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Thread: I'm looking to build a reliable featherweight but don't know where to start

  1. #1
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    Sam Witts
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    Hi,

    I'm looking to build a featherweight rambot that's tough and reliable, and I have no idea where to start with regards to the components.

    Can anyone offer advice for reliable components?

    Thanks

    Sam

  2. #2
    typhoon_driver's Avatar
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    Welcome to the forum Sam. To save fatigue from people answering the same questions time and time again, I would recommend reading through previous threads. I counted at least 3 "I'm new to bots" threads on the front page of the feather section alone. There is a lot of good information and discussion in a lot of these.

    Once you've read through them you will be able to ask more targeted questions.

  3. #3
    Doodle2411's Avatar
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    Welcome Sam,
    From what people have told me on my post. If you want a tough and reliable robot, the best way to go would be to design the robot before you make a shopping list.

    I'd agree with Gary, check out other posts. They are really useful and are what I am currently looking at for my first featherweight Trident.

    As for components, as you won't have any weapons, your main focus should be on armour that can take abuse from other robots as well as a good shape to push other robots.

    Finally, look at other examples, there are a bunch of pushing robots to look at, the first that pops into my head is Tiny Toon. But, as Mrsam replied on my post, specify what kind of event you plan to go to, do you want to be fight spinners and drums and many more in Robo Challenge or, do you want to go for the safe route and face flippers, axes and other Wedges at Robot Wars, either way, you will need tough components and armour ment and a decent shape. Can't wait to see how it turns out, as we are in the same boat, I can't wait to see you at an event.

    Enjoy the life of a roboteer
    Doodle
    Last edited by Doodle2411; 19th July 2015 at 15:07.

  4. #4
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    A beetle or ant weight would be an easier first-build as you you can buy all the running gear "off the shelf". With a feather you will have to sort hubs and gearboxes etc. at some point.

  5. #5
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    The difficulty of the above is what makes it worthwhile. Learning happens hard and fast in feathers and that's a good thing^

    For a simple featherweight you need a few basic components:

    Radio gear, ie, a transmitter and receiver set. Lots of options here, must be a 2.4Ghz type to be legal.

    You need drive motors and some sort of reduction (gearing) after them so they have enough torque to drive the robot. Popular choice here is the insides from cheap cordless drills (there are a few videos on YouTube about how to make use of these).

    You'll need ESCs (electronic speed controllers) to control the drive motors. These read the receiver's signals (which mimic what you're telling it to do from your transmitter) and control the drive motors to suit. Botbitz ESCs are popular as they are rugged and affordable.

    A power source, as in a battery. A few years ago the norm was NiMH battery packs, these are now mostly forgotten with the arrival of LiPo (lithium) batteries. However these require additional care and respect as they are complicated to charge/maintain and have immense potential power. I might recommend starting with NiMH, which will be absolutely fine for most robot types and are generally more forgiving. Not a rule if you're simply sensible about LiPos and do the research on how to be safe with them.


    You'll need to build a chassis around the resulting pile of components. The way in which this comes to be depends on your skill level, access to tooling, and creativity. The last one is absolutely the most important.

    As for sourcing what specific components the above equates to, that depends on what kind of bot you want to make and figuring out actual parts from there.

  6. #6
    HereticBlue's Avatar
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    Sam, the best feather to look at for the basics is Ricochet. It's a very simple shape, all you'll need to cut the HDPE is either a table saw or a jigsaw then drive bolts and shafts through to hold everything together.

    Always keep it as simple as possible, the more complex the design, the more likely it is to bugger up and the last thing you want is to have is a twisted chassis/body. As for fixing everything down, make sure you get your measurements and stick to them. Always plan ahead and don't rush it like I did. Best advise I could possibly give.

  7. #7
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    After a few months in the pipeline, I've finally come up with a design, alongside a basic circuit diagram.
    Robot design.jpgRobot Circuit Diagram.jpg

    I'm trying for a low to the ground, compact, fast and maneuverable rammer. The design shows I'm going for a 4WD approach, and the circuit diagram shows a compact looking design. The only issue is how to create the 4WD system with only two motors, I can't decide between the heavier and possibly more fragile drive chain and sprocket approach, or the lighter and possibly more durable belt driven approach

    With regards to event types, I'm unsure about going to Robochallenge unless I have a lot more experience (knowing fully well that robots like Mr Mangle, Drumroll 2, amongst other spinners could tear it apart) so at least for now the live tour events.

    I've figured out what components I'm going for:

    - 2 REEDY Wolfpack NiMH Battery Sticks (with Deans plugs)
    - XT60 - Deans plug adapter, three way XT60 adapter for a Safety link mount, with a XT60 for a safety link
    - Sabertooth Speed Controller/BotBitz 85a v2 Brushed ESC
    - 2 Argos Value Drill Motors
    - 20mm HDPE
    - Ranglebox M6 Threaded Bar with M6 bolts
    - Colson Performa wheels

    A quick question on speed controllers, out of the Sabertooth and Botbitz 85a which one is recommended for a 4WD robot with two motors?

  8. #8
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    Welcome Sam. I'm sure plenty of advice and help will be given. I'm in the same boat as you in that I'm starting a feather build for my 1st bot.
    From reading posts here it seem that the botbitz 85a controllers converted for brushed motors are popular but also hard to obtain.
    I'll be creating a build thread once i get a design i want sussed out. Like you im going for 4wd driven off belts system to allow some forgiveness to the motors.
    It'll have a BB85A each side to handle the load. Failing the availability ill try and pair up the 30A versions if possible. I'm stuck on weapon at the mo but I'd love to do either a lifter or a drum spinner.
    Good luck in whatever route u choose .
    Andy
    Last edited by cnc_machinist_andy; 18th March 2016 at 10:07.

  9. #9
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    Nice to get a mention by name! Just so the ripping and tearing doesn't happen, here are my suggestions:

    * Chains VS belts is an endless debate and mostly down to personal preference. Chains are always going to be heavier than belts, which means lightening up the frame or armour. Belts are usually bulkier (wider) than chains. Belts are more fussy about the correct tension than chains, but adding a tension adjuster is easy and helps prevent both belts and chains from falling off. Chain length can be adjusted with half links and a tool called a chain breaker, while belts are a set length. You can get around length issues with a larger tension adjuster wheel. My personal preference is belts, but only by a small margin.

    * I don't have any experience with the Sabertooth ESCs, but have heard more negative comments than for the TX85a controllers. There is plenty of community support for the Botbitz ESC, which can be hugely useful - you can often buy or borrow one at events, something that won't happen with the Sabertooth ESC.

    * The Colson wheels are a great choice, you won't regret it! Have you thought about how to attach the sprockets or pulleys to the wheels and what sort of bearings to use?

    * With the connector choices, it sounds like you are trying to avoid soldering. Its a good basic skill to have and almost impossible to avoid when building bots. A soldering iron with an 80 watt rating is the perfect size for connectors and power wiring.

    * I don't see a fuse in the circuit diagram. Soldering a cut-down car fuse to the back of the XT60 power link is a convenient and space saving place to put it.

    * HDPE is never a bad choice for a frame, look at barrel bolts and tee nuts to hold everything together. Sheet metal screws are OK for holding internal parts to the frame, but will not stand up to much of a beating when holding the frame together.

  10. #10
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    Sam Witts
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    Hi,

    Thinking about using a Hardox plate for the front scoop, what's the most common grade used and where is the best place to get it?
    Also, I'm looking for some colson wheels and hubs to allow for a 4wd setup (within the UK), where is the best place to get them?

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