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Technic free gyro
The rotor's spin axis is free to point in any direction WRT the base. Spin-down times from a maximum speed of ~4,100 RPM exceed 60 sec. Directional stability is quite good.
About this creation
Please feel free to look over the images and skip the verbiage.

My ongoing fascination with high-speed rotary motion in the LEGOŽ realm continues with this fully functional free gyroscope.

Such gyros are also known as "universally mounted" or "2-DOF" gyros, where the "DOF" stands for degree of freedom.



The directional stability of the rotor axis is quite good considering the simple plastic construction -- especially the plastic-on-plastic revolute (1-DOF rotary) bearings. LEGOŽ precision molding really shines here.

This free gyro differs from the traditional toy "gyroscope" in the cover photo in that the spin axis of its rotor experiences very little in the way of torque due to motions of its base and no torque whatsoever due to gravity.

As seen above, a free gyro's rotor axle is supported at both ends by a rigid inner gimbal supported in turn at both ends by a rigid outer gimbal. The last is also supported at both ends, this time by the gryo's rigid base or housing.

When the rotor's center of mass is fixed at the centers of both gimbals, at it is here, the result is a rotor free of any gravitational torque, regardless of orientation.

Low-friction revolute bearings in the 3 mutually perpendicular pairs of supports provide the inner gimbal with 2 rotational DOFs relative to the base. (Hence the name "2-DOF gyro".)

With good bearings, this arrangement effectively decouples 3D motions of the free gyro's base from those of its rotor.



The toy gyroscope's rotor is also supported at both ends by a rigid ring akin to the free gyro's inner gimbal, but the similarity ends there.

The toy's ring is typically supported at only one end at a point in line with the rotor axis. As a consequence, the toy's rotor is subject to torques due to both gravity and motions of the ring.

Hence, the toy gyro is really little more than a spinning top in a ring that can be handled without touching the rotor.

On this page...Warning! Always wear eye protection when working or playing with high-speed LEGOŽ rotating machinery and keep valuables and bystanders (including pets) a safe distance away -- especially when testing new designs.




Design and construction

This MOC's rotor consists of 2 new-style motorcycle wheels (88517) sandwiched between clear 10x10 dishes servings as fairings.



I chose these wheels because most of their mass is concentrated in the rim, far from the spin axis. Their axial radius of gyration (given by the square root of the moment of inertia per unit mass) is about the highest you can get in any LEGOŽ part I know of.

The detaching high-speed motorized spin-up tool (below) uses an original Technic 9V motor (2383) with a no-load speed of ~4,400 RPM. The rotor plateaus at ~4,100 RPM while driven by the spinner at full power.



Given that the motor has little torque left at ~4,100 RPM (93% of its no-load speed), this is strong evidence that aerodynamic braking and bearing friction in this gyro are quite low.

True axles are a must for rotors this fast. Luckily, my stock of 12L axles happened to include a perfectly straight one -- a great rarity, even among brand-new axles.

Importantly, the rotor fairings aren't just for looks. They more than double spin-down time -- mainly by blocking axial airflow through the spokes of the rotor. Using 8x8 instead of 10x10 dishes works almost as well, and there might even be some benefit to 6x6 fairings.



Very lightweight inner and outer gimbals allow the rotor to adopt any 3D orientation WRT the base -- hence the name "universally mounted gyroscope".



The gimbals rest on the lowest-friction bearings I could muster: Tan 2L axle-pins running in pin holes. Spin-down times are a good bit shorter when the axle-pins are replaced with 2L tan pins without friction ridges.

The inner gimbal's spin axis commonly locks onto the outer gimbal's axis as the rotor approaches standstill. As seen in some of runs captured in the video, gimbal lock is also likely when the angle separating the inner and outer gimbal axes starts off small.

The stand is reasonably rigid.





The only non-LEGO component: Tiny dabs of silicone lube on the rotor and gimbal bearings.

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More photos





NB: After posting this MOC, I ran across a slower one of similar gimbal design but without rotor fairings here.

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Specifications

Rotor diameter:75 mm
Rotor mass:59 g
Gimbals:2
Total gimbal mass:23 g
Degrees of freedom:2 at inner gimbal
Maximum rotor speed:~4,100 RPM with spin-up tool shown
Spin-down time:>60 sec from ~4,100 RPM
Motors:1 (2383) in detaching spin-up tool
Electrical power supply:Old 9V LEGOŽ train transformer (spin-up tool only)
Modified LEGOŽ parts:None
Non-LEGOŽ components:Silicone lube on rotor and gimbal bearings
Credits:Original MOC

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Comments

 I made it 
  November 4, 2017
Quoting Verbal Gerbil Very cool! Would you mind if I use the general design for something?
Thanks! You're more than welcome to borrow anything I post -- as long as you don't weaponize it.
 I like it 
  November 4, 2017
Very cool! Would you mind if I use the general design for something?
 I made it 
  October 15, 2015
Quoting Michiel Norp You certainly give a spin to the mocpages
Thanks, Michiel!
 I like it 
  October 15, 2015
You certainly give a spin to the mocpages
 I made it 
  July 15, 2015
Quoting Henrik Jensen Cool educational build! It`s amazing to see your video, it demonstrates very well the stable position of the gyro wheel, very fascinating.
Many belated thanks, Henrik. I've since stiffened up the base with perhaps a slight improvement in spin-down time.
 I like it 
  May 14, 2015
Cool educational build! It`s amazing to see your video, it demonstrates very well the stable position of the gyro wheel, very fascinating.
 I like it 
  April 8, 2015
It's amazing how a build with so simple parts can be so impressive. 5/5
 I made it 
  April 7, 2015
Quoting Walter Lee Your gyro is soo cool. I don't know if you can see NHK world but they have a two part series on a gyroscope challenge that you might be interested in ...I've asked them to rebroadcast episode 1 which occur April 3 ...episode 2 is this Friday on April 10 http://www3.nhk.or.jp/nhkworld/english/tv/supremeskills/
Thanks, Walter. I've definitely gotta see those videos. Will set a reminder for the 4/10 broadcast.
 I made it 
  April 7, 2015
Quoting David Roberts That's a great idea and nicely constructed too. I like the removable charger for getting it up to a decent speed. I'm surprised by how long the two bike wheels spin for (I suppose that the silicon helps!). A super video that very neatly shows how a gyroscope works as well.
Thanks for the kind words, David. The lube definitely made a difference, but a minor one compared to the run time gain obtained by fairing the rotor with the 10x10 dishes. After umpteen projects now involving high-speed rotary motion in the LEGO realm, I'm still impressed with the impact air resistance can have on performance.
 I like it 
  April 7, 2015
Your gyro is soo cool. I don't know if you can see NHK world but they have a two part series on a gyroscope challenge that you might be interested in ...I've asked them to rebroadcast episode 1 which occur April 3 ...episode 2 is this Friday on April 10 http://www3.nhk.or.jp/nhkworld/english/tv/supremeskills/
 I like it 
  April 3, 2015
That's a great idea and nicely constructed too. I like the removable charger for getting it up to a decent speed. I'm surprised by how long the two bike wheels spin for (I suppose that the silicon helps!). A super video that very neatly shows how a gyroscope works as well.
 I made it 
  March 14, 2015
Quoting Nick Barrett An excellent toy and it really works! Kudos to Lego's precision and your skills.
Thanks, Nick.
 I made it 
  March 14, 2015
Quoting David FNJ Another unique piece! This could definitely be a fun desktop piece! Masterful!
Thanks for the kind words, David.
 I like it 
  March 13, 2015
Another unique piece! This could definitely be a fun desktop piece! Masterful!
 I like it 
  March 13, 2015
An excellent toy and it really works! Kudos to Lego's precision and your skills.
  March 5, 2015
Thanks! Sorry, what I meant by freeze was seize due to overheating. Lack of clarification on my part.
 I made it 
  March 5, 2015
Quoting jds 7777 Great! Thanks! At what RPM would you say Legos need to be lubed so they don't overheat or freeze? I'm working on a custom Lego motor for PF, and the motor I have in mind does about 6000 RPM. And lastly, what is the benefit of a gyro over a regular top? Does the tilting ability affect the spin time?
jds, No problem with bearings overheating up to 4,000 RPM or so without lube, which I used only to lengthen spin times. No experience with or without lube at higher speeds or temperatures below 20F. Free gyros like this one, toy gyros, and tops differ mainly in how their rotors are mounted. That in turn determines the extent to which motions of the surfaces on which they rest can affect the motions of their rotors. Each serves a different purpose. You'd need a "free" gyro like this one for navigational purposes, as it's the only one with a mounting that mechanically isolates the rotor from the supporting surface. Lots of good material on Wikipedia.
  March 4, 2015
Great! Thanks! At what RPM would you say Legos need to be lubed so they don't overheat or freeze? I'm working on a custom Lego motor for PF, and the motor I have in mind does about 6000 RPM. And lastly, what is the benefit of a gyro over a regular top? Does the tilting ability affect the spin time?
 I like it 
  March 4, 2015
Great creation ! Well executed, and very informative as ever. I can see some nice physics in this moc. Great video as well! 5/5
 I like it 
  March 4, 2015
I can't wait to see this gyro mounted on a boat of yours! Than you will earn the "MOCpages Magellan" degree
Jeremy McCreary
 I like it 
Kain .
  March 3, 2015
very nice gyro
 I made it 
  March 3, 2015
Quoting jds 7777 Awesome! Silicon lube wipes off when you're done, right?
Thanks, jds. Yes, it comes off cleanly without marring any surfaces. The =only= problem: Getting the last little bit off involves paper towels, soap, and patience. (Ditto for your hands if they get lubed, too.) Anybody have a have a faster way?
 I like it 
  March 3, 2015
Awesome! Silicon lube wipes off when you're done, right?
 I like it 
  March 3, 2015
Man, that's cool.
 I made it 
  March 3, 2015
Quoting Topsy Creatori This is very cool! Before GPS aircraft like the C5 used gyroscopes in their inertial navigation! :)
Thanks, Topsy. Ships, too. Hmmm, per Walter's suggestion, one of my big powerboats based on the 74x18x7 hull could carry a smaller version.
 I like it 
  March 3, 2015
Wow! That is something else!
 I like it 
  March 3, 2015
This is very cool! Before GPS aircraft like the C5 used gyroscopes in their inertial navigation! :)
 I made it 
  March 3, 2015
Quoting Kevin Moyer Now that's pretty cool.
Thanks, Kevin.
 I made it 
  March 3, 2015
Quoting Turbo Charger Absolutely stunning! I want one!
Thank you very much, Turbo Charger. Old-style motorcycle wheels and 8x8 dishes work almost as well for even less money.
 I made it 
  March 3, 2015
Quoting Walter Lee Very impressive! After seeing your work on spinning tops - I was wondering when you would make a gyroscope. Your design is perfect - it is simple, inexpensive, and complete - something that would be perfect in a class room setting. However, to demonstrate why a gyro is such a navigational wonder - one needs to show how a gyro maintains its orientation while it is constantly moving - to this effect may I suggest a video of your gyro constantly maintaining its orientation while it is mounted on a constantly moving Lego Train track? As the speed of the train varies one could show how the gyro's orientation stays the same regardless of the speed of the train.
Great idea, Walter! Don't have a working train, but my tractor with gooseneck trailer (video on YouTube under my name) would accomplish the same thing.
 I made it 
  March 3, 2015
Quoting Giorgio Ferrannini Wow Jeremy another clever and amazing MOC. I want to build this, but I have not the 10x10 dishes. you think this would work without them?
Thanks, Giorgio. Yes, still worthwhile without any dishes at all. Quite sure that even a single 8x8 dish would also slow spin-down a good bit. A 6x6 dish or 2 would also be worth a try.
 I like it 
  March 3, 2015
Now that's pretty cool.
 I like it 
  March 3, 2015
Absolutely stunning! I want one!
 I like it 
  March 3, 2015
Very impressive! After seeing your work on spinning tops - I was wondering when you would make a gyroscope. Your design is perfect - it is simple, inexpensive, and complete - something that would be perfect in a class room setting. However, to demonstrate why a gyro is such a navigational wonder - one needs to show how a gyro maintains its orientation while it is constantly moving - to this effect may I suggest a video of your gyro constantly maintaining its orientation while it is mounted on a constantly moving Lego Train track? As the speed of the train varies one could show how the gyro's orientation stays the same regardless of the speed of the train.
 I like it 
  March 3, 2015
Wow Jeremy another clever and amazing MOC. I want to build this, but I have not the 10x10 dishes. you think this would work without them?
 
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