Well if you arent familiar with what it is.. http://www.btinternet.com/~jean.darc/gfx/resource/craddle.html
Thats what it is.
Here is the task- Make one much much larger than those that are made for novelty items. As in stick it in your front yard "hey look its art!" large. This is for my friends dad, so my neighbors wont be wondering about my intelligence. Just his.
What we need is the balls. We purchased a novelty one, and observed a few thigns-
1) This thing is a peice of crap because its not built close enough to perfect that it doesnt rock straight.
2) We need massively strong foundations for this. Sooo.. metal poles in concrete forms?
3) An adjustment system for where and how long the cables/strings are is needed for fine tuning.
4)The longer the strings are, the slower and longer the oscillation goes on.
So with that in mind,
1) Is this feasable?
2) Where do we get balls? Do they make 10" Ball Bearings?
Another consideration-
Could we make this thing musical at all? There are these chinese exercise balls that are completely enclosed, but chime. They work like a wind chime, as they have a ball rolling around inside and it hits the chimes. The intent of the ball is to roll it around without making a noise. or should we just attach a bell to the bottom of each ball?
I'm sure I have more considerations for this project, as I have given it several days of thought. But, since we are all DIY's here, and our minds run rampid, I'm looking for ideas and mental support.
Thank you for all ideas!
Thats what it is.
Here is the task- Make one much much larger than those that are made for novelty items. As in stick it in your front yard "hey look its art!" large. This is for my friends dad, so my neighbors wont be wondering about my intelligence. Just his.
What we need is the balls. We purchased a novelty one, and observed a few thigns-
1) This thing is a peice of crap because its not built close enough to perfect that it doesnt rock straight.
2) We need massively strong foundations for this. Sooo.. metal poles in concrete forms?
3) An adjustment system for where and how long the cables/strings are is needed for fine tuning.
4)The longer the strings are, the slower and longer the oscillation goes on.
So with that in mind,
1) Is this feasable?
2) Where do we get balls? Do they make 10" Ball Bearings?
Another consideration-
Could we make this thing musical at all? There are these chinese exercise balls that are completely enclosed, but chime. They work like a wind chime, as they have a ball rolling around inside and it hits the chimes. The intent of the ball is to roll it around without making a noise. or should we just attach a bell to the bottom of each ball?
I'm sure I have more considerations for this project, as I have given it several days of thought. But, since we are all DIY's here, and our minds run rampid, I'm looking for ideas and mental support.
Thank you for all ideas!
I just got my self 10 IRF9610's with cut off fins ...
If they will do the job you can have them.
Rosey
If they will do the job you can have them.
Rosey
onebadziggy said:
The 1st thing that came to mind was bowling balls, PVC pipe (perhaps filled with concrete), and picture hanging wire.
dave
An externally hosted image should be here but it was not working when we last tested it.
What are these? I'm sorry but I have no idea.
planet10, I'm intriged by your pvc/concrete idea. I might go with steel supports however, because I love welding and dont get to do it enough.
How much are bowling balls usually? I think they will take the force, but I will do some testing/dropping to see first.
onebadziggy said:
I was thinking 2nd hand stores....
if you like welding then steel is the way to go.
dave
The balls need to be made of non lossy material.
Concrete and pvc would not be suitable.
Bowling balls ought to work well.
Eric.
Concrete and pvc would not be suitable.
Bowling balls ought to work well.
Eric.
Well, I dont think we were going for concrete/pvc balls if thats what your saying. But, we are in the process of finding a bowling ball that we can test to see is it will hold up to the abuse. I'll have pics if we shatter it.
I’m no expert on this (or any other subject for that matter) but I was under the impression that bowling balls tend to have cork cores. Perhaps this is just for the lighter kids balls, but I wouldn’t be surprised if after drilling it you find that it is not homogeneous.
I'm assuming your shopping at second hand stores. This could make it take some time to get 6 equal mass balls.
Have you considered using large old magnets (from 12” speakers?) aligned to repel like poles? It would be much quieter.
I'm assuming your shopping at second hand stores. This could make it take some time to get 6 equal mass balls.
Have you considered using large old magnets (from 12” speakers?) aligned to repel like poles? It would be much quieter.
A long time ago, I saw one made out of old bowling balls that were thrown away from a bowling alley. It worked quite well for the purpose, but I couldn't personally see a reason to build one. Bowling balls can definately take the abuse, and even previously abused bowling balls will work for the task.
I would search second hand stores as dave mentioned.
--
Brian
I would search second hand stores as dave mentioned.
--
Brian
I am very interested in this magnetic idea! I may just have to build a small one too see how well it would work. Only problems I would see are the magnets rotating and attracting, but thats easily remedied. But will there be energy lost in the compression of the magnetic force between the two magnets?
Th only reason we are doing this is becasue we can. And im not the one with the wallet for this one, so im up for it.
Well, since bowling balls tend to be the consensus of what we need, im sure we will go with those. We will most likely purchase new ones that arent drilled into for the real project. The tester ball will but just that, and I will have to rip it open to see what the inside looks like.
Th only reason we are doing this is becasue we can. And im not the one with the wallet for this one, so im up for it.
Well, since bowling balls tend to be the consensus of what we need, im sure we will go with those. We will most likely purchase new ones that arent drilled into for the real project. The tester ball will but just that, and I will have to rip it open to see what the inside looks like.
The twisting can be remedied either by placing the suspension points of the drivers sufficiently far apart or by suspending the magnets by some form of rigid levers.
The repulsion of the magnets should, I think, behave like any other elastic collision. Conservation of momentum is maintained with losses being attributed to heat generated by the collision.
When the magnets reach their closest point, they should then be repelled with an equal but opposite force.
The repulsion of the magnets should, I think, behave like any other elastic collision. Conservation of momentum is maintained with losses being attributed to heat generated by the collision.
When the magnets reach their closest point, they should then be repelled with an equal but opposite force.
If you go with magnets you'll have to be careful about the strength of the fields and the spacing between them. Each magnet acts like a much bigger object as far as the bumping into each other goes. I would think that they would behave like larger balls of soft material. If you put them too close together, the odd pairs of magnets will attract each other (at a lesser force than the adjacent magnets will repel, so the motion could get quite chaotic.
MR
MR
Magnets - wierd .....
This would work in reverse !
Can anybody predict how it would behave ?
I think starting it off might be a challenge.
I would really like to see this !
Dave
This would work in reverse !
Can anybody predict how it would behave ?
I think starting it off might be a challenge.
I would really like to see this !
Dave
I think I see what you are getting at.
With solid spheres the energy of the collision on one end is transmitted though the bank of stationary spheres until it reaches a free one that will be forced into motion.
Not so with a stationary bank of magnets.
1st: the spacing will have to be made such that they will remain stationary at the point where the force exerted by the oposing fields will allow the suspension to be 90 deg to the horizon.
2nd: When an end magnet is raised and released it will accelerate towards the bank of stationary magnets until the opposing fields cause the rate of acceleration to decrease (damping the motion). The motion will decelerate at the point where the energy is transferred to the stationary object sufficient to set it into motion.
(Jeesh, I should have kept my brain shut)
Unlike the touching solid spheres, we will not have the equivalent of a collision (provided that the fields are strong enough and the maximum velocity is low enough)
The motion will be transferred from magnet to magnet reciprocally until it reaches the opposite side at which point the end magnet will swing free but not equal and opposite to the motion of initiation. As some damping will undoubtedly occur in each inter magnet reaction, it is likely that some energy will be lost.
It might be possible to tune the device so that under the proper input force and with proper spacing, the harmonic motion of the total system might resonate for a certain amount of time in a visually interesting pattern.
Well now that I've avoided working long enough, and amazed everyone with how much I really don’t know about physics, I think its time that I call it a night and get out of here.
-Dave
They might not be homogeniously solid, but bowling balls are probably much better to work with.
How bout a nice Foucault pendulum?
With solid spheres the energy of the collision on one end is transmitted though the bank of stationary spheres until it reaches a free one that will be forced into motion.
Not so with a stationary bank of magnets.
1st: the spacing will have to be made such that they will remain stationary at the point where the force exerted by the oposing fields will allow the suspension to be 90 deg to the horizon.
2nd: When an end magnet is raised and released it will accelerate towards the bank of stationary magnets until the opposing fields cause the rate of acceleration to decrease (damping the motion). The motion will decelerate at the point where the energy is transferred to the stationary object sufficient to set it into motion.
(Jeesh, I should have kept my brain shut)
Unlike the touching solid spheres, we will not have the equivalent of a collision (provided that the fields are strong enough and the maximum velocity is low enough)
The motion will be transferred from magnet to magnet reciprocally until it reaches the opposite side at which point the end magnet will swing free but not equal and opposite to the motion of initiation. As some damping will undoubtedly occur in each inter magnet reaction, it is likely that some energy will be lost.
It might be possible to tune the device so that under the proper input force and with proper spacing, the harmonic motion of the total system might resonate for a certain amount of time in a visually interesting pattern.
Well now that I've avoided working long enough, and amazed everyone with how much I really don’t know about physics, I think its time that I call it a night and get out of here.
-Dave
They might not be homogeniously solid, but bowling balls are probably much better to work with.
How bout a nice Foucault pendulum?
for the balls look at www.skf.com
they should make ballbearings up to about 2000 mm Diameter and 200 broad.
they should make ballbearings up to about 2000 mm Diameter and 200 broad.
2000mm?! Thats outragoulsy ridiculous! Then again, so is this project. Very nice info.. Thank you much.
The damping motion that Da5id4Vz talked about is what my concern was. I can see it in one respect, becasue, when you hold magnets and push them togther, it feels damped, and if something is floating, like a monorail, it feels like its riding on air.
But, another good point was brought up. Energy could only be lost in heat. It can also be lost in sound, and friction, but since they wont "clack" together, there will be no sound, and the friction will be negligble for the model's purposes.(possibly a problem for a large one).
Wouldn't the effective collision carry the same amount of energy and therefore transfer the same amount? Sure, the transition isnt complete until the 1st magent ends its movement, But instead of like the balls being an instant transfer, the magnets will be drawn out in time, and have the same effectiveness.
But, how do the extended collision and damping problems combine into one? Is there both principles at work or just one?
The damping motion that Da5id4Vz talked about is what my concern was. I can see it in one respect, becasue, when you hold magnets and push them togther, it feels damped, and if something is floating, like a monorail, it feels like its riding on air.
But, another good point was brought up. Energy could only be lost in heat. It can also be lost in sound, and friction, but since they wont "clack" together, there will be no sound, and the friction will be negligble for the model's purposes.(possibly a problem for a large one).
Wouldn't the effective collision carry the same amount of energy and therefore transfer the same amount? Sure, the transition isnt complete until the 1st magent ends its movement, But instead of like the balls being an instant transfer, the magnets will be drawn out in time, and have the same effectiveness.
But, how do the extended collision and damping problems combine into one? Is there both principles at work or just one?
Da5id4Vz said:
Those images won't work very well because the link is pointed to your hard disk.
Use the [File...] button * in the Attach File area at the bottom of the edit area to attach a single picture off your HD (the file is sucked off of your HD onto the diyAudio server).
* i have seen a reference to this button by a different name by Windoz users.
dave
Thanks, Planet10, for the tips on how to get the images attached.
Here is an extract (reproduced without permission) from "The Cartoon Guide to Physics" by Gonick and Huffman. It’s a great little book if you ever need a light refresher about why the world behaves the way it does.
Cell-3 (this one shows the math)
Here is an extract (reproduced without permission) from "The Cartoon Guide to Physics" by Gonick and Huffman. It’s a great little book if you ever need a light refresher about why the world behaves the way it does.
Cell-3 (this one shows the math)
Attachments
Thanks, Planet10, for the tips on how to get the images attached.
Here is an extract (reproduced without permission) from "The Cartoon Guide to Physics" by Gonick and Huffman. It’s a great little book if you ever need a light refresher about why the world behaves the way it does.
Cell-4
Now if I can just find a way of deleating post 19 and 20...
Here is an extract (reproduced without permission) from "The Cartoon Guide to Physics" by Gonick and Huffman. It’s a great little book if you ever need a light refresher about why the world behaves the way it does.
Cell-4
Now if I can just find a way of deleating post 19 and 20...
Attachments
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