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Bitza Mk2

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  • #76
    Re: Bitza Mk2

    So thought I'd do a quick event breakdown of how Team Bitza got on. This is probably more for our benefit and will be a load of text, but I'll put up some more build photos and vids soon.

    In short the robots all performed pretty badly. Spinza never even got started on, let alone finished in time.
    BitzaWood was structurally sound, and half wired up, but in our attempts to finish the job at the GSL we managed to wire the weapon motor the wrong way so it span down. Reversing the polarity broke the relay, which by this point was the one out of Bitza since I was unsure of how to wire the one I had in BitzaWood originally.

    As for BitzaMk2, well we just ran out of time and it had some quite major issues to iron out. The weight being the main one, meaning we could either run was armour or weapon. Given the first fight against Cobalt armour seemed sound, and we took no damage, but I suspect Kenny held back a bit. Then DoorStop was replaced with LH, so quickly put the armour back on for the 2nd round too.
    By this point it was very apparent we had a major problem, no traction. There was too much weight over the front of the robot so the wheels just span beneath us.
    For the final fight we put the drum on. But a combination of an additional 3.2kgs over the front and the gyro force meant it didn't drive at all.
    Pretty pleased with the drum, spins up very quickly, good RPM it was only when we drove into the wall that we sheared the bolts holding one tooth on, and then the vibration meant we slipped the chain and the drive axle worked loose. Still got a knockout though!

    As for the next model, shorter and wider, with more weight over the drive axle. Thinking we may ditch the exoskeleton design. We like being different and it's very strong but difficult to work with, hard to mount anything and heavy. So we'll be looking at a base plate or bulkhead design.
    Things worth keeping? The drum seemed sound, just need bigger bolts in the teeth. The car fan motor provided more than enough power to spin it up and didn't draw much current. The one way bearing worked well as did the chain. We think it slipped because it stretched so far.
    Our 15a Electronize controllers got rather warm but still working so happy to keep them, same with the dewalt drive motors and gearboxes.

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    • #77
      Re: Bitza Mk2

      Just worked out something interesting. In turning this old weight into the sprocket guard I left roughly 51 of it's original 56 lbs on the lathe bed!

      No wonder it took 12 hours to turn!

      [attachment=1:2na1njra]Photo-0014.jpg[/attachment:2na1njra]

      [attachment=0:2na1njra]DrumGuardMockup.jpg[/attachment:2na1njra]
      Attached Files

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      • #78
        Re: Bitza Mk2

        That's a whole lot of swarf!

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        • #79
          Re: Bitza Mk2

          Bitza Mk2 - The Journey......

          http://www.youtube.com/watch?v=R6aOtYp70ZY

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          • #80
            Re: Bitza Mk2

            Can't remember if I did a 2012 Champs PM..... So here is a slightly belated one...

            As many of you saw BitzaMk2 had a couple of serious problems. Namely being overweight, which we are working on, but secondly it didn't drive.... Like at all....

            You can see the problem briefly in this clip:
            http://www.youtube.com/watch?v=R6aOt...tailpage#t=73s

            The wheels seem to gain and lose traction intermittently making it impossible to drive. We initially put it down to the wet floor outside (and the dusty floor when inside) but we had the same problem at the champs, and with the drum on it was even worse!

            I have an idea why this is, and some thought about how we can solve it, but thought I'd open it up to the forum first to see if there's anything obvious I've missed and for some more experienced insight.

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            • #81
              Re: Bitza Mk2

              Maybe there is too much friction on the bottom and top plates which makes it hard too drive?

              small bit of hdpe under that should make it easier

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              • #82
                Re: Bitza Mk2

                I would guess the problem may be lack of weight over the back wheels and lots o weight at the front where it scrapes along the ground making a lot of resistance.
                It may help to put some ball castors at the front to reduce the resistance and if you make it so the robot is slanted backwards then more weight may shift to the back? You could also possible move the fan motor further back or the wheels further forward.
                Did you just use normal bike chain for power to the drum? Did you use 1 or 2 chains?

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                • #83
                  Re: Bitza Mk2

                  Move the wheels more to the sides and the middle with the drive motors behind the wheels. It will improve the handling immensely. We had the same issue as you with Blackdevil Warzone, and it is simply due to not enough weight leaning on the wheels and the wheels being too close together. It works great for a straight line but specially cornering is horrific like that.

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                  • #84
                    Re: Bitza Mk2

                    Thanks for the input guys, pretty much confirmed what I thought.

                    The drum is 3.5kgs, the fan motor 1.5kgs, plus the box section uprights, chain (just the one) one way bearing are all in the front of the wheels, which is just scrapping on the floor.

                    Hoping to move the drum closer to the wheels, move some components behind the wheels (to balance it out) and put some BTUs in the front.

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