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Thread: Scottie Builds things some times. Eric the destructor - first beetleweight robot

  1. #11
    If you don't mind me asking, how are you planning to attach the metal mounts to the base? are you going to tap threads through them, or are you using some other method?

  2. #12
    Hey there! I have attached the metal mounts to the base by drilling and tapping directly into the metal, shown below.

    IMG_20180116_200255.jpg
    Unfortunately i have had to drill and tap by hand, and i have the finesse of an ogre when in comes to using power tools!

  3. #13
    Here is the latest installment of Erics saga.

    I first tapped and screwed together my diy pulley attached to the blades. these are 6 holes for m3 screws. all the teeth are more or less aligned and it looks pretty good. Not bad considering i had to find the teeth dimensions on an obscure forum and with out the ability to cross check that it was correct, something i wouldnt want to do again!
    IMG_20180116_202322.jpg IMG_20180116_202340.jpg
    next I fitted some bearings into the blade. And what i mean by me a really mean a technician at my university as when i got them made i didnt factor in tolerances of the manufacturing process i was using. The blades were a little to tight for the bearings to fit in so i had to get them machined out on a lathe.
    IMG_20180116_202548.jpg
    I then assembled the blades by screwing everything together through those 3 holes. The other 2 holes are there for a safety pin to be inserted. Once assembled I placed them onto a titanium dead bar and placed it on the left metal arm. At this stage I also attached the weapon motor and its pulley to the same arm as well as fit the pulley belt.
    IMG_20180116_214939.jpg

    IMG_20180116_214932.jpg
    You probably spotted the front plate on the left side of the bot this had to go on in before i fitted the blade. both front plates are 1.5mm titanium.

    IMG_20180116_231357.jpgIMG_20180116_231424.jpgIMG_20180116_231413.jpg
    at this point I wanted to see what it looked like with the motors, wheels and battery inside it. None of them are screwed in yet so everything looks a bit closer than it should. I am however a bit concerned for the left most batter and the motor wires placed ontop of it. they are going to be a bit to close to those to motors for comfort so i need to find a way hold them down securely. I am open to suggestions for this.

  4. #14
    Ocracoke's Avatar
    Team Kaizen

    Sweet mercy that looks impregnable.

    I am however a bit concerned for the left most batter and the motor wires placed ontop of it. they are going to be a bit to close to those to motors for comfort so i need to find a way hold them down securely.
    If there is any sideways movement, move the batteries a little closer to the centre, drill 2x M3 bolt holes, one either side of where the battery is going to be, thin HDPE plate with a hole at each end of it and then with a nut and washer, wind the nut+washer onto the plate with the battery in between that and the rear plate to sandwich it in is how I would do it.
    Team Kaizen - Build Diary for all the robots

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

  5. #15
    Surprise time! I was waiting to post about it when my robot was fully operational, but i think i just do it now anyway. For me, part of making a beetle weight robot is to learn something new. I can safely say, interfacing bldc motors with gear boxes not designed for them, working with hdpe and assembling a weapon system that was not just a motor and a 20g blade has been a pretty valid experience! But i wanted something more, what could i do? Tbh there is only so many ways you can make a vertical spinner, but there are loads of ways you can make it look different aseptically. So i though perhaps i could anodise the metal bits. And that is what i am doing.

    I have two types of metal on my robot, Titanium (front armour plate) and Aluminium (blade and internal structure). Both can be anodised. This post will just be about anodising Titanium as they both require slightly different processes, and i haven't started anodising my aluminium parts yet.

    Preparation.

    Before i anodised the titanium I wanted to polish them. I bought the plate from ebay and it had a rough finish on the surface, which was pretty ugly. Whatever surface finish you have will also be present post anodising. So i bought a buffing kit off ebay. This had aluminium and steel buffing compounds, 3 types of buffing discs for drills and some vienna lime. I couldn't find buffing compounds optimised for titanium so i just used the steel buffing compounds. buffing is pretty simple so wont document how i did it (I didnt actually document it in the first place DOH!), lots of tutorials on youtube though. Here is a side by side comparison of before buffing (below) and after (top).
    IMG_20180120_162045.jpg

    The basics

    By using a weak acid electrolyte and passing a DC voltage through it via a titanium anode and aluminium cathode, An oxide layer forms on the anode. This oxide layer on the titanium is transparent, allowing light to pass through it and reflect off of the titanium surface. Some light also reflects off the top of the oxide layer. These two reflections can add constructively to make a certain colour to be more visible, making the surface of the titanium appear coloured. By varying the oxide layer thickness different colours can be produced. This is achieved by varying the DC voltage. Typical voltages are anywhere between 12V-120V. Caveat, you can only increase the voltage to produce different colours as a greater voltage creates a thicker oxide layer.

    Anodising equipment

    Weak acid - I used distilled vinegar for pickling. (You can use coke for this)
    A plastic tub big enough for your part to be anodised and the cathode to be submerged in
    some titanium wire
    A DC supply (I required up to 74V)
    Alumium cathode - I used some take away lasagna trays
    crocodile clips and power cables
    Volt meter
    And importantly your titanium part, which is your anode

    My requirements

    I would like to have my plates coloured purple and to produce this I could use to voltages ranges, 18V or 70-74V. At 18V you get a sort of dark purple, it looked kind of washed out to me and i wanted something more vibrant. So I decided to use 74V.

    my setup
    I looped some titanium wire around some screw holes in my titanium armour plate. I connected the titanium wire to the positive of the voltage supply via some crocodile clip terminated wire. I connected the aluminium cathode to the negative of the supply.
    IMG_20180124_224305.jpg

    Problems

    My initial setup used a 64V DC supply in conjunction with a 1Ah 11.1V Lipo battery. I didn't think about how long this would take and the process draws around 500mA initially due to the size of my plates. Yeah my battery went flat in 30 minutes. So I ended up with this really weird colour that I could never replicate, let alone understand the colours that it produced (below).
    IMG_20180124_190728.jpg
    This is was rather frustrating as you cannot re anodise it without removing the oxide layer, which I did by rebuffing the surface. I solved the voltage issue by using a variable DC-DC boost converter that could output up to 80V from a 12V supply.

    Processing and end results

    It took about an hour to fully anodise the surface of each plate to the colour I wanted. Initially I started at a low voltage and then turned the power off around 20V. Here is what it looked like half way through the process.
    IMG_20180120_195415_01.jpg
    I then increased the voltage to 74V and let the process complete. Here are some side by side comparisons from before and after anodising with pre anodising plates in rough and shiny finishes.
    IMG_20180120_210759.jpgIMG_20180120_210806.jpg
    and here is the end result.
    IMG_20180125_000015.jpg
    The plate on the left is the plate i had to re anodise. Its slightly greenish on the bottom, probably due to me leaving some oxide layer from the previous attempt. It also looks slightly duller due to being buffed twice and thus is more reflective.
    Last edited by Scottie; 26th January 2018 at 18:16. Reason: Grammar and things

  6. #16
    I must say your beetle looks truly awesome! And anodising the case is the cherry on top. Never thought of attempting that - already thinking Evil K'Weevil will need an upgrade and not built him yet. I decided to fit a slow motor on weapon to avoid restrictions but could go faster and perhaps have interchangeable motors. But he is direct drive.

    P.S. I have a similar vertical spinner weapon design concept for a featherweight. Be interested to see how you get on.

  7. #17
    Thank you very much! Anodising, atleast with titanium, is pretty straight forward. Aluminium is a bit more involved and requires an unpleasant electrolyte. More on that later. And same to you about your robot. I am very much looking forward to seeing it complete! Im a bit unsure what you mean by restrictions though, perhaps i should reread the rules. But having interchangeable motors sounds like a great idea. having different types of motors should allow for greater flexibility in different situations as well as enhanced redundancy.

  8. #18
    Ocracoke's Avatar
    Team Kaizen

    In theory, Shu! has interchangeable arm motors (a 67:1 and a 131:1) - I can't see why this wouldn't be allowed in the rules... unless you are talking about the rotational weapons section?

    The anodising looks awesome and will look neat with the white plastic underneath, can't wait to see it at the Beetle Brawl.
    Team Kaizen - Build Diary for all the robots

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

  9. #19
    Thanks Ocracoke! All the electronics are now assembled (welcome to the jungle?). Hopefully ill have it fully assembled by the end of the weekend so i can show it's functionality. I have some videos of the blade spinning but its doesn't quite show what i want to demonstrate.

  10. #20
    [QUOTE]Im a bit unsure what you mean by restrictions though, perhaps i should reread the rules. But having interchangeable motors sounds like a great idea. having different types of motors should allow for greater flexibility in different situations as well as enhanced redundancy.[/QUOTE]

    Yes I was thinking of the 500rpm regulation and competitions allowing spinners. But as I am noob perhaps I need to check rules.

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