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Thread: Featherweight Horizontal Bar Spinner

  1. #1
    mullinsj08's Avatar
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    Hi all,

    I'm yet another first time bot-builder currently designing a FW horizontal bar spinner which has the working name 'Little Spinner'.

    I have a few questions but we'll start with my current predicament: I started designing the body of the robot before choosing parts (I know, I know) and now I've realised that the Gimson motors (GR-EP-45E) don't actually fit in the machine end-to-end (See below).


    Screenshot 2018-10-09 at 13.29.19.png

    I guess have 3 options:

    1) Install the motors side-by-side and have a belt/chain to the wheels.
    2) Re-design the chassis to be wider so I can fit the motors end-to-end.
    3) Use shorter motors

    At the moment its ~32CM long, ~33CM wide and 10CM tall...no idea about weight!

  2. #2
    Ocracoke's Avatar
    Team Kaizen

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    Hey there, welcome to the forum!

    Personally, I'd make it wider. Having the motors go through a belt/chain drive when they've already gone through a planetary gearbox is a little redundant (in my opinion) and adds another failure point.
    Team Kaizen

    AW: Osu, Ikari, Ramu
    BW: Shu! (Build Thread)
    FW: The Honey Badger (Build Thread)
    MW: Kaizen (Build Thread)

  3. #3
    Maxamuslead's Avatar
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    welcome to the forum. I have three suggestions. 1) don't build a spinner as your first robot they are very dangerous and unforgiving. 2) change the name as Team Titanium (big nipper) has made spinners in the past with either the same name or very similar. 3) get an internal layout first (drive weapon motor key bulkheads) first before getting too far into the design. also, bear in mind you may need to repair it in a hurry so making something hard to access is going to make you stressed

  4. #4
    James Williams's Avatar
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    Hi Josh

    Of the options you've listed the one I'd recommend most is redesigning the chassis. One issue with the Carbide/Tombstone style bar spinner is you have to sacrifice a large portion of your internal space for the weapon as it spins. Also keep in mind you will still need room for a weapon motor as well as the electronics. If you're desperate for space you could mount the wheels externally.

    Changing to smaller motors is also a viable option, if you haven't bought the 45E's already. I use common HRS-550S 18v drill motors (Gimson sell them too) & they haven't let me down yet, even when the rest of the bot was falling apart around them.

  5. #5
    mullinsj08's Avatar
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    Hi Michael,

    Thanks for the feedback. I'll see what I can do in a couple days. I've been to a few live events to try and get a sense of scale for the featherweights but it's very difficult when you're 15ft away!

    I was pretty sure I was being dim when I suggested adding a belt/chain when there's already a gearbox but I wasn't sure.
    Petersfield Combat Robotics - https://www.facebook.com/PetersfieldCombatRobots/

    Little Spinner (FW) - Designing

  6. #6
    mullinsj08's Avatar
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    Hey Mark.

    I won't be doing this alone (thankfully), while I'm good with electrics and stuff, I'll have a more mechanically-minded person helping me with this also. I don't know if its too clear in my avatar but I've already thought about weapon locking bars as I've designed in some holes in the top/bottom panels to hold the bar while arming up.

    Little Spinner is just a working name, if/when it gets brought to competitions it will be named something more imaginative (Someone at work suggested BANG! but I haven't done too much checking to see if anyone is using that one yet).

    I'm probably going to spend some time today actually working out what parts I need and maybe getting sizes and physically laying out bits of cardboard on the floor to get a sense of size/area needed.
    Petersfield Combat Robotics - https://www.facebook.com/PetersfieldCombatRobots/

    Little Spinner (FW) - Designing

  7. #7
    Maxamuslead's Avatar
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    Grab a VIP ticket ASAP then you can have closer look

  8. #8
    Ocracoke's Avatar
    Team Kaizen

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    Indeed, grab a VIP ticket so you can have a tour of the pits. It is worth the money. For what it is worth, my first iteration of my featherweight was 36cmx36cmx22cm (length x width x height). With a robot of that sort of dimension, it is worth laying out the components in cardboard, as you say. It is also worth noting that unless properly planned out, wiring is a pain in a small robot like this.

    However, I am going to second what Mark said. Spinners are dangerous and having had done a spinner as my first robot, even as a low power variety, I've had spinner arms/tips fly off at speed, not a pleasant experience to put it mildly. You can't really test a spinner either in anywhere else other than an arena either simply because of the dangers of them exploding. There is also the problem of the live events (thinking of Robots Live! here) not always accepting spinners because of the arena not having sufficient protection for them. Extreme Robots can handle spinners, as can RoboChallenge (who do the FW Championship at the moment) but Robots Live! can't so it does limit the number of events you can go to.

    I was pretty sure I was being dim when I suggested adding a belt/chain when there's already a gearbox but I wasn't sure.
    I mean, you could use a 1:1 belt or a simple 1 stage 1:1 gearbox but as I noted, it adds another failure point and more weight/complexity. With that said, You could offset the wheels to allow for this.
    Team Kaizen

    AW: Osu, Ikari, Ramu
    BW: Shu! (Build Thread)
    FW: The Honey Badger (Build Thread)
    MW: Kaizen (Build Thread)

  9. #9
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    Agree with what the others have said
    Keep it simple and fail fast - trying different designs and finding your style is important
    Getting something together and driving experience is more important than a sophisticated design - its amazingly frustrating to be the guy repairing your robot all the time rather than driving it

  10. #10
    mullinsj08's Avatar
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    Thanks for all the advice guys, this is very helpful!

    I will definitely see if I can grab some VIP tickets for ExR Guildford next year so I can have a closer look at some FW's. I went to RoboGames this year hoping to do the same but it turned out they were middleweights (I mainly went hoping to see Last Rites)!

    I'll have a think about starting out with something different, if I have time at the weekend I will see if I can design perhaps a lifter that down the road can be converted into a vertical spinner (Can you tell I like kinetic energy weapons?) later down the road when I'm more comfortable with how things work.

    The only thing I'm really precious about in the current design is the shape of the back...it took me ages to get that right in SolidWorks!
    Petersfield Combat Robotics - https://www.facebook.com/PetersfieldCombatRobots/

    Little Spinner (FW) - Designing

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