Helicopters B

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jander14indoor
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Re: Helicopters B

Post by jander14indoor » December 15th, 2012, 9:41 am

2017Kortman wrote:Okay, my coach gave us some homework, and I need to know how rotor pitch affects flight time. <SNIP>
Sorry, tell your coach the question needs work. The only way to answer is to assume everything else is fixed and then make a whopping bunch of assumptions. And then its messy because its a messy, non-linear system that also depends on available ceiling height. The theoretical answer depends on math WAY beyond MS, and there is no good rule of thumb.

Here's a way to answer the question. Build three copters with different pitches, but same weight, same blade area, number of blades, blade shape.

Now, pick the middle pitch, and match a motor to it to make it fly reasonably good in the space you have. Once you have a good motor size for that pitch, fly the other two motors with the same motor size & winds. What's the answer?
Next, check that result by matching a motor to the lower pitch. Probably different size and winds than before. Use that motor, size and winds on the other two copters and see what happens.
Match a motor to the high pitch copter. Try on the two other copters. Result?

Was the result consistent, wherever you started?

If you don't understand what I'm saying when I say match the motor to the pitch, look back up this string.

Hope that helps,

Jeff Anderson
Livonia, MI

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Re: Helicopters B

Post by Itsanthonguise » December 16th, 2012, 11:09 pm

does anyone know if thicker or thinner rubber is better? i know how to make the general helicopter well, but i still need to work on the rubber. Also, what would be the ideal weight of a helicopter.
2012 Events
State: Shock Value - 8th place
Nationals: Helicopter Egg Drop - 6th place
2013 Events
Regionals:
Helicopters-2nd place
Rotor Egg Drop-3rd place
State:
Helicopters:-5th place
Rotor Egg Drop-5th place
Nationals:
Helicopters:-17th place
Rotor Egg Drop-46th place

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Re: Helicopters B

Post by jander14indoor » December 17th, 2012, 4:28 am

Easy part first, the ideal weight of ANY flying object is as low as possible. Since the rules say it MUST weigh 3.0 gm, ideal weight is 3.01 to 3.05 gm. Seriously. I'd suggest 3.00, but you don't want to get second tiered with a construction violation.

Thickness, not so easy. That IS the challenge in this event, read back up this discussion string to see how to figure it out. Note, it is a combination of thickness and length you are looking for to maximize flight time, not just thickness. Ballpark starting point, 1/8 wide. But that's not likely to be exactly right for your copter.

Jeff Anderson
Livonia, MI

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Re: Helicopters B

Post by Itsanthonguise » December 17th, 2012, 8:50 pm

thanks, but do you know how long should the rubber be? Right now mine is as long as my helicopter.
2012 Events
State: Shock Value - 8th place
Nationals: Helicopter Egg Drop - 6th place
2013 Events
Regionals:
Helicopters-2nd place
Rotor Egg Drop-3rd place
State:
Helicopters:-5th place
Rotor Egg Drop-5th place
Nationals:
Helicopters:-17th place
Rotor Egg Drop-46th place

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Re: Helicopters B

Post by jander14indoor » December 18th, 2012, 6:45 am

Whatever length it needs to be to maximize the flight time. Check back up this string, there is NO reason for the motor length to match the helicopter length.

And we really can't tell you how long it should be, nor exactly how thick. You have to match BOTH to YOUR helicopter to maximize the flight time. All we can suggest is starting points where your helicopter will at least FLY, and then how to test things in an organized fashion to find YOUR maximum. To maximize flight time by adjusting the motor width and length to your rotor design is the core of this event!

Jeff Anderson
Livonia, MI

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Re: Helicopters B

Post by chamender3 » December 18th, 2012, 12:49 pm

For OH SO my team is needing to either find a place to buy a motor or how to build one.

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Re: Helicopters B

Post by foreverphysics » December 18th, 2012, 12:53 pm

If you refer back to earlier in this thread, you would see that Freedom Flight is highly recommended for first-time builders and general kit starting.
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Re: Helicopters B

Post by A Person » December 18th, 2012, 1:13 pm

chamender3 wrote:For OH SO my team is needing to either find a place to buy a motor or how to build one.
How would you build a motor?
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Re: Helicopters B

Post by retired1 » December 18th, 2012, 3:09 pm

You buy tan super sport rubber in the desired width, cut it to a desired length, tie a good knot in it and attach it to the prop hook/hooks. Google it and you should get lots of hits. Starting would be 0.125 and as you get better, you will go to a bit wider on most choppers. You will need a winder, 10 to 1 is my choice.
You really should start out with a kit. Freedom flight has a 2 week back log as or Monday. the parlor chopper is not a great one, but it is a starting point.

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Re: Helicopters B

Post by Maxwellc007 » December 20th, 2012, 1:06 pm

retired1 wrote:I will probably get yelled at for this, but for a beginner or first timer, I will recommend the chopper from Freedom Flight as the best one out there. A couple of the other ones that were out there the last couple of years are not worth the money! The kit is good and the instructions functional. After you build a few, you can make changes.
We use a couple of modifications of his kit and the C teams have had times of right at 3.00 minutes at state. 2.5 min normally will win most states.
The set seems legit. Here's the link:

http://www.freedomflightmodels.com/paypal.htm

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