatever it's called. Even on thick wall tubing you will be able to see a slight deformation in the tube on the inside of the bend if it goes through a semi-circular follower as compared to one that is even slightly oval. The one in the picture is far more out of round than is necessary to prevent flattening. Most people just live with a little flattening as it's almost umpossibkle to see if you don't know what you're looking for.

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Re: Tube Bending

Post by Maz » Sun Dec 04, 2011 8:13 pm

Here's the main frame rails for my GS550 project after I've done the first bends - look as closely as you like - the tube looks fine and after checking the die tonight, I can confirm this was done with a circular section die....
GS550 Bobber 045.jpg
GS550 Bobber 045.jpg (137.82 KiB) Viewed 1183 times
and here it is on the jig...
GS550 Bobber 061.jpg
GS550 Bobber 061.jpg (194.01 KiB) Viewed 1183 times
I guess there are many schools of thought on this but it probably comes down to a combination of using the right materials and the appropriate tools.....

Maz xx
Blonde, blue eyes, English Custom Bike builder and Biker Mistress!!!

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