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Thread: To Polycarb, or not to Polycarb, that is the question?!

  1. #1
    Hello everyone,

    I have an idea for a new robot for next season but I have a few questions about the material.

    I love the idea of Polycarbonate so everyone can see the internals when its fighting as well as I can plaster it with LEDs xD I currently use 20mm HDPE which has held up great both to Neon and Shrapnel at Maidstone Extreme Robots! But it being so thick, I was able to use insert nuts (the ones that screw in with a course thread and then you can screw a machine thread screw into it) but the thickest polycarbonate i can find solid is 12mm. I am guessing this is a standard size but it introduces the issue of not having enough material to screw in the insert nuts.

    The gentleman behind Unicorn (really sorry I have forgotten his name ) said that you can use those insert bar things that you get with flat pack furniture (the ones that you push into a hole one direction and then screw a threaded screw in from the other direction if that makes sense? lol) to join two bits of HDPE together so I was wondering weather there any adverse effects of using them with Polycarb?.

    Also I know Polycarb is fairly resilient else they wouldn't use it for the arena lol but building a robot pretty much exclusively from the stuff, would it be fairly tough like HDPE?

    Any opinions and information is much appreciated!

    Thanks a lot

    Will
    Some Idiot Team
    FW: Stabby McUnicornface,
    FW: Caractacus (In Development)

  2. #2
    Ocracoke's Avatar
    Team Kaizen

    I can tell you from experience that Polycarbonate is fairly resilient but it does crack under pressure if it is hit in the right place. Typically, this is between hole to hole because Polycarbonate is notch sensitive, meaning where you drill it, it becomes weaker around that area.

    The method of attachment you are talking about sounds OK to me. I tend to run a big bolt through a bottom panel of Polycarbonate through a block material (in my case, steel box section but a thick block of HDPE will work) and then a top panel of Polycarbonate and bolt it all together with a compression fit.

    Done right, Polycarbonate is a good, strong material to work with but I wouldn't exclusively build out of Polycarbonate. I tend to pair it with HDPE for the sides for spinner impact protection and a hard material, like steel, to build a body out of. I'd be happy to show you Azriel or Jibril if you are going to EXR Cheltenham.
    Team Kaizen - Build Diary for all the robots

    AW: Amai, Ikari, Osu, Ramu
    BW: Shu!, The Honey Badger
    FW: Azriel
    MW: Jibril, Kaizen

  3. #3
    Your meaning the barrel nuts or Cross dowels, https://www.screwfix.com/c/screws-na...els/cat7280106

    Polycarb is good across larger flat surfaces, but around holes as mentioned above, it is weak and can crack across on impact. My wheel bearing holders are machined from polycarbonate, and on large impacts (shrapnel and arena roof) the plates cracked straight across the holes.
    I believe Killerhertz suffered quite a bit from cracked panels from mounting holes?
    Last edited by Roboteernat; 28th October 2019 at 15:51.

  4. #4
    Quote Originally Posted by Ocracoke View Post
    I can tell you from experience that Polycarbonate is fairly resilient but it does crack under pressure if it is hit in the right place. Typically, this is between hole to hole because Polycarbonate is notch sensitive, meaning where you drill it, it becomes weaker around that area.

    The method of attachment you are talking about sounds OK to me. I tend to run a big bolt through a bottom panel of Polycarbonate through a block material (in my case, steel box section but a thick block of HDPE will work) and then a top panel of Polycarbonate and bolt it all together with a compression fit.

    Done right, Polycarbonate is a good, strong material to work with but I wouldn't exclusively build out of Polycarbonate. I tend to pair it with HDPE for the sides for spinner impact protection and a hard material, like steel, to build a body out of. I'd be happy to show you Azriel or Jibril if you are going to EXR Cheltenham.
    Thanks for the info! I didn't know it could crack like that! I shall have a redesign and see what I can come up with combining the two. I'm not building it till the end of Robodojo 6 so would love to see your robots down at Cheltenham! Look for the idiot in pink :P

    Quote Originally Posted by Roboteernat View Post
    Your meaning the barrel nuts or Cross dowels, https://www.screwfix.com/c/screws-na...els/cat7280106

    Polycarb is good across larger flat surfaces, but around holes as mentioned above, it is weak and can crack across on impact. My wheel bearing holders are machined from polycarbonate, and on large impacts (shrapnel and arena roof) the plates cracked straight across the holes.
    I believe Killerhertz suffered quite a bit from cracked panels from mounting holes?
    Thanks mate Yea they are the ones! So if I was to add polycarb, I would do well to have spares xD Ill have to have another nose around at ER Cheltenham and see what others are using. I know Tom from Mad Catz Robotics said he uses the barrel nuts for his wedge!
    Some Idiot Team
    FW: Stabby McUnicornface,
    FW: Caractacus (In Development)

  5. #5
    Ocracoke's Avatar
    Team Kaizen

    To add some context, here is the base panel of Jibril which uses a 10mm thick polycarbonate panel.
    JPEG_20191014_182258.jpg
    Team Kaizen - Build Diary for all the robots

    AW: Amai, Ikari, Osu, Ramu
    BW: Shu!, The Honey Badger
    FW: Azriel
    MW: Jibril, Kaizen

  6. #6
    Ah I see its just cracked. I suppose its good and touch in some directions but if you get hit in a certain way it breaks. Is there a proffered way to mount polycarbonate that minimises that?

    Thanks again
    Some Idiot Team
    FW: Stabby McUnicornface,
    FW: Caractacus (In Development)

  7. #7
    If you use polycarb for your top panel make sure there are more than 2 bolts holding it on and its not taped together in the middle. Speaking from experience...

  8. #8
    Quote Originally Posted by TechAUmNu View Post
    If you use polycarb for your top panel make sure there are more than 2 bolts holding it on and its not taped together in the middle. Speaking from experience...
    I shall bear that in mind xD How did you anchor yours? Barrel nuts or somthing else?
    Some Idiot Team
    FW: Stabby McUnicornface,
    FW: Caractacus (In Development)

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