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  1. #1
    BobL is offline Member: Blue and white apron brigade
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    Default Loan of a Steel hoop or piece of steel with a hole about 350 mm in diameter

    I have a 400 mm diameter x 4 mm thick Al plate in which a 200 mm diameter hole will be cut out of the middle (LHS in pc) and would like to make it slightly dished/conical shaped with a press and some heat. Basically I want it to look like ether blue one but without teh collar.
    IMG_3055.jpg

    I have a strong steel pulley that is 250 mm in diameter and now need a loan of a ~350 mm steel hoop or piece of steel with a hole about 350 mm in diameter to act as a temporary die/base. The amount of dishing from outer edge to edge of the inner hole needs to be about 20 mm. I have no idea if this will work or not.
    IMG_3058.jpg

    I was going to use wood for the 350 mm hoop but given that heating with a propane will be involved then wood is out

    Can anyone local loan me a hoop or a piece of steel with a ~350 mm hole in it? If not then I will make one out of some strap.

  2. #2
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    I've no experience, but from what I've seen and read about, you might more easily get what you want by hydroforming.
    No die might be needed, but if accuracy is important a die could be used I think.

  3. #3
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by nadroj View Post
    I've no experience, but from what I've seen and read about, you might more easily get what you want by hydroforming.
    No die might be needed, but if accuracy is important a die could be used I think.
    Thanks for the info No accuracy needed - I just want to slightly conicalize (is there such a word) the Al plate

  4. #4
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    Can you use the pulley as a mandrel in a lathe to spin the aluminium plate to shape?

    Graham.

  5. #5
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    Hi Bob, have you thought about using a car rim?? Possibly something like a 13 inch wheel might be close for what is required or a rim off a Mini?
    Hope this helps,
    Kryn
    To grow old is mandatory, growing up is optional.

  6. #6
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Oldbikerider View Post
    Can you use the pulley as a mandrel in a lathe to spin the aluminium plate to shape?

    Graham.
    Good idea and I also thought of that but a couple of problems with spinning are;
    The swing on my lathe is only 9" and this disc is 390 mm in diam.
    I've tried spinning 1 mm thick, 290 mm diameter Al plates on my and can just do that so theres no way I could do 4mm.
    I went to the mens shed to look for something and on their scrap pile they had a 200 mm long section of 20mm thick steel pipe that was 20 mm too big!
    Could be handy so its going to live at my place for a while.

    Anyway I have bent and welded up a MS hoop from some 25 x 5mm thick flat bar I picked up doing council verge collections - I like it when these little side projects cost naught.

  7. #7
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    Quote Originally Posted by nadroj View Post
    I've no experience, but from what I've seen and read about, you might more easily get what you want by hydroforming.
    No die might be needed, but if accuracy is important a die could be used I think.
    Hydroforming, while a good idea, is practically impossible without a high pressure pump, I doubt a karcher will do it.
    Kryn
    To grow old is mandatory, growing up is optional.

  8. #8
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    Unless you can restrain the outer flange with some sort of pressure ring as well you will not get good results.

  9. #9
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    Jordan, I don't have any experience either with hydro forming, just going by what I've read and seen on You Tube type clips. It takes a lot of pressure to do such items. Saw a clip of hydroforming tube/pipe for Harley frames and was several thousand PSI to correct the freeform flow of the tubes.
    Kryn
    To grow old is mandatory, growing up is optional.

  10. #10
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by Techo1 View Post
    Unless you can restrain the outer flange with some sort of pressure ring as well you will not get good results.
    Thanks for that - I was going to cut up 12, 25mm thick 32 mm diameter steel spacers and G-clamp these outside the hoop between the the plate being bent, and a 12mm thick base plate. at about the position of the dozen holes around the outside.

    Something like this (no spacers shown here) and maybe with some bits of angle between adjacent clamps?
    Bending jig.jpg

    I will anneal the plate before I try to bend it.

  11. #11
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    Quote Originally Posted by Techo1 View Post
    Unless you can restrain the outer flange with some sort of pressure ring as well you will not get good results.
    I think the edge restraint also needs to have a substantial steel ring beneath the G clamps, I could see the clamps moving and puckering occurring between the clamps if they were the sole edge restraint.

  12. #12
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by bob ward View Post
    I think the edge restraint also needs to have a substantial steel ring beneath the G clamps, I could see the clamps moving and puckering occurring between the clamps if they were the sole edge restraint.
    I agree and was thinking of putting pieces of 5 mm thick angle under the clamps as it does not matter if the start of the outside bend eventuates in a 12 sided bend.

    Screen Shot 2018-05-16 at 8.53.01 am.png

  13. #13
    BobL is offline Member: Blue and white apron brigade
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    Well I stuffed up along the way but I made something that will be good enough for what I want it to do.

    Setup 1 shows 32 mm hoop and 32mm spacers

    Setup1.jpg

    Setup 2 with the clamps and angle pressure plates in place.
    Setup2.jpg

    Top view
    Setup3.jpg


    Nothing happened till it got to about 5 tons and then I thought it was going crooked but it sort of straightened itself.

    Then at 8 tons a cheap Chinese clamp holding down the outer rim down shattered so I called it quits, as by then it looked like I had enough dishing
    clamp.jpg

    The final dish is doming to 25 mm at the inner lip which is what I was hoping for.
    dish.jpg

    Here you can see I cut the hole in the Al section a tad too large but I JUST had enough overhang to the use 4mm CS screws to attach the PVC bell mouth hood.
    Dish1.jpg

    Underside -
    So now its a "mega bell mouth hood" - I'm happy enough with the final result
    It would have been MUCH easier if I had use 3mm Al and cut teh hole the right size - or maybe not as less hole means less to bend?.
    Dish2.jpg

  14. #14
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    And the flat belt pulley lives to see another day. Good news all around!

    Graham.

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