Helicopter Testing

teamnsquared
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Helicopter Testing

Postby teamnsquared » January 31st, 2011, 12:37 pm

We were wondering if we could get a suggestion on how to build a static tester that would rest on the bottom of our helicopter and stand on a scale. We saw an example of this at the Clio invitational we attended last Saturday.

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illusionist
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Re: Helicopter Testing

Postby illusionist » January 31st, 2011, 1:45 pm

Here is a post on last year's forum by jander14indoor:
"I then rigged up a test stand to test rotor lift. It had a heavy base to keep the copter from flying, and a bearing to lock onto the motor stick allowing it to spin, but preventing flight for now.
Set the whole thing on a digital scale, tare it out to zero. Wind the rubber and spin the thing up. The negative weight on the scale is the lift.
Now, play with pitch on the rotors until the lift matches min copter weight about halfway through the wind down. Note, the best pitch settings may NOT be with both rotors equal! Also time the process to get estimates of flight time. For all time the lift exceeds copter weight you are climbing, below is descending.
Now, go back and build a copter to min weight using the pitch info you gained from testing and fly it.
Once that's going well, consider different shape rotor blades. Try different width motors. Use the test stand to evaluate. Consider 3 or 4 bladed rotors.

And so on.

Hope that helps,

Jeff Anderson
Livonia, MI"
2012-2013 Building Event Captain
Rule 7d. "Event Supervisors are allowed to break any competitors' devices" -bearasauras

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Re: Helicopter Testing

Postby jander14indoor » February 1st, 2011, 6:34 am

More details on that tester (twas my static tester at Clio you saw as well as the comments illusionist looked up, thanks).

The base was just a cross of balsa pieces to sit on the scale stably, weighted enough to make sure it stayed put, but was within the scales limits.
In the center was a bearing like this: www.a2zcorp.us look under model supplies, thrust bearings, you want the small white bearings, second row, on right I think. Item code is PA001

Note, it was installed so the wide end was down. I used a length of 0.032 wire, bent a T on the lower end and added a teflon washer between the T and the bearing. The idea is to minimize friction in this bearing because it won't be there in real life.

The upper end was glued into a fixture that fitted the helicopter I built last year so it could be attached and removed. You could just as easily attach it to a permanent motor stick that you attach the rotors you are testing to and change them out as needed.

Jeff Anderson
Livonia, MI

WCarneyJX
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Re: Helicopter Testing

Postby WCarneyJX » February 2nd, 2011, 2:56 pm

Hello All,

Below is a link to a video of the S.O. Helicopter my son and I have designed and tested for 2011. The model complies with the current rules and builds out to a little over 4 grams as shown. I'll post a couple pics in the Gallery. Note that we were able to test right in our shop without having to go to the school gym!

http://www.youtube.com/watch?v=lqV_y-CSznM
River City Science Academy - Florida 2010 Wright Stuff Champs
Coach for:
Storm the Castle
Helicopter

"My kid and my latinum go to Starfleet Academy"

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aubrey048
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Re: Helicopter Testing

Postby aubrey048 » February 2nd, 2011, 3:00 pm

I have another question, guys!

My helicopter partner and I did a test run of helicopter as a proof of concept, and to see what sort of design changes we might need to make (i.e Wing shape, wing angle, body length, etc). Our helicopters body spun and the wings remained fixed. :o We unwound it and tried winding the opposite direction. Same story. What's happening and how can we accommodate our design to fix it? :?

Thanks!

:)

Another thing... (@WCarneyJX)
Which set of propellers on your helicopter is fixed, top or bottom? Thanks! This info will really help my partner and I.
Plotting the function of the universe for efficiency without your permission.

Projected 2011-2012 Events: Anatomy, Microbe Mission, Disease Detectives, Tower, Optics, Helicopter.
Past Events: Anatomy (7th), Helicopter (6th), Mission Possible (1st), Write It Do It (4th, 8th), Ornithology (5th).

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Re: Helicopter Testing

Postby WCarneyJX » February 2nd, 2011, 3:21 pm


Another thing... (@WCarneyJX)
Which set of propellers on your helicopter is fixed, top or bottom? Thanks! This info will really help my partner and I.

Hi aubrey,
Both of our rotors spin - in opposite directions. Hope this helps.

Bill
River City Science Academy - Florida 2010 Wright Stuff Champs
Coach for:
Storm the Castle
Helicopter

"My kid and my latinum go to Starfleet Academy"

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Re: Helicopter Testing

Postby WCarneyJX » February 2nd, 2011, 3:55 pm

Aubrey,
It sounds like you have your rubber motor set up to drive a single rotor AND the other rotor is free-wheeling. This causes the motor stick to spin as the rubber spins the object with the least mass/momentum/drag. Either secure the other rotor or as we did have the motor drive both rotors.

Bill
River City Science Academy - Florida 2010 Wright Stuff Champs
Coach for:
Storm the Castle
Helicopter

"My kid and my latinum go to Starfleet Academy"

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aubrey048
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Re: Helicopter Testing

Postby aubrey048 » February 2nd, 2011, 6:56 pm

Our design right now is one fixed rotor, one rotating (on top). (Hope this info helps)

How would you have the rubber band drive both rotors? :?:
Plotting the function of the universe for efficiency without your permission.

Projected 2011-2012 Events: Anatomy, Microbe Mission, Disease Detectives, Tower, Optics, Helicopter.
Past Events: Anatomy (7th), Helicopter (6th), Mission Possible (1st), Write It Do It (4th, 8th), Ornithology (5th).

WCarneyJX
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Re: Helicopter Testing

Postby WCarneyJX » February 2nd, 2011, 6:59 pm

Both rotors have their own hooks and prop hangers are both connected to the rubber band.
River City Science Academy - Florida 2010 Wright Stuff Champs
Coach for:
Storm the Castle
Helicopter

"My kid and my latinum go to Starfleet Academy"

WCarneyJX
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Re: Helicopter Testing

Postby WCarneyJX » February 2nd, 2011, 7:00 pm

Maybe this will help:

3291|68/stevensheli2b.jpg
River City Science Academy - Florida 2010 Wright Stuff Champs
Coach for:
Storm the Castle
Helicopter

"My kid and my latinum go to Starfleet Academy"


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