 | | Re: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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(...) And if we were talking about a hovercraft in an elevator - I'd be agreeing with you. Dumb pedantry doesn't work here. The **WEIGHT** of the hovercraft is just as important/relevent/applicable as the **MASS** of the hovercraft when we are (...) (23 years ago, 30-Nov-02, to lugnet.robotics)
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| | Re: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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(...) Ok, remember you asked... Let's take example 1- You're in an elevator. The elevator goes down. Your weight decreases but your mass does not. Q: Where did the weight go? Did you mass change? Example 2- Take a 1lb weight and a scale. Scenario a: (...) (23 years ago, 30-Nov-02, to lugnet.robotics)
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| | Re: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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(...) How? It seems to me that as long as acceleration due to gravity is constant (i.e. same altitude, same planet; in this case, 9.8 m/s/s) then weight and mass have a simple proportional relationship. (23 years ago, 30-Nov-02, to lugnet.robotics)
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| | Re: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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(...) That's a pretty basic physics mistake <shrug>. -- ___...___ We don't see things as they are, ravage@ssz.com we see them as we are. www.ssz.com jchoate@open-forge.org Anais Nin www.open-forge.org ---...--- (23 years ago, 29-Nov-02, to lugnet.robotics)
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| | Re: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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(...) So long as we are down here on the surface of the earth talking about the air pressure under the skirt of a hovercraft and whether it'll lift or not, weight and mass are equivelent concepts. (...) Yes - I understand that. (...) Yes...although (...) (23 years ago, 29-Nov-02, to lugnet.robotics)
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| | Re: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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(...) I think you need a MUCH bigger area under the craft. If all the motors and stuff on top weighed (say) 100 grams, and you have just 16cm diameter skirt then you need a pressure of: 0.1 / (PI x 0.008 x 0.008 ) kilograms/square meter ...in order (...) (23 years ago, 29-Nov-02, to lugnet.robotics)
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| | Re: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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(...) So is Hans Madsen on this list? I'm always skeptical of things that are just throwaway lines like that...was this pure lego? How much cheating was involved? There was a couple of photos of a lego helocopter that could really fly on the list a (...) (23 years ago, 29-Nov-02, to lugnet.robotics)
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| | Re: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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(...) We aren't interested in power, we're interested in moving a volume of air. They are very fast, high rpm. Trade off rpm with suitable gearing. You may need two or more (which is why small may be better). I've never used them myself except for (...) (23 years ago, 29-Nov-02, to lugnet.robotics)
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| | RE: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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(...) Get rid of this fixation with 'lift own weight' (you're -completely- ignoring the -primary- factor of time). Consider the exhaust of a car, pump it into a bag and you can lift the car to change the tire but you can stop the car by simply (...) (23 years ago, 29-Nov-02, to lugnet.robotics)
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| | Re: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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(...) There's an echo in here ;)...you'll get to the answer faster if you'll think of mass and force instead of weight. (...) Which is where the ratio of the input plenum to the skirt (the output plenum) comes into play. (...) No, that's a function (...) (23 years ago, 29-Nov-02, to lugnet.robotics)
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| | RE: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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I just tried a 5V processor cooling fan a 12V computer PSU cooling fan a 3V ducted fan of the sort used to cool your face (run at 5V without on-board batteries) with a 16cm dia polystyrene plenum. None could really lift their own weight - although (...) (23 years ago, 29-Nov-02, to lugnet.robotics)
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| | Re: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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(...) I was thinking of more a complete LEGO solution--the only thing non-LEGO in my plans is the skirt, which probably will be a bicycle innertube. What I plan first is to get hte motor, the fan and turn it on and see if I can dry my hair with it (...) (23 years ago, 29-Nov-02, to lugnet.robotics)
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| | Re: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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(...) You'll have to answer that for yourself. A lot of what I find fun would probably bore/scare most to death. For example, I find all these transformers and such that a lot of Mindstorm folks rave over completely and utterly uninteresting, and (...) (23 years ago, 29-Nov-02, to lugnet.robotics)
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| | RE: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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Hi Dave :) (...) Cool :) (...) I'm thinking of a thin "plastic film" usually used to wrap around food to keep it fresh and air tight (I don't know how's it called in english). mc. (23 years ago, 29-Nov-02, to lugnet.robotics)
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| | RE: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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(...) When I was about to give up, after some tests with a non-LEGO propeller and *without* a "skirt", I saw this interview of LEGO Master Builder Hans Madsen ((URL) where he says he made one (I assume) *LEGO* "Hovercraft that really flies": "What (...) (23 years ago, 29-Nov-02, to lugnet.robotics)
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| | Re: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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(...) to how to do it... After work I'm going home and rip apart my modified 8448, take the 8475 motors out of it, and throw on a znap prop on those motors and see what the air flow's like. Putting my current project on hold, I'll try and whip (...) (23 years ago, 29-Nov-02, to lugnet.robotics)
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| | Re: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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(...) Non-lego motor -- for lower weight and higher RPM. Non-lego skirt -- because there isn't anything in Lego that can do that. Non-lego propellor -- because the Lego ones are crap Non-lego decking -- for lightness and rigidity. ...hmmm it's (...) (23 years ago, 29-Nov-02, to lugnet.robotics)
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| | Re: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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(...) The micro cars (the ones about an inch long) are down to $30 - including two channel RC and battery charger. However, the motors aren't all that powerful. I read somewhere that the motors they are using are from the 'vibrators' inside pagers (...) (23 years ago, 29-Nov-02, to lugnet.robotics)
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| | Re: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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(...) You know that the pressure of the air inside the skirt multiplied by the area of the ground enclosed by the skirt has to equal the weight of the hovercraft. If the skirt made a perfect leak-proof seal against the ground, and there were no (...) (23 years ago, 29-Nov-02, to lugnet.robotics)
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| | Re: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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but wher is the fun? my skirt has been done as a cut of the sphere the same shapa as the tunnel has to hav (i think) so it was a middle part of sphere without upper and lower domes that's why i said "a little bit hard to do it" :)) you said CD is (...) (23 years ago, 29-Nov-02, to lugnet.robotics)
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