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Old 11-10-2012, 12:29 AM   #1
earthsciteach
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Default Rotor Egg Drop

I coach Science Olympiad in my school district. A new event at the middle school level is called Rotor Egg Drop. The competition entails dropping an egg from a height and slowing its decent with some form of rotational means. The winning device will take the greatest amount of time to descend without breaking the egg.

The egg is to be held in a paper cup that is attached to the device. The cup with egg must be the first part of the device to touch the ground.

This poses an interesting aeronautical challenge. The simplest solution (which, in my interpretation of the specs, is not allowed) would be to use a rotational parachute. This means the rotor must be rigid.

My current thinking is that blade design should be a cross between a wind turbine and an autogyro. A wind turbine is designed to convert a straight-line wind into rotational velocity. An autogyro creates lift through the rotation of the blades due to the forward motion of the aircraft. The goal of the egg drop rotor device is not quite either of these.

The blades are driven by the weight of the device falling toward the ground. Ideally, there will be enough lift generated by the outer portion of the blades to quickly reach a terminal velocity and fall slowly.

I can't quite wrap my brain around the twist and taper of the blade design to optimize the ratio of rotor velocity to descent velocity. Does anyone have any thoughts or ideas they'd be willing to share?

Thanks!

All of my landings are three point landings if you count the spinner, too
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Old 11-10-2012, 12:36 AM   #2
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Study the Maple seed.
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Old 11-10-2012, 12:41 AM   #3
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Dang. You said a TON in just four words. Thanks!

All of my landings are three point landings if you count the spinner, too
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Old 11-10-2012, 12:52 AM   #4
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Originally Posted by earthsciteach View Post
I coach Science Olympiad in my school district. A new event at the middle school level is called Rotor Egg Drop. The competition entails dropping an egg from a height and slowing its decent with some form of rotational means. The winning device will take the greatest amount of time to descend without breaking the egg.

The egg is to be held in a paper cup that is attached to the device. The cup with egg must be the first part of the device to touch the ground.

This poses an interesting aeronautical challenge. The simplest solution (which, in my interpretation of the specs, is not allowed) would be to use a rotational parachute. This means the rotor must be rigid.

My current thinking is that blade design should be a cross between a wind turbine and an autogyro. A wind turbine is designed to convert a straight-line wind into rotational velocity. An autogyro creates lift through the rotation of the blades due to the forward motion of the aircraft. The goal of the egg drop rotor device is not quite either of these.

The blades are driven by the weight of the device falling toward the ground. Ideally, there will be enough lift generated by the outer portion of the blades to quickly reach a terminal velocity and fall slowly.

I can't quite wrap my brain around the twist and taper of the blade design to optimize the ratio of rotor velocity to descent velocity. Does anyone have any thoughts or ideas they'd be willing to share?

Thanks!
Remember those toys that used a propeller glued on to a stick? You wrapped a string around the stick and yanked it. That prop would take off and climb up to pretty high altitudes.

Makes you wonder if one of those slow flyer props could be used to bring that egg back to the ground. A dowel could be glued to the prop, with the other end attached to the egg's basket. This could be expanded to put two or three props on the same shaft for stability.

Those props are cheap at the local hobby shop, so buying a bunch of different sized props would be reasonable in cost.

DennyV
Retired and the days are just too short, busier than ever!
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Old 11-10-2012, 03:45 AM   #5
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OH MAN,DOES THIS BRING BACK MEMORIES!!!! i used to lead a group of boys[18 of them] called boys brigade at our chapel. our chapel is 3 stories tall from the highest window to the parking lot.

the egg drop was a huge hit. give them an egg and a hand full of materials to protect the egg.... a handful of foam packing kernels ,a thin gift box the size to hold a coffee mug ,string ,straws, small plastic zip lock bags[4],a paper sandwich bag,1 paper towel, roll of scotch tape...... add fun and an object lesson.

then take their inventions up to toss down while they stand around the parking lot cheering each toss.....many eggs broke some survived the first year.

boy brigade lasted for this group of boys till they reached Jr teen group age[brigade lasted 6 years]. each year we did the toss and more eggs survived the fall each year. toward the end of teaching this group they had learned to use the small plastic zip locks as air bag cushions and pack the egg as best as possible to protect it in the box......but the idea came to take the paper bag and straws and make a parachute to direct the fall to land on the inflated ziplock bags.many great designs and many more survivals. great fun! thanks for bringing back those great memories teach! sounds like your student are going to have a blast and there will be lot of laughing...

narrow is the place to land...wide is the space to crash....choose the narrow way!
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Old 11-10-2012, 08:59 AM   #6
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get a blade from a cox helicopter and copy it

http://www.ebay.com/itm/Cox-Attack-C...item3ccc0e4e14


I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
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Old 11-10-2012, 12:41 PM   #7
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Originally Posted by kyleservicetech View Post
Remember those toys that used a propeller glued on to a stick? You wrapped a string around the stick and yanked it. That prop would take off and climb up to pretty high altitudes.
That does bring back memories such as tearing an aluminum can in half (alum cans were fairly new back then) and pushing it back together making a shorter can, and then wedging a firecracker in the tab opening with nearly all of the firecracker inside the can. The cans had the old tab style with a teardrop opening, where the tab was pulled off of the can. Of course there are major thrust losses due to the large tab opening, but we could still get 50 feet vertical launch from the top half of the can.


Originally Posted by CHELLIE View Post
get a blade from a cox helicopter and copy it

http://www.ebay.com/itm/Cox-Attack-C...item3ccc0e4e14


I had to check your link, to see if that was for real.
I thought you "photoshopped" a cox engine on top of a toy helicopter.
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Old 11-11-2012, 10:33 AM   #8
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Originally Posted by Bill G View Post
That does bring back memories such as tearing an aluminum can in half (alum cans were fairly new back then) and pushing it back together making a shorter can, and then wedging a firecracker in the tab opening with nearly all of the firecracker inside the can. The cans had the old tab style with a teardrop opening, where the tab was pulled off of the can. Of course there are major thrust losses due to the large tab opening, but we could still get 50 feet vertical launch from the top half of the can.





I had to check your link, to see if that was for real.
I thought you "photoshopped" a cox engine on top of a toy helicopter.
Cox Made a few different styles of free flight helis

http://www.google.com/search?q=cox+h...w=1440&bih=719

I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
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Old 11-11-2012, 03:56 PM   #9
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Thanks for the replies, guys! I'm going to have the kids to some exploring into Turner's suggestion. The maple seed idea is great!

Kyleservicetech-This particular event does not allow commercially produced rotors, but a series of large, slow fly props would probably work great!

Stuart - Glad to bring back some fond memories. Working with Science Olympiad is one of the most rewarding things I do. Seeing those kids win medals at the competitions and the pride they get from that is very special. You know it means a lot to them when, on the first day of school the next year, they are pushing us to get this going. And, these are not the typical "nerdy" kids. The group from last year was mostly young ladies who are involved in sports, music, dance and are socially popular. We came within 4 spots of going to the national competition.

Chellie - that is the weirdest looking thing I've ever seen! LOL!

All of my landings are three point landings if you count the spinner, too
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Old 11-11-2012, 11:28 PM   #10
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Originally Posted by earthsciteach View Post
Thanks for the replies, guys! I'm going to have the kids to some exploring into Turner's suggestion. The maple seed idea is great!

Kyleservicetech-This particular event does not allow commercially produced rotors, but a series of large, slow fly props would probably work great!

Stuart - Glad to bring back some fond memories. Working with Science Olympiad is one of the most rewarding things I do. Seeing those kids win medals at the competitions and the pride they get from that is very special. You know it means a lot to them when, on the first day of school the next year, they are pushing us to get this going. And, these are not the typical "nerdy" kids. The group from last year was mostly young ladies who are involved in sports, music, dance and are socially popular. We came within 4 spots of going to the national competition.

Chellie - that is the weirdest looking thing I've ever seen! LOL!
Your right Teach but they fly great


I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
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Old 11-11-2012, 11:39 PM   #11
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Hey, This might work


I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
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Old 11-12-2012, 12:07 AM   #12
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Also, Make the rotor blades long and wide, about 1 1/2 ft feet long each blade and 8" wide, make a balsa wood rotor frame with arched dollar tree foam to make the blade cover, remove the paper from the foam, cup the foam in the rotor frame and pitch the blades at 15 degrees, use 6 blades. make some kind of a bushing or bearing for the rotor center, hang the cup on the rotor blade center with strong string, Cheat a little and fill the cup with the egg in it with instant foam LOL

I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
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Old 11-12-2012, 12:09 AM   #13
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That is good stuff, Chellie. Thanks!

All of my landings are three point landings if you count the spinner, too
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Old 11-12-2012, 12:31 AM   #14
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We had an afternoon work session at school today. I had a chance to firm up the requirements in the specs. The entire device must fit within a 51 cm cube. That means the maximum linear distance possible would be about 88 cm.

We made a couple of models that were about 5x the size of a maple seed and found the performance to scale well to that size. The girls are going to make a model that is 88 cm long with a tennis ball in place of the egg. Turns out, a tennis ball is pretty close in weight to a grade A large egg (58-60g).

The maple seed is quite fascinating! Lockheed and others have developed mini-UAVs based on the mono-rotor design.


The asymmetry and weight distribution of the seed really enhances rotation speed, therefore lift, as compared to an equivalent, balanced multi-rotor rotating around a fixed axis. I found a handful of seeds at the base of the gas pump when I stopped for gas on the way home tonight. Working on getting dimension ratios and figuring out the weight distribution of the seed, now. Pretty interesting stuff!

All of my landings are three point landings if you count the spinner, too
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Old 11-12-2012, 12:58 AM   #15
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Really thrilled you are going down this road. I haven't seen a maple seed for over forty years. I grew up in New England with a big maple tree in the back yard. I can still see the seeds twirling their way slowly to earth. I hope this proves a winning strategy.

That Boomerang is crazy. Would like to see a close-up. Weird sounds.
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Old 11-12-2012, 09:45 PM   #16
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Whoever is flying that boomerang really made some good choices for a career path.

As long as he didn't really want to be an accountant...

OTOH - http://www.youtube.com/watch?v=Dgung7ugcVw
and many other references to the McCutchen Flying Machine, AKA 'Charybdis'

Of which, oddly enough, I had a couple back in England. 'All' that was missing was the radio, I feel.

D
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Old 03-25-2014, 08:20 PM   #17
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Originally Posted by earthsciteach View Post
We had an afternoon work session at school today. I had a chance to firm up the requirements in the specs….
So what ever happened with this?
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Old 03-26-2014, 02:20 AM   #18
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I did this way back when in design school (UC (Cincinnati)) ~'78 or so. I don't remember the exact rules, but mine was made from a single 8.5 x 11 piece of paper. The rotor blade portion simply made it so the thing fell "point down". There were three concentric paper cones glued to the bottom of the egg to absorb the shock. Worked fine .

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