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Thread: Obligatory First Featherweight Build Log (FeatherDozer)

  1. #31
    Ocracoke's Avatar
    Team Kaizen

    Looking good as always, hope you do well in the May RoboDojo event!
    Team Kaizen - Build Diary for all the robots

    AW: Amai, Ikari, Lafiel, Osu, Ramu
    BW: Shu!, The Honey Badger
    FW: Azriel
    MW: Jibril, Kaizen

  2. #32
    Mr Manuva27
    FeatherDozer looks great as always!

    Well excited for tomorrow now, hopefully we get the chance for a good scrap!

  3. #33
    Great to see this machine in the (robotic) flesh Sam, really nice piece of work. Hope to see you at the next one too!

  4. #34
    Event 3 - Robodojo 31/05/21

    It's been a while!

    In the time I have not been posting, 2 events have come and gone for FeatherDozer.

    Due to other commitments, I will be unable to attend either Robodojo Sportsman events in August so what better time to get up to date with this build/ event/ blog diary. As before, I will evaluate each event as well as any repairs/ changes towards the fading path of combat robotic perfection (FYI there isn’t one otherwise things would get very dull, very quickly).

    The first event of the year for me was Robodojo Sportsman 31/05/21. The event videos can be found on the Team Tilly YouTube channel. Thank you Shane for recording and uploading the videos!

    I thought I would slightly adjust my event summaries based on how well the changes made between events faired up against real testing/ combat.

    Relay & link outer protection

    These were a great success! They took direct hits from Hells Angel 2 that could have rendered the bot/weapon immobile but did their job. They also helped to tuck away the link from most overhead attacks which is an added bonus. Though, in future events, I will probably bring spares as they are intended to be sacrificial. The image below is the best hit they took which really showed how affective they can be to protect one of the major possible failure points.


    New drive speed controllers

    Put simply, driving FeatherDozer was a real joy to drive during this event. Taking the time to dial the drive made a world of difference, which meant that I could go on that attack and play to the robots strengths. Practice is still required (the first fight with no barriers against Panda is proof of this), but I found that running the current setup on 4S works well with these BLHeli_S ESCs.

    New Lifter motor

    This upgrade was relatively underwhelming to be honest. Yes, the weapon was slightly faster and had the power but it is still too slow which resulted in a number of judges decisions which could have contributed to being placed 6th for the day (Still very good points though!).

    Damage during event

    Over the course of the event, FeatherDozer did sustain its first non-superficial damage during the closely fought fight with Hells Angel 2 (which ended in a close judges decision win for me). I also realise that I had foreshadowed myself as an axe blow to the left side drive gear resulted in significant tooth damage to both the motor pinion and drive gear. However, the whole drive assembly is a live axle retained by a nyloc nut. This nut had sufficient play to shift the assembly meaning that the gears could still rotate to complete the fight. After the fight I had to take the drive side off and hand file the material away to continue the event.

    PXL_20210531_112339075.jpg PXL_20210601_100249579.jpg

    The very last fight of the day for FeatherDozer was against Red Hot 2 (again). Midway through this fight some of the drive gremlins returned to the already damaged left side which worked the motor and ESC so hard that the ESC melted the protective heatshrink around it. Though this was a worry, everything was still fully functional and is still used in the robot today (with new heatshrink).


    So, all-in-all, a great start to events in 2021! This also helped to determine the way forward for upgrades etc.

    In the next entry (which will be ASAP) I will go through repairs, upgrades and bad decisions building up to the next dojo at the end of June.

    Last edited by Sam_Gad; 17th August 2021 at 16:02.

  5. #35

  6. #36
    Repairs & Brushless Lifter Take 1

    So, there is a lot to cover and now the 2021/22 Robodojo season is complete, it’s time to get this build log up to date. For this post we are going all the way back to May/ June 2021.

    Drive Geartrain Protection

    As the gears took a direct axe hit in the previous event, it was clear that like the relay wires to the weapon, addition protection was required. Damage to both the pinion gear and axle gear are shown below.



    Luckily, there is plenty of bolt holes that can be used to mount the upper drive gear covers which, of course needed to complex due to the tight packaging and weight restrictions.

    With the repairs out of the way, we can get onto the fun part: Brushless lifter.

    Brushless Lifter Shenanigans

    This is still (as of April 2022) an ongoing upgrade but, it is still worth going through how we got to the present setup.
    To get the most benefit out of this upgrade, the setup needed to be as fast as I saw comfortable (or at least faster to full lift than the brushed setup). The existing brushed motor (Vex 775Pro) has a max RPM of 18730 which is then overvolted slightly. The brushless motor chosen therefore had to be faster with the same output shaft to mate to the existing gearbox. The motor chosen was an 1800KV outrunner motor usually used in helicopters. The original motor I wanted was out of stock at the time so this much cheaper motor was the alternative. This gave a max RPM of around 30000RPM on a fully charged 4S lipo (16.8V). This gives a lot of leeway should I need to down the final speed.
    The next stage was to battle harden the magnets in the motor and attach the pinion for the planetary gearbox. The is a surprisingly easy process once you get over the fear of possibly ruining a motor just after you bought it. After this success I went back and battle hardened the drive motors.



    The switch from brushed to brushless resulted in a much smaller package and a nearly 500g weight saving.



    Early testing looked very promising with plenty of speed and power. I decided for the first iteration to use that same speed controllers as the drive as I had spares plus, they can be swapped between the systems easily.
    However, it became very clear the use of limit switches would more critical than ever to stop the design for tearing itself apart. Luckily, an off-the-shelf solution was made available which would work with a speed controller to set the PWM output to centre-point (usually 1.5ms) when a limit switch was pressed.

    So, with the first iteration of fully brushless FeatherDozer complete, it was time to reassemble ready for the next event that was on 26/06/21.

    Last edited by Sam_Gad; 18th April 2022 at 09:55.

  7. #37
    Event 4 – Robodojo 26/06/21

    So where to begin with this event.......

    As before I will quickly summarise the event with the good, bad and ugly damage caused. Unfortunately, not all fights are available for viewing but where required, I will attach images.

    Brushless Lifter – It was all going so well

    After initial testing, I knew that a major change in a short time might come back to bite me. But the main thing to take away was that the mechanism is indeed a lot quicker. What I found was in order to get a “proper lift”, I needed to set aside my mechanical sympathy and just push the stick on the transmitter as quickly as possible. In the future I will be playing with acceleration settings to better utilise the power.
    Now to address the elephant in the room. The lifter functioned for around one and a half fights which turned out to be due to the intermediate limit switch board. I will go into this in a later post as it is something I am still looking to rectify. This meant that I did not have a weapon for the remainder of the event.

    The Ogrelord Fight

    As most may know, Sam Price makes some pretty good, destructive robots. With the allowed inclusion over overhead saws in sportsman for this year, we were all looking forward to finding out how destructive the weapon type could be.
    This fight happened to be the one that the lifter failed. I got one lift in, reset the arm and it never moved again. This wasn’t the main event of this fight however due to the gourmet damage inflicted on FeatherDozer that was great to watch (probably). This is one of the fights that I unfortunately do not have recordings for, but the damage is clear to see.


    As you can just see in the image above, Ogrelord just got to the ESC, but did not fully sever the power wires so it kept working.




    Once it was clear that Ogrelord could go through Hardox with ease, Sam let off slightly (Ogrelord be scary).

    Despite the damage and lack of a weapon, I manged to win a couple of fights and place 7th overall for the day which isn’t too bad considering.

    So, in the next post we will be going over the many repairs from this event and the further testing on what went wrong to the brushless lifter mechanism.

  8. #38
    Mr Manuva27
    This is one of the fights that I unfortunately do not have recordings for, but the damage is clear to see.
    I do!

  9. #39

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