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Bamboo copter Flying Ripcord Launcher
Flying Lego Version 2 - bamboo dragonfly - Chinese top - bamboo copter - taketombo - zhuqingting -
About this creation
This is a version of Anna Vuurzoon's Flying Lego [1] , also known as a Bamboo copter - bamboo dragonfly - Chinese top [2]. I was very impressed with her design so I had to test out a version of it on my own. This is the end result. My ripcord launcher is more basic but functions in a similar manner. Like the Vuurzoon Launcher, my launcher is using an 8 teeth gear but I've raised the launch platform to accomodate my larger hand - my parts are more common place than hers. I found that the Technic three blade liftarm rotor was essential to this design (part 44374) because it had the ability to hold onto the propellers despite the centrifugal forces acting on it. I found that the propeller assembly could work with just one(1) three-blade-liftarm-rotor instead of two(2) that was used in the original design but that the(1) liftarm rotor arrangement wasn't as strong/robust as the original two(2) liftarm rotor arrangement. The Technic three blade liftarm rotor is a semi-rare piece so its a bit harder to find. My version of the original propeller is white because I got them from a Ninjago Ice Dragon (2260). I also created a second flying propeller using the windmill blades from my Lego Education Renewable Energy Add-on kit (9688). The windmill blades already had a deflection angle so to get the same angle of the original propeller I used angle "4" for the Windmill blades instead of original angle "3" connectors that were used on the original propellers. The windmill blade propeller has more surface area and thus it had better lift and flew higher than the original propeller design using the same energy. While I had to tug at the ripcord pretty vigoriously - both flew rather nicely. Gearing up(1:8) the launcher introduce too much torque and made it even harder to get the propellers to fly so I agree with Vuurzoon that a single 8 tooth gear was really the best solution. The launcher access port for the ripcord is not a tight fit so attempting to pull out the ripcord too fast or too hard (against the gearing) caused my ripcord to fall apart (I was using some old legos which I suspect had less clutching power. I might be able to fix this by using all new lego pieces OR by using some glue). I am very impressed with this design. If I had to do this over again I would focus on improving the overall strength of the ripcord so it would be more reliable and be capable of transferring higher/faster initial velocities.

[1] http://www.mocpages.com/moc.php/288875
[2] http://en.wikipedia.org/wiki/Bamboo-copter



Comments

 I made it 
  March 27, 2014
Quoting Family Vuurzoon Hi Walter, Great explanation. Let's make Lego fly!
Thank you for the inspiration.
 I made it 
  December 10, 2013
Quoting David Luders I too built Anika Vuurzoon's "Flying Lego" ( http://www.mocpages.com/moc.php/288875 ) using the big Lego Renewable Energy rotor blades. I used six blades instead of three, but they did not fly any higher due to their increased weight. You're right about the "slop" in the launcher -- that's the limiting factor. The challenge is, how does one get the central axle up to a speed far faster than "escape velocity" while still holding it down on the launcher?
To fly higher you need more lift force. Higher speed can created more lift force but it is not the only way. One can also increase the lift force of a propeller by increasing the blade's surface. My (book) research indicates that making propeller blade longer is more efficient than making it wider. And that given the same blade surface area a two blade propeller is more energy efficient than a four blade propellor. Why? It is because the Lift energy efficiency of a propeller increases as the surface area is farther from the spinning central axle of a propeller because the farther the lift surface is from the central axle the longer the lift surface travels (because it has a longer circumference/radial path than the inner section of the lift surface of a propeller. The problem with making a longer propeller is that to generate lift we need a very ridge surface which can withstand the torque/power of a very fast rotational speed - at some point the lego clutch power isn't strong enough and the entire assembly falls apart! sigh...
 I like it 
  June 5, 2012
Hi Walter, Great explanation. Let's make Lego fly!
 I made it 
  January 29, 2012
Quoting David Luders I too built Anika Vuurzoon's "Flying Lego" ( http://www.mocpages.com/moc.php/288875 ) using the big Lego Renewable Energy rotor blades. I used six blades instead of three, but they did not fly any higher due to their increased weight. You're right about the "slop" in the launcher -- that's the limiting factor. The challenge is, how does one get the central axle up to a speed far faster than "escape velocity" while still holding it down on the launcher?
I've already done some torque/power studies with the Lego Education Renewable-energy windmill rotor blades - so I know that three blade and two blade propeller rotor configuration (blades on the same geometric plane) are the most energy efficient at lower speeds ( under 2000 RPMs, this is about the upper limit of most Lego motors wrt to driving a propeller load). To get the highest flight, push the launcher away from you as you pull the ripcord towards you. If you use old legos for the ripcord and you press it too hard on the rotor gear the ripcord will disintegrate (oh the embarassment!). Newer lego has more clutch (gripping power) than older legos (san the use of glue). Both the original blade and the windmill blades rise up into the air about the same speed and nearly the same height BUT the renewable energy windmill blades seem to stay up in the air a bit longer. When I have some time - I'll do a video of this so you can see for yourself.
 I like it 
  January 28, 2012
I too built Anika Vuurzoon's "Flying Lego" ( http://www.mocpages.com/moc.php/288875 ) using the big Lego Renewable Energy rotor blades. I used six blades instead of three, but they did not fly any higher due to their increased weight. You're right about the "slop" in the launcher -- that's the limiting factor. The challenge is, how does one get the central axle up to a speed far faster than "escape velocity" while still holding it down on the launcher?
 
By Walter Lee
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LEGO models my own creation MOCpages toys shop Bamboo copter Flying Ripcord Launcher Technic


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