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Thread: New bot builder - general advice required

  1. #1

  2. #2
    Ocracoke's Avatar
    Team Kaizen

    Hi Mike, welcome to the forum! To try and answer your questions directly:

    - What is the best weight class to start with? I would assume either beetleweight or antweight but I am not sure
    This depends on what you feel comfortable with. For a completely new beginner, I'd recommend either the Beetleweight or Featherweight classes simply because of the availability of the parts and the scale of the parts. Antweights is another option but they can be, in my experience anyway, fiddly.

    The flipside is that AWs have quite a range of events throughout the year (Ant Freeze, AWS, BotFest and so on though disclaimer, I run the BotFest events :P). BWs tend to be a little few and far between but they are growing. FW's tend to share with the larger events like Extreme Robots and Robots Live. There is also the RoboDojo events in Leeds which is a FW only event with a beginner friendly sportsman level.

    - What is the simplest weapon to install to make sure that an active weapon system works and I can actually program it?
    In my experience, a lifter is perhaps one of the simplist while teaching the basics of active weaponry with axes next. You might imagine a saw or something would be easy but I wouldn't ever recommend these to a beginner because of the capacity for things to go diasterously wrong.

    - Where would be an ideal place to source materials from (transmitters, motors etc.)
    HobbyKing is generally a good place to start for RCs. Motors, depends on the weight class but FWs tend use drill motors as a starting motor. BWs, try here: https://shop.bristolbotbuilders.com/

    - What is a usual budget for building a machine?
    This is one of those questions that is quite subjective personally. If I had to price up one of my previous FWs as a "basic" machine from scratch... about £350 all in. One of my BWs... about £150 all in (so that is motors, wheels, shell, fixtures, ESCs, wiring, RC control). This does, however, greatly depend on what specific parts you get.
    Team Kaizen - Build Diary for all the robots

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

  3. #3

  4. #4
    Ocracoke's Avatar
    Team Kaizen

    Sounds good, hope to see something come out of this.

    As a recommendation, do read the existing build threads here as they'll inform as to what does, and more importantly, doesn't work.
    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. #5

  6. #6
    Ocracoke's Avatar
    Team Kaizen

    When I built my first BW (Shu!), I used PVC rods as uprights and screwed into that. That worked but wasn't very strong overall though in all fairness, the boxy shape didn't help and PVC itself is not a good material for this - HDPE is much better.

    I opt to use threaded inserts into square rods these days to bolt two panels together. Barrel nuts are another option but at the BW level, I find the inserts work well enough.
    Team Kaizen - Build Diary for all the robots

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

  7. #7
    Hi Mike, welcome to the forum! I think Lucy has covered most of the important stuff here. I'd broadly agree with the comments on weight classes - I've spent ages trying to make an Antweight that I'm happy with, and I do find the fiddly teeny bits frustrating. This is speaking as someone whose other hobbies include painting Warhammer figures and playing the ukulele, so it's not just that I have giant clumsy hands. However if you want to just get something built and have access to a 3D printer there are loads of free STL files for Ants.

    I haven't yet built a beetle but I get the impression that the "scene" is pretty competitive. That might make beetles less attractive to a complete beginner. That said, Robodojo do have a "Sportsman" beetle competition (i.e., no nasty spinners). There are also events like "Bodgebots" in Bristol. (I say "there are", what I mean is "there used to be and hopefully soon will be again!")

    The first robot my friends and I built was a featherweight and I found that pretty good to start out with - there's lots of room for wiring and such, and the end result feels pretty satisfying. However, we had access to the Hackspace in Nottingham, which made the physical size of the robot less of an issue. If you are building at home and don't have a workshop, beetle is probably the way to go.

    As far as building a chassis goes - I think most people tend to build a box, generally from HDPE sheet. You don't need to build a ladder frame or use spacers made from rods. Just cut out flat bits and fix together with barrel nuts like Lucy says, or take the gash solution that I used and just use loads of woodscrews.

  8. #8

  9. #9
    Ocracoke's Avatar
    Team Kaizen

    I'm currently in the process of drawing out plans for a new panel lifter/flipper design, but I wanted the machine to be rather compact. I was looking at around H - 8cm L - 15cm W - 12cm but I'm not entirely sure whether that would be to compact since from what I have seen, a lot of bots at the weight class are much longer than this.
    Doesn't matter about the dimensions so much if the design is something you are happy with. :P

    Would using this be more protective than HDPE or polycarbonate? I know that the bot will not be fighting for a while, but I feel like I want to slap together something I feel will work and then work from there.
    I am on the fence. I certainly think it'd work in what you are planning to use it for but then again, admittedly at a different weight class, I found angled polycarbonate to work just as well. HDPE is very energy absorbing though.
    Team Kaizen - Build Diary for all the robots

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

  10. #10
    Another thing to keep in mind is that it's worth leaving some wiggle room inside the bot. Your outer dimensions sounds fine, but when you come to pack everything in you might struggle with wiring and stuff like that if you pack it in too tightly (this is certainly a mistake I made!).

    Aluminium is not a great material for taking impacts. It's not awful but HDPE is much better. Keep in mind that HDPE is about 1g/cm³ vs 2.7 for aluminium, so for the same sized panels you could either have 4mm thick Al or 10mm thick HDPE and the weight is about the same. The HDPE version is not as strong or stiff but will take impacts far better - the aluminium will tear, dent, pull out from its screw holes, etc, whereas HDPE will get gouged but only "locally". Plus, HDPE is much easier to work with.

    All that said - if it's held together right, a 4mm aluminium shell isn't going to disintegrate in a stiff breeze or anything.

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