main
front page
CJC
essays
profiles
register
moves
links
videos
gallery
tips
chat
clubs
maps
forum
FAQ
events
|
videotape your contact juggling routines.
this site is sponsored by Infinite Illusions
General
| New ball |
Author: Klas
Date: 04-06-02 12:18
Bought me a new ball yesterday, wrote some stuff about it here in the forum, but the post disapperaed somehow, well, that's just as good as some of it was wrong.
Found a crystal clear 4 inch sphere in a shop and bought since the price was quite ok, 475kr (SEK) (£31.71 GBP, €51.86 EUR, $45.75 USD).
I was sure it was acrylic even though the shop owner said it was chinese crystal. It looks very much like acrylic and for the price it couldn't be anything else.
I got it with a box, a ball stand and some instructions about how to use it.
As I come home and picked it up I realised that this thing is heavy, so much more heavy than my 3 incher, but i thougt that was okey, it's supposed to be heavier since that extra inched makes a lot of difference on the volume. I'm also have a bad cold at the moment and feel very weak.
As my girlfriend came home she picked it up and commented on it beeing very heavy. So we checked the weight, 1.5kg, compared to less than 400g for my 3 incher. Thats a density of more than 2.5, acrylic is closer to 1.5, glass is supposed to be about 2.5 so I guess it really is glass (or chinese crystal :))
So now I have a 4 inch glass ball, extremely clear, it looks perfect (one of the reasons I thought it was acrylic). And the price was less than what I would have to pay for an acrylic. Don't know if I ever will be able to do much with it since it's so heavy. But it's really cool. :)
If anyone is bored I would be happy if you checked my math or the weight of your own 4 inchers. I may have caluclated something wrong and it really is acrylic, and they really are that heavy, I've never played with one before.
Klas |
|
Reply To This Message
|
| Re: New ball |
Author: ICU812
Date: 04-06-02 18:00
Ok, I'm not an expert, but when I received my 4" acrylic, the first words out of my mouth were, "Shizam! That's heavy!". This is only because it's way heavier than a 3". So, a 4" acrylic IS much heavier than a 3" acrylic. Now, this is also true of a 4" glass or crystal ball. The only thing that makes crystal different from glass is that it has a butt-load of lead in it to make it real shiny. The more lead, the shinier it is, the heavier it is. You might be able to take it to a jeweler and they could tell you what it's made of just based on it's refraction or something like that. I personally wouldn't want to drop a crystal ball on anything hard, cause it won't bounce and it won't scuff, it'll probably either break into little pieces or a cloud of dust like in Labyrinth :)
Jacques
"We are what we repeatedly do. Excellence, then, is not an act, but a habit."
-Aristotle |
|
Reply To This Message
|
| Re: New ball |
Author: Ferret
Date: 04-06-02 18:56
I'm pretty bad at math Klas, but I do know this.
If you take any material and make it into a sphere, measure it's diameter, than weigh it.
For every one half inch that you increase the diameter, you will double the weight.
A 3 inch acrylic weighs 9.5 ozs
Therefore a 4 inch acrylic would weigh.
38 ozs
There is a math formula that works this out, but I'll be damned if I know it.
The Golden Chicken would.
Ferret |
|
Reply To This Message
|
| Crystal is strong |
Author: Rich Shumaker
Date: 04-06-02 22:00
So there I was with my shiney new crystal balls. I paid like a million dollars for them at the time because it was a long time ago(inflation) and because I was a dishwasher(lowest income earner on the planet). I was fliping and flopping it and OHHHH NO I was throwing it. DAMN DAMN DAMN.
I must have broken it.
I must have ruined it.
I was right and wrong. I didn't break it. I flawed it which did ruin it. Crystal doesn't shatter it flaws. The flaws look like craters in the moon.
Crystal balls would have to hit a muti prong piece of concrete from a very high altitude to shatter.
Good luck if it is crystal as you won't want to practice with it. Over time my crystal has gotten scratches on the surface and they aren't as shiney any more.
That reminds me my sister got me a crystal ball one year for christmas that was HUGE. I need to find where I packed that, measure it, and weigh it. Then if I go to the gym I can use it for a free weight.
Rich Shumaker
The Other Contact Juggler
Rich@ContactJuggling.com
www.ContactJuggling.com |
|
Reply To This Message
|
| Re: New ball |
Author: Klas
Date: 04-06-02 23:04
Almost correct.
It's true that increasing the diameter of a sphere will make much more difference in volume (and size), e.g. if you double the diameter the volume will be much more than double (times 8 I think).
The halv inch rule is however not correct.
The volume for a sphere is:
V = 4/3 * pi * r^3
So the volumen for a 3 inch acrylic is:
4/3 * pi * 1.5^3 = 14.14 cubic inch (231.67 cm^3)
And for a 4 incher:
4/3 * pi * 2^3 = 33.51 cubic inch (549.14 cm^3)
So it should be a bit more than double the weight.
My 4 incher weights more than 3 times, almost 4 times, more than my 3 incher.
I've seen Kae's glass balls and this thing looks very different, it refracts the light much more like acrylic, and it's very perfect and homogenic, just like acrylic.
It feels a bit different, cooler, but I didn't feel this until after I started to suspect that it wasn't acrylic, so it may be a fabrication by my mind.
I'd be happy for someone to check my math. I'd probably be happier knowing that it is acrylic since that's a material I know, and wouldn't be afraid to break. I would also know that other people works with the same weight and that it is possible.
But no matter what it is, I'll use the ball, if it breaks, to bad, i bought it for cjing and it's not of much more use in my bookshelf than in two halfs on the floor.
And as for the extra weight, that's a challenge, it may not be a subsitute for a 4" arylic, but it's something really cool and different. Will have to build some strength first though, since I find it difficult to hold it in the cradle.
The only thing i really tried with it so far (still sick and don't have any good place to play) is isolations, and that's really easy. I've also tried to balance it on different places on my arm and that works great. The outer elbow hold is very solid with so much weight. I'll try to avoid the outer elbow fly away though, since a bad catch could result in broken bones.
I think that enough of me going on about my big and shiny ball, next please.
Klas |
|
Reply To This Message
|
| Re: New ball |
Author: mdamelio
Date: 04-06-02 23:08
You could always try a scratch test, from what I know of crystal it takes a bit more to scratch it than acrylic does. And if it's acrylic you can just buff it out. But if that guy told you it was crystal it probably was, I imagine he know's what he's talking about.
~Mickey |
|
Reply To This Message
|
| Re: New ball |
Author: Klas
Date: 04-06-02 23:21
It's a she actually. And I hope I'll don't offend anyone to much by saying this. But I don't put to much trust into people running new age shops. Talking to this lady makes me look for the space ship she arrived in.
Klas |
|
Reply To This Message
|
| Re: New ball |
Author: Klas
Date: 04-07-02 00:00
Just to add some more data.
According to physics handbook (Nordling/ Österman):
The density (10^3 kg m^-3) for:
Acrylic: 1.2
Glass (common) 2.5
Which gives that a glass ball should be approx double the weight as an acrylic of the same size. Can't imagine there beeing to much of a difference between different types of glass.
Also
Thermal conductivity (W m^-1 K^-1):
Acrylic: 0.2
Glass (common): 0.9
So the a glass ball should feel a bit cooler than an acrylic.
I promise that I'll shut up about my new ball for a couple of hours now.
Klas |
|
Reply To This Message
|
| Re: New ball |
Author: ICU812
Date: 04-07-02 00:28
crystal is heavier than ordinary glass...just another FYI
"We are what we repeatedly do. Excellence, then, is not an act, but a habit."
-Aristotle |
|
Reply To This Message
|
| Re: New ball |
Author: Klas
Date: 04-07-02 12:00
Yes that make since due to the extra lead. And my measurements do give a higher density, they are however not very precise, but do put the density much closer to glass than acrylic.
So it's very likely that it really is a crystal ball, which I think is really cool. :)
Klas |
|
Reply To This Message
|
| Re: New ball |
Author: Rob
Date: 04-08-02 12:04
Klas, your maths is correct, and as you say the half inch rule cannot possibly be correct - there is no constant factor that you can multiply the weight by every time you add half an inch to the diameter. You just have to think about extremes to see how ridiculous this idea is. Imagine a sphere of only 1/8 of an inch in diameter. If you add half an inch to its diameter you end up with a sphere of 5/8 of an inch in diameter. Anyone can see that a sphere of the same material with 5 times the diameter is going to be a lot more than double the weight. Now imagine a sphere the size of the earth. Adding just half an inch to the earth's diameter wouldn't double its mass!
The only time that adding half an inch to the diameter would double the weight of a sphere would be going from a 1.92 inch sphere to a 2.42 inch sphere. (a simple manipulation of the equation for the volume of a sphere gives this result)
I make the weight (mass) of a 3 inch (76mm) acrylic to be around 276g and the weight of a 4 inch (101.6mm) acrylic to be around 659g.
Rob |
|
Reply To This Message
|
| Re: New ball |
Author: Klas
Date: 04-08-02 13:37
Fun to see that someone else is entertained by the math stuff around this.
Your calculations seems right, I think may 3 incher weightet a bit more, but the scale I used isn't the best.
Klas |
|
Reply To This Message
|
| Re: New ball |
Author: Kae Verens
Date: 04-08-02 14:08
Don't forget refraction, while you're talking about physics...
Glass has a refraction index of about 1.3 - just about the same as water. From what I see, acrylic refraction tends to be a little lower - giving the ball less refraction, and more of the bubble effect.
I keep my glass balls in the same bag as my acrylics, and every time I pick one up I am still amazed by the weight...
Kae |
|
Reply To This Message
|
| Re: New ball |
Author: Klas
Date: 04-08-02 14:58
I haven't forgot the refraction, but haven't done anything to check it.
Just by looking at the ball I can't say that it's a different material, would probably be easier if I had a 4 inch acrylic to compare to.
And I'm to lazy to dig up the laser I have in a box somewhere. (Sweet little thing though HeNe, class II).
Klas |
|
Reply To This Message
|
| Re: New ball |
Author: mdamelio
Date: 04-08-02 16:06
Is this giving anyone else a headache? :-) And where the hell is Chicken I'm surprised he isn't all up in this mathematical mess. My Girlfriend is a math minor, and I thought I could get away from it here on .org but it seems to follow me. j/k I don't have any idea where you guys are figuring that stuff out from, this is beyond my meager liberal arts education.
~Mickey |
|
Reply To This Message
|
| Re: New ball |
Author: remy
Date: 04-08-02 19:42
forumla? (4/3)(pi)[(radius--2in. in this case)^3]*density=weight
density=weight of 3 inch ball/{(4/3)(pi)[(radius--1.5 in. in this case)^3]}
or, more simply(all the ugly numbers worked out...
33.41 cubic inches*density(weight/cubic inch)=weight of 4 inch
density=weight of 3 incher/14.01cubic inches
but I haven't got a scale..best of luck
rem |
|
Reply To This Message
|
| Re: New ball |
Author: ICU812
Date: 04-08-02 23:03
And how, I just wanna know what the ball is made of. The scientific method is cool and all, but it's beyond me.
Jacques
"We are what we repeatedly do. Excellence, then, is not an act, but a habit."
-Aristotle |
|
Reply To This Message
|
| Re: New ball |
Author: Ferret
Date: 04-08-02 23:37
Damn now I have to kill my math teacher, (lieing bastard)
Of course he would only say that I didn't pay attention in class, which is sadly true, but I asked him specifically about the differences in weight of a sphere between a 2.5 and a 3 inch several years ago, (he lives down the road from me) and that is what he told me.
Could it be that he was trying to make me look stupid for gluing everything to his desk all those years ago?
Hummm…..they say that revenge is a dish that is best served cold.
As I said I don't know math, but I think I will pay a visit to Mr. Kershling sometime soon.
Oh and Remy, please don't do that again, it made my head hurt.
Ferret |
|
Reply To This Message
|
| flame test |
Author: silver
Date: 04-09-02 00:41
Acylic melts and burns, chars, blackens and bubbles.....
Glass will retain its shape until its glowing nicely red(more or less) and you'll need a fairly fierce heat to do it with.
I'd love to hear about the results of this surefire experiment(oh god that was a bad pun)
Go on, you know you want to.......
Silver |
|
Reply To This Message
|
| boring answer |
Author: silver
Date: 04-09-02 00:45
my acrylic 4" weighs approx 650 gms.
exactly what the boffs would predict.a little less than your 1500 gms. and in a spooky ratio of 1.2:2.5 ,ummm quelle surprise
Its Glass Klas.....
oh god there i go again
Silver
commit senseless acts of beauty. |
|
Reply To This Message
|
| Re: flame test |
Author: ICU812
Date: 04-09-02 03:39
I'm with Silver. Burn it and let's see what happens...you know, in the name of science. Although, I was under the impression that acrylic could wistand some pretty intense heat, maybe not fire huh?
Yeah burn it. And if it melts you know you got robbed, at which point I could give you a couple other ideas as to where to put that ball. :)
Jacques
"We are what we repeatedly do. Excellence, then, is not an act, but a habit."
-Aristotle |
|
Reply To This Message
|
| Re: |
Author: remy
Date: 04-09-02 03:44
sorry--math major in college for a little too long--I'd done the calculation before with shifty, I think.
rem |
|
Reply To This Message
|
| Re: New ball |
Author: Klas
Date: 04-09-02 08:08
Not that much figuring out going on. Mostly trying to remember the math I learned in school many, many years ago. This is after all not higher level stuff.
Klas |
|
Reply To This Message
|
| Re: New ball |
Author: Klas
Date: 04-09-02 08:09
That's okey Ferret, your can still be our hero, even without math skills. (:
Klas |
|
Reply To This Message
|
| Re: boring answer |
Author: Klas
Date: 04-09-02 08:11
Yes, I'm quite sure it is glass, even without the flame test (but it is tempting).
And as for the name jokes, bring em on, would be fun to hear some new ones.
Klas |
|
Reply To This Message
|
|
