RC Attack Blimp (construction)

Discussion in 'Other Toys/Hobbies' started by Ken_hislop, Sep 11, 2007.

  1. Ken_hislop

    Ken_hislop Member

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    Howdy

    A few friends of mine are getting together and having a robot wars type battle in about 6 months. The only difference being they must be blimps!
    1.5m max length is the only rule, projectiles allowed.

    As budget is an issue I wanted to run a few things by all the RC wizz's here

    My plan was to use 3 of those balloons from hospitals and the like, round but flat on the top and bottom. For extra lift I would place a down facing fan (like a helicoptor and for steering another prop at the rear.

    Very very quick drawing to show you what I mean.
    [​IMG]
    Click to view full-sized image!
    Hosted by UGBox Image Store

    My aim is for about 1 KG of lift.

    I was going to see if I could use either a remote or petrol driven car engine to power the props or see if I could get a 2nd hand heli and use that.

    Would love to hear your constructive critisim and any recommendations as to engine types etc what to look for or even if I could use one of those $50 helicopters you get at the markets?

    thanks!
     
  2. Da Madness

    Da Madness Member

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    I don't know much about engines and lift... but I'll just point out the obvious... Keep the balloons armored, they'll be the weak point.
     
  3. Simwah

    Simwah Member

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    Friend and i did this with helicopters, we are licensed pyrotechnicans, so we had real missiles ;)
     
  4. isaaus

    isaaus Member

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    Depending upon what projectiles are used, i would suggest balsa wood box for the blimp as it would protect it against tiny projectiles. Also try to mount the balsa wood at an angle of 45degrees, reason being if you do that, most of the projectiles will be thrown up or down rather than hitting the ballons :thumbup:

    Subscribed as i wanted to make a similar thing for ages.

    Cheers
     
  5. OP
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    Ken_hislop

    Ken_hislop Member

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    I was thinking of using that super tough clear plastic they use to cover things like headphones or PDA's as armour, tought and light.

    edit: Balsa's not a bad idea, I think I'll have to weigh both materials, the only thing is I have a suspicion one of my opponents will be using flame...

    @ Simwah
    haha thats freaking awesome! I originally wanted rocket pods but couldn't really think of materials to use besides fireworks. Any suggestions in that department would rock!

    My current weapon ideas include spring loaded flaming darts in tubes or a pin shooter using compressed gas (like soda bulbs).

    But first I need the thing to fly!
     
  6. Menthu_Rae

    Menthu_Rae Member

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    Oh man, this is awesome... I've always wanted to strap weapons to RC stuff and battle with them :D

    Will be keeping an eye on this... whatever you do, when the time comes, VIDEO!!!! :thumbup: :thumbup: :Pirate:
     
  7. SLATYE

    SLATYE SLATYE, not SLAYTE

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    Those helicopters weigh 10g (according to the manufacturer). I wouldn't count on them being able to provide more than ~10g of lift (after taking away the helicopter's own weight).

    You're going to need a lot of them to lift 1kg, and even more if you want to lift batteries for a longer flight time.

    I wouldn't bother using a fan for lift. It'll use too much power and it won't provide much lift anyway (maybe a few hundred grams for a ~$150 helicopter). You'll also have to keep it properly aligned and supported, which just adds more weight. Better to put that money towards more balloons.

    To lift 1kg with helium:

    Air density = 1.3g/L
    Helium density = 0.18g/L
    Difference = 1.12g/L

    We want 1000g or 893L of helium.

    This is equivalent to a spherical balloon about 60cm in radius (1.2m diameter).

    You'll need a bit more than that because the helium inside the balloon will be at a somewhat higher pressure than the air outside (and therefore a higher density). You also need to take into account the weight of the balloon itself and everything holding the blimp together.
     
  8. Coney

    Coney Member

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    How about the plastic shells that the RC cars use? They pretty strong and light.
     
  9. Joehax

    Joehax Member

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    I wouldn't try to armour the balloon as it will add too much weight.

    You would be better off with a more durable rubber or plastic (or whatever material the balloon will be made of).

    Wonder how well a loose layer of tinfoil would work to protect it against a direct flame..:?
     
  10. SLATYE

    SLATYE SLATYE, not SLAYTE

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    I think I'd probably make it roughly round. That gives minimum surface area for maximum volume, and it also means that it'll go equally well in any direction. Put several fans on it (three should do) so you don't actually have to turn around before moving in any particular direction. This also has the advantage that you can use two fans to ram the other fan into another blimp - I would imagine that doing this would make quite a mess out of any lightly-armoured balloon.
     
  11. Simwah

    Simwah Member

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    Haha no, not helping anyone blow themselves up, after all fireworks are explosives and even the tiniest one can kill you if not used correctly.
     
  12. Da Madness

    Da Madness Member

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    Just make it big enough to hold a nail gun.... They work in Quake so they should, in theory, work on your attack blimp.
     
  13. OP
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    Ken_hislop

    Ken_hislop Member

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    @ Simwah
    Aww but i've never blown myself up with fireworks before!


    Hmm I was thinking to get away with smaller balloons/ extra weight I'd need the downward fan. What sort of engine would I be looking at to give me say 700g lift?

    I've seen blimp bladders on the net for like $200

    The spherical bladder idea is good, i'm just a stickler for looks and I love the traditional blimp look.

    I'll re-think the armour but wont be able to properly go over everything until I get the blimp part sorted. Will post back then.
     
  14. mshagg

    mshagg Politburo

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    Weight is going to be the enemy. To be specific... POWA... is going to be the key headache. The $35 little choppers have a 50mah LIPO battery... this provides about 5 mins of run time and is prob the heaviest thing on the chopper.

    Earlier advice re: having it lighter than air is the key to generating the lift IMO... Then some BASIC radio gear to steer the thing.

    You can prob get away with 2 channels for the radio... a left and a right motor, steer the thing like a tank.
     
  15. Da Madness

    Da Madness Member

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    Don't you also need a control to fire the nail gun?
     
  16. Diehard

    Diehard Member

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    Quality Electrics is a must.
     
  17. SLATYE

    SLATYE SLATYE, not SLAYTE

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    Is it still a blimp if it's got a lift-fan providing 70% of the total lift?

    I would guess that something like this could provide ~700g lift, in addition to lifting its own weight. You could get a bit more lift by removing the un-needed parts of the helicopter. However, that's still an electric one, so you'll probably only get ten minutes of use out of it.

    Nitro-powered ones would last longer, but they're a lot more expensive (about $600) and a lot more complex. You may well have trouble actually making the blimp move with one of those just because the motor would be so heavy.

    You might have to consider using two lift fans. If you've only got one, the blimp is going to tend to rotate about the lift fan axis (which is why helicopters have a tail rotor).

    It'd be a good idea to put a fairly strong duct of some sort around the fan. Even my little ~300g one is quite scary to be around when it's running; I wouldn't go anywhere near a 1kg model.

    I would agree with mshagg here. Don't bother using a fan to provide lift, because it'll be complex and it provides a very firm limit on maximum run-time. It also means having at least one extra channel on the radio controller - in fact you'll probably have to buy a 4-channel model.

    Better to be able to use a simple 2-channel transmitter/receiver (as used in most cheap RC cars) and just rely on the balloons to keep it at the right level.
     
    Last edited: Sep 11, 2007
  18. doug81

    doug81 Member

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    If you go helium, use a lot of chambers. If one is punctured, you're not completely fucked
     
  19. OP
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    Ken_hislop

    Ken_hislop Member

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    Sounds like the fan Idea must go i guess, perhaps I'll try it in the 2nd round. Balloons it is! I'll post back with pics.


    ooo Anyone know where to get those huge rubber balloons, like weather ballons?
     
  20. OP
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    Ken_hislop

    Ken_hislop Member

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    Would a nitro RC car engine work or be too heavy? As in are the engines designed with heavier metals or something?
     

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