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Thread: Malum Gun Sub-thread

  1. #21
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    Re: Malum Gun Sub-thread

    My loader design is a finely engineered piece of machinery (and by that I mean dozens and dozens of trial and error 3D prints) and when used properly will provide many jam free battles.

    I've used it on two Mechs in MFBA19, two Mechs in Robogames 2018, and in multiple Mech Brawls here in Tucson without jams. I've also provided it to multiple other teams (yourself included), who have messed with it and have jamming issues (which I do find a bit amusing - engineering types can't help but "improve" things).

    Theoretically, I guess it does have a single jam point (which you show above) and I have tried to minimize. The components have slopes up or down that force the BBs up or down. I dunno, but the maybe the BBs pushing down from above help as you suggest or maybe just the free play in the wheel mounting itself allows the BBs to jiggle into place.

    As for the "Mysterious Holes", it is my "belief" that they are not needed. I didn't use them when I was testing this version of the loader. I've answered what they are for I think above or in another thread. That said, I still use them for good measure. Immortal (and I think Numa?) didn't use them in MFBA19 and I am not aware of any jamming issues they had.
    Last edited by GhengisDhon; 1 Week Ago at 08:11 AM.

  2. #22
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    Re: Malum Gun Sub-thread

    "Mysterious Holes" in loader filled with piper cleaner to provide a "soft" point of indecision
    Click image for larger version. 

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  3. #23
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    Re: Malum Gun Sub-thread

    I think one good thing about the wheel is that it has the entire rotation of the wheel for another bb to fall into place, if you leave the entire upper surface of the wheel open for bbs to fall into. Only at the very end does it have the indecision point. I use it in immortals guns since it is so compact. I did have a little issue feeding sometimes but it wasn't from jamming, it was more because I was using two different gear ratios for my hopper motors and I didn't really have time to tune them both separately.

  4. #24

    Re: Malum Gun Sub-thread

    Right! My path of inquiry is "Dhon's design has a theretical pinch point and seems to work great in practice; what's specific about those features that make that pinch point not interfere in practice?" I e, if I can take away some general principle (above "experiment until it works") then that would be a huge win!

    It makes me want to throw Monte Carlo simulation and Bayesian modeling at the study... but Fusion doesn't make it easy to script randomized physical simulation at high enough speeds to get the necessary data set to make that work out. I did work on an open source double-precision physics engine a decade or two ago, though ... (Leave it to a software engineer to turn a mechanical problem into a software problem :-D)

    Even though I want to, I can't just copy your design and move on, because I simply don't have space for it :-(

    One possible path forward is "make space for it!" If I lift up the gun, I would be tempted to also add articulation and stabilization (cribbing from jpieper!)
    Last edited by jwatte; 1 Week Ago at 12:44 PM.

  5. Re: Malum Gun Sub-thread

    For those of us who do have enough space and are maybe looking to crib GenghisDhon's design (thanks for sharing Don), where was/is it posted?

  6. #26
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    Re: Malum Gun Sub-thread

    Quote Originally Posted by jwatte View Post
    Even though I want to, I can't just copy your design and move on, because I simply don't have space for it :-(
    So what you're saying is I really should put in a bit of effort into making this ~2"-OD x ~6"-L fully self-contained airsoft cannon holding ~320 BBs in a single-file ratcheting magazine with breech loading and magazine incrementing actuated by the air-pulse and/or 'charging' mechanism.

    Click image for larger version. 

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    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

  7. #27

    Re: Malum Gun Sub-thread

    Yes, I think that's a reasonable conclusion!

  8. #28
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    Re: Malum Gun Sub-thread

    Quote Originally Posted by jpieper View Post
    For those of us who do have enough space and are maybe looking to crib GenghisDhon's design (thanks for sharing Don), where was/is it posted?
    I've just been emailing to people who request it. I can send it to you.

  9. #29
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    Re: Malum Gun Sub-thread

    Quote Originally Posted by jwatte View Post
    Even though I want to, I can't just copy your design and move on, because I simply don't have space for it :-(
    Ok... just so I fully understand the problem at hand and the conundrum your in...
    1) I believe you had the largest Mech at MFBA2019... maybe not by weight (that honor goes Josh) but by diameter.
    2) You had the highest power servos... so even then weight shouldn't be an issue
    3) And you can't find room for a 2" diameter x 1/2" loader that can essentially pipe the BBs to any location on your Mech...
    4) So your going go throw MC simulation at it, which probably won't give meaningful results anyway unless you go ground it with meaningful test data (I'm not familiar with Fusion but I assume you need things like frictions & material compliance to model contact stresses, etc...)
    5) Your then going to go machine it in aluminum instead of 3D print it, which I have to admit is much more impressive
    6) And then probably have to repeat the process (multiple) times...

    So is it safe to assume, 2 weeks before MFBA2020 you will be madly trying to get your Mech together again and be competing with a gun that jams?

    We have a saying for people like you... "Better is the Enemy of Good Enough"

  10. #30

    Re: Malum Gun Sub-thread

    I believe you had the largest Mech at MFBA2019... maybe not by weight (that honor goes Josh) but by diameter.
    I'm not sure about that. By leg span when walking, maybe? but the hip-to-hip distance is only 137 millimeters -- a hair over 5". When "curled up," it's actually quite small! (Onyx was bigger hip-to-hip.)

    So is it safe to assume, 2 weeks before MFBA2020 you will be madly trying to get your Mech together again
    I hope not! That's why I work on it now! My backup plan is to go back to the BBs-above-the-barrel design, which works okay. It has some dry firing, because of the gravity feed, but it doesn't jam much. Also, I haven't ruled out lifting the gun up a bit, which would give me plenty of space.

    The reason I didn't go with it for BAMF was that I actually took your agitator design, and shrunk it slightly so it fit into the area on the side of the gun in the previous picture, and put a holding tube on top of it. It worked really well in isolation (taken from the best!) but the tube was too narrow, causing jams on the way to the agitator, rather than in agitator.

    You are obviously correct in the implication that, if the goal was to get the best possible gun with the minimum possible cost/investment (i e, actually do "engineering,") I would be absolutely crazy to go this way. So, either I actually am absolutely crazy (which I haven't ruled out) or I do this for some other reason. (Such as learning and practicing a bunch of hands-on skills...)

    "Better is the Enemy of Good Enough"
    Indeed. In my professional life, I make exactly that argument on a frequent basis. ("I prefer to call it 'fast and efficient,' not 'quick and dirty!'")

    This, I do for the experience! (Btw, your designs and suggestions have been super helpful, so I hope you don't feel like throwing water on a goose here ... you've taught me a lot already! Thank you.)

    Btw:

    You had the highest power servos
    Speaking of which: It looks like the too-sharp impacts of walking on concrete with steel balls and all-metal frame is what broke that servo that curled up on me ... Spray some rubber on the steel balls on the feet? Bring a foam flooring square whenever I test it? Some deviously complex spring-loaded shock absorber doodad? Bringing the foam sounds easiest. Different thread, though.

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