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  • Solid Seat Pan Thickness

    What is the general consensus regarding minimal thinness for an alluminum solid seat pan?

    I weigh ~150lbs
    "What is the first business of one who studies... To part with self conceit. For it is impossible for anyone to begin to learn what he thinks he already knows." -Epictetus (55-135) Greek Philosopher

  • #2
    Originally posted by Covathalis View Post
    What is the general consensus regarding minimal thinness for an alluminum solid seat pan?

    I weigh ~150lbs
    I use a 6mm plywood for my first chair, too hard

    Second chair, 3mm 7020 aluminum sheet, just nice, it will bent nicely when sit on top, but does not absorb impact when dropping curb.

    Third chair, the worse seat pan I ever sit, 1 mm welded 6061 aluminum sheet with reinforce hole drill (see picture 1), and it is solid like anything. Even with cushion on, my bottom still pain like anything.

    So I cut off the aluminum, replace with 5mm polycarbonate, it hold me firm, and absorb impact when dropping curb.(picture 2)

    To conclude, follow this rules when choosing your seat pan thickness:

    1. Choose something that will bent nicely when you sit on top, which fit your butt contour.
    2. Choose something that will bounce a little to absorb impact.
    3. Don't go for really hard material.
    4. Choose something that can bear your weight.


    Picture 1
    Click image for larger version

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    Picture 2
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    Life is meaningles, though you create the purpose.sigpic

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    • #3
      Originally posted by sowseng View Post
      To conclude, follow this rules when choosing your seat pan thickness:

      1. Choose something that will bent nicely when you sit on top, which fit your butt contour.
      2. Choose something that will bounce a little to absorb impact.
      3. Don't go for really hard material.
      4. Choose something that can bear your weight.
      Do you think something like this would be suitable for a seat pan? http://www.ebay.co.uk/itm/Clear-Acry...1%26rkt%3D1%26

      But I wouldn't know what thickness to go for? My chair is 15" and I weight 8.5 stone and thought 4mm seems about right? But I don't know, I want it to dish slightly but not snap so I end up with my bum wedged in the frame! Btw do the side rail holes need to be elongated to allow the sheet to flex?

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      • #4
        Originally posted by Mr Tippy View Post
        Do you think something like this would be suitable for a seat pan? http://www.ebay.co.uk/itm/Clear-Acry...1%26rkt%3D1%26

        But I wouldn't know what thickness to go for? My chair is 15" and I weight 8.5 stone and thought 4mm seems about right? But I don't know, I want it to dish slightly but not snap so I end up with my bum wedged in the frame! Btw do the side rail holes need to be elongated to allow the sheet to flex?
        Do not use acrylic board, it will break.
        Just use velcro attach to the frame, it will flex very nicely.
        8.5stone? how many lbs?
        Life is meaningles, though you create the purpose.sigpic

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        • #5
          Do you have more details on the polycarbonite you're using ?
          How heavy is it ?
          grade type ?

          1 stone = 14lbs

          8.5 stone = 119lbs



          Originally posted by sowseng View Post
          Do not use acrylic board, it will break.
          Just use velcro attach to the frame, it will flex very nicely.
          8.5stone? how many lbs?

          Comment


          • #6
            Originally posted by NW-Will View Post
            Do you have more details on the polycarbonite you're using ?
            How heavy is it ?
            grade type ?

            1 stone = 14lbs



            8.5 stone = 119lbs
            Click image for larger version

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            My polycarbonate sheet is 37.5cm x 35.5cm, 5mm thick, it almost weight 1kg.
            I am not happy with the weight, may be it is not a good quality polycarbornate, it is made in China.

            Will try other polycarbonate later, hopefully stronger and lighter.
            Last edited by sowseng; 09-22-2016, 06:39 AM.
            Life is meaningles, though you create the purpose.sigpic

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            • #7
              hi sorry this might be a little off topic but im sure when i was looking at a solid seat pan there was someone who weighed both the canvas and the seat pan strips to find out how much both weighed in comparison, does anyone know the weights or where i can find out? thanks

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              • #8
                Cheers.

                Yes be interested to hear about your polycarbonite experiment.. I'm still messing around with plywood.

                for the americans
                37.5cm = 14.76 inches
                35.5cm = 13.96 inches
                1kg = 2.2lbs







                Originally posted by sowseng View Post
                [ATTACH=CONFIG]58866[/ATTACH]

                My polycarbonate sheet is 37.5cm x 35.5cm, 5mm thick, it almost weight 1kg.
                I am not happy with the weight, may be it is not a good quality polycarbornate, it is made in China.

                Will try other polycarbonate later, hopefully stronger and lighter.

                Comment


                • #9
                  Originally posted by NW-Will View Post
                  Cheers.

                  Yes be interested to hear about your polycarbonite experiment.. I'm still messing around with plywood.

                  for the americans
                  37.5cm = 14.76 inches
                  35.5cm = 13.96 inches
                  1kg = 2.2lbs
                  Plywood is cheap and easy to work with, it does not bent when you sit on top, but not as solid as those really hard material, still a very comfortable choice.
                  Life is meaningles, though you create the purpose.sigpic

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                  • #10
                    Originally posted by sowseng View Post
                    Do not use acrylic board, it will break.
                    Just use velcro attach to the frame, it will flex very nicely.
                    8.5stone? how many lbs?
                    Hi, sorry I missed your reply, 8.5 stone is approx 120lb (US).

                    I always get confused between acrylic and polycarbonate. But I've suddenly remembered that safety spectacles lenses are made of polycarbonate. Is the difference between polycarbonate and acrylic that polycarbonate is laminated and thus stronger?

                    I'm having trouble finding polycarbonate sheet in the UK. If I search eBay UK it just returns corrugated polycarbonate sheet for use in greenhouses, but no flat sheeting? http://www.ebay.co.uk/sch/i.html?_fr...sheet&_sacat=0

                    EDIT: I've managed to find some solid polycarbonate sheet at a reasonable price here. http://www.ebay.co.uk/itm/161981671914

                    I'm not sure what thickness to go for, I want it to flex some when I sit on it but not too much. I was thinking of perhaps 3mm or 4mm?

                    What do you think?
                    Last edited by Mr Tippy; 10-12-2016, 11:17 AM. Reason: New info

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                    • #11
                      is there not a plastics company near you? i know company near me called bay plastics and they do everything, i would pop in and see what they can do for you if you have one near by

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                      • #12
                        Originally posted by rAdGie View Post
                        is there not a plastics company near you? i know company near me called bay plastics and they do everything, i would pop in and see what they can do for you if you have one near by
                        Thanks for that, I might check out the local industrial estates.
                        Also what I've just learnt is that solid polycarbonate sheet isn't particularly easy to cut. I don't think you can use a jigsaw as it shatters? I think the only DIY method is to use an angle grinder?
                        Typing this reply and your suggestion has just made me think of glazing firms? I wonder if they stock the solid sheeting, cos they would also be able to cut it to size. I shall investigate and report back.

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                        • #13
                          the plastic company in my area, ive been inside everywhere as i used to do the maintenance on their alarm system before my accident so i got to see the people working on the plastics etc and storage, vacuum forming machines etc, lightly burning the edges of the cut plastic to make it more clear instead of rough etc, im not so sure about glazing companies but it wont hurt to ask, if you do find a plastic company just tell them the size and thickness and if they recommend a particular plastic to use for your intended purpose, if you get stuck i could always give you the number of the company near me, they could give you and idea or know a local company to you or you could even buy from them :P

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                          • #14
                            Originally posted by Mr Tippy View Post
                            Hi, sorry I missed your reply, 8.5 stone is approx 120lb (US).

                            I always get confused between acrylic and polycarbonate. But I've suddenly remembered that safety spectacles lenses are made of polycarbonate. Is the difference between polycarbonate and acrylic that polycarbonate is laminated and thus stronger?

                            I'm having trouble finding polycarbonate sheet in the UK. If I search eBay UK it just returns corrugated polycarbonate sheet for use in greenhouses, but no flat sheeting? http://www.ebay.co.uk/sch/i.html?_fr...sheet&_sacat=0

                            EDIT: I've managed to find some solid polycarbonate sheet at a reasonable price here. http://www.ebay.co.uk/itm/161981671914

                            I'm not sure what thickness to go for, I want it to flex some when I sit on it but not too much. I was thinking of perhaps 3mm or 4mm?

                            What do you think?
                            how heavy you are? I am 49kg, 5mm thickness work well for me, it flex enough to give me comfort, and solid enough which does not sack.

                            I tried 3mm, it bent too much, lower my rear seat height. May be I want to try 4mm later.

                            I am thinking of drill some holes to cut some weight.
                            Life is meaningles, though you create the purpose.sigpic

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                            • #15
                              Lexan/polycarbonate won't shatter as long as you keep it away from acetone. It's used in making bullet proof glass/windows. I think a 1/4 thick piece will stop a 22 caliber bullet.

                              I use a rotary tool with a dremel carbide cutting wheel, made for wood and plastic when cutting thin sheet. I've cut 1/4 inch thick polycarbonate using a rotary tool.

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