Helicopter B/C [Trial]

[jander14indoor]

For those who want helicopter design/idea

http://www.illinoisolympiad.org/iso/fil ... copter.pdf
<SNIP>

That design is a variation on the Wright Bat. Note, plastic blades are NOT allowed in the national rules. But there are a lot of other ways to get there. If built to minimum weight and max rotor size it should fly well.

What's the rotor size on your copter? What's your weight? Shouldn't need to spin fast to lift a 4.0 gm copter with 40 cm span rotor. Note, that's as big as a Wright Stuff Wing that has to lift 7.0 gms! You shouldn't need a lot of speed to lift your copter. But just like Wright Stuff, in helicopter you need to maximize your rotor and minimize your weight for good flights. My slightly under weight prototype with two 40 cm rotors spins so slow you can count the revolutions by eye.

i'm not sure if anyone asked this already, but is there a specific reason why helicopters use rotors not propellers?(and vice versa) <---this face looks cool

For a hovering copter, there is no real difference between a rotor and a propeller, this is one of those arbitrary differences that engineers sometimes make for their own convenience. Note, a copter that moves horizontally MAY want a rotor designed different than a prop, as you need to take that horizontal motion of the air past the rotor into account. That may be where the terms differentiated for the convenience of designers.

Jeff Anderson
Livonia, MI

[ChrisYim]

also, does it matter what the rotors are made out of? (my friend said it didn't matter but i just wanted to double check)

[jander14indoor]

also, does it matter what the rotors are made out of? (my friend said it didn't matter but i just wanted to double check)

Read the rules, they limit you to certain materials.

Other than that, they have a job to do, so the allowed materials have to be arranged to accomplish the task.

And finally, see all my other comments about weight, so even though its wood, lignum vitae (a wood dense enough not to float) is probably right out.

Jeff Anderson
Livonia, MI

[NJman-77]

can somewon plz post a pic of what a competing one might look like?

[jander14indoor]

I'm not sure anyone KNOWs what a competitive design will be yet. We don't have a large body of data like for WS from the Free Flight communities experience (though there is some) to say what will work best to these rules.

That said, here are some examples:
Hard core indoor designs, much lighter than these rules allow: http://www.indoorfreeflight.com/heli.htm Designs similar to these, but meeting the SO rules have flown better than a minute and a half. A very competitive time from reports at this stage of the events development.

This design is a single rotor, too heavy and too small a rotor. As is though, it is capable of 30 secoond flights. Not great, but better than most at this point. I don't know how far it can be developed. Lots of ways to lose weight though and you could make the rotors bigger for more performance to start. http://www.smallflyingarts.com/Current_ ... tick_1.htm

Hope that helps you get started,

Jeff Anderson
Livonia, MI

[GoNerdHerd]

What is the best design?

[jander14indoor]

No, since they haven't been established yet. Though expect them to follow the national trials and pilots in general.

Jeff Anderson
Livonia, MI

[S4BB]

Hello Jeff,

I had a question for you on one of the helicopters you posted a link to. On the helicopter from Jim Richmond, it shows a Stick and Vein, I am guessing the Vein fits into the Stick to rotate, is this correct. Looking at the drawing I am trying to figure out all the parts. Any input you could give me would be greatly appreciated. Thanks.

[jander14indoor]

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

[OlympiadLover]

How long should be the average flying time? And what does it mean by helicopter, can it also be a plane like device?