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Thread: (BW)TornBot - Team TornTech

  1. #1
    Hi all,

    So i am not around here. well, newly registered. Been a stalker for a while!

    Entering into the robot building world for the first time and am hoping this thread will aid on me explaining my plan. and being educated that my plan is flawed lol (Please do! i want to learn!!)

    So first off i am going to attempt to create a Beetle Weight, i've been doing a considerable amount of research and am pretty confident on some things... But don't have a clue on some other... hopfully some of the big experienced people who have got it wrong before can correct me before i go down the wrong path also..

    Before we go any further it should be noted that although i'm going to be building it to code.... Its 50/50 if im actully going to fight it or just use it as a challenge to learn from/build up a set of parts to use for prototyping future bots.... cost effective is my number one goal! reliable.. but cheap.

    These are the things i am unsure about:

    I am unsure if i should go with 2 Wheels, 4 wheels or 6 wheels.... and do I drive each of them, don't really fancy messing around with belts or chains on my first bot but i guess 4/6 motors and controlls will impact on weight and battery power...

    I have selected the following motors: (http://www.ebay.co.uk/itm/330751682081) Pretty standard 12v 100RPM motors used in this weight class. however are the eBay ones OK? or should i spend more on one from an offical site?

    Speed controllers? Everyone i see is raving about the BitBots Motor controllers, however the price and availability are a bit of a problem for me... is there cheaper ones? are they worth it??

    addionally. will this combination work:

    These couplers
    http://www.ebay.co.uk/itm/331515531587?var=540681332212

    used with these types of wheels:
    http://www.ebay.co.uk/itm/122020936384

    What is the usual size of beetleweight wheels?

    Thanks for your help. there will be lots more questions as i contine my journey... hopfully i should have some CAD and build photos soon too!!

    Tom.
    Last edited by TornTech; 21st July 2016 at 16:45.

  2. #2
    Roboteer

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    Good choice of motors, however most beetleweight wheels are a little smaller in the 35mm to 50mm range.

    I use brushless drive which uses separate motors and speed controllers but is a lot more fiddly.

  3. #3
    Niels - Team K.a.L.M.'s Avatar
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    Hi there, I too use those couplings with RC wheels. And they work well enough, although they are a heavier solution in comparison to other methods. Because of the bigger outer diameter you might want to look at the 800rpm or even 600rpm 25mm gearmotors. This will give you a lower speed but more pushing power for the same amount of weight.

    Anyways, welcome and enjoy.

  4. #4
    Quote Originally Posted by Pinski1 View Post
    Good choice of motors, however most beetleweight wheels are a little smaller in the 35mm to 50mm range.

    I use brushless drive which uses separate motors and speed controllers but is a lot more fiddly.
    Hmm...I will have to design the bot up in CAD and play around with the wheelsize... i am swinging towards a pizza box type bot potenally with the wheels coming through equally as much on the otp as it does on the bottom to allow it to drive when inverted.... maybe larger wheels may be better for this?

    Brushless motors huh? that does sound quite tempting... i like the idea of using slightly cheaper(they are cheaper right?) ESC's.... do they need gearing or can they connect directly onto a coupling and then onto simular RC wheels like above?



    Quote Originally Posted by Niels - Team K.a.L.M. View Post
    Hi there, I too use those couplings with RC wheels. And they work well enough, although they are a heavier solution in comparison to other methods.
    Glad to hear the method works well. it seems the easiest to me as a newbie to get started.... heavier solution. do you mean effecting weight limits or that its a little overkill for a beetleweight?


    Quote Originally Posted by Niels - Team K.a.L.M. View Post
    Because of the bigger outer diameter you might want to look at the 800rpm or even 600rpm 25mm gearmotors. This will give you a lower speed but more pushing power for the same amount of weight.
    hmmm... I didn't think about gearing the motors down to a lower RPM... do you not think 1000RPM motors on 60mm wheels will work well then?

    Quote Originally Posted by Niels - Team K.a.L.M. View Post
    Anyways, welcome and enjoy.
    Thanks, i have a considerable amount still to learn but this forum is a massive archive of experience and help...

    My birthday money(sound like a kid still lol) is coming together and im going to want to nail down my first set of components ready for biting the bullet and making a purchase...

  5. #5
    Niels - Team K.a.L.M.'s Avatar
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    What I meant with the heavier solution is that the couplings with the rc wheels weigh more than fingertech clamps and foamwheels. But I reckon they are far less fidgety to use. (no experience with fingertech t.b.h.)

    Using 1000rpm motors with 60mm wheels will give you a machine that has a higher speed than the opposition and if you find that important it will work fine. If you want to be able to push your opponents around better (not saying you can't with 1000rpm) you could look at the lower rpm ones that uses the same motors but different gearing. They will have less trouble turning your wheels while pushing.

    Remember there are possibly 1000's of way to build a bot, and a few hundreds ways to build a decent one.
    There really isn't a single way to go about it. Anything can work. It's up to your preferences and your opponent as to what will work perfectly. Any design has it's flaws/weaknesses that can be exploited and the crappiest machine on paper can take the trophy home.

  6. #6
    Pinski1 Could you give me some info on your brushless set up?

    What are the benefits of using Brushless vs Brushed motors? IE why did you choose them over brushed?

    Are the ESC's going to be cheaper?

    what about motor price compared to 12v Brushed?

    Do they need gearing?

    I am presuming you just use the same type of coupling to RC car wheels?

    Thanks

    Tom.
    Last edited by TornTech; 21st July 2016 at 11:36. Reason: typo

  7. #7
    Quote Originally Posted by Niels - Team K.a.L.M. View Post
    What I meant with the heavier solution is that the couplings with the rc wheels weigh more than fingertech clamps and foamwheels. But I reckon they are far less fidgety to use. (no experience with fingertech t.b.h.)
    The concept of foam wheels for a battlebot turned me off a little... are they resilient? i havn't paid much thought about weight... TBH... im merely doing this to develop a set of prototyping parts and to learn the process. i HIGHLY doubt this bot(or at least this version) will ever go to competition....

    Quote Originally Posted by Niels - Team K.a.L.M. View Post
    Using 1000rpm motors with 60mm wheels will give you a machine that has a higher speed than the opposition and if you find that important it will work fine. If you want to be able to push your opponents around better (not saying you can't with 1000rpm) you could look at the lower rpm ones that uses the same motors but different gearing. They will have less trouble turning your wheels while pushing.
    undecided if speed or grunt is what i am after..... a nippy little bot is quiet appealing though....

    Quote Originally Posted by Niels - Team K.a.L.M. View Post
    Remember there are possibly 1000's of way to build a bot, and a few hundreds ways to build a decent one.
    There really isn't a single way to go about it. Anything can work. It's up to your preferences and your opponent as to what will work perfectly. Any design has it's flaws/weaknesses that can be exploited and the crappiest machine on paper can take the trophy home.
    Thanks, all your advice is really helping

  8. #8
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    Hi Tom,

    I'm part of Hitchin Hackspace, it'd be great to see you down there and talk robots :-)

    The 1000rpm motors you've selected should be fine with those wheels. My beetles all use four of those motors for drive with 55mm wheels and they've all had really good speed and pushing power. If you're only going to have two drive motors, like many beetles are, then you may find the acceleration is a bit slow but the top speed will still be there. That's probably why people are suggesting smaller wheels.
    I use 3d printed hubs with my tyres. They've very lightweight but not really robust enough for combat. For a first bot, the ones you've selected should be good: easy and strong.
    I also use the botbitz ESCs. they're some of the smallest available and actually fairly cheap on the scale of things. The Dimension Engineering speed controllers used to be an alternative but they're £45 each for an equivalent controller! There's also the VEX motor controllers: http://www.vexrobotics.com/276-2193.html They're much cheaper but lower voltage and lower current, you'll need to test or calculate if they'd be suitable for your drive setup.
    Brushless isn't really used for lower cost drive systems, its because its lighter/smaller for the same power. They usually need slightly more gearing than an equivalent brushed setup as the motors are faster, so a common approach is to transplant a brushless motor onto a 500rpm gearbox. I think Pinski1's described his setup in another thread.

    cheers

    Mark

  9. #9
    Quote Originally Posted by mark_m View Post
    Hi Tom,

    I'm part of Hitchin Hackspace, it'd be great to see you down there and talk robots :-)
    Nice. I am hoping to get down there. Hopefully this coming Monday. Get over the awkwardness of being the new guy and not knowing anyone lol


    Quote Originally Posted by mark_m View Post
    The 1000rpm motors you've selected should be fine with those wheels. My beetles all use four of those motors for drive with 55mm wheels and they've all had really good speed and pushing power.
    glad to hear there are others using these, do you find it better driving all 4 wheels with their own motor instead of 2 motors driving a pair of wheels each side?[/QUOTE]

    Quote Originally Posted by mark_m View Post
    I use 3d printed hubs with my tyres. They've very lightweight but not really robust enough for combat. For a first bot, the ones you've selected should be good: easy and strong.
    I like the pricing and the variety on offer with the RC car wheels. that and i get get a few sizes and experiment without having to mess about with different hubs and connections.

    Quote Originally Posted by mark_m View Post
    I also use the botbitz ESCs. they're some of the smallest available and actually fairly cheap on the scale of things.
    Sounds like these are the go to ESC for BW robots. will wait for them to come back into stock and pick some up.... I am presuming you are driving one motor per ESC? so 4x in total.

    Quote Originally Posted by mark_m View Post
    The Dimension Engineering speed controllers used to be an alternative but they're £45 each for an equivalent controller! There's also the VEX motor controllers: http://www.vexrobotics.com/276-2193.html They're much cheaper but lower voltage and lower current, you'll need to test or calculate if they'd be suitable for your drive setup.
    Yeah, £45 X a potential of 4 makes their not V cost effective. the Vex ones seem nice but seem to top out 8.5V and 4 amps.... doesn't leave much headroom..

    Quote Originally Posted by mark_m View Post
    Brushless isn't really used for lower cost drive systems, its because its lighter/smaller for the same power. They usually need slightly more gearing than an equivalent brushed setup as the motors are faster, so a common approach is to transplant a brushless motor onto a 500rpm gearbox. I think Pinski1's described his setup in another thread.
    Will leave brushless for an experiment down the road

    I am tempted to maybe build my own dual H-Bridge motor controller though..... although i really should keep it as simple as i can to start with with off the shelf items!

  10. #10
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    I have a 2 wheel drive beetle wedge. I run bog standard 1000rpm motors on 60mm Pololu wheels and couplers with a simple fifty quid dual motor controller (below) and I'm yet to find a robot I can't slam into walls and snap wheels off

    http://www.technobotsonline.com/sabe...ontroller.html

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