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Tubing bender kinking tube

Discussion in 'The Garage' started by tx_sub, Mar 8, 2005.

  1. tx_sub

    tx_sub 1/2 ton status

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    I'm trying to bend some 1.25" OD .049" wall chromoly tubing for a buggy chassis. I have a JD3 bender. Once I go past about 15 degrees it kinks the tube on the inside of the bend. I have the correct dies. Lubricated the tube. What am I missing? Is the tubing just too thin? Any help is appreciated. And if you are asking why that size tube, its for a mini baja car competition that is sponsored by SAE.
     
  2. sled_dog

    sled_dog 1 ton status

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    sounds like tubing is just too thin.

    JD lists the minimum wall thickness as either .58 or .83 depending on what radius you are using.
     
  3. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    yes the tube is too thin
    it depends on the CLR, but from the JD2 site, everything BUT the 3.5 CLR die the minimum thinkness is .058 and the 3.5 CLR is .083
     
  4. tx_sub

    tx_sub 1/2 ton status

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    Bummer. Do you think a little heat would help? My project manager is going to sh*t himself because he thought we could save weight going with this tubing.
     
  5. kgblazerfive

    kgblazerfive keymaster Premium Member GMOTM Winner

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    go old school and put sand inside of the tube it should support the tube enough to bend it, might have to cap and pack it tight but try it
     
  6. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    acording to this weight calculator
    the .049 weights .6285 lbs/ft
    the .058 weights .7383 lbs/ft

    so your saving 2 lbs for every 20 foot.

    you might be able to heat it, but it may get too thin on the outer edge.
     
  7. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    If you heat it it will buckle even worse. I'd try packing it with sand just because...but I'd be prepared to jump up a size of wall thickness. The hard part will be to get the sand packed enough to help, and to keep it that way.

    Rene
     
  8. tx_sub

    tx_sub 1/2 ton status

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    WE ordered about 100 ft of this tubing. Got it in 8 ft lengths to get it shipped fast. Is there an easy way to pack it with sand? I'm thinking duct tape and a funnel. thanks for the input gentlemen.
     
  9. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    Duct tape won't hold the sand good enough you need to use some type of a plug. If the sand has anyroom to move around then you will kink the tubing. Last time I tried this we had to heat up the tube.
     
  10. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I'd say tack weld a cap on one end, fill with the funnel until full, then tack weld another cap on the end. Then bend. That's the way I'd try it anyways.


    Rene
     
  11. tx_sub

    tx_sub 1/2 ton status

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    I tried the sand trick. I used the finest play sand from the home depot. No luck, still kinking. I am sure it can be done. I was checking out other mini baja websites and they use the same tubing. They had some bends that were almost 90 degrees. Is there a different bender that can prevent kinking. I would consider paying a shop or working in an equipped shop to get this tubing bent. If all else fails, mitre't cuts are in order. Anyone else have anything?
     
  12. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    i believe a mandrel would prevent the tube from kinking, not sure where to get it and how to set it up though. i believe the dies are the same.
     
  13. dontoe

    dontoe 3/4 ton status GMOTM Winner

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    If ya was up North, or had access to a huge freezer.

    I saw on a show bending thin wall brass into trumpets by filling them with water and freezing the tubing. Don't know if that would work for the size you're doing but it might!
     
  14. tx_sub

    tx_sub 1/2 ton status

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    the freezing idea is interesting, but not plausible for me. I too would like to know if I can get a mandrel to fit my tube at a reasonable price. problem is "reasonable". Another bit of info I think I should include is that the die I am using is for a 3" radius. I realize now that that is very tight. Could that alleviate my problems? Any one have a 1 1/4" OD 5" radius die for a JD2 bender they want to unload cheap?

    The more work I put into doing this right, the more attractive mitre cuts look. :mad:
     
  15. velocitiii

    velocitiii Registered Member

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    I've bent a few tubes with the sand method. I was on the formula team back in school and do fab work now. like they said, tack weld caps on both ends leaving unwelded area for hot air to escape. then get yourself an unsuspecting brake rotor (or other piece of metal to use as a die) and clamp everything to the welding table and heat the tube nice and red and bend away. Just heat a small area ( an inch or so) at the beginning of the curve and proceed around the bend letting the bent part cool as you continue around the bend.

    I assume you're using 4130? 0.049 is plenty for what you're doing and you all are right about trying to save weight. With only 8 HP every pound matters. Especially since it's got to float(guessing they still do?).

    A larger radius die should also help. Maybe the company yours came from would be willing to trade.
     
  16. CyberSniper

    CyberSniper 1/2 ton status Premium Member

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    Our minibaja team used to use wet mason's sand in the tube. I don't know what they do anymore, been a long time since I was in their lab.
     
  17. ntsqd

    ntsqd 1/2 ton status

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    Weld a cap on one end, then pack with sand. Then make a tapered wood plug for the other end. Make the taper reasonably long, and drive it in with a BFH. This method will compress the sand more.
    If you think you're going to get anywhere near the sand packed tube with a smoke wrench, make damned sure that you use DRY sand.
     

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