Film
Designing a Hovercraft
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This proably doesn't belong in the film category but it's the closest fit. This is a short look at a hovercraft that I built as a science fair project during my junior year in high school. It was entirely designed and built by me over the course of 7 months. My project received a first place at the York County Science and Engineering Fair where I also won a free college class at Penn State. The total constuction costs were under $900. The hovercraft measures 3x6x3 feet and can lift several hundred pounds. It is powered by 2 two-stroke gasoline engines; one is a 29cc leaf blower and the other is a 2HP engine equiped with a 29" aircraft propeller.
Comments
I am not trying to be pretentious, or cocky, or "seem more knowledgeable than I am" and I honestly don't know why you think so. All I am saying is that for my application I needed to machine my flange precisely. This is both based on my calculations and the guidelines of the propeller manufacturer. I would imagine that you are using a pre-made flange that is already CNC machined to precise specs. I made mine myself and I wanted to minimize any chances of error.
CNC machining? Which parts?
Dude, what are you talking about? I run a 20 HP engine on a hovercraft with 1/8 clearance and there is no issue with "off-axis" force. I appreciate what you've done, but you don't do yourself any favors by trying to seem more knowledgeable than you are.
If I were you, I'd look for a local hobby shop. I found one near my house that could sell you virtually every piece of your project. Pay particular attention to model aircraft parts/kits - they contain powerful little engines (many run on gas) and propellers.
It probably going to have one fan for the lift and two for steering, each powered by seperate motors. The lift fan will have a separate battery pack to the two for steering as it'll be on more. Erm, as for the RC I'm not sure at the moment, maybe take apart an old rc car controller of something, or maybe buy a tradio transmitter with several recievers. Do you happen to know where I could get something like that quite cheap?
Most of my "calculating" was trail and error. i.e. trying different skirt materials to see which one works best. Sketch the whole design out on paper with measurements beforehand. My only real number-crunching had to do with the propeller/engine but since you're working on a smaller scale, you probably don't have to be as meticulous. Keep it light - that's my best advice. How are you planning to power it and do the RC?
Very impressive! :) I'm looking at making one myself (a much smaller RC one mind) did you have to do many calculations before the build?
Wow, sorry for the delayed response - I didn't see your comment. I couldn't tell you exactly how much it cost because it was a birthday present. (Yes I asked for a propeller for my birthday.) But I do know it was purchased on Ebay. Sorry I can't give you more info.
may i ask wer did you get the airplane prop and how much did it cost
regardless speed will have a more adverse effect on the prop than the torque to turn it.
No, the speed is important but it is not the decisive factor affecting the machining precision. Torque is dependent on the rotational force applied and the length of the lever arm. My prop has much more mass than yours and is much, much longer. This requires more torque to make it do 1600 RPMs. It is that extra torque that amplifies the effects of an alignment error. Sensenich, the manufacturer of the propeller can confirm that for you; they did for me.
was i being rude? i was just stating that you don't have to use big words etc to be smart.and just curious, why would torque matter? isnt it with speed that you should be more concerned about?
Also, your r/c plane's engine operates with a mere fraction of the torque of my 2 HP engine and the propeller/flange is much smaller and lighter. Of course it doesn't have to be as precise. And as to your "you don't need college credentials or classes to be smart kid" comment, that is exactly what I meant by a "crude, useless comment." Keep posting garbage and I WILL delete it. I'll be happy to have a genuine discussion with you, but not if you continue to be so rude.
I don't think I'm nearly as smart as you think you are...
I do not just "think," I KNOW that it must machined be that precisely - it can be proven with very simple physical formulas. In fact, I had an in-depth conversation about it with a college professor/engineer who is an expert in this field and would be happy to back me up. I can share his email address with you if you would like to discuss this with someone of some authority.
you don't need college credentials or classes to be smart kid
lol you must really think you are smart. i will post a vid in a week or two of my "lathe" and "drill press". but you really think that .0005" off will matter? i got an r/c plane, and im pretty dam sure the prop isn't that accurate, and it spins faster than 1600 rpm.
I uploaded my flange designs JustinAyers(dot)com/images/flange.jpg
I'd like to see you measure 1.0625" with your lathe and drillpress.
When you are spinning it at 1600 RPMs, you had better be precise to the 1,000th of an inch or you're generating several newtons of off-axis force. That would eventually rip the propeller off the shaft or worse: the entire engine. If you tried your 'method' you would wind up dead. I don't say things without reason.
My parents payed for the majority of it, and I am very grateful that they did. For somebody who "does lots of projects" I am surprised that you underestimate the cost. There are multiple gasoline engines, an airplane propeller, custom CNC machining, and a heck of a lot of structural implements to make it safe and efficient. When you build a nicer hovercraft for less money then you can criticize me all you want. Until then, save your useless, crude remarks - they are helping no one.
and i dont get the "precise equipment". a lathe, drillpress, and a steel blank. and there is your flange.
Yes, that's correct. It is a surprise. You got a job or did mommy and daddy pay for it? i just couldnt believe you spent that much for it. there isnt much there. i mean, yea, you finish with some green flames? im not trying to be a dick, i just didnt think you would spend that much for about nothing. MAYBE if you bought everything brand new. and shit if you spent that much, i woulda made it look a lot nicer. but then again i do a lot of projects myself, not requiring other peoples work hours
Yes, that's correct. Is that a surprise?
that's what you got for almost 900 bucks?
Ebay. It's a Sensenich 29" diameter, 22" pitch wooden airplane propeller. Mounting hardware is not on the market so I had to custom CNC-machine a flange from steel stock to mount it on a 2HP small engine (also from Ebay). Unless you have access to VERY precise machining facilities, I DO NOT recommend this method. Try to find a propeller which already has mounting hardware included. Please let me know what you come up with.
Where did you get the fan you used on the back?