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Author Topic: Big Top in construction 200kg  (Read 1554 times)

the Earl of Whirl

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Re: Big Top in construction 200kg
« Reply #15 on: October 11, 2023, 06:52:25 PM »

Where in NYC?
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paulstewart

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Re: Big Top in construction 200kg
« Reply #16 on: October 14, 2023, 11:34:32 AM »

My answers to fill in the needed information maybe too vague, but here it is:  Max diameter is 56cm off the deck.  Wall thickness is fairly consistent 22-23mm except where it's not.  The inside is a smooth curve matching the outside that flairs to meet the solid tip, tip is 20cm tall.  The rings that make the crown are thicker do to limitation of stacked laminated octagon shapes that make the turning blank.  Stack laminations are Pine 2x4's, or 2x6 to meet the tip and crown needs.The bolt on top is 1" x 3.5" with nut and washer.  The tip is a stair rail part off eBay probably 3mm thick, the wood is turned to match the tip and the steel is glued on.  This is likely too vague to make accurate calculations on, but you've given insight on whips I wasn't aware of.  Hopefully one of these days I'll coordinate someone with a tool to measure rpm.

In my limited experience with a 'normal size' whip top, I thought I was whipping the tip.  Now I understand this was not so and that whipping the tip of my top would not work.  Maybe a Big Whip Top build is in order.  I will not make it anywhere near 200kg, since I would not want to deal with handling that.

The electric scooters for rent in Brooklyn are available through an app.  Revel is the brand.  Scooters are driven from point A to B then left.  The next rider unlocks the scooter to ride from B to C.  The app tells the user where the nearest available scooter is.  They claim a top speed of 30+ mph, mid level chaos. 
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Jeremy McCreary

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Re: Big Top in construction 200kg
« Reply #17 on: October 14, 2023, 07:47:40 PM »

My answers to fill in the needed information maybe too vague, but here it is:  Max diameter is 56cm off the deck.  Wall thickness is fairly consistent 22-23mm except where it's not.  The inside is a smooth curve matching the outside that flairs to meet the solid tip, tip is 20cm tall.  The rings that make the crown are thicker do to limitation of stacked laminated octagon shapes that make the turning blank.  Stack laminations are Pine 2x4's, or 2x6 to meet the tip and crown needs.The bolt on top is 1" x 3.5" with nut and washer.  The tip is a stair rail part off eBay probably 3mm thick, the wood is turned to match the tip and the steel is glued on.

Thanks! That new data gives me a pretty good idea of Dorothy's mass distribution. My hollow spherical cone model is starting to look too crude, but not giving up quite yet. Still hunting for subtle model or spreadsheet errors, and better geometric approximations would involve much nastier math.

Hopefully one of these days I'll coordinate someone with a tool to measure rpm.

Since Dorothy's dots are evenly spaced and contrast well with their background, the only tool you need to get speeds is an inexpensive handheld laser tachometer. I like this one for its ergonomics and one-handed operation via the Auto button:

https://www.amazon.com/Ehdis-Digital-Tachometer-Non-Contact-Reflective/dp/B0765XP9LS/ref=mp_s_a_1_1_sspa?crid=2UULHU9TTHNUG&keywords=laser+tachometer&qid=1697322328&sprefix=laser+tachometer%2Caps%2C164&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9waG9uZV9zZWFyY2hfYXRm&psc=1

If there are 8 dots along a given circumference, just keep the laser pointed there and divide the RPM reading by 8 to get the top's spin rate.

I rely on these tachometers quite a bit in my own topmaking, and I think @Iacopo would say the same. For a given top and starting method, just knowing the actual operating speeds (from max launch to toppling speed) can help a lot when optimizing for spin time or play value or a certain optical effect or spin-down behavior.
« Last Edit: October 14, 2023, 07:52:00 PM by Jeremy McCreary »
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Iacopo

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Re: Big Top in construction 200kg
« Reply #18 on: October 16, 2023, 03:43:42 PM »

I rely on these tachometers quite a bit in my own topmaking, and I think @Iacopo would say the same.

Yes I do, when they are tops for the longest possible spins, in my case.
Comparing the spin times is the simplest way for to evaluate the best tops but I prefer to use the tachometer, for to have more complete data and for to understand better the reasons that a top spins longer than another one. With a tachometer I can essentially evaluate four different parameters: the starting speed, the toppling down speed, the spin decay at high speed, (which is related mainly to the aerodynamics), and the spin decay at low speed, (related mainly to the tip friction).
These data of different tops allow for a reasoned comparison and help to improve the design of the top.

I am finishing a couple of new tops in these days, they are tops for longest spins, I will show them here soon.
It was a difficult year for me, (too much work), and I never stopped making tops for so many months before. I hope that this will not happen again because I love making tops, also I have some new ideas that I want to try.
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Jeremy McCreary

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Re: Big Top in construction 200kg
« Reply #19 on: October 23, 2023, 11:48:22 PM »

I rely on these tachometers quite a bit in my own topmaking, and I think @Iacopo would say the same.

Yes I do, when they are tops for the longest possible spins, in my case.
Comparing the spin times is the simplest way for to evaluate the best tops but I prefer to use the tachometer, for to have more complete data and for to understand better the reasons that a top spins longer than another one. With a tachometer I can essentially evaluate four different parameters: the starting speed, the toppling down speed, the spin decay at high speed, (which is related mainly to the aerodynamics), and the spin decay at low speed, (related mainly to the tip friction).
These data of different tops allow for a reasoned comparison and help to improve the design of the top.

I am finishing a couple of new tops in these days, they are tops for longest spins, I will show them here soon.
It was a difficult year for me, (too much work), and I never stopped making tops for so many months before. I hope that this will not happen again because I love making tops, also I have some new ideas that I want to try.

Well put. Our tops, construction methods, and spin times are worlds apart, but we go after longer spin times in much the same way.

LEGO construction opens up a vast new design space for tops, and it's fun to explore. That often means prioritizing behavior or appearance at rest or speed over spin time. But I still make every design spin as long as it possibly can. A laser tachometer's a big help — especially when trying to lower critical speed.
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ta0

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Re: Big Top in construction 200kg
« Reply #20 on: February 27, 2024, 07:34:16 PM »

Tall whip tops are not easy to keep upright:



Considering how fast the drill got it spinning, this was somewhat of a failure. This might be an unmodified tank. Perhaps with a better tip it could have worked better.
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