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Thread: [BW] GR-01 Build Diary

  1. #31

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  4. #34
    Eggbeaters are generally much easier to make - it depends what methods you use. I get beaters cut from steel plate by water jetting and then have axles turned on each end by the same company - all I have to do is draw the part and throw cash at them . To make a beater yourself is still easier than a drum but requires a mill. If you use a hardened steel like Hardox (highly recommended), you will also need carbide cutters.

    Beaters have other advantages over drums:
    * one piece construction - no screws or welds to break.
    * Higher kinetic energy for the same weight & diameter. The beater keeps most of its weight at the perimeter for efficiency.
    * More tooth bite. The beater is usually better when going head-to-head against a similar drum.

    The main disadvantage is poor aerodynamics. The beater acts like a fan and requires a larger motor and battery compared to a drum.

  5. #35
    Max's Avatar
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    Quote Originally Posted by overkill View Post
    The main disadvantage is poor aerodynamics. The beater acts like a fan and requires a larger motor and battery compared to a drum.
    I wonder if this could've solved by making 2 half drums out of say fibre glass and bolting them on to an eggbeater, effectively making it a drum but without using the drum for structural purposes. They might even let you into the drum-off!

  6. #36
    You're going to have to put wedges or something on the front because I guarantee that thing is going to keep flipping over in a hit.

  7. #37
    Quote Originally Posted by Max View Post
    I wonder if this could've solved by making 2 half drums out of say fibre glass and bolting them on to an eggbeater, effectively making it a drum but without using the drum for structural purposes. They might even let you into the drum-off!
    I already tried that and it didn't go well at all! The centrifugal force threw the drum halves off the beater, which managed to cut one half to shreds.

  8. #38
    A way of quantifying how aerodynamic beaters are, Conker 3 has 2 2.7Ah 6S Lipo's driving its weapon. If I floor the weapon, it goes from 0-11K RPM in under 1 second, and then will drain the batteries flat [Or more specifically to the 3.2V cut-off point built into the ESC I use] in under one minute! [Keep in mind the fights can be up to 3 minutes :P ]

    That said, provided they are designed right [the first beater for C3 wasn't strong enough so it bent], they are much easier to make and probably cost less than drums [not sure on that but you use maybe 2-3 steps & less material, where as drums require more complex machining and a big billet of Alu/Ti for the body]

    A point against beaters is that usually they don't tie together the front bulkheads, where as a Drum design does which makes it much stronger. Beaters are vulnerable to having their bulkheads pulled apart by horizontals for this reason where as drums are less likely.
    Last edited by Eventorizon; 15th August 2015 at 22:18.

  9. #39
    Build it properly then unlike jamie;

  10. #40
    As much as it pains me to say it, Dave is right.

    The first video you linked to Alex, the shaft wasn't bolted either side of the bulkheads (namely due to time and lack of facilities), and in the second video, the shaft was bolted using M6 bolts. M6 vs NST, it's obvious who is going to come out on top
    It didn't help that back then, I thought that the standard hole size prior to tapping was 0.5mm less than the thread you were going to cut, regardless of how big or how small the hole was. Got it right this year, though typically didn't face any horizontals.

    It's also worth pointing out that the drum on the 2011 and 2014 versions didn't span the entire width of the bulkheads, which meant there were gaps that were perfect for NST's bar to bite into and throw the bulkheads apart (the 15mm ali came off worse in 2014 than the 16mm Nylon did in 2011) but again, this year saw the drum span the entire width, meaning that any horizontals are more likely to catch the drum rather than the bulkheads.

    Moral of the story is, wait for someone else to perfect your design and then copy the living daylights out of it.

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