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Thread: Léim - Beetleweight Spring Flipper Build Diary

  1. #11
    Shooty's Avatar
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    I've monitored a few for their resist value with a multimeter and they seem to be the same, but swapping a few in and out shouldn't hurt. I'll do that soon and keep this post updated.

  2. #12
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    In reply to your post.
    I assume you mean to swap one of them out with another resistor?
    That is what I meant.

    My thought with this, is that the servo is centered around a voltage that is not exactly half way between the rails. This test will check that you are using the right resistors:

    1) set your trim to 0 on your transmitter
    2) solder the potentiometer back onto the servo (don't attach it mechanically to the servo)
    3) turn everything on
    4) Your servo will probably move, so adjust the potentiometer until the servo stops moving. This should now operate like we want it to (in continuous mode), so move the sticks on the transmitter to make sure.
    5) use a multimeter to measure the voltage on each side of the potentiometer*1.
    6) the ratio of these voltages should be the ratio of the resistors you use*2.

    Let me know if I haven't explained something well enough.

    footnotes:
    *1) If you are not sure how the potentiometer is wired, measure the voltage across each pair of legs (ie measure pin 1 to 2, 2 to 3, 3 to 1). The two smaller voltages should add up to the larger one (ignore any minus signs). Its the two smaller voltages we care about.
    *2) For example, if the voltages you read are 2.4V and 2.6V, then the ratio will be 2.4/2.6. You have a 2.2k resistor, so we can calculate what the other resistor should be: 2.2k * 2.4/2.6 ~= 2k. The larger resistor should go across the place you measured the larger of the two voltages.

  3. #13
    Shooty's Avatar
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    Ah, I see, very clever! Cheers for the explanation. I believe that this also means that in a pinch, just having the potentiometer soldered to the servo but not attached to the main drive gear can act as a resistor combo, though is probably more fragile then the resistors and needs extra care. Thanks again!

  4. #14
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    Yes, you can use the potentiometer if you have to. The potentiometer can be imagined as two resistors, which change value depending on how much you turn it.
    I think if you glue the potentiometer it in place so it can't turn it should work, but that doesn't seem quite as robust.

  5. #15
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    Jamie McHarg
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    This is how I used to modify servos for 360° rotation too. Take the output gear off, cut the tab and bore out the underside with a drill to remove the slot that goes over the potentiometer, turn the pot manually to centre the servo from the transmitter and dollop some superglue on the pot to stop it from moving. Never had an issue in many years.

  6. #16
    Shooty's Avatar
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    Time for more updates! Léim has progressed far more quickly than I'm used to with my other builds, and should reach its goal of being ready before the end of August, in spite of me being completely removed from my workspace for these first two weeks of the month.

    While new connectors arrived for the batteries, they used a different pin system as well, and after trying for a week to change the pins around, I just couldn't do it. So instead, I've cannibalized some balance connectors from my antweight batteries and soldered them on to the new beetleweight batteries. It means that work on my antweights has become a little trickier due to not being able to charge the batteries, but at least I now have a power source that's lightweight, and whose weight is evenly distributed.


    The new battery configuration


    A moment of silence for a fallen comrade

    Thanks to the batteries now being finished, I was able to test out all of the electronics together. To my pleasant surprise, everything seems to be working first try! The wheels haven't been completely secured yet on account of not having the correct Alan key, but even with this handicap the machine controls beautifully, far better than anything I've ever built. I'm starting to feel like the 500RPM motors will pay themselves off in spades in combat, so long as arena hazards exist in any arena I fight in.


    All of the electronics laid out

    Drive Test:


    As well as all of this, a huge amount of the work on the body has been cut, with only the top plates and flipper arm left to prepare, as well as hollowing out the right flipper bracket. I've decided to change the armour on the front from 10mm to 15mm HDPE, which should hopefully do the job against the new wave of horizontals in beetleweights, especially since that'll be where the batteries are. The hollowing out job I've done on the flipper bracket is something I'm particularly proud of. All that's left is to assemble the parts together with barrel nuts, and thanks to the angled cuts on the wall pieces, the machine should be particularly effective at taking inward blows.


    A shot of the outer walls with headphones for scale


    The work done on one of the flipper brackets that will allow the machine to stay underweight

    I ended up bringing up my electronics with me to this island holiday to be certain the servo works once and for all with the clipped potentiometer, but unfortunately I ended up leaving the receiver at home, so that was a bust! Everything is place, I just need to confirm that it works. I've also sent in the titanium to a metal cutting crowd in Galway, and while I'm certain that all the pieces will be cut to my specifications, I'm always a little anxious when the timeframe is this thin. Still, the machine has come along very well so far, and it's always great to see my drawings coming to life in front of me. The only things still left on the checklist are to check if the flipper mechanism actually works, and the paintjob.


    A shot to give a rough idea of where everything will be, barring the left side battery


    The point at which I've had to leave the build. At this point, I'd say it's roughly 60 to 70% done

  7. #17
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    This is looking great - Can't wait to see the weapon!

  8. #18
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    Well it's been a while since I've updated this build log, but now that it's aired, I can say a bunch of stuff about the build I wouldn't have said usually. So as most of you are aware, Léim was actually being built for Bugglebots, and its performance in the competition was... mixed. But before going into that I still have some catching up to do in the building perspective.

    So in between all of the work I was doing on getting Barróg ready for KOB UK/Insomnia 63, I still had far more to do with Léim, so much so that I was working on it during the event to show the TO's, who were competing at KOB themselves, proof of my weapon's functionality. Fortunately, I was able to do quite a lot of work in the little over a week I had between coming back from a holiday and travelling to Birmingham. Most importantly, I was able to rig up my weapon system. I originally bought a metal servo head for the linkage, but unfortunately its teeth didn't mesh with the servo head, so I ended up using the plastic one instead. After a broken first attempt and quite a bit more money than what it probably should have been, my titanium scoop and linkage arms arrived, and I was actually quite happy with these! I tested flicking the chassis by hand with the springs at their max tension, and the bot actually self-righted, which I thought to be a good sign as well.


    The flipper mechanism mostly set up with the servo in place. It needed to be recessed, and doing that without a mill was quite the challenge!


    The two spring setup in place. In theory, this would be able to lift 4kg at the tip, provided I could wind it down to that point.

    After getting back from KOB UK, it was simply a matter of getting everything wired in place, and getting the final pieces prepared. Unfortunately, one of these pieces included the 5mm top plates, and I seemed to misplace all the 5mm plastic I had at Insomnia. Fortunately, I put out a call for help and Nicholas Cole (Builder of Sir-Lance-A-Frog) offered to cut the pieces himself, and just give them to me at the competition. Massive thanks to him! With that in mind, and as time was running short, I cut placeholder pieces out of 1mm polycarbonate, and opted to paint them along with the front plate, and just bolt the painted pieces on top of the HDPE.


    A drive and weapons test shortly before leaving for Bristol.


    The machine test-weighed. I knew the HDPE would add something, but my weight at this point allowed it.


    Painting the top plates and front piece in Dublin, essentially mid-travel. Was nervous it wouldn't be dried before leaving for the plane!

    Unfortunately, things weren't all great. The main thing I discovered during testing was that the servo would stall when trying to wind both springs down to their loaded position, evidently I had miscalculated somewhere along my planning. So to even have a working weapon at all, I had to downgrade to one spring, with a max force (in theory) of 2kg. Not really a flipper at this point, but it was all I could do in the short time, and at least I could show off the mechanism as a proof of concept. As well as that, in my rush to paint the top panels, I ended up painting the wrong side of one of them! As a quick solution, someone in the Bugglebots crew suggested using the dark-green spray paint used for the arena, so that's why the top is in such a different shade of green!


    The choo-choo with no tension...


    And the choo-choo at max tension.


    The machine, nearly ready for battle!

    With that, all that was left to do was to transfer the wholes from the polycarb plates to the HDPE panels, get through tech-check and weighing, and I was ready to go! With that, I did my intros and interviews (my teams usual green shirt caused some headaches for the green screen crew!) and prepared for the fights ahead...

  9. #19
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    FIGHT 1: ROUND 1

    I was slotted in for heat 4, and my first opponent was Claws 2 from Team Luna-Tic. I had faced the team before in my second Insomnia melee, and I knew how determined this family team was, as well as how well driven these machines were. With the chance of flipping them being questionable at best, I instead hoped the "flipper" would lift them slightly off the ground, enough to gain a control advantage in what I was sure would be a pushing game, similar to US spring flipper BW Butterfly Effect. I loaded into the arena and prepared to fight my first beetle battle.

    (Skip to 14:14)

    Some observations from this fight:


    • One weird thing about the drive on Léim was for some reason braking was enabled on one of the Vex 29's and disabled on the other. This meant whenever I'd let go of the stick Léim would essentially do a 180. As I only really discovered that in this fight, I had to adapt quickly, and so much of the start of the fight was dedicated to learning how to drive the bloody thing.
    • Claws 2's weapon was really the perfect shape for grabbing Léim, but there weren't too many times I was properly "grabbed" as it were. Still though, they definitely gave Felicity the control advantage, and as I couldn't win the wedge game I had to focus on getting around Claws 2 instead.
    • During the pin on Claws 2 about a minute in I was desperately activating the flipping mechanism in the hopes it could lift something. Unfortunately, Claws 2 didn't move a milimeter, and it was at that point I knew the flipper was a failure. Sigh...
    • Despite the weapon performing poorly, I honestly felt I had the slight edge in the control game for the first two minutes of the fight, and so long as I kept the flipper loaded, the titanium frontpiece still could be a decent wedge. Shame the flipper distracted from that I suppose.
    • Unfortunately, in the last minute of the fight, I lose drive on one side, and I can only really limply try to agitate Claws 2 as I'm bullied around until the judges decision finally arrives (fun fact: as all round 1 fights were filmed together, this was the first judges decision of the competition).


    POST-FIGHT:

    I knew even before the decision was read out that I'd lost, and fair play to Chris and Felicity, that is a nicely built and controlled bot. It was certainly disappointing for me however, this was really the first bot I'd ever built which just didn't work how it should've, and I felt I had done no favour to the image of spring flippers. Once I took the bot back to the pits, I saw what caused me to lose drive in one side. One of the grub screws holding the wheel hub to the motor had come loose; I knew this was an issue with Banebots hubs beforehand, but I didn't have the time or the tools to fix it before the competition, something I definitely paid for. I was still in the competition however, and there were still things I wanted to prove with Léim, one way or another. I wanted to see how far I could push the bot with sheer willpower alone.

    https://i.imgur.com/4MAc3oW.mp4
    The grub screw, barely holding on in this instance it seems.

    FIGHT 2: REDEMPTION MELEE

    My redemption melee battle put me against The Berg, a nasty drum spinner who lost their first fight due to unfortunate link placement, and Apex BW, a nasty overhead bar spinner which suffered numerous failures in its opening fight. As well as being built as a flipper, Léim was designed to tank hits, that front had 1.8mm titanium, and the walls at the front were 15mm HDPE (for comparison, Barróg has 10mm walls, my beetle is thicker than my feather). Both of these bots would be great tests for Léim's durability, and I was especially glad to finally face an Apex bot after missing out in my third Insomnia qualifying match only a few weeks ago. With these goals in mind, I loaded up, and prepared to fight to survive.

    (Skip to 23:31)

    Some observations from this fight:


    • I got some nice sparks from The Berg in those opening hits, and I seemed to tank many of Apex's hits with no problems. All was going well so far!
    • It seems that my wires inside the machine kept getting caught in the wheels, and so while I only properly started losing wheels in the final minute, I had mobility problems throughout the fight.
    • Fortunately these problems subsided long enough for me to get a well-timed charge on The Berg, and somehow managed to pit my biggest threat at that moment while staying out of it myself. Pretty happy about myself for that one.
    • At this point Apex was having issues again, and both of us were now struggling to move towards the other. I had more movement, but only barely, and the multiple hits seemed to knock something in the pentiometer loose, causing it to flip uncontrollably.
    • At one point, I lay off Apex completely to allow him to spin up. I came in here to prove I could take the hits, and by god, I wanted to see that happen, one way or the other. Unfortunately, Apex just couldn't shake its curse, and so I was left to limply charge at him once more.
    • Nearing the end, I was actually feeling fairly confident I could win via a judges decision, due to my control earlier in the fight and the way I tanked earlier hits. Unfortunately, my re-tightening of my wheels just didn't hold, and so they gradually gave way, knocking me out with only seconds left. So close and yet so far...


    POST-FIGHT:

    So I was out of the main competition without a single win. Certainly a disappointment after a stellar run with Barróg only a few weeks prior, but it wasn't all bad. Léim gave me a chance to prove my building talents, and no matter its results, I'm still proud I could get it, as my first beetle, up and running for a tight deadline when so many other builders couldn't make it. The bot took hits well, and while yes it did lose functionality in several places, it certainly lasted longer than some of the other competitors, so I could take credit for that. It was also just fun being at the event, everyone was lovely and the fights, pits, and competitors were all brilliant for me to witness in the flesh, even more so as I was still so new to this whole thing.

    https://i.imgur.com/Pa6KKKy.mp4
    A quick sweep of the bot post-Berg and Apex. Some small nicks here and there, but otherwise, it's 100% structure-wise.

    I'm still going to hold off on some more thoughts, as this actually wasn't my last fight at Bugglebots. There is still more to come from Léim, and I'll wait to update you all on those, as well as some concluding thoughts, once the entire series is out. Cheers for reading, the rest of the show will be a hoot!

  10. #20
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    I really liked Léim on Bugglebots; I've always thought there must be a way to make an effective spring flipper, especially in the beetle class where I guess there's no suitable option for pneumatics, so I was really interested to see how you'd got it to work. It is a shame you didn't quite crack it this time but kudos for having a go. Given you're working with a pretty novel concept it's good going to make something that kinda does the right moves, even if the power isn't there yet. I'll be interested to see how you develop the concept - it's got a lot of potential, so I hope you'll stick with the idea!

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