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6082 aluminium heat treating, help?

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  • #31
    Well have you worked out how you are going to get the pivots to work?
    They have to be able to rotate perfectly with each other at the same time then when you stop leaning return to their upright position. Also I think you are going to hit your legs on the ski posts, after all the foot pegs are attached to them. They are vertical where your legs angle up to your hips.

    The skis have to be able to rotate front to back so they can ride over bumps or they will spear into a mound of snow and you will go over the bars. When in the air gravity will make the front of the ski point towards the ground. If you land like this over the bars. Take look at some other designs you will see a lanyard attached to the front of each ski.

    Ji
    Grip it and Rip it

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    • #32
      bungee chords! And I'm beginning to think that I might put the vertical box section on the rear leaning in.

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      • #33
        Bungee cords.
        Well if you offset the connection bracket to counter balance the ski's weight you will not have to completely rely on the cord. You can test the position with maths or trial and error.

        Ji
        Grip it and Rip it

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        • #34
          On the subject of heat treating the frame, filler metal is an important consideration. 4043 or 5356 filler metals are not likely to have the same response to heat treatment as the base metal, so the weld metal will be the weak link. 4643 filler metal is designed for welding 6XXX series aluminum with post weld heat treatment.

          The T6 aged condition strength is due to precipitation of alloying elements (magnesium and silicon) in the aluminum. If you weld in the T6 condition, the heat affected zone will lose strength due to overaging. The heat treater will solution anneal the frame to re-dissolve all of the precipitates, then artificially age the material to T6 temper again. Solution annealing requires a quench and can result in distortion of your weldment. If you weld in the naturally aged T4 temper you can age the frame to T6 without having to solution anneal first.

          Regards,
          Bill
          "The more I learn about welding the more I find there is to learn..."

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          • #35
            Unfortunately I can only get T6...

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            • #36
              I've found a place where I might be able to buy the aluminium in T4 so hopefully that'll work out. I need to order the metal ASAP so will order more than necessary, as I said I'm going to overbuild, strength is more important than weight. Do you think 2mm without a heatreat will be ok or should I do the heatreat or/and use 3mm?

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              • #37
                None of us can tell you what to do we can only advise. After all this is your design.
                Bill was not suggesting you use T4 he was just filling in some gaps.
                As he stated the T6 process will distort or buckle the frame and that is why mountain bike frame builders don't post heat treat.

                Seeing how there is no shock absorbers in your design here is a test you can do that may help with thickness choice.
                Get a 2mm thick flat bar and a 3mm thick flat bar.
                Put one in a vice, drill a 10mm hole in it, slide a 10mm steel round bar or bolt through the hole, now place a steel channel over the flat bar so the legs of the channel are resting on the round bar only. Take a 10 kilo weight and drop it onto the channel from a set height say 1 meter. Remove the bolt and see if the hole is now oval shaped. Measure and record elongation. Repeat the process for the other flat bar. Increase weight and height dropped until you get a result. This will be what happens in the rear swing arm area of your frame but with more force and with more times done.

                Ji
                Grip it and Rip it

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