Author Topic: Diabolo Spin Rate / Speedometer  (Read 7701 times)

diabololi

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Diabolo Spin Rate / Speedometer
« on: December 14, 2004, 10:12:04 AM »
HI!

Don't you think it would be great to have a diabolo speedometer to actually see how fast it spins! You could also see which tricks speed up / slow down the diabolo. Is it possible?

Oli

-Fred-

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Diabolo Spin Rate / Speedometer
« Reply #1 on: December 14, 2004, 12:14:22 PM »
Hi!

It's possible to know when a diab speed up or slow during a trick with a spintastic (diab with one way ballbering). When the diab speed slow, you can heard some noise and when it speed up, there's no noise.

You have to found a spintastic now :wink: .

--- Fred ---

diabololi

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Diabolo Spin Rate / Speedometer
« Reply #2 on: December 14, 2004, 01:23:30 PM »
Yeh, good idea. I guess the chinese yoyos would be better because they get louder as they get  faster. But I really want to know how many MPH I can spin a diabolo!

Oli

milka

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Diabolo Spin Rate / Speedometer
« Reply #3 on: December 14, 2004, 01:44:29 PM »
Ludovitch has already worked on that question : the results (in French) here and here. I don't understand anything except the result but I trust him =)

kragen

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Diabolo Spin Rate / Speedometer
« Reply #4 on: December 14, 2004, 01:57:26 PM »
I like the harlequins because the pattern on the cups makes it fairly easy to see (relatively) how fast the diabolo is, when I get my finesse im gonna have to attach some tape to the cups or something.
Justin
Gravity Vomit - Gravity pulls down, we throw up.

Dave P

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Diabolo Spin Rate / Speedometer
« Reply #5 on: December 14, 2004, 02:02:00 PM »
Anybody got a laser tachometer lying around?

Arjan

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Diabolo Spin Rate / Speedometer
« Reply #6 on: December 14, 2004, 02:42:44 PM »
you need something to find out how many RPM`s your diabolo makes ;)

el_grimley

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Diabolo Spin Rate / Speedometer
« Reply #7 on: December 14, 2004, 04:17:32 PM »
Quote from: Dave P
Anybody got a laser tachometer lying around?


No but I might know someone that does. I'll investigate. I did physics at uni and still know a few people in the department.

Milka: that is an ace link

diabololi:
Quote
Height is quite easy to work out, if you want to know that. S=ut+1/2at^2. Which means if you time the compleate flight time of you diabolo you can work out how high it went.

The deceleration of the diabolo going up and the acceleration of the diabolo going down are the same, ingoring the bit where you fling it right at the start. Which means time going up is equal to time going down. Acceleration is 9.81ms^-1 and u=0 when at the top of the arch. So input your flight time divided by 2 and that'll give you the height. The error is huge, like 20% because of the timing and ignoring the bit where you fling it.

example, 20 seconds for up and down. gives t=10s u=0 a=9.81ms^-1
s=0*10 + .5*9.81*10^2
 =0 + 490.5m

So that'll be nearly 500m.

I guess most high throw flight times are arround 5 or so seconds which puts most people arround the 30m range. Which is still pretty high.


Graham
Its got to be going home time. At least going to the pub time.

Evan

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Spin rate
« Reply #8 on: February 05, 2006, 11:08:05 PM »
Based on a photo of a friend diaboloing with my light kits on I have taken an estimate of the spin rate has anyone else tried to do this and if so are my sums correct

35 revolutions in the photo (if i can count correctly)
1.6 second exposure time
35/1.6*60=1312.5 RPM

this seems to be insanely fast (given he was actually not spinning it that fast) any comments?

based on that it means the outside edge of the cup is moving at 30.9kph

(2*pi*r(6.25) = 39.27 circumference
39.27*1312.5 = 51541.75 cm per minute
51541.75*60 = 3092505.268 cm per hour = 30.9 kph (in fairness this is a little rough as i cont find a ruler at the moment it was a finesse G2 if anyone wants to actually measure it rather than guess)

[EDIT - Thanks for merging these threads I did search but missed this completely]

JGherkin

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Diabolo Spin Rate / Speedometer
« Reply #9 on: February 07, 2006, 08:26:05 AM »
For my physics coursework I put a strip of black electrical tape down one side of my diabolo and was able to measure the RPM using an Optical Tachometer.  Most of my trials were performed at around either 500 or 1000 RPM however I did do a few extra experiemtns to see how fast I could actually spin it but these were useless as the Optical Tachometer couldn't measure these faster speeds.

JugglerRick

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Diabolo Spin Rate / Speedometer
« Reply #10 on: February 13, 2006, 09:54:41 PM »
The easiest way to find out for sure would be as JGerkins did. A single mark in the edge of the diabolo and a strobe light that can be adjusted to flash at a known rate. When the mark appears to stationary the flash rate would be equal to the speed of rotation (same technic used to set the timing on an engine).
The problem is that I do not think a diabolo ever stays at a constant rate. It is constantly speeding up or slowing down.
Rick

JGherkin

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Diabolo Spin Rate / Speedometer
« Reply #11 on: February 13, 2006, 11:39:37 PM »
Thats not how I did it, I did consider that method but figured if i was doing 100-200 odd trials I might get a bit of a headache.  I just used a lil gadget called an Optical Tachometer that measures the amount of times the black line goes past it each second and calculates the RPM for me and displays it.

Jonnyh

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Diabolo Spin Rate / Speedometer
« Reply #12 on: February 17, 2006, 09:54:01 PM »
Henry's Micro diabolo's were advertised as being able to spin up to 10000rpm. When they were still around.

mrpink

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Diabolo Spin Rate / Speedometer
« Reply #13 on: February 18, 2006, 08:44:58 AM »
If you have a rough idea how fast the diabolo is spinning you can calculate an exact value if you put a smal dot on the cup and film the diabolo with a high framerate. Just watch 2 frames and calculate how much the diabolo spin in this time. The rest is simple multiplication.

To get a rough estimation of the spin
You culd meassure how long it takes to do the "circle whip" without much force. If the diabolo is neither sped up or slowed down it moves on the string without slipping much. So its easy to calculate the spin then.
For example: Assume  that the wrapped diabolo moves the whole string ,1200 mm in 1.1 seconds and the hub has the diametre 10 mm.
The spin rate will aproximatley be
1200*60/(3,14*10*1,1)=2085rpm
Probbably quiet a big margin of error if you do it this way though.

jammy

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Diabolo Spin Rate / Speedometer
« Reply #14 on: February 18, 2006, 09:43:23 AM »
this is all to much for me! lol
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