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Wind-up biconic top starter
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When you have an unhealty attraction to spinning objects, everything looks like a top -- including this unusual die. I just needed a little help getting it started. Best spin time = 204 sec (3:24)!
About this creation
Please feel free to look over the images and skip the verbiage.

GAMESCIENCEŽ sells this BIG "50" TOPPER as a "50-sided" biconic die to be spun on its equator for gaming purposes.



But there are no facets to disallow in-between rolls -- just 25 numbers staggered on each side of a perfectly circular equator. Not exactly "50-sided", then.

When I first ran across this die, I saw nearly all the makings of a great "biconic top" to be spun on one if its poles -- decent heft, favorable mass distribution, great aerodynamics, and a smooth, low-friction tip. But in practice, the lack of facets makes it hard to grip, much less twirl the way I'd envisioned.

.

All it needed, I thought, was a detaching polar stem kinda like the ones I made for these clutch tops.

But twirling the detachable stem (not shown) generally gave spin times of at most a few seconds by hand. To really shine as a top, the die would need a high-speed starter.



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. Really.

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Polar top starter

I happened to be testing a wind-up mug mixer (coming soon) for my morning coffee when my biconic tops -- I mean dice -- arrived.



Dropping the mixer, I tore open the package and spent the next 20 minutes trying to spin them on their poles without much success. Clearly, they needed much higher release speeds and more secure polar grips with much better tilt control.





Then I remembered the mixer and all the attachments I'd made for it. The pull-back motor certainly had the speed and torque, and the winding ratchet and trigger release were pretty convenient.

All the mixer lacked to become a good biconic top starter, then, was an adapter capable of keeping the polar axis aligned with the starter shaft while applying torque to the die's upper cone.





Three friction pads provide adequate traction, and they even out the torque applied to the die. But they don't do enough to enforce the sine qua non of a successful high-speed start: Poles perfectly coaxial with the starter shaft at all times during spin-up.



The added DGB pole cup helps a lot in this regard, but the die still tries to slip out from under the adapter on low-friction surfaces. That makes the starter fiddly at first, but a little practice goes a long way here.

Most of the starter's best features came from the mug mixer:I ordered 3 dice with the intention of giving 2 to friends, but now that I've seen how well they do as tops with the starter, I'm having second thoughts!



Video spin times and power levels on glass platter above: 144 sec (2:24) at 17.5 half-turns of the winder (full power), 134 sec (2:14) at 12 half-turns, and 114 sec (1:54) at 6 half-turns!

Based on how the winder tightens with each additional turn, I'm convinced that the diminishing returns here are mainly a reflection of the rapid nonlinear growth of aerodynamic drag with speed.

Update! After the video, the starter turned in a 204 sec (3:24) spin on the granite in the photo before last.

This latest record indicates that the supporting surface also influences spin time via friction at the tip -- at least toward the end of the spin, where drag is lowest. Rolling resistance (not quite the same thing as friction) comes into play only during the rapid precession accompanying the top's fall.

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Equatorial die adapter

When spinning this 50-outcome biconic die on its equator for gaming purposes, you're really much better off doing so by hand for reasons having mainly to do with the pace of play.

But did that stop me from cooking up an equatorial starter adapter? Of course not!







When you press the adapter down onto the die, the inner rubber friction pads grip the upper part of the equator and hold its plane vertical.



Equatorial adapter with the much smaller and simpler polar adapter for comparison.

Above ~8 half-turns of the winder, the equatorial adapter's ability to keep the equatorial plane vertical becomes unreliable, and that can spell big trouble at high speed. But no matter. Three half-turns suffice to randomize outcomes, and spin times are then short enough to keep the game moving.

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LEGOŽ biconic top

Not to be outdone by GAMESCIENCEŽ, I made my own roughly biconic dice with LEGOŽ.



The LEGOŽ version needs a polar starter even more than its 50-outcome counterpart, but the latter's polar adapter doesn't work with it at all.

With practice, this simple polar adapter works reasonably well on surfaces with some friction and a little sinkage (e.g., a folded newspaper). But I have yet to get one to work on low-friction surfaces like the granite above.



When spinning on a pole, the LEGOŽ version shows some very interesting behaviors not seen its 50-outcome counterpart. These are probably related to differences in tip-CM distance and the ratio of axial to transverse moment of inertia about the tip.

As with the 50-outcome die, there's no good reason to use an equatorial starter with the LEGOŽ version, but the equatorial adapter already shown works well with both.

An ideal unmarked biconic has a single polar axis of continuous rotational symmetry with an infinity of indistinguishable 2-fold symmetry axes in the equatorial plane.

The numbers on the 50-outcome die break the continuous symmetry by dividing its equator into 50 longitude bands of equal width, each labeled by a single unique number. The numbers also effectively distinguish the poles, but with just one pole for each number, there's no doubling of possible outcomes.



Likewise, the holes along the LEGOŽ die's equator divide the latter into 2 sets of 4 identical longitude bands -- those with holes and those without. Hence, the LEGOŽ die's symmetry and lack of markings allow only 4 distinct outcomes in 2 binary layers.

In the layer associated with rotation about an equatorial axis, the outcome is "polar" if the polar axis points within 45° of, say, the viewer's direction. Otherwise, it's "equatorial".

In the layer associated with rotation about the polar axis, the outcomes are "hole" when the die comes to rest with the contact point in one of the hole-bearing longitude bands and "between" otherwise. Since the holes serve as attractors for the resting contact point, the LEGOŽ die isn't really fair about the polar axis.

If the chosen direction in the LEGOŽ die photo is toward the viewer, the black and white one is showing a "equatorial, hole" outcome, which like the "polar, hole" outcome carries a probability of somewhat more than 25%.

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Specifications: Biconic top starter with polar adapter

Overall dimensions:142x132x66 mm (LxWxH) including adapter
Mass:106 g
Motor:pull-back (12787c01, 6x5x3)
Maximum half-turns:17-18 to full power
Safety features:Winding ratchet with latch
Top adapter:3-prong with rubber tips and pole cup
Modified LEGOŽ parts:None
Non-LEGOŽ parts:None
Credits:Original MOC
See also:Clutch tops and wind-up flying rotor launcher

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Specifications: GAMESCIENCEŽ" biconic die and top

Distinct single-roll outcomes:50
Overall dimensions:48x50 mm (DxH)
Mass:52.4 g
Center of mass height:25 mm when vertical
Volume:~3.5e-5 m3
Mass density:~1.5e3
Axial moment of inertia (AMI):~1.8e-5 kg m2
Transverse moment of inertia about tip (TMI):~5.2e-5 kg m2
AMI/TMI ratio:~0.35
Release speed at full power:n/a
Spin time at full power:144 sec (2:24)
Source:GAMESCIENCEŽ Dice"

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Comments

 I made it 
  May 3, 2017
Quoting [ Ketros ] Very interesting!
Thanks!
 I like it 
  May 3, 2017
Very interesting!
 I made it 
  May 1, 2017
Quoting Nick Barrett A tricky blighter to get going, but once it does.... great stuff!
Thanks, Nick! Nothing more heartbreaking than a top not living up to its potential.
 I made it 
  May 1, 2017
Quoting jds 7777 Very cool! The new pull-back motors are awesome. So much torque! Legos and elastic energy seem to work together so well - perhaps even better than the electric components. The plastic bits are perfectly suited to the relatively low-weight and stress from elastic energy sources. This stuff is what got me hooked on Technic in the first place!
Couldn't agree more! Pull-backs are vastly underrated as power sources. I used 12787c01 here, but motor6 and motor8 also pack a wallop. On the other hand, 61100c01 (with the handy built-in ratchet and push-button release) is too weak to do much of anything.
 I made it 
  May 1, 2017
Quoting Sven ;o) Again a magnificent construction from you my friend :) Very nicely done!
Too kind, Sven!
 I like it 
  May 1, 2017
Very cool! The new pull-back motors are awesome. So much torque! Legos and elastic energy seem to work together so well - perhaps even better than the electric components. The plastic bits are perfectly suited to the relatively low-weight and stress from elastic energy sources. This stuff is what got me hooked on Technic in the first place!
 I made it 
  May 1, 2017
Quoting Oliver Becker Hahaha, I've to think about THAT a little longer, my good friend! ;) Hope the inspiration comes along drinking the next cups... :)
OK, but not too long, Oliver! Think of how sad and lonely and utterly unwound those stored pull-backs must feel.
 I like it 
  May 1, 2017
Again a magnificent construction from you my friend :) Very nicely done!
 I like it 
  May 1, 2017
A tricky blighter to get going, but once it does.... great stuff!
 I like it 
  April 29, 2017
Hahaha, I've to think about THAT a little longer, my good friend! ;) Hope the inspiration comes along drinking the next cups... :)
 I made it 
  April 29, 2017
Quoting Daniel H. That's awesome!!
Thanks, Daniel!
 I like it 
  April 29, 2017
That's awesome!!
 I made it 
  April 29, 2017
Quoting Oliver Becker My head is spinning, my friend! Love the coffee- mixer, even I like my espresso pure... ;) I'm wondering about what to do with a various selection of pull-back motors I'd stored after buying a box full of used technic!
Thanks, Oliver! You might be interested in an attachment I'm developing for the centrifugal removal of coffee grounds in espresso. If only I could get the coffee to stay in the cup while it's working! Pull-back motors languishing in storage?? The horror! All you need to do here is hold one in your hand, wind it up and release it a few times to get a feel for the speed and torque, and then look around your workshop. With an imagination like yours, the ideas will come.
 I made it 
  April 29, 2017
Quoting Doug Hughes I love your gadget tinkering as the results are always so great!
Very kind, Doug! I hope one day that tinkering with LEGO will become one of my centers of excellence, right up there with losing hats.
 I made it 
  April 29, 2017
Quoting Clayton Marchetti That's awesome!
Thanks, Clayton!
 I made it 
  April 29, 2017
Quoting Gabor Pauler Jeremy, one day you will invent a gigantic spinning UFO-starter, and the aliens/CIA/both will kidnap you. How you will then post to MOCPages, from back side of Pluto?
Already on it, Gabor! You say this prediction like it would be a bad thing, but doesn't it feel good to have people fighting over you? And I've wanted to go to Pluto since I was a little boy. But don't worry about getting my MOCpages back to Earth. They're very progressive on Pluto. Free wifi everywhere.
 I like it 
  April 29, 2017
My head is spinning, my friend! Love the coffee- mixer, even I like my espresso pure... ;) I'm wondering about what to do with a various selection of pull-back motors I'd stored after buying a box full of used technic!
 I like it 
  April 29, 2017
I love your gadget tinkering as the results are always so great!
 I like it 
  April 29, 2017
That's awesome!
 I like it 
  April 29, 2017
Jeremy, one day you will invent a gigantic spinning UFO-starter, and the aliens/CIA/both will kidnap you. How you will then post to MOCPages, from back side of Pluto?
 
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LEGO models my own creation MOCpages toys shop Wind-up biconic top starter


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