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Thread: First BW Build (Orchid Mantis)

  1. #1
    Hey everyone,
    For my first robot I'm planning on building a beetleweight, but unfortunately I don't really know what I'm doing yet, so this is my ‘help me fix my idea’ thread.
    I've got a quick concept CAD done to show what kind of design I want to go for, a dustpan with a gripping claw:
    mantis1.jpgmantis2.jpg
    Named Orchid Mantis, same as the design I submitted for the RWRA2 Mod.
    I tried to make it about the right size, based on the dimensions for the wheels using 50.8mm Fingertech snap wheels. The robot itself is 30cm wide x 34.5cm long x 4cm tall, but that’s definitely subject to change based on how much room the internal components would take up, and how much everything weighs. I made the mockup with 10mm HDPE in mind for all the sides, with a 2mm aluminium baseplate and top (on the main chassis bit, not including the dustpan).
    The claw on top is pretty much a placeholder – I’m not yet sure of the best shape/materials for it, nor what should power it.
    Not sure what the dustpan should be made from either, or how it should be fitted. Could I maybe use a hinge to get 0 ground clearance on it?
    As far as parts go I was looking at the mini 1000rpm motors and 10a brushed ESCs from Ranglebox, as well as this radio + receiver: http://www.hobbyking.co.uk/hobbyking...x_Mode_2_.html
    And this battery: http://www.hobbyking.co.uk/hobbyking...Lipo_Pack.html

    So am I on the right track here?
    Thanks for your time

  2. #2
    Looks good! I'm a beginner too, currently building my first featherweight, so probably take stuff I say with a pinch of salt. I'd expect you'd want some kind of little linear actuator for the claw, depending on how much force you want out of the end. Although obviously as a beetleweight, you're gonna want to keep the weight down. Was it just a gripper you wanted, or is it meant to crush as well? Obviously, that'll affect what you need to make it out of and power it with. In any case, you'll want to make the arm pretty solid if you're going in with spinners, I've seen even beetleweight spinners can be quite nasty, and you don't want it getting torn off or bent straight away.

    You could definitely hinge the wedge, I know quite a few 'bots do. But you'd obviously have to redesign it a little, and be careful of getting stuck on things if the floor isn't perfectly flat. Also, did you check that the TX/RX failsafes on all channels? That's an important requirement.

    Best of luck, there are probably a good many others who can give more valid advice than I.

  3. #3

  4. #4
    Yeah. With the transmitter I went for the 'buy nice or buy twice' philosophy, and got me a DX6i. It might be worth making sure it'll be suitable for any future robots you make, though it probably will.

  5. #5
    For just a grip a high power servo should be enough.

    www.hobbyking.co.uk/hobbyking/store/__43054__TrackStar_8482_TS_910_Digital_1_8_Truggy_ Monster_Truck_Servo_30_6kg_0_14sec_66g.html

    Just as an example, but that has over 1.5kg of force at the end of a 20cm arm and it weighs 66 grams.

    You don't need to worry about hinging the wedge, with the wheels near the back it will sit flush on the front of the pan.

    As for the arm design, if you want you can make it a combined lifter with some kind of wedge front to get under but more importantly with the right shape it will right itself even with a relatively low degree of movement.

    Not sure why you have the red wedgelets on the back.

    Not sure if you have thought it through but I assume the win condition for you is to grab and then drop someone down the pit (I assume this is for kinematics and assume the pit will remain a feature) so you need to consider how your pan achieves scooping them in, holding them as they try to escape and then dumping them in a controlled manner when they won't want to. Most pans are great at the first but struggle with the second and get the opponent out by spinning.

  6. #6

  7. #7
    Here is a good illustration of what I mean

    www.battlebots.com/robot/bite-force/

    See how the grip arm forms a natural wedge when it closes entirely. Your arm would be something like a flat surface. Its a tiny tweek but gives you a dual use weapon.

    I wasn't discouraging a pan scoop design, I personally like it, just saying you may struggle to release someone down the pit if its too long. There are a few solutions the simplest is just being fast and going from full speed to zero right next to it.
    Last edited by Phill; 7th April 2016 at 23:37.

  8. #8

  9. #9
    Okay, I've made some progress
    Motors from ranglebox are on their way, and I've made a new claw design:
    newclaw.png
    Still not sure about materials for the claw, and I imagine that might have an impact on the design.
    Right now though what I'm most unsure about is the ESC. Since the 10a one from ranglebox is out of stock I'm pretty lost on what to get. I looked at the recent thread asking for alternatives, but the hobbyking one that looked like the best choice for me in that thread is also out of stock. Any guidance on what I should be looking for in alternatives would be great.
    Also, I'm not sure if the servo for the claw should go through the ESC or connect straight to the receiver. I'm guessing that latter?

  10. #10

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