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Miniature Hovercraft Project

  1. Jun 8, 2007 #1
    Miniature Hovercraft Project !!!!!!!!!!

    Hi everyone,

    M supposed to build a hovercraft for a race. I want your help. I understood the basic concept of a hovercraft. This hovercraft need not have anyone to align it. It shud go without a load.

    length and breadth limits are 70 and 40 cms respectively. IC engine of less than 3.5 cc must be used OR motor or less than 12volts supply must be used.

    the race track is completely straight. Pls help me out wid the best design possible. I am from India, so anyone who has already done it, pls help me out. Where do I get the necessary items?
     
  2. jcsd
  3. Jun 8, 2007 #2
  4. Jun 8, 2007 #3

    Danger

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    I think that it's a bit late for that link, Ank. The first post in this thread is a duplicate of the last one in the other, so he's seen it already. :rolleyes:
     
  5. Jun 8, 2007 #4
    oh yeah, i m bit late.
    anyways Gambit, when is this competition??
     
  6. Jun 9, 2007 #5
    maybe a stupid one this time around. since the hot air is lighter so cant we use hair drier for the purpose of filling up the under belly of the the the craft.
    don't get mad on me for such a stupid suggestion !!!!!!!!!!!!!!!!!!!!!!!!
     
  7. Jun 9, 2007 #6
    Well, to be precise. I think its in Guwahati or Madras. Not sure. My frnd only told that the event is abt hovercrafts. Can i know ur name? and where u stay? My name is Vignan. M frm Hyderabad.
     
  8. Jun 9, 2007 #7
    Hey ANK buddy.......r u online?
     
  9. Jun 9, 2007 #8

    FredGarvin

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    A word to all on this forum...Three suggestions to get the maximum amount of help from people here:

    1) You have to post questions that are not broad in context. If you simply ask for someone to give you the best design for something, you're not going to get any help.

    2) Show us some effort on your part. If you just show up with no post count and ask us to do your work for you, you won't get a lot of support.

    3) DO NOT use text message grammar here. It is not appreciated by most of us. Take the time to make well thought out questions and posts. If you don't take the time to make your posts legible and somewhat professional, you are going to limit the number of people willing to assist you.
     
  10. Jun 9, 2007 #9

    @Fred,

    Sorry about that. I should have been more specific about the help. Anyways, I will try from my part and ask for help only when stranded.

    I am new to this forum. Hence it is understandable that i wont have many posts to my credit.

    What I actually meant to ask was, with the given dimensions and the requirments, me using the equipments used on the usual Hover-crafts wont work right? Thats the reason, i asked for the help. Like I wanna know more about Balsa wood and anyother substitute for that.

    Also, for the given Dimensions, what motor or IC Engine would be sufficient? I dont want to go and buy a motor which wont be able to lift it. thats why i am asking for your help. Also, for the forward propulsion, which IC engine would suffice? I dont want it rocketting ahead without any control. So, I am trying to ascertain the optimum equipments for the Hovercrafts. I am not having any experience with making such things. Just a step Climber thats all.

    Besides, I have observed that many of the forum members are not from India, the price and estimates could vary according to your country. Thats another problem I have.

    Thank you.
    Vignan a.k.a Gambit
     
  11. Jun 9, 2007 #10

    Danger

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    Much better post, Gambit. :approve:
    For a model of the size that you specified, material choice isn't terribly critical. Although lighter material is better, you could use thin-wall tubing and sheet aluminum without losing too much performance.
    Balsa is strong, light, and fairly inexpensive, but it has limitations. For one thing, you pretty much have to glue it. In my experience, at least, it doesn't hold screws or nails very well. That makes design alterations almost impossible once you've started construction. (I guess that you could mock it up with pins or nails and then glue it when you're satisfied.)
    You don't need to use 2 motors unless you want to. Thrust can be provided by simply building a diversion duct to capture some of the lift fan output. A moveable flap in the duct can serve as a 'throttle'.
    Russ posted a link to a 'lift calculator' a while back. It's bookmarked on the computer at work, so I'll re-post it when I get there in a couple of hours.
     
  12. Jun 9, 2007 #11
    You can also use light plastic or wood beams and nylon, like some moden airplanes or.. don't know the english word - the white soft stuff that food containers and water jars for single use are made of (calcar - if that means something in English lol ). You also need a skirt. About the egnine - maybe a small vacuum cleaner engine could also do ? Like those small hand held table cleaners for the kitchen type on batteries.
     
  13. Jun 9, 2007 #12
    thats the problem with me also. most of the time, you are not gonna get things which seems to be easily accessible to people in europe and US. they are simply not here. but this lack of resources is the mother of inventions (hehe, or jugaad:tongue2: as you may understand it). i searched it all, but we dont have a single hobby shop in whole India(stupid place). i needed 2 OS .61 FX for my project and i ll get them in less than 2 months from now(record time) thanks to a friend. so you have to pretty much look for something from an old machine or go for electric motors.
    anyways i m from new delhi
     
  14. Jun 9, 2007 #13

    What about the material for skirt? Would i find a motor or IC engine which could lift something like a balsa wood and also the weights of the motors/engines?

    Also the center of weight plays a critical role i guess. Would it be better if I place the motor for lift in the dead centre with the propeller? I read a post by another member about Gunter propellers. Now I don't know where i can find them. Can I use another propeller instead? Or should I make a propeller with some material? The price of the propeller can be cheap according to your exchange rates. But it will become a costly affair once I try to order it from another country.

    Another thing, sorry about sounding dumb. But I still cant believe that something like a hovercraft can ACTUALLY hover in air. I know the mechanism, I am not sure if it will work when I do it :shy:
     
  15. Jun 9, 2007 #14
    Yes. Those stuff can be used. I am not planning about keeping it and using it for years. I want it to full-fill the purpose for only sometime. 1 month is more than enough. If you can suggest any cheaper alternatives, it would be better. I was thinking about alluminium rods with thin metal sheet around it.

    I dont hav vacuum cleaner. The motor i can use is limited to 12 volts motor. and the IC engine I could use is limited to only 3.5 cc engine.

    I hope I am a little clearer. would these suffice for the lift and propulsion? Also, suggest a propeller. Also about the skirt, what if I use polythene as skirt? Can it withstand the weight? How I get the necessary shape for the skirt? Can you provide any tips on shaping the skirt?
     
  16. Jun 9, 2007 #15
    mythbusters made some hovering machines (a chair and a surfing board, yeah believe it) in season 2, episode 4. you can get a fair idea from there.
    and why cant you believe that a hover craft can hover, i cant believe it.
    forget about the custom made props and engines, you aint getting them even in next 5 years in India. think for a substitute, like a vaccum cleaner unit
     
  17. Jun 9, 2007 #16
    Nice. Are you interested in participating in this event? I suppose its in IIT Guwahati. If you know about any place we can get our equipments, please suggest. You seem to be in Mechanical Dept. How much do you think a 3 or 3.5 cc IC Engine would cost me?
     
  18. Jun 9, 2007 #17
    Buddy !!! I just sent you a PM with my email id. hope we can get in touch
     
  19. Jun 9, 2007 #18

    Danger

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    Hi again.
    It's best to centre your majority of mass such as the motor, if it's simply a self-supporting machine, but the placement of the fan doesn't matter. If it's to be used to transport something, though, you should offset the motor/batteries to serve as a counterbalance for that load.
    While on that same subject, a fan rather than a propellor is generally used for the lift air. If you're restricted to 12 volts, maybe the cooling fan from a car will work. Some of them are small enough to fit your design. You don't need a lot of power to get the thing off of the ground. (I'll find Russ' calculator link in a minute and paste it into this post.)
    Since your model is kind of in limbo between being a toy and being a recreational vehicle, the skirt material might be a bit iffy. Something that would be used for a full-scale machine will be too rigid, and something for a toy won't be strong enough. Heavy gauge polyethylene, such as used for vapour barriers in houses, should work well. Just form it into a (+/- 4") tube as long as the perimeter of your deck with the valve from a beachball glued in, seal it with something like silicone, glue it to the deck, and blow it up.

    edit: Here's that calculator. It's great. http://www.hoverhawk.com/lcalc.html
     
    Last edited: Jun 9, 2007
  20. Jun 9, 2007 #19
    Thanks for the link.

    Now, You mentioned about using a beachball valve right? But such valves are used for restraining air from going out of the skirt i guess? But I suppose the hovercraft works on the principle of the rate of flow of air through the skirt using the fan. Then, why use a Valve?

    Also, the maximum dimensions are 70X40 centimeters. So would a car's cooling fan work there? Shouldn't the fan be a little smaller? Something more common like the car's cooling fan which is easy to get.

    I was suggested to use a small vacuum cleaner. Would that work?
     
    Last edited: Jun 9, 2007
  21. Jun 9, 2007 #20

    Danger

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    There seems to be some misunderstanding of how the skirt works. In a toy, it's just some sort of soft edging that surrounds the plenum. A real hovercraft, however, has a large permanently inflated bag rather than a single layer of material (althought the preferred method is actually a series of smaller independent bags beside each other).
    The air leakage is from the plenum under the skirt, not from the skirt itself.
    As for the car fan, I didn't mean the single large fan that most cars have. Some have two small ones to either side of the radiator. I should have specified that. I don't think that any 12V vacuum cleaner will supply enough air. I can't even get mine to pull cat hair off of the couch. Remember that it has to not only pressurize the plenum in the first place, but also constantly replenish the amount that leaks out. While not a lot of power is required, you do need a substantial flow rate.

    edit: I should have specified that the skirt on a large unit is permanently inflated while it's hovering. Part of the lift air is bled off to keep it that way. It collapses upon landing.
     
    Last edited: Jun 9, 2007
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