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Author Topic: Re-thinking spin dynamics for world's largest top  (Read 9336 times)

jim in paris

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Re: Re-thinking spin dynamics for world's largest top
« Reply #15 on: March 30, 2012, 04:15:27 PM »

hi joe hi all
i think there's still a lot more power to gain with the team of people dragging the rope: i have seen a team from Thailand working together at a kite festival
it's the traditional "chula" kite that they maneuver with 10 people
they run and drag the rope in the movement with very precise gestures and the whole thing in a small perimeter.. they kind of run in a circular motion and the effect energy produced is stunning
i have watched them train one morning at Dieppe: they warm up , stretch, wear the same white gloves , it's almost like sports team
you could work in that direction too

besides : have you ever thought of profiting from the spin to insert a power generator in the top?


jim

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JMauk

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Re: Re-thinking spin dynamics for world's largest top
« Reply #16 on: April 05, 2012, 10:08:53 PM »

Hi, getting caught up on some posts.

Alan, one of the stipulations of Guinness for this particular category is that it is presumed to be spun by a string or rope pull.  I am not sure how the Japanese did their 1986 record top.  But it seemed to me that the stipulations I received from Guinness were kind of a response to what the Japanese had done and Guinness made it much more strict this time to be sure any record breaker was obviously and visually parallel to recognizable spin tops in existence.  I have noticed they now have a mechanical top category for longest spinning top by a toy company in Viet Nam.  They are not spun by string.  It is very unclear to me how Guinness actually categorizes top spinning records, seems to be on an as-needed basis.  I will copy the stipulations they sent to me for my attempt in the largest spinning top category.

Claim ID: 354939
Membership Number: 312585

Dear Rev Joseph Mauk,

Thank you for your enquiry regarding your intention to attempt the record for 'Largest spinning top'.

RECORD

The current record (current as at the date of this letter) is:
A team of 25 from the Mizushima Plant of Kawasaki Steel Works in Okayama, Japan created the world's largest spinning top 2 m. (6 ft. 6.75 in.) tall and 2.6 m. (8 ft. 6.25 in.) in diameter, weighing 360 kg. 793.6 lb., and spun it for a record-breaking 1 hr. 21 min. 35 sec. on November 3, 1986.


RULES for this record

We have attached the specific set of Guidelines for this record category which detail the requirements and rules you must follow during your record attempt. You must ensure that all those participating at the record attempt are aware of the contents of these Guidelines.

These Guidelines are appropriate for attempting this particular record as at the date of this letter. However, please be aware that as and when required, the Guidelines may be updated by Guinness World Records and without directly contacting to you.

LARGEST SPINNING TOP
DEFINITION OF RECORD
This record is for the largest item in terms of physical size.
This record may be attempted by an individual or a team of unlimited size.
This record is measured in (metres and centimetres / square metres / litres etc)
GUIDELINES FOR ‘LARGEST SPINNING TOP’
1. For the purposes of the record a spinning top is defined as a toy that can be
spun on an axis, balancing on a point. This motion is produced by holding the
axis firmly while pulling a string. An internal weight then rotates, producing an
overall circular motion.
2. The top must be an outsized to scale replica of an existing, commercially
available top.
3. This category is open to all spinning tops and will not be further subcategorized
by the specific type of top used in the attempt.
4. The item must be demonstrated to spin freely and without being attached to any
frame, like a normal sized top would in front of the witnesses.
5. To be acceptable the item must surpass the current record in all dimensions.
GENERAL ‘MANUFACTURED ARTICLE’ GUIDELINES
§ The name of the organisation, company or person(s) making the attempt must
be given, along with the date and place.
§ The event must take place in a public place or in a venue open to public
inspection.
§ Even if items are not made by commercial/professional enterprises, reasonable
standards of workmanship are required.
§ The item you elect to manufacture must be operable as the regularly sized
version. For example, if you are making the smallest television, it must be
capable of receiving a clear picture; or if you are making the largest guitar, it
must be playable.
§ As a guide, large items (that do not have current records) must be at least ten
times the size of the original product. But this is ultimately up to editorial
discretion. If in doubt, it is best to check with Guinness World Records prior to
your attempt.
§ The object must be measured by a qualified surveyor in the presence of the two
witnesses.
§ Any item submitted must be made from exactly the same materials as the
original. So, a football would be made of stitched leather, a vase made of clay on
a potter's wheel, a dustbin made of metal or plastic, a candle of wax and so on.
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JMauk

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Re: Re-thinking spin dynamics for world's largest top
« Reply #17 on: April 05, 2012, 10:11:35 PM »

Jim, thanks for the tips, we will be working on improving manual technique before going to the weight pulling force again.  Have not thought of a power generator but the video crew wants to mount a camera on the top of it next time! (Like a helmet camera)
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JMauk

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Re: Re-thinking spin dynamics for world's largest top
« Reply #18 on: April 05, 2012, 10:14:59 PM »

Kyle,thanks for the help, I think I have enough info now to seek to reach a 200-300 rpm spin. Have to do some stabilization of the launch structure first, will experiment manually, then try the adapted weight pull technique.
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Spinningray

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Re: Re-thinking spin dynamics for world's largest top
« Reply #19 on: April 11, 2012, 06:51:33 PM »

Thanks for posting the details Joe. Some interesting guidelines. Was the top based on a commercially available top? Making it from exactly the same material as the original could make the top very heavy. Sounds like they are a little lenient  on the guidelines.
The rope will definitely present a safety challenge with that much energy being transmitted through it. Take great care and good luck with any future spins.
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JMauk

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Re: Re-thinking spin dynamics for world's largest top
« Reply #20 on: May 23, 2012, 11:29:32 PM »

SpinningRay, I think the force of the commercially available stipulation was to guarantee the the biggest item in the world actually was recognizable as something people see and know.  I suspect, and have not been able to find any pictures at all of this, that the prior world record of Japan was more of a flywheel design and not as recognizable as a top.  Mine is certainly recognizable as a top and, for the record (literally), it was modeled on an old Duncan Beginners top.

Update on improving technique:  Been busy and have not checked back here for a month or so. We get 10,000 visitors to our center in Philippine summer (April/May).  I have received delivery of 120 meters of rail, a flatbed mining car and a stopper mechanism fresh from China (no surplus/used materials this time!).  We are constructing three concrete posts to attach tension rods to the support arm and top bearing to insure there will be no springback action of the bearing when the top leans on it.  When finished, will test manual techniques while assembling rail ramp for car.  Will test car and track thoroughly before adding weight to car.  Will test car and weight before trying on top.  This process will be another 2-3 months.  Starting a new video shoot for my tops show tomorrow, will post details separately.
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ta0

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Re: Re-thinking spin dynamics for world's largest top
« Reply #21 on: May 24, 2012, 08:47:20 AM »

Wow!  120 meters of rail, a mining cart . . .  this is a really serious and ambitious project!  I am very impressed.  I look forward to hearing about your progress.

Will the construction be permanent? I would love to visit and see it for myself one day.
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JMauk

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Re: Re-thinking spin dynamics for world's largest top
« Reply #22 on: May 24, 2012, 12:08:00 PM »

Yes we plan to make the structure permanent and give it a go on an almost daily basis for our guests.  Would love to have you come check it out.  Of course, we need to make it actually work, efficiently and repetitively, first. 
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Watts' Tops

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Re: Re-thinking spin dynamics for world's largest top
« Reply #23 on: June 05, 2012, 06:30:02 PM »

Joe,  You make me smile every time I check out what's up.  How I would love to see the finnished product work.  God bless you in your ministry. ;D ;D
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ta0

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Re: Re-thinking spin dynamics for world's largest top
« Reply #24 on: June 11, 2014, 01:02:31 PM »

The minimum required RPMs is a critical consideration.  If the top is not spun fast enough it won't be able to spin freely like the Guinness Book of Records wants. Obviously, this is a case when it is better to have a theoretical estimate before building it. So I tried to calculate it using the equation I recently mentioned on this post.

I assumed the top was a perfect cone made of expanded styrene. Adding the wooden and metal plates and the shaft only gave a small correction.  Some of the assumptions and calculations are below for anybody interested in checking them, but the final result is that the critical spin at which wobble starts to increase rapidly is 127 RPM
However, the goal is to be significantly above, so say about double: 250 RPM.
On the manual spun, only 100 RPMs were achieved.

================
[Nerdy alert]

I modeled the top as a cone with height h = 3.88 m and radius r = 1.815 m.

The volume of the top is V = pi x r2 x h / 3 = 3.1416 x (1.815 m)2 x 3.88 m/ 3 = 13.4 m3

The weight of expanded styrene is only about 15 to 45 kg/m3  (it is mostly air). I assumed 20 kg/m3 as this is compatible with a total weight of the top of 450 kg.

The mass of the Styrofoam cone would be M = 13.4 m3 x  20 kg/m3 = 268 kg.

The moment of inertia of a cone around its axis is available from tables like this one, and it is:
I = 3/10 M r2 = 3/10 x 268 kg x (1.85 m)2 = 275 kg m2

I did add the moments of inertia of the plywood boards and steel plates (the shaft and spool are close to the spin axis and can be neglected) and it only gave me a small correction (*)

The final value was  I = 289 kg m2

The center of mass of a cone is ¾ the height away from the apex, so in our case: L = ¾ x 3.88 m = 2.91 m

Plugging these values in the formula of the critical spin rate:
w = sqrt {4 M g L / I} = sqrt {4 x 450 kg x 9.8 m/s2 x 2.91 m / 289 kg m2 }= 13.3 rad/sec

or

w = 127 RPM

========
* The moment of inertia of a cylinder or disk of radius r and mass m is: I = 1/2 m r2

Four 4ft diameter 3/4 inch Plywood disk: 
From web:  3/4 in thick plywood weighs 10.4 kg/m2, so the mass of one 4ft disk is: 1.17 m2 x 10.4 kg/m2 = 12 kg
I (four plywood disks) = 4 x {1/2 (12 kg) x (0.61 m)2} = 8.9 kg m2

14ft long, 2 inch diameter, steel shaft
Weight: 7900 kg/m3 x 0.0086 m3 = 68 kg
I (shaft) = 1/2 (68 kg) x (0.0254 m)2 = 0.022 kg m2

Four 2ft diameter steel plates
Weight: 490 - 268 - 4x12 - 68 = 106 kg
I (four steel disks) = 1/2 x (106 kg) x (0.3 m)2 = 4.8 kg m2

I (total) = 275 + 8.9 + 0.022 + 4.8 = 289 kg m2
« Last Edit: June 27, 2014, 11:21:15 AM by ta0 »
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JMauk

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Re: Re-thinking spin dynamics for world's largest top
« Reply #25 on: June 11, 2014, 06:15:03 PM »

Wow, thanks for the great calculations.  Wish I understood them!  But it was reassuring as I have been hoping to get to a 200-300 RPM speed, trying to at least double the speed of 100 RPM of the manual pull.  So the calcs let me know I am on target.  Trevor Hill just arrived here Monday from Australia.  He is working on getting the pulleys fabricated, a roof over the top installed, and a means to operate the rail car locking mechanism from the ground.  When the pulleys and new electric winch are installed, we will start testing the rail car, first by itself with no weight but from full height, then gradually adding weight before we try putting 1.5 ton Bumblebee onto it.  May also test how the pulling of the top works with lighter weight before going full bore.  Trevor also plans to buttress the back wall of our tire holding bunker and possibly adding some other slowing mechanisms prior to the bunker in anticipation of Bumblebee slamming into it at velocity.  Hmm, how fast do you think it will be going rolling 60M down from an 8M height?
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Kirk

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Re: Re-thinking spin dynamics for world's largest top
« Reply #26 on: June 12, 2014, 12:56:36 AM »

Hmm, how fast do you think it will be going rolling 60M down from an 8M height?
If it were to roll freely it would be going quite fast. But it will be pulling the top rope.

A key to this kind of calculation is keeping the units straight
Let's say we get the top to 300 Revolutions / minute
Now let's also say the pulley at the bottom of the top is 4 feet around per rev (I'm trying to remember photos from construction)

Speed of the rope  300 Revs / minute * 4 feet / rev = 1200 feet / minute
(Revs are on the top and bottom of the fraction and thus cancel giving feet / minute.)

Speed of rope  = speed of sled

Now convert to something more familiar.
60 minutes in one hour -- feet / minute * Minutes / hour = feet / hour
1200 feet / minute * 60 min/ hr.  =  72000 feet / hour (this time minutes cancel)
There are 5280 feet / mile (or 1 mile / 5280 feet)
    SO
72000 feet / hour * 1 mile/ 5280 feet   (feet cancel)  =  13.63 miles per hour

========================
pulling it all together

speed of top( in RPM) * distance around the pulley( in feet) * 60 / 5280 = speed of sled (in MPH)

I hope this helps. be sure to use to correct distance around the pulley to get a good estimate.

13.6 MPH does not sound too fast but there will be lots of weight to stop.  Perhaps the sled could hook a rope stretched above the track.  The rope would be connected to sand bags or other weights to drag over the ground.

Keep us posted Be Safe and God Speed
Kirk
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ta0

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Re: Re-thinking spin dynamics for world's largest top
« Reply #27 on: June 12, 2014, 11:03:48 AM »

I agree: with that much weight even a small speed is difficult to stop without proper brakes.
If you are concerned about the maximum speed if the rope breaks at the top of the ramp, it would be 45 km/h (28 mph) regardless of the weight and slope (the same as a free fall from 8 m).

On the previous thread about the dynamics of your giant top The first calculations (Edit: I moved the relevant posts to this one) I had made calculations assuming the top was made from a single material (the 450 kg distributed equally) so I had a higher moment of inertia.  The value above is more exact (e.g., the shaft contributes to the weight but not the the rotary inertia).

In theory it would be possible to convert all the gravitational (potential) energy of the weight into spin energy, but in practice that would require some variable pulley/gear system ending in a very high gear ratio (so the weight arrives at the bottom with zero speed).  In practice I am guessing a 50% conversion efficiency is a good goal.

For a 50% conversion efficiency, with a mass of 1500 kg and a height of 8 m you get (see calculations below) 194 RPM.

If you increase the weight to double (3 tons), the spin increases by the square root of 2, or about 40%, to 274 RPM.
Likewise, if you could increase the efficiency to 75%, the spin rate increases by 22%.

You are pretty lucky, you are right in the ball park!  ;D

=======

The potential energy of a weight of mass M at a height h is: 
E(weight) = M g h  (where g is the acceleration of gravity, 9.8 m/s2)

The kinetic spin energy of the top with moment of inertia I and spin rate w is:
E(spintop) = 1/2 I w2  (in radians/sec)

If e is the efficiency of the conversion, the final equation in RPM units is:

w = sqrt{2 e M g h / I} x 9.55


By the way the final speed of the cart with a 50% conversion is 32 km/h (20 mph).
« Last Edit: June 27, 2014, 11:24:21 AM by ta0 »
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ta0

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Re: Re-thinking spin dynamics for world's largest top
« Reply #28 on: June 27, 2014, 12:09:20 PM »

Note: I merged the calculations into the same thread so they are together.

This thread made me read the "Yo-Yo Physics, An Engineer's Notebook" by Don Watson, aka Captain Yo (5 little volumes.) I have had them for years but hadn't read them until now. Because of the spool you are using, the giant top behaves very similar to a dropped yo-yo. The difference is that the mass that provides the gravitational energy is independent of the moment of inertia.

He has quite a bit of experimental data compared to calculated values. The calculations are similar to the ones above, but what struck me is that yo-yo's are actually very efficient, converting well above 90% of the initial energy into spin energy. Assuming no slippage, friction, bouncing, etc, it only depends on the gear ratio (as Kirk pointed out), more specifically:
e = 1 /[1+ r2 /k2]
where r is the shaft diameter and k the "radius of gyration" (= radius of a ring with the same moment of inertia).

For a 90% conversion efficiency, with a mass of 1500 kg and a height of 8 m you get 258 RPM. The velocity of the weight at the bottom is 14 km/h (8.9 mph).
Looking good!
« Last Edit: June 27, 2014, 12:16:16 PM by ta0 »
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JMauk

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Re: Re-thinking spin dynamics for world's largest top
« Reply #29 on: September 06, 2014, 01:57:24 AM »

Wow, I just saw this.  Thanks for the calcs.  I will be happy with around 250 rpm I think.  Check out the video of the attempt today.  Any rpm estimates?
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