Rotors

[smartkid222]

By further down do you basically mean farther away from the free rotor?

[illusionist]

Yes, basically one at each end of the motor stick. Instead of the one here: http://picasaweb.google.com/jeffrey.hoo ... 7835332994

[Danny Smith]

I took your suggestion and moved the fixed rotor all the way to the bottom. The helicopter does wobble much less, but it still succeeds to go up, then flip. Should i add weight to the bottom/make the top lighter? Does the pitch of the top or bottom blades have anything to do with this?

[illusionist]

I took your suggestion and moved the fixed rotor all the way to the bottom. The helicopter does wobble much less, but it still succeeds to go up, then flip. Should i add weight to the bottom/make the top lighter? Does the pitch of the top or bottom blades have anything to do with this?

The pitch shouldn't have too much effect in my opinion. To be honest, I actually have my lower blades at a steeper pitch than my upper blades... If you are below 4 grams, or very close to that, then try adding the extra weight to the bottom, but be careful: "Weight is your enemy, it kills flight time."-jander14indoor

[jander14indoor]

Another consideraton, do you rotors V downwards from the center to the tips? If so, you are having a dynamic, not static stability problem. Make sure they are flat or V up slightly. Think of dihedral like a plane.

PS, I have no problem with stability with both rotors near the top.

Jeff Anderson
Livonia, MI

[new horizon]

I was flying my 2 rotor helicopter, but the free rotor couldn't get enough speed to produce lift. I thought maybe it was because of the rotor's shape, it was a V shaped rotor, so the ends weren't tapered, which could have caused drag/turbulence and prevented the speed required to fly.

However, there's designs out there that have the exact same V shape, so I'm confused on why it didn't take off.

The weight was 4 grams, the rubber band was 1/8 of an inch, so I don't think torque was an issue.

Oh, and I have a question. Why is it that the rotors are shaped so that the meeting point of the rotors is not in the center, and why is one rotor much shorter than the second? http://gallery.scioly.org/details.php?image_id=2959 that might clarify what I mean.

[illusionist]

Oh, and I have a question. Why is it that the rotors are shaped so that the meeting point of the rotors is not in the center, and why is one rotor much shorter than the second? http://gallery.scioly.org/details.php?image_id=2959 that might clarify what I mean.

The intersection of the rotor spars appear to be off center due to the angle of the picture when it was taken. If you could look at the rotor form the top, it would look like they meet in the center. As for one being shorter than the other, I think that may also be due to distortion by the camera, or due to poor construction.

[new horizon]

I want to say I disagree. If you look through all the kits, all the pictures in the scioly helicopter gallery, a lot of them have the exact same design.
I'm confused why.

[jander14indoor]

illusionist is right. Those spars are the same length, and cross at the center. They don't touch each other though because they are off set vertically to give the right curve to the rotor. Called helical pitch.

As to your copter not flying, how hard did you wind your rubber? Thickness is only part of the equation, you have to WIND it to get any torque out. If you haven't flown these events before you'll be surprised how many winds you can get into your motor if wound right. As to not enough speed, both rotors should rotate at the same speed in opposite directions if they are roughly the same size and pitch. If not, suspect something hanging up in the bearing.

Jeff Anderson
Livonia, MI

[Danny Smith]

I believe my rotors are flat. And i am actually over weight slightly, so there is no room to add anything. I may just scrap this model and restart. But to avoid the same problem on my next model, i have a few general questions. Should i keep the rotors at opposite ends or move them both to the top, and how long should my motor stick be aprox. ? How much weight do you allow for the average motor stick? How do you go about making sure the pitch of each blade is exactly the same as the others? Would it be adviseable to "V" the blades up slightly? I appreciate the help.