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  • #61
    EXR Portsmouth 2019
    After getting up at 3am to get down to EXR Portsmouth with Voodoo 2 and Jibril, there was a fair bit to do. The speed controller needed repositioning, the axe mechanism needed testing and the big Scythe needed to be fitted onto the mechanism along with a slot being cut in the front beam.

    Many thanks to Theo and Nat helping with the front beam, it was eventually cut and the axe now cleared it nicely. The ESC was repositioned and tested with the separate receiver, which eliminated the jitters so on went the big metal Scythe. A few people had commented on how heavy it felt and I was a little concerned myself after it was attached, so I fitted a rudimentary bump stop to raise it up a little from the flat to help it get moving.

    With Jibril ready, I was all set for my first fight, which was against Voodoo 2 but moments earlier, when loading, the transmitter fell on the floor and broke one of the switches, so the transmitter wouldn't turn on, meaning I had to be swapped out with You Little Ripper. I wasn't best pleased but got it fixed anyway. This meant I missed my chance to fight in the first show.

    In the second show, a few HWs had dropped out so I was made an honorary HW and was promptly placed into 1v1 with Team Shock's Earthquake. This, despite losing, was a fun way to lose. The Scythe did fire but it's slow and when turned over lacked the power to self right. Eventually, the drive ESC receiver wires were snagged in the drive wheels and the whole robot stopped. The fight lasted 1:55, which isn't bad when you consider the 50kg+ weight difference :P

    The battle damage was pretty much on the Scythe, which Jibril landed on several times. The 10mm shaft for the output gear was bent, the axe ESC had also broke again (the soldering failed) and the drive receiver disappeared completely. A hasty rewire to use the Scythe receiver as a drive receiver and removing the Scythe itself and Jibril was running again as a rambot.

    1558194519183.JPEG

    The next fight it was involved in was a Heavyweight Melee with 2 Headed Death Flamingo, Ripper and Earthquake. This is one of those "flying lessons" battles where Jibril was sent flying by both Earthquake and Ripper, the latter causing Jibril to hit the ceiling at one stage. I knew I wasn't going to win but I would have liked to have survived the fight. Sadly not to be, the radio receiver wires for the Axe ESC exploded and caused the receiver to conk out with some smoke. At least I wasn't thrown out of the arena, so there is that.

    Despite the damage, the event was fun. It was great meeting a new fellow Middleweight in Bump and Grind and the event itself was quite full on. The fact I was placed with robots weighing nearly 3x than me didn't bother me in the slightest, I found the experience to be hilarious and insightful as to what works and what doesn't work. I would have liked to have fought a Middleweight but such is the draw, many thanks to Greg for putting me in where he could.

    So with that in mind, for Jibril 1.1, the following needs to happen:

    • New drive wheels with more traction
    • The Scythe needs better gearing, approaching 12:1 with a thicker final shaft.
    • Fix the Scythe ESC again
    • Replace the lost receiver
    • Replace the power LEDs
    • Replace the locking pin guides
    • Secure the wiring properly.


    The thing is, I may not have all of these done for a potential day at EXR Guildford (the last 5 definitely need doing). I'll know over this week as to what really needs doing but if it doesn't make it to EXR Guildford, it will go to RL Grantham.
    Last edited by Ocracoke; 19 May 2019, 01:32.

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    • #62
      Happy to have met you and assist you with the small bit of beam cutting too.
      Sorry to hear about the TX but glad is fixed, and maybe the rx appeared in the scrap pile art the end of the clear up? and that amount of damage from going up against the HW is good compared to what could have been done so that is a great achievement
      Hopefully catch you at Guildford, if not later on in the year

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      • #63
        I wasn't around for the scrap pile. It isn't a big deal, I have one I can rob from another robot, just a pain. TBH, I'll probably treat myself to a new TX later on in the year.

        Yeah, the damage wasn't bad all things considered. It occurs to me that had I fought in the weight class I was meant to be in, I would have likely come out without knowing these weaknesses so yeah, quite happy with the result overall. I'd still fight a HW again.

        I've managed to get the bent shaft out and replaced it with a higher tensile bolt which will do for now. I've been plotting to replace the single stage reduction with a two stage to get more torque so it can self right which I am hoping to do later on in the year. I'll be mending Jibril on Wednesday as much as I can so I'll find out if I'll be going to EXR Guilford by Thursday.

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        • #64
          If Jibril can happily go into the arena with Heavyweights and take the kids of punishment they dish out, well, nicely done

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          • #65
            ahhahaa, thanks. It certainly told me where the weak spots were. Time to go and fix those :P

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            • #66
              So I've had a look at Jibril and I am going to tentatively say yes, it will be at EXR Guildford.

              The radio receiver is stone dead, killed most likely due to either a overdraw when the radio wire caught fire or a short somewhere. I found that the main power supply to the drive ESC fell out so I guess what happened was that this happened and the draw through the Axe ESC, which I left plugged in for some reason caused the radio wire to blow. Had I been using 2 receivers as normal, this would not have been an issue.

              The top panel, as noted, is cracked. I have a spare but I want to use that when I implement the two stage gearbox. The original panel can still be used, I'll just have to tie it together with a metal bar.

              Time to order some new receivers and replace the axe ESC again. I've managed to rescue the second ESC and secured the dodgy item with that wondrous thing known as electrical tape. With any luck, this will hold out but I've been planning a contactor setup to get shot of this. I'll see about prototyping this later on in the year.

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              • #67
                Portsmouth sounded like a bit of a baptism of fire! Seems Jibril acquitted itself well, in any case.

                How did you select the original gearing for the scythe? Do you do calculations or is it just gut feel? I find I seem to swing wildly between intricately constructed spreadsheets and "that looks about right and more importantly fits in the available volume"...

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                • #68
                  The gearing for the Scythe wasn't meant to be as high as it is. I was originally meant to have a 19T pinion gear but it turned out that the engineers couldn't get one so offered me a 18T or a 20T. Since the 18T didn't come with a 12.7mm bore, I had to get a 20T. It could have been higher but at the time, I only had the equipment for a 10mm bore and the biggest drive gear with a 10mm bore was a 90T. 90/20 = 4.5:1

                  Kaizen
                  used a 3:1 ratio but that was when I was first experimenting with gearboxes like this (I'll be reusing that assembly for Azriel with different gearing). Ultimately, with the power of the motor driving the Sycthe (around 2.3HP peak), I took a slightly educated guess as to wherever it would swing given the heavy weight on the end.

                  The planned two stage box is going to be slightly more complex but not that much more so. A 20T motor pinion to a 70T gear to give 3.5:1 and then that gear connected to another 20T gear to the 90T gear to give 4.5:1, multiply that together to make 15.75:1. I'll try and work out the maths behind it soon enough.
                  Last edited by Ocracoke; 24 May 2019, 16:24.

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                  • #69
                    The top panel is tied back together with a big metal strap and the Scythe reinstated. I've had to swap out the high tensile bolt with a threaded rod since it didn't reach. I might get a new longer bolt if I can get time to order one.

                    Next week is replacing the ESC (again), getting new Lemon RX receivers installed and then actually get some damn testing done on this robot.

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                    • #70
                      Jibril
                      Sigh
                      The drive ESC is dead. Although a weak point on the Cytron boards seems to be a coil, this one also has a damaged capacitor and I lack the facility to repair this properly so a new ESC is en route. The new Lemon RX receivers are in and they seem to work so that is a plus. I need to pickup the LEDs but once the new drive ESC is here, I can finally put this robot back together.

                      The longer term plan is to get the two stage box in for the Scythe and put some side skirts on the robot. I think I can place the F30 further back into the robot to correct a fairly annoying weight bias. Having a custom gearbox also allows for a locking pin that won't bend upon being turned upside down. However, I am in two minds. I want the new gearbox done before EXR Bolton, where I hope to get some family to come and actually see a robotics event but I do need to get Azriel running as well.

                      In fairness, Azriel just needs a body and chassis which can be done in a few days. Things like the axe and the drive are already done so hmm... I am hoping to return back to RoboDojo with it but perhaps I might get to RL Grantham with the pair instead.

                      Comment


                      • #71
                        Post a pic of the failed esc and the coil you think it was, and perhaps someone could repair it, or if your along to Guildford I could take a look and advise

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                        • #72
                          This is a picture of the capacitor. Spot the damage. :P

                          JPEG_20190530_172234.jpg

                          So this and the knackered coil (which I don't have a picture of) were the only visible damage I can see. The coil I have fixed before on the Scythe ESC so I know the procedure to fix it but I don't have a spare capacitor of that rating around.
                          Last edited by Ocracoke; 2 June 2019, 13:02.

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                          • #73
                            Are you sure the capacitor has died? It looks like surface damage that hasn't gone all the way in entirely.

                            if you have a multimeter you can test if it has died or is behaving oddly. Incase you don't know how, set the meter into high ohms (anything above 20k to a sensible number high works), when the capacitor is linked in line it should start at 0.00 then slowly rise to infinity. You'd need to desolder the capacitor to do this test, else the circuit will suck up the energy, if you happen to have an ESR meter you could do it inline without desoldering. If the number stays at 0, the capacitor is dead or the leads were attached with the wrong polarity. Can also do capacitance tests on it if the multimeter supports it to see if its reaching its target (or within a few % of it), te ohm test is a basic "all or dead" test.

                            Before you start and when done testing, I personally find a metal screwdriver and short the capacitor at the pins, just to make sure its discharged entirely.
                            Last edited by ; 2 June 2019, 21:41.

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                            • #74
                              What is the rating of the cap? Looks like it may be slightly dented and scuffed. Would be easy to repair that too. What’s the spec and I can take a look in the components tub, also spec of the coil too and can check

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                              • #75
                                if you have a multimeter you can test if it has died or is behaving oddly.
                                It was one of the first things I tried to do but the multimeter I have here died as well. Needs a new battery. I've been watching a few electronics videos and the subject of capacitor discharge has come up a few times, good advice though, I'll remember to do that.

                                The capacitor feels like it has blown out, there is a definite outward pattern to the mark and a raised ridge. It does smell like electrical burn but it isn't clear to me.

                                What is the rating of the cap? Looks like it may be slightly dented and scuffed. Would be easy to repair that too. What’s the spec and I can take a look in the components tub, also spec of the coil too and can check
                                The coil is a "680" coil, so I assume it is a inductor coil like this: https://www.mouser.co.uk/ProductDeta...4bT3wBwsbAQ%3D

                                The capacitor is a 63V 2200uF version (CD11X). Luckily, Cytron (the maker of the ESCs) stock all these parts separately so I believe it is one of these: https://www.cytron.io/c-electrolytic...gory.discovery

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