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chia
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Re: Duration

Post by chia »

twototwenty wrote:For the past month or so, I have been working on a chinook design and after several failed attempts the best I have gotten is ten seconds-the thing doesnt even reach the ceiling of the classroom i am testing in.

The main problem, besides the fact that is is spectacularly heavy(which I am working on), is that the rotors do not rotate at exactly the same speed, causing it to flutter in uncontolled spirals until it hits the ground...
Does anyone have any suggestions as to how I can make the rotors rotate equally? States is in a week, and although we have a fallback, I am getting worried.
This is my take on this (I just finished building one myself, though I haven't yet tested it):
1. Are your rotors almost identical? Generally, you probably want them to be as close to the same as possible, though depending on your design (eg. the rotors overlapping) this may result in the lower one spinning faster b/c air is already sped up by the top one, though I don't know if that would result in crazy spiralling.
2. Is the helicopter as a whole unbalanced? Making sure that the helicopter isn't more heavy on one side (axle) than the other might help with stability a little, though it won't solve the rotor speed problem.
3. Are your rubbers as close as possible to the same size (weight)? This is what probably affects rotor speed the most - try to measure the two rubbers as close to the same weight as you can.

If I missed anything/said something wrong, I'd like to hear any other advice anyone else has as well.
*EDIT: Okay, I definitely want to hear other perspectives, because I went and tried mine and it's doing the same thing. I won't say my exact times, but the wild see-sawing is definitely taking away time, especially since I don't have much clear space to test it - it keeps running into stuff and I don't want it to break.

BTW, how heavy is spectacularly heavy? I managed to get mine down to 4.72 g :D though I don't yet know if it'll stand up to the strain of actually flying (I sure hope so...)
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Re: Duration

Post by AlphaTauri »

Won the region with a 1:32 on a 30 or 35-foot ceiling, though my region isn't exactly the most competitive at building events, especially balsa builds.
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Re: Duration

Post by twototwenty »

AlphaTauri wrote:Won the region with a 1:32 on a 30 or 35-foot ceiling, though my region isn't exactly the most competitive at building events, especially balsa builds.
Congrats!
chia wrote:BTW, how heavy is spectacularly heavy? I managed to get mine down to 4.72 g :D though I don't yet know if it'll stand up to the strain of actually flying (I sure hope so...)
It was a whopping 9 grams (I am currently rebuiling it to be around 4.5, which should also help me out quite a bit. Thanks for your suggestions; I'll certainly make sure to take not of them in this next helicopter.

Out of curiosity, what is the basis of your design? (obviously, no specifics expected, particularly if it does well, but I had such a hard time getting one that flew at all, I am extremely interested in others' approaches.)
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Re: Duration

Post by chia »

twototwenty wrote:Out of curiosity, what is the basis of your design? (obviously, no specifics expected, particularly if it does well, but I had such a hard time getting one that flew at all, I am extremely interested in others' approaches.)
Well, it's got two rotors, two axles, and some rubber for power... ;)
For reals though, I can't yet judge how it can perform - I need to get space to test in.
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Re: Duration

Post by lucwilder42 »

A chinook copter won my region yesterday, didn't get a good look though
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Re: Duration

Post by chalker7 »

lucwilder42 wrote:A chinook copter won my region yesterday, didn't get a good look though
Any idea how much time it got?
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Re: Duration

Post by lucwilder42 »

chalker7 wrote:
lucwilder42 wrote:A chinook copter won my region yesterday, didn't get a good look though
Any idea how much time it got?
Beat us by a second with a time of 2:20
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Re: Duration

Post by twototwenty »

The 2:20 was with the 3x multiplier though, right? Otherwise...
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Re: Duration

Post by lucwilder42 »

twototwenty wrote:The 2:20 was with the 3x multiplier though, right? Otherwise...
With the multiplier, so like a 40- something second flight
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Re: Duration

Post by danyalukin »

Got a 2:10 minute flight in my basement tonight with a chinook, mass 3.86g, .125" rubber. A score of 6:30. Going to NY states this weekend. I'll post more info later, busy with other events right now. I'm not secretive about my design, ask if you have questions.
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