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Technical Bending header tubing...

Discussion in 'The Hokey Ass Message Board' started by CNC-Dude, Mar 26, 2019.

  1. CNC-Dude
    Joined: Nov 23, 2007
    Posts: 887

    CNC-Dude
    Member

    I'm sure many on here have done it with a manual bender like a JD2 or similar. Were you pleased with the bends? Any wrinkles or kinks? Who's bender did you use?
     
  2. Atwater Mike
    Joined: May 31, 2002
    Posts: 10,154

    Atwater Mike
    ALLIANCE MEMBER

    My bud has a muffler shop, Huth bender...sliding mandrels, nice bends, no wrinkles/kinks, but some 'thinness' of cross section at the instep of sharp bends.
    Was Jerry Huth the original patent holder of this marvelous design???
    I remember the power tube bender being introed in Hot Rod Magazine, early '60s...

    But the first mechanical ones came from an independent mfr., L.A. or San Fernando Valley?
    ...took some square footage of shop area, a friend had one...I thought it was like Manna from heaven! Bend tube, master anything. Same problem as the big one in tight bends...
     
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  3. Mike VV
    Joined: Sep 28, 2010
    Posts: 1,979

    Mike VV
    Member
    from SoCal

    Also watch out for the inner radius being pushed into the tube...
    That is, the tube diameter is less in the bends than it is in the unbent areas.
    I've never seen a muffler shop bender NOT do this to some extent...hence the need for mandrel benders.

    This is the big reason for "section" headers. Buying sections and welding them together as required.
    Then if you want them smooth, grind the welds flush. A bit of work, but it...works.

    Mike
     
  4. wvenfield
    Joined: Nov 23, 2006
    Posts: 5,077

    wvenfield
    Member

    I made mine with sections. If someone can do it otherwise without a proper mandrel bender then dang, good for them.
     
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  5. jimmy six
    Joined: Mar 21, 2006
    Posts: 6,677

    jimmy six
    Member

    That's what I do. I bought a lot of J bends with an extra 90* from a supplier, sometimes Speedway, 1-5/8" and 1-3/4"cut and weld what I need. Granted they are not show quality but do the job I need. They have different radii which also helps.
     
  6. CNC-Dude
    Joined: Nov 23, 2007
    Posts: 887

    CNC-Dude
    Member

    Yes, I would intend on using a mandrel.
     
  7. lake_harley
    Joined: Jun 4, 2017
    Posts: 1,012

    lake_harley
    Member

    I have a JD2 bender and with the 1 3/4" die that has a 5.5" or 6" centerline bend radius it will bend down to 16 Ga. but it will almost always slightly wrinkle the inside of the bend. As far as I'm concerned 5.5" or 6" radius is still quite a large radius for headers. I think to do something with a tighter radius to make the bends smooth and not thinned in the bend as mentioned above, the tube would almost have to be bent on a bender that uses an inside mandrel. Just my opinion.

    Lynn
     
  8. seb fontana
    Joined: Sep 1, 2005
    Posts: 6,519

    seb fontana
    Member
    from ct

    Yes..Had tube benders at work that would bend 2.5 dia x .035 wall stainless steel tube in a real tight radius, some where around 4" at center of tube..
     
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  9. CNC-Dude
    Joined: Nov 23, 2007
    Posts: 887

    CNC-Dude
    Member

    Anyone try the filling the tube with sand trick to help with wrinkles or kinks?
     
    Paul likes this.
  10. There are instrument companies who freeze a liquid inside the bell of trumpets/trombones/etc to make a clean bend in the tapered brass tubing... wonder if that would work for steel?
     
  11. wvenfield
    Joined: Nov 23, 2006
    Posts: 5,077

    wvenfield
    Member

    If you can weld at all (if not, that is why they make grinders) it's not that hard to make them off bends. I think I only have a bit over $100 in mine. (I got the flanges for free).

    I know mine aren't a thing of perfection but for a first try........they will be fine.

    gasserpontiac.jpg
     
  12. CNC-Dude
    Joined: Nov 23, 2007
    Posts: 887

    CNC-Dude
    Member

    I'm just looking to get as nice a bend as possible in thin wall tubing and wondering if a simple manual bender and die can provide that.
     
  13. wvenfield
    Joined: Nov 23, 2006
    Posts: 5,077

    wvenfield
    Member

    It can make nice bends. It's not going to make completely wrinkle free bends. IMO.
     
  14. Bending a tube comes with the natural consequence of both shrinking and stretching or all of one and none of the other.
    The stretching on the outside of the gives you some material thinning and the shrinking on the inside gives you the wrinkles. Without any thinning along the outside you'll have plenty of wrinkles and without wrinkles you'll have lots of thinning.
    The mandrel controls the shrinking whike letting it stretch around the outside with no wrinkles and the muffler shop bends don't stretch too well or too much and they can't shrink tubing the best but they can crowd the metal on the short side and got the wrinkles to prove it.
     
  15. Paul
    Joined: Aug 29, 2002
    Posts: 14,886

    Paul
    Editor

    Something I've always wanted to try, well ever since junior high metal shop anyway, the teacher had put together a box with several burner heads and said with it you could make a tube bend like a wet noodle
     
  16. RidgeRunner
    Joined: Feb 9, 2007
    Posts: 856

    RidgeRunner
    Member
    from Western MA

     
  17. Stueeee
    Joined: Oct 21, 2015
    Posts: 220

    Stueeee
    Member
    from Kent, UK

    I had tried this with limited success, but was given a "hands on" tutorial from a mate of a mate who has been building/rebuilding space frame era racecars for a living for many years.

    The "trick" to get a wrinkle free bend without the tube collapsing is to limit the heat input and limit where the heat goes. Ian used a heating rose on an OA torch. He just brought up a dull red spot on the outside of where the bend was to start, took the torch away, pull the tube round to start the bend, reheat the tube to a dull red slightly further forward on the tube, pull it round a bit more and repeat along the tube to form the bend, It's possible to get a fairly tight radius by this method, but not as tight as a mandrel bend. The sand needs to be well packed in the tube and absolutely dry -I baked some building sand in the oven at home before I started.

    The only picture I have of work done this way is on my off topic racecar. All the bends including the roll bar and home made exhaust headers were done by the sand packing method -the rear 2 into 1 was actually two part bends welded together to get the very tight radius in an attempt to equalise the secondary tube lengths.
    [​IMG][/url]

    The Aluminium coolant tube in this picture was bent using sand packing too -obviously Ali doesn't get red hot, but smearing bathroom soap on the tube and heating it till the soap turns black indicates the right temperature to start bending.
     
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  18. Somewhere on the hamb is a Video of a Japanese craftsman making MC exhaust headers. Great one to watch
     
  19. 1946caddy
    Joined: Dec 18, 2013
    Posts: 1,674

    1946caddy
    Member
    from washington

    Haven't done any headers but I bent these tubes for my Cad frame. welded one end solid and pour and packed dried sand in the tube. I then pounded a wood dowel in the other end. I bent them on my steel work bench (1" thick) around a jig, clamping one end. You need to make it long so you have someyhing to hold onto, it gets hot. When I removed the wood plug,I had to tap the tube to get the sand and newly formed glass out of the pipe.
    003.jpg
     
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  20. seb fontana
    Joined: Sep 1, 2005
    Posts: 6,519

    seb fontana
    Member
    from ct

    NO! The thin wall is the problem..1/8th wall 2" is not a problem but when you get down to 14/16 gage the tubing needs inturnal support at the tangent of the bend.. I don't think anything else works..
     
    Last edited: Mar 31, 2019
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  21. dreracecar
    Joined: Aug 27, 2009
    Posts: 3,029

    dreracecar
    Member
    from so-cal

    If you can't cut the middle of the bend, rotate 180*,and fuze weld it back together without rod, then the bend is garbage. Preformed bends are too cheap for the results not to use
     
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