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Author Topic: Air tops  (Read 3608 times)

Jeremy McCreary

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Air tops
« on: March 03, 2016, 05:16:55 PM »

Admin Note: I split this topic from the Turbine Top thread

++++++++++++++++++++++++++++

This post was inspired by Dalton Bissell's "turbine top" at http://www.ta0.com/forum/index.php/topic,4197.0.html -- a fascinating idea beautifully executed! All of Dalton's tops on Shapeways are elegant and clever, but the turbine top's definitely on my shopping list.

Having no fabrication skills to speak of, I design LEGO tops -- hundreds to date (see http://www.moc-pages.com/folder.php/188421). One big advantage to the LEGO medium is the flexibility to go way outside the usual top design box, and I now see from Dalton's work that 3D printing does exactly the same.

Tank Top (rotor ring from inverted LEGO tank treads)



Tops with ring-like rotors have long been a favorite genre for me, both for the visuals and the performance.

As Dalton clearly knows, in top design, you can generally either fight the aerodynamics or turn them to your advantage. Here, Dalton managed to do both while capitalizing on the wagon-wheel effect due to the spokes. Bravo!

Made the simple "Znap tops" below over a year ago from some cool-looking LEGO plastic wheels from their long-discontinued Znap line. (Details at http://www.moc-pages.com/moc.php/422867.)



https://www.youtube.com/watch?v=fGlb-8GEoyc

I was aware of the aerodynamic potential of the airfoil-shaped spokes at the time but dismissed it as insignificant on finding that the direction of spin had no effect on spin time -- even at 4,000 RPM or so. (The thinking was that spinning them in the lift-generating direction would de-weight the tips, thus reducing tip friction, but no go.)

However, I never thought to blow down on them from above until I saw your video. Sheer genius!

Well, I just now put the Znap tops under the wife's hair dryer, and behold! The large ones work quite well as "turbine tops", but the small ones do nothing for lack of swept area at the blades. The large ones self-start under the dryer, can be re-accelerated while spinning, and can even be followed around with the dryer and steered by it! They even show a slight tendency to self-center within the air stream.

Don't worry -- these large Znap wheels are very hard to find now.

Video to follow. Much to be explored in this new "turbine top" genre you invented. Very excited.

BTW, the spokes on the large Znap tops also generate nice wagon-wheel effects. The effect is especially dramatic under overhead LED lights on a standard pulse width modulation dimmer.
« Last Edit: March 07, 2016, 01:01:53 PM by Jeremy McCreary »
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Dalton Bissell

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Re: Air tops
« Reply #1 on: March 03, 2016, 09:01:39 PM »

Thanks for the complements guys.

Alan, I learned a huge amount from making the Tornado Top. I believe this one is better in quite a few ways. I do love the Tornado tops look and feel, but the Turbine Top is much closer to a performance top. I believe that a ball bearing or ruby sphere tip is going to be the next step towards a more perfect design.

Jeremy, those Lego tops are awesome! Also...I tried to get the tornado top and the turbine top to lift off. With the same theory as you had about the lift reducing drag. I found out soon enough than the drag would slow it down more than the friction. I did have a lot of fun trying though, I used an air compressor at 140 psi. That top revved up and sounded just like a turbine screaming. But was soon out of control as well. Fun, slightly dangerous, and worth it. Lastly, it made me try to think of a different way to make it fly like I wanted. So, spoiler alert, levitation is my next subject. Wish me luck, there is a lot to learn.
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Jeremy McCreary

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Re: Air tops
« Reply #2 on: March 04, 2016, 03:10:08 AM »

Dalton: Yeah, drag appears to trump tip friction in nearly all of my tops. I was hoping that the large Znap tops would be sleek enough to let friction play a proportionately bigger role, but apparently not big enough. Spinning them on a digital scale showed at most a few grams of lift at several thousand RPM.

I do have some tops that will lift off the table momentarily, even when spun up by hand. Here's an example:




These blades function as curved-plate airfoils. Not hugely efficient, but not bad. I work hard to avoid glue in my LEGO building, but these blades became very dangerous shrapnel at high speed without it. Not a word to my wife about the nicks in the walls.

The same blades generate a decent amount of lift in the rotors below:

https://www.youtube.com/watch?v=P2kgdPR9r94



With this rotor, the wind turbine generates ~0.5 watts of electrical power from the wind of a floor fan.
« Last Edit: March 07, 2016, 01:20:29 PM by Jeremy McCreary »
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ta0

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Re: Air tops
« Reply #3 on: March 04, 2016, 12:01:24 PM »

Jeremy: your house must be built out of lego blocks!  :o

There are some antique tops that would fly off the ground, like these Marklin from Dan's collection:



On this thread you can see them flying and also see a blow top (from Cyril's collection):
(air)blow top and flying top

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Jeremy McCreary

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Re: Air tops
« Reply #4 on: March 04, 2016, 03:04:24 PM »

Tao: What a collection of tops! Is the plunger-style starter I saw at the link you gave available for purchase?

Wife says I have way too much LEGO. I say she has way too many shoes, and that I have nothing compared to a friend with a LEGO collection insured for $150K. Doesn't help one bit.

BTW, if anyone wishes to try their hand at some LEGO tops, and I hope they do, note that buying sets is generally not the best way to get parts. I get 95% of my parts through http://www.bricklink.com.
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ta0

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Re: Air tops
« Reply #5 on: March 04, 2016, 11:20:25 PM »

Tao: What a collection of tops! Is the plunger-style starter I saw at the link you gave available for purchase?

Wife says I have way too much LEGO. I say she has way too many shoes, and that I have nothing compared to a friend with a LEGO collection insured for $150K. Doesn't help one bit.

BTW, if anyone wishes to try their hand at some LEGO tops, and I hope they do, note that buying sets is generally not the best way to get parts. I get 95% of my parts through http://www.bricklink.com.

Those flying tops are old Marklin brand (but there are a few other brands) and all vintage (I think most 1910s - 1930s from Germany). You will need to pursue them on Ebay.

That bricklink.com website has a huge catalog! I think my wife has given away all the lego-like sets we had now that the kids have grown up but I am thinking that I should make myself a lego top. But it should be an "acrobatic" (trick) top, of course! Mm, I think we may have a contest on the forum sometime in the future . . .  ;)
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the Earl of Whirl

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Re: Air tops
« Reply #6 on: March 05, 2016, 09:18:09 AM »

Now.....this makes sense..... http://www.bricklink.com.

Thanks for that link.  Are the stems you use for the finger spinners from the parts listed under "bar"?
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Jeremy McCreary

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Re: Air tops
« Reply #7 on: March 05, 2016, 01:32:59 PM »

ta0: Guess I'm gonna have to learn some top tricks.

EW: The stems you asked about are listed under "Technic axles" in the BrickLink parts catalog. We just call them "axles" or "cross-axles" for the splines.

All kinds of LEGO parts find use in tops. "Technic" refers to LEGO's line of technical sets and parts. Some Technic parts have studs to mate with other "studded" parts like a classic LEGO brick. The many "studless" Technic parts are generally joined with small pins. The pins in the large studless top below are black.




Technic parts have 2 different kinds of holes to receive these axles: (i) Cross-shaped holes we call "axle-holes", and (ii) smooth-bore holes we call "pin holes" for the pins just mentioned.

An axle in an axle hole becomes keyed to the part bearing the latter. An axle in a pin hole spins freely with remarkably little friction. All the parts in the "Cheeseburger" top below are keyed to a through-going central axle.




Using a bare central axle as a tip results in a somewhat wobbly top that walks a lot in a rather interesting way. That's great for a battle top, but to get a smooth spin, you have to cover the bottom end of the axle with an appropriate tip assembly.

BTW, part sizes on BrickLink are generally given in LEGO units (LU or just L). 1 LU = 8 mm. Hence, a 12L axle is 96 mm long. To adapt non-LEGO parts to pin holes, you need to know that ID of a pin hole is 4.8 mm or 3/16".

"Bars" are straight rods with 3 mm ODs. Many parts have bars on them, and many other parts have holes or clips to receive bars, always with a snug fit. A bar will also fit snugly in the central part of an axle hole. I use bars for stems in small tops like the ones below. (The smallest rotor is 24 mm in diameter.)




« Last Edit: March 05, 2016, 07:19:18 PM by Jeremy McCreary »
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Neff

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Re: Air tops
« Reply #8 on: March 06, 2016, 05:02:14 AM »

The Turbine Top is fantastic!

Jeremy your Lego skills are downright scary.  Really slick looking builds man keep it up.
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ta0

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Re: Air tops
« Reply #9 on: March 06, 2016, 12:53:56 PM »

Jeremy your Lego skills are downright scary.  Really slick looking builds man keep it up.

No doubt!
I have to ask: the device with the planetary gears (differential gearbox?) behind the top, is not used to speed up the top, is it?  :-\
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Jeremy McCreary

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Re: The Turbine Top
« Reply #10 on: March 07, 2016, 12:41:50 PM »

Dalton: Sorry, didn't mean to hijack your thread. Your turbine top is a truly spectacular piece of top design and fabrication with great play value. When will it be out of beta?

ta0: Yes, that's a spinner, starter, spin-up tool. (Not sure of the proper term.) The ergonomics aren't all that great, but it was the best I could do with the only LEGO ring gear available.

https://www.youtube.com/watch?v=Gu93GZffA58

Since each carrier-in, sun-out planetary stage has a 1:4 overdrive, the 2-stage version shown has a final overdrive of 1:16. The 2-stage is my workhorse, but a 1-stage struggles less with my heaviest (highest AMI*) tops. On a low-friction surface, the 3-stage version (1:64 overdrive) can take an aerodynamically clean LEGO top of moderate AMI to over 2,500 RPM.

Details and photos at http://www.moc-pages.com/moc.php/421861.

* AMI == axial moment of inertia.
« Last Edit: March 07, 2016, 12:50:09 PM by Jeremy McCreary »
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Jeremy McCreary

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Re: Air tops
« Reply #11 on: March 07, 2016, 12:58:30 PM »

Neff: Thank you very much!
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ta0

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Re: Air tops
« Reply #12 on: March 07, 2016, 01:26:35 PM »

Dalton: Sorry, didn't mean to hijack your thread.
I split the threads.

What can I say? Amazing variety of lego tops and very nice planetary gear spinners!  :o  8)
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Jeremy McCreary

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Re: Air tops
« Reply #13 on: March 07, 2016, 03:39:48 PM »

ta0: Thanks for the kind words. Glad you spit the thread, as I unintentionally pulled it too far from Dalton's original intent.

Wondering if Reply#1 above from Dalton should also be moved/copied back to the original?
« Last Edit: March 07, 2016, 03:50:20 PM by Jeremy McCreary »
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Jeremy McCreary

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Re: Air tops
« Reply #14 on: March 07, 2016, 03:43:03 PM »

ta0: Oops, forgot: Is there a preferred term for a spinner like this -- one for start-up only, not for regeneration?
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