Page 14 of 20

Re: Helicopter B/C [Trial]

Posted: April 14th, 2010, 3:55 pm
by S4BB
Don't think so. The vein is just an extension of the motor stick to hold the upper rotor. It is fixed to the motor stick and rotor on this design. The lower rotor is held in a bearing and is free to rotate with respect to the stick. I suspect the 'vein' is a separate piece to keep its weight down (no motor torque to deal with) while extending the overall length of the copter for stability. For some reason the builder doesn't want the motor stretched that long.

In flight, the rubber is attached on one end to the lower rotor which is free to rotate in the bearing. On the other end its attached to the motor stick (which is attached to the upper rotor). Note, the motor is twisting on BOTH the lower rotor and the motor stick and upper rotor. When you release the copter, the upper rotor AND stick spin one way and the lower rotor spins the other. Equal and opposite reactions and all at work. About the only thing not spinning in that style copter is the center of the motor, it unwinds from both ends!

Oh, a thought, as a starting point consider using the distribution of weights from those designs as your budget for distributing your heavier weight to maintain a similar balance. Example, one prop weighs .08 gm / .34 gm total weight or . So your props should weigh about 1/4th the total weight budget, or one gram. That leaves around 50% or two grams for the motor stick. this is only a starting point, but probably a good one.

Hope that makes sense. If not, just ask.

Jeff Anderson
Livonia, MI
Thanks for the feedback Jeff, just starting to look at this now. It was very interesting to see the trial event at states, it looks to be a lot of fun.

Paul

Re: Helicopter B/C [Trial]

Posted: April 14th, 2010, 4:11 pm
by new horizon
Hi, I was wondering where you would get a plank of balsa large enough and light enough to be used as a rotor. I had one of my teammates check michaels and he said they only have bass wood, and it's very small (length and width wise).

I know about specializedbalsa but I don't really want to wait for the shipping (which I hear is rather long), so is there another place to get balsa wood?

Re: Helicopter B/C [Trial]

Posted: April 14th, 2010, 5:54 pm
by andrewwski
A local hobby shop should have it.

Re: Helicopter B/C [Trial]

Posted: April 17th, 2010, 6:54 pm
by OlympiadLover
So it can be a plane?

Re: Helicopter B/C [Trial]

Posted: April 17th, 2010, 9:28 pm
by blue cobra
At least in the rules NY is using, it says that you can have no other lifting surfaces besides the rotors, so it could not be a plane.

Re: Helicopter B/C [Trial]

Posted: April 19th, 2010, 3:53 pm
by brobo
OH CRAP
I just got put into this event today and State is on FRIDAY!!! Luckily my partner is Chlorine Kills who is pretty good at building stuff, but I have no clue about how a helicopter works! He has a little idea, but still....

So I need advice. What is the best way to approch this event? What is a good design that we could build in a few hours? We are not looking to place, just get anything above last. I don't care if it flies for 5 seconds, I just want it to fly. If we design our own, what should it kind of look like? Are there key components that we should put on it?

I know its a lot, but any help would be greatly appreciated.

Re: Helicopter B/C [Trial]

Posted: April 19th, 2010, 6:32 pm
by smartkid222
http://www.illinoisolympiad.org/iso/fil ... copter.pdf
look at that if you haven't. Can't really say too much else to help.
If you end up with NOTHING, get materials that meet the construction requirements and throw it up into the air as high as you can. It will get you out of last place.. trust me, i've seen it done before LOL.

Re: Helicopter B/C [Trial]

Posted: April 19th, 2010, 6:37 pm
by jander14indoor
As usual, READ THIS STRING BACK A FEW PAGES!!! Sorry for the shouting, but really, 10 pages, 136 notes and you ask for an explanation? At least cite things you didn't understand.

OK, off high horse. Go back a page or two in this string and see my note pointing to some pages for designs.

Now, only a couple of days. SIMPLIFY! Use flat plate blades for your rotor, concentrate on keeping the weight LOW, as close to 4 gm as possible. Allow about 1 gm for each of two rotors, 2 gm for motor stick and rubber hooks. Pick and angle, say 20 degrees for the blades, make sure they are counter rotating and TRY it. You might be surprised.

Hope that helps a little.

Jeff Anderson
Livonia, MI

Re: Helicopter B/C [Trial]

Posted: April 19th, 2010, 6:40 pm
by jander14indoor
Careful of the Illinois sample design. The plastic blades aren't legal under the trial rules as written on the national site, nor as used in most state. It will of course depend on your event supervisor's interpretation, but I thought it was pretty clear, and even Illinois explicitly clarified the rules to allow plastic in their contest.

Now, replace the plastic with flat plates of wood, or even better, warped plates, and there you go.

Jeff Anderson
Livonia, MI

Re: Helicopter B/C [Trial]

Posted: April 19th, 2010, 7:11 pm
by SOCoach
Do the wings on the helicopter need to have airfoils like the wing of a wright stuff plane, or simply flat with a twist? I guess I am not sure how it generates its lift . . . . simply by moving the air?