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Reuleaux top
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The studded rotor of this large, heavy top takes the form of a Reuleaux triangle. Still can't believe I found a workable suspension system for it.
About this creation
Please feel free to look over the images and skip the verbiage.

A month ago, a suggestion by favorite builder David Roberts led to my first rubber band boat, X-ray. Now David's done it again with the striking spacecraft section in tow behind his Achatina Space Tug.

The cargo's elegant Reuleaux triangle cross-section drew as many comments as the tug itself. In response, David pointed us to www.BrickBending.com, where LEGOŽ artist Jeff Sanders posts his stunning "brick bending" creations and some very helpful tutorials as well.

Of course, one man's spacecraft section is another man's top rotor.



And of course, that other guy would be top-obsessed me.

On this page...


Rotor

The Reuleaux triangle rotor consists of 3 layers of overlapping 1x2 bricks. The rest of top's mostly studless.





End-to-end tolerances between bricks are such that each side of the rotor had to be at least 200 mm (25 LU) long to get the triangle to close with a comfortable degree of stress. That made for a rather large rotor.





Since the side midpoints had to be pushed out another 1-2 mm to accommodate the hub and spokes, the sides ended up a little more strongly curved than would be the case in a true Reuleaux triangle.

The good news: The resulting hoop stresses in the rotor stiffen the entire top considerably.

Suppressing nutation (a nodding motion superimposed on precession) is one of the keys to a smoothly spinning top. A floppy top is a sure-fire recipe for excessive nutation, and that's especially true in large LEGOŽ tops, where the necessary rigidity can be hard to come by.




Spokes, hub, and tip

Building the rotor turned out to be the easy part. From its size alone, prospects for a reasonably stiff, well-centered suspension system seemed slim. Then, as so often happens in the LEGOŽ realm, a miracle happened: It all came together.





The hollow stud of a black 2x2 dome holds the tip -- the severed end of a black round-tipped 4L antenna -- firmly in place. The best purist tip solution (a Technic ball mounted directly on the through-going center axle) makes the top a lot jerkier at all speeds.

The spokes burned up a lot of expensive thin 1x5 liftarms with axle holes, but I couldn't think of any other way to span the rotor with a suspension system rigid enough to keep the top spinning smoothly.



Considering the rather forced fit, the hub and spokes are remarkably well-centered within the rotor.






In motion

The top in motion looks pretty wild in the video at times, and even wilder in some of the stills.









The top may look like it's sleeping in some of these photos, but it's actually precessing at a small inclination, as is its strong preference. The odds of spinning a sleeper are well under 10% in my hands, and I've had lots of practice.

The optical effects in motion can get pretty trippy. The photo below captured the top at high speed just after release.



Lower speed during spin-down.



Most twirls result in fairly smooth precession with a slight but noticeable nutation that I just can't get rid of at this rotor size.

Spin times average ~15 sec by hand.




Specifications


Overall dimensions:
188x96 mm (DxH)
Mass:126 g
Diameter:188 mm
Side length:200 mm
Side chord:196 mm
Average spin time:~15 sec
Modified LEGOŽ parts:Tip cut from 4L antenna
Non-LEGOŽ parts:None
Credits:Original MOC inspired by the cargo of David Roberts' Achatina Space Tug





Comments

 I made it 
  November 15, 2015
Quoting Oran Cruzen Very nice how you put a spin on this great Lego creation of yours!
Thanks, Oran!
 I like it 
  October 26, 2015
Very nice how you put a spin on this great Lego creation of yours!
 I made it 
  October 8, 2015
Quoting Nick Barrett It seems to work well and the shape is mesmerizing in motion. Lovely stuff.
Thanks, Nick!
 I like it 
  October 8, 2015
It seems to work well and the shape is mesmerizing in motion. Lovely stuff.
 I made it 
  October 6, 2015
Quoting Nerds forprez The images make me feel like I've been popping colored bricks all day.... lol...
And you weren't?? Everybody knows that everybody on MOCpages pops colored bricks all day everyday.
 I made it 
  October 6, 2015
Quoting Henrik Jensen I think it`s great that you saw the possible use of Davids Reuleaux triangle as a subject for a spinning top, and I like how you made the Technic hub to balance it. I got to try out this brick bending technique myself, I love it!
Many thanks, Henrik. Todd Wilder (http://www.mocpages.com/home.php/4568) also does some nice brick-bending. Ran across his work over a year ago now but forgot all about it until David posted his space tug.
 I like it 
  October 6, 2015
The images make me feel like I've been popping colored bricks all day.... lol...
 I like it 
  October 6, 2015
I think it`s great that you saw the possible use of Davids Reuleaux triangle as a subject for a spinning top, and I like how you made the Technic hub to balance it. I got to try out this brick bending technique myself, I love it!
 I made it 
  October 6, 2015
Quoting David Roberts Excellent. I knew that you'd do something interesting with this. In the same that one man's chunk of spaceship is another man's top; I like the way that the rotor attaches and it presents some interesting possibilities for spaceship construction. I like the way that the frame rate makes patterns on the video (plus a nice bit of Bach too) and the blurred triangular shape in the still photo lokms great too. I hope that this isn't your last adventure in brick bending.
Many thanks for the kind words and the Reuleaux triangle idea, David. Better to be lucky than good: At one magical point in the video, the top seems to be spinning in both directions at once with the piano perfectly in step.
 I made it 
  October 6, 2015
Quoting Ian Spacek That's a lot of fun!
Thanks, Ian! This top is a great example of one of the things I enjoy most about LEGO tops: They have very different personas at rest and in motion, and the moving personas also vary when seen in person, in videos at various frame rates, and in stills at various shutter speeds. The in-person personas can also vary strongly with light source, with overhead LEDs on the usual pulse-width modulation dimmers providing some of the most spectacular dynamic patterns.
 I like it 
  October 6, 2015
That's a lot of fun!
 I made it 
  October 6, 2015
Quoting Topsy Creatori History has always shown that innovative concepts often revolve around the exchange of ideas between top notch analytical/imaginative thinkers... an intriguing top! :)
Too kind, Topsy! Stealing ideas from David Roberts would seem to be a rich vein to mine.
 I like it 
  October 6, 2015
Excellent. I knew that you'd do something interesting with this. In the same that one man's chunk of spaceship is another man's top; I like the way that the rotor attaches and it presents some interesting possibilities for spaceship construction. I like the way that the frame rate makes patterns on the video (plus a nice bit of Bach too) and the blurred triangular shape in the still photo lokms great too. I hope that this isn't your last adventure in brick bending.
 I made it 
  October 6, 2015
Quoting The Royal Brick Very nice! This top looks really neat in motion!
Thanks, Royal! Had no idea the stills in motion would come out like this -- a very pleasant surprise.
 I made it 
  October 6, 2015
Quoting Gabor Pauler Top of tops.
Thanks, Gabor!
 I like it 
  October 6, 2015
History has always shown that innovative concepts often revolve around the exchange of ideas between top notch analytical/imaginative thinkers... an intriguing top! :)
 I like it 
  October 6, 2015
Very nice! This top looks really neat in motion!
 I like it 
  October 6, 2015
Top of tops.
 
By Jeremy McCreary
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Added October 6, 2015
 


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