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  1. #21
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    call this guy...

    YouTube

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    Use 11/4" tube and swage it down.

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  4. #23
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    Rody, Jones, Santana, Walt, and others (myself included) make handlebars. If you're doing aluminum, you’ll have to bulge it pre bending or hydroform it and have a really solid heat treatment system in place. Ti bars are a different animal and nearly all are sectioned and welded.

    For steel, the easiest is just to make them straight 25.4 and then use a problem solvers adapter. Next up is sleeving and brazing or plug welding, but don’t ever braze/weld the sleeve to the bars, because you’re putting all that heat right into the clamping zone of a safety critical element. Bad things will and do happen especially if you’re not heat treating. Make the middle section with the “clamp” complete, and then join that to your drops, risers, or whatever. Lastly is bonding with epoxy, not recommended here as it is kind of a “if you have to ask how, you shouldn’t” situation.

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    Also DO NOT USE 035 WALL! Start at 065 and then send a pair to ACT-LAB (or whoever) for handlebar testing, you’ll be surprised how they fail. Your insurance company will also require third party testing results before you can equip any to a bike.

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    Quote Originally Posted by digger doug View Post
    Hmmm...Simple split die of MS with (4) bolts holding together, accurately placed black powder "blob"....BackYard, cover with dirt, 3' long fuse.
    good advice, this is what happens when the fuse is too short and not enough bolts

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    Quote Originally Posted by jz79 View Post
    good advice, this is what happens when the fuse is too short and not enough bolts
    Been thinking more on this:
    1. qty (2) 12 ga shot shells pushed in from each end, touching in middle.
    2. electric firing, get both to fire at same time.

  8. #27
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    Quote Originally Posted by digger doug View Post
    Been thinking more on this:
    1. qty (2) 12 ga shot shells pushed in from each end, touching in middle.
    2. electric firing, get both to fire at same time.
    Ooh! Hey, hold my beer while I try somethin' ...

    Sent from my Lenovo TB-8504F using Tapatalk

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  10. #28
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    Quote Originally Posted by awake View Post
    Ooh! Hey, hold my beer while I try somethin' ...

    Sent from my Lenovo TB-8504F using Tapatalk
    Your suggesting adding a tiny "pit" of u-235 in the middle ?

  11. #29
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    No, I just got excited at the idea of shooting one shot gun shell at another.

    Sent from my Lenovo TB-8504F using Tapatalk

  12. #30
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    Quote Originally Posted by awake View Post
    Ooh! Hey, hold my beer while I try somethin' ...

    Sent from my Lenovo TB-8504F using Tapatalk
    Are you mad? Asking me to hold your beer is probably the biggest risk you'll take in your lifetime.

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  14. #31
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    Quote Originally Posted by digger doug View Post
    Hmmm...Simple split die of MS with (4) bolts holding together, accurately placed black powder "blob"....BackYard, cover with dirt, 3' long fuse.
    Blackpowder is dead wrong for predictability. Too frissant. Too hygroscopic. Nasty combustion byproducts and "fouling". Too unpredictable. Just as happy to shatter the mold as work hard and tight into it.

    Also riskier to store and handle than modern nitrates.

    Ignorant "smokeless" powder. Think "ramset" technology and its colour-coded predictability writ sideways. Or "fire forming" cat'ridge cases.

    Smarter to bulge it whilst still STRAIGHT, as mentioned, common exhaust shop technology. Also already mentioned.

    Connect the dots.

    Bending wants to distort the bulge? Restrain it as part of the process.

    And/or reform to final spec with EXTERNAL working. It will hold more accurately to size and shape that way in any case.

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    Quote Originally Posted by thermite View Post

    Bending wants to distort the bulge? Restrain it as part of the process.

    And/or reform to final spec with EXTERNAL working. It will hold more accurately to size and shape that way in any case.
    Uh...that was the "split MS die" part.....

    Wether or not the straight knurling could be incorporated in the die, remains to be seen.

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    Add to the mix that most all high end bars made by actual companies... not custom bespoke cottage guys... are taper wall and it gets more complicated real quick.

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    Quote Originally Posted by digger doug View Post
    Uh...that was the "split MS die" part.....

    Wether or not the straight knurling could be incorporated in the die, remains to be seen.
    No it don't. Won't work well atall. Tubing here, no anvil inside of it.

    N'er mind. Yah jest ROLL that in. Think modified tubing cutter, many "rounds", this DIY small-batch s**t.

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  21. #35
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    EmanuelGoldstein is 100% correct that the only way to do it economically is before bending.

    A low buck way that might work is grease hydraulics. You'll need to make two mandrels long enough to reach halfway through with appropriate seals at the business ends. One mandrel would be fixed and the other driven by a hydraulic jack. In use, the center of the tube would be surrounded by an appropriately shaped split die. A lump of grease would be placed in the tube and then pressed so it was trapped between both mandrels and the tube center. It may take a 10 ton jack cylinder to do it and unless the tube is properly supported along its length it may bend before the center bulges. Safety will be an issue and you'll need shielding to protect against injury if something goes wrong.

    If it works please update your post. Good luck.

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  23. #36
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    I am far from having all the answers, hence my post here. And the bending isn't the problem -- I use a JD2 bender (which is way beyond the grade my local hardware store sells), a collection of their dies and dies I've turned myself. The results for (unbulged) bars have been pretty good. Good enough to equip my grand daughter with custom bars for her custom balance bike. Not good enough yet for the commissioned racing bikes I build for gravel racers.

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    Great advice. I've followed Rody's methods for a few things, including a gate separator for belt drive seat stays.

  25. #38
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    Quote Originally Posted by thermite View Post
    No it don't. Won't work well atall. Tubing here, no anvil inside of it.

    N'er mind. Yah jest ROLL that in. Think modified tubing cutter, many "rounds", this DIY small-batch s**t.
    I know that, it was in jest. No way to get that fine detail knurling into the die
    with no matter how much pressure, hence the rollers doing it in a very small cross section, exceeding the compressive strength of the material.

    Of course we are all discussing doing the bulging in the straight section, that is a given.

  26. #39
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    Freeze it out with a water filled chamber?,
    Lateral thought exercise
    Mark

  27. #40
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    After watching what goes into a commercial bar, and possible liability concerns, I would not do the job.


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