Newton's cradle
 

OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?
This very large version has some rings, which is what I am
considering:
http://i48.tinypic.com/1euurq.jpg

But people are likely to pull the balls out if they can, and I would
rather have a couple of large rings, one on each side, centered on the
point of impact. I'll have to tie them together somehow. Cable ties?
I'll probably use heavy monofilament nylon to hold the balls in line.
Unless someone thinks of something better.
I have to make this in the next few days!

Newton's cradle
 

On Jul 3, 2:19*am, Matty F wrote:
OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?
This very large version has some rings, which is what I am
considering:http://i48.tinypic.com/1euurq.jpg

But people are likely to pull the balls out if they can, and I would
rather have a couple of large rings, one on each side, centered on the
point of impact. I'll have to tie them together somehow. Cable ties?
I'll probably use heavy monofilament nylon to hold the balls in line.
Unless someone thinks of something better.
I have to make this in the next few days!

You are far too fat headed for a successful operation. Not even brain
surgery will help you. Have you considered mummification?

Newton's cradle
 

On Jul 3, 4:45 pm, Weatherlawyer wrote:
On Jul 3, 2:19 am, Matty F wrote:

OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?
This very large version has some rings, which is what I am
considering:http://i48.tinypic.com/1euurq.jpg

But people are likely to pull the balls out if they can, and I would
rather have a couple of large rings, one on each side, centered on the
point of impact. I'll have to tie them together somehow. Cable ties?
I'll probably use heavy monofilament nylon to hold the balls in line.
Unless someone thinks of something better.
I have to make this in the next few days!

You are far too fat headed for a successful operation. Not even brain
surgery will help you. Have you considered mummification?

Having a bad day are you? I've managed to make many things so far.
Often people in here have ideas that I had not thought of.
The Newton's cradle is for a science show that thousands of people
will be looking at.

Newton's cradle
 

Weatherlawyer
wibbled on Saturday 03 July 2010 05:45

On Jul 3, 2:19 am, Matty F wrote:
OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?
This very large version has some rings, which is what I am
considering:http://i48.tinypic.com/1euurq.jpg

But people are likely to pull the balls out if they can, and I would
rather have a couple of large rings, one on each side, centered on the
point of impact. I'll have to tie them together somehow. Cable ties?
I'll probably use heavy monofilament nylon to hold the balls in line.
Unless someone thinks of something better.
I have to make this in the next few days!

You are far too fat headed for a successful operation. Not even brain
surgery will help you. Have you considered mummification?

Are you austistic or just hard of thinking?

--
Tim Watts

Managers, politicians and environmentalists: Nature's carbon buffer.

Newton's cradle
 

On 03/07/2010 02:19, Matty F wrote:
OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?
This very large version has some rings, which is what I am
considering:
http://i48.tinypic.com/1euurq.jpg

But people are likely to pull the balls out if they can, and I would
rather have a couple of large rings, one on each side, centered on the
point of impact. I'll have to tie them together somehow. Cable ties?
I'll probably use heavy monofilament nylon to hold the balls in line.
Unless someone thinks of something better.
I have to make this in the next few days!

How about making a net of six rings (top, bottoms and four sides)? The
rings could be made out of fishing line and joined together by the same?

Newton's cradle
 

On Jul 3, 7:27 pm, Peter Watson wrote:

How about making a net of six rings (top, bottoms and four sides)? The
rings could be made out of fishing line and joined together by the same?

Yes, they would end up being roughly squares.
On the other hand I'm coming around to the idea of using epoxy glue to
glue an attachment to the top of the balls so the fishing line can be
attached. Most cradles have a gap betwen the attachments but why can't
both lines be at the very top?

Newton's cradle
 

Matty F :
OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?
This very large version has some rings, which is what I am
considering:
http://i48.tinypic.com/1euurq.jpg

But people are likely to pull the balls out if they can, and I would
rather have a couple of large rings, one on each side, centered on the
point of impact. I'll have to tie them together somehow. Cable ties?
I'll probably use heavy monofilament nylon to hold the balls in line.
Unless someone thinks of something better.
I have to make this in the next few days!

Jubilee clips.

--
Mike Barnes

Newton's cradle
 

On 2010-07-03, Matty F wrote:
On the other hand I'm coming around to the idea of using epoxy glue to
glue an attachment to the top of the balls so the fishing line can be
attached. Most cradles have a gap betwen the attachments but why can't
both lines be at the very top?

Ideally you want the balls only to swing about the axis
through the top of the cradle. If you mount them at the very
top, they can wobble about that point and twist around it,
so it's better to support them from two points lower down.

You could machine rings with a groove around the inside of
each and cut them through (making an almost-closed C shape)
so that it will spring open far enough for the ball to pop
in.

--
Jón Fairbairn
http://www.chaos.org.uk/~jf/Stuff-I-dont-want.html (updated 2009-01-31)

Newton's cradle
 

.... Most cradles have a gap betwen the attachments but why can't
both lines be at the very top?

Doesn't the gap serve to stop the balls rotating about the vertical
axis? There's no way my addled brain can model such things these days
but I think such spin would be a "bad thing" - unless you are also
trying to demonstrate snooker shots :)
--
Robin
PM may be sent to rbw0{at}hotmail{dot}com

Newton's cradle
 

On Jul 3, 8:57 pm, "Robin" wrote:
.... Most cradles have a gap betwen the attachments but why can't
both lines be at the very top?

Doesn't the gap serve to stop the balls rotating about the vertical
axis? There's no way my addled brain can model such things these days
but I think such spin would be a "bad thing" - unless you are also
trying to demonstrate snooker shots :)

Yes spin would be a bad thing. So I need a gap.

Newton's cradle
 

On Jul 3, 8:39 pm, Mike Barnes wrote:
Matty F :

OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?
This very large version has some rings, which is what I am
considering:
http://i48.tinypic.com/1euurq.jpg

But people are likely to pull the balls out if they can, and I would
rather have a couple of large rings, one on each side, centered on the
point of impact. I'll have to tie them together somehow. Cable ties?
I'll probably use heavy monofilament nylon to hold the balls in line.
Unless someone thinks of something better.
I have to make this in the next few days!

Jubilee clips.

At first I laughed. But they would be a good idea if they looked OK.
Perhaps I can make some elegant brass clips.

Newton's cradle
 

"Matty F" wrote in message
...
OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?
This very large version has some rings, which is what I am
considering:
http://i48.tinypic.com/1euurq.jpg

But people are likely to pull the balls out if they can, and I would
rather have a couple of large rings, one on each side, centered on the
point of impact. I'll have to tie them together somehow. Cable ties?
I'll probably use heavy monofilament nylon to hold the balls in line.
Unless someone thinks of something better.
I have to make this in the next few days!

A couple of large rings as you say, then just wire them together and twist
the wires.
Four wires spaced around the rings should be OK.
The supporting nylon can be attached to the top two wires and I am sure you
can twist a loop in the wires to attach them.

Why not get your angle grinder out and just mill a couple of notches in the
top, drill the bit that now sticks up and attach to that?

Newton's cradle
 

"Matty F" wrote in message
...
On Jul 3, 7:27 pm, Peter Watson wrote:

How about making a net of six rings (top, bottoms and four sides)? The
rings could be made out of fishing line and joined together by the same?

Yes, they would end up being roughly squares.
On the other hand I'm coming around to the idea of using epoxy glue to
glue an attachment to the top of the balls so the fishing line can be
attached. Most cradles have a gap betwen the attachments but why can't
both lines be at the very top?

The gap makes them swing straight, if you just have one the balls will just
bounce to one side and not impart all their energy to the next ball.

Newton's cradle
 

"Matty F" wrote in message
...
OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?
This very large version has some rings, which is what I am
considering:
http://i48.tinypic.com/1euurq.jpg


One approach could be to grind a flat on the top of each ball. Manufacture a
plane disk whose diameter matches the flat. A metal disk would enable you
to solder or braze or machine two pickup points at the edges of the disk,
diametrically opposite one another.

DDS

Newton's cradle
 

On Jul 3, 10:08 pm, "dennis@home"
wrote:
"Matty F" wrote in message

...

OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?
This very large version has some rings, which is what I am
considering:
http://i48.tinypic.com/1euurq.jpg

But people are likely to pull the balls out if they can, and I would
rather have a couple of large rings, one on each side, centered on the
point of impact. I'll have to tie them together somehow. Cable ties?
I'll probably use heavy monofilament nylon to hold the balls in line.
Unless someone thinks of something better.
I have to make this in the next few days!

A couple of large rings as you say, then just wire them together and twist
the wires.
Four wires spaced around the rings should be OK.
The supporting nylon can be attached to the top two wires and I am sure you
can twist a loop in the wires to attach them.

I can probably make the rings out of wire.

Why not get your angle grinder out and just mill a couple of notches in the
top, drill the bit that now sticks up and attach to that?

If the cradle doesn't work that well or management decides that they
are a danger to small kids, I'd like to sell the balls as billiard
balls again!

Newton's cradle
 

dennis@home wrote:

The gap makes them swing straight, if you just have one the balls will
just bounce to one side and not impart all their energy to the next ball.

The motion wants to be:
(a) In-plane, and
(b) Irrotational.

Even with separated attachment points, flexible lines will permit a degree of
out-of-plane movement, which tends to grow. Probably the most satisfactory
compromise between in-plane constraint and low wind resistance would be a solid
strip (or two, to obviate out-of-plane deflection) of a rigid material, aspect
ratio say 5:1, with the long dimension in the plane of motion. If this was
rigidly attached to the ball, and hinged at the top, the various requirements
would be met quite well. A bearing or two (one each side of the strip) would be
better than a hinge, but might be overkill.

Newton's cradle
 

Duncan Di Saudelli wrote:

One approach could be to grind a flat on the top of each ball. Manufacture a
plane disk whose diameter matches the flat. A metal disk would enable you
to solder or braze or machine two pickup points at the edges of the disk,
diametrically opposite one another.

The suspender could be made from a strip of alloy, bent twice to make a thin
square U shape. The bottom of the U could be glued to the flat on the ball. At
the other end, a ball bearing glued to each outer face of the strip, or if
that's too complicated, a simple low-friction hinge. Alignment of the hinge
axis perpendicular to the plane of motion could be a trick.

Newton's cradle
 

John Rumm wrote:
On 03/07/2010 08:46, Matty F wrote:
On Jul 3, 7:27 pm, Peter wrote:

How about making a net of six rings (top, bottoms and four sides)? The
rings could be made out of fishing line and joined together by the same?

Yes, they would end up being roughly squares.
On the other hand I'm coming around to the idea of using epoxy glue to
glue an attachment to the top of the balls so the fishing line can be
attached. Most cradles have a gap betwen the attachments but why can't
both lines be at the very top?

The spacing prevents the balls twisting...

I would have thought a couple of rings - a bit less than the ball
diameter, which were then lashed or tied together with the ball
sandwiched between them.


With fishing line, and the sort of separation envisaged, the spacing will reduce
but not prevent twisting, IMO.

Newton's cradle
 

Matty F wrote:
OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?
This very large version has some rings, which is what I am
considering:
http://i48.tinypic.com/1euurq.jpg

But people are likely to pull the balls out if they can, and I would
rather have a couple of large rings, one on each side, centered on the
point of impact. I'll have to tie them together somehow. Cable ties?
I'll probably use heavy monofilament nylon to hold the balls in line.
Unless someone thinks of something better.
I have to make this in the next few days!

Forget the billiard balls and go looking for the largest ball bearing
available. They might come from some very heavy machinery, not
necessarily with wheels! Steel is much more elastic than billiard ball
material. I mean elastic in the physical sense not like rubber.

R

Newton's cradle
 

In message
,
Matty F writes
OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?

Large scrotal sack

Funnily enough, Roencrantz and Guildernstern are Dead is on t'telly ATM
- there was a newton's cradle a few minutes ago on't screen using
terracotta pots. Needless to say - one broke

Just thought I'd share this gem with you

drill the fukkers - else you know full and well, it'll all fall apart



--
geoff

Newton's cradle
 

In message
,
Matty F writes
On Jul 3, 4:45 pm, Weatherlawyer wrote:
On Jul 3, 2:19 am, Matty F wrote:

OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?
This very large version has some rings, which is what I am
considering:http://i48.tinypic.com/1euurq.jpg

But people are likely to pull the balls out if they can, and I would
rather have a couple of large rings, one on each side, centered on the
point of impact. I'll have to tie them together somehow. Cable ties?
I'll probably use heavy monofilament nylon to hold the balls in line.
Unless someone thinks of something better.
I have to make this in the next few days!

You are far too fat headed for a successful operation. Not even brain
surgery will help you. Have you considered mummification?

Having a bad day are you? I've managed to make many things so far.
Often people in here have ideas that I had not thought of.
The Newton's cradle is for a science show that thousands of people
will be looking at.


Drilled then

don't forget the advertising


--
geoff

Newton's cradle
 

In message , Mike Barnes
writes
Matty F :
OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?
This very large version has some rings, which is what I am
considering:
http://i48.tinypic.com/1euurq.jpg

But people are likely to pull the balls out if they can, and I would
rather have a couple of large rings, one on each side, centered on the
point of impact. I'll have to tie them together somehow. Cable ties?
I'll probably use heavy monofilament nylon to hold the balls in line.
Unless someone thinks of something better.
I have to make this in the next few days!

Jubilee clips.

Demonstration to be seen by half the population of the southern
hemisphere (except the sheep) and you want him to use jubilee clips and
chewing gum?

Doomed, doomed, I say




--
geoff

Newton's cradle
 

In message
,
Matty F writes
On Jul 3, 8:39 pm, Mike Barnes wrote:
Matty F :

OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?
This very large version has some rings, which is what I am
considering:
http://i48.tinypic.com/1euurq.jpg

But people are likely to pull the balls out if they can, and I would
rather have a couple of large rings, one on each side, centered on the
point of impact. I'll have to tie them together somehow. Cable ties?
I'll probably use heavy monofilament nylon to hold the balls in line.
Unless someone thinks of something better.
I have to make this in the next few days!

Jubilee clips.

At first I laughed. But they would be a good idea if they looked OK.
Perhaps I can make some elegant brass clips.


Like this ?

http://www.uh.edu/~rfc/eng.htm


--
geoff

Newton's cradle
 

geoff wrote:
In message
,
Matty F writes
OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?

Large scrotal sack

Sack? I use a wheelbarrow.

Newton's cradle
 

In message , Gib Bogle
writes
geoff wrote:
In message
,
Matty F writes
OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?
Large scrotal sack

Sack? I use a wheelbarrow.

That might explain your sexual problems



--
geoff

Newton's cradle
 

On Jul 4, 11:55 am, Roger Dewhurst wrote:

Forget the billiard balls and go looking for the largest ball bearing
available. They might come from some very heavy machinery, not
necessarily with wheels! Steel is much more elastic than billiard ball
material. I mean elastic in the physical sense not like rubber.

I've already considered steel balls. If they were the size of billiard
balls or bigger, they would be very heavy and would squash the fingers
of the unwary and OSH would be nasty to me.
I have considered steel rods in wooden balls. I may go back to that
seeing as the billiard balls are going to be more expensive than I
thought.

Newton's cradle
 

geoff wrote:
In message , Gib Bogle
writes
geoff wrote:
In message
,
Matty F writes
OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?
Large scrotal sack

Sack? I use a wheelbarrow.

That might explain your sexual problems

How did you hear about those?

Newton's cradle
 

geoff :
In message , Mike Barnes
writes
Matty F :
OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?
This very large version has some rings, which is what I am
considering:
http://i48.tinypic.com/1euurq.jpg

But people are likely to pull the balls out if they can, and I would
rather have a couple of large rings, one on each side, centered on the
point of impact. I'll have to tie them together somehow. Cable ties?
I'll probably use heavy monofilament nylon to hold the balls in line.
Unless someone thinks of something better.
I have to make this in the next few days!

Jubilee clips.

Demonstration to be seen by half the population of the southern
hemisphere (except the sheep) and you want him to use jubilee clips and
chewing gum?

They're not all like the ones we're used to

e.g. these in stainless steel:

http://www.jubileeclips.co.uk/pdfs/L...uperclamps.pdf

(you could DIY a slightly neater looking version I'm sure)

or these if the crimp marks could be concealed:

http://www.jubileeclips.co.uk/pdfs/L...0O%20Clips.pdf

In any event clips would be good for quick non-destructive testing of
the dynamic properties of various ball materials.

--
Mike Barnes

Newton's cradle
 

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Gib Bogle
saying something like:

How can I hold the balls in position?

Large scrotal sack

Sack? I use a wheelbarrow.

That sounds unfeasible.

Newton's cradle
 

On Fri, 2 Jul 2010 18:19:18 -0700 (PDT), Matty F wrote:

But I would rather not drill into the balls or try to glue things on
them. How can I hold the balls in position?

Not wishing to damage the balls makes things tricky... Getting a ring
of individual rings to stay in the right place under the shocks may
also prove interesting, the rings on the image you linked to show
them displaced...

But people are likely to pull the balls out if they can, and I would
rather have a couple of large rings, one on each side, centered on the
point of impact. I'll have to tie them together somehow.

6 rings sized so that they just meet at four points when placed onto
the surface for the ball? Suspension points taken from opposite
points on one ring, stops the possible twisting problem.

Joining the rings might be fun, how about some netting with a 3/4" or
there abouts mesh? Make into a draw string bag perhaps witha solid
ring to make the "draw string" and provide suspension points.

--
Cheers
Dave.

Newton's cradle
 

Dave Liquorice
wibbled on Sunday 04 July 2010 11:47

On Fri, 2 Jul 2010 18:19:18 -0700 (PDT), Matty F wrote:

But I would rather not drill into the balls or try to glue things on
them. How can I hold the balls in position?

Not wishing to damage the balls makes things tricky... Getting a ring
of individual rings to stay in the right place under the shocks may
also prove interesting, the rings on the image you linked to show
them displaced...

But people are likely to pull the balls out if they can, and I would
rather have a couple of large rings, one on each side, centered on the
point of impact. I'll have to tie them together somehow.

6 rings sized so that they just meet at four points when placed onto
the surface for the ball? Suspension points taken from opposite
points on one ring, stops the possible twisting problem.

Joining the rings might be fun, how about some netting with a 3/4" or
there abouts mesh? Make into a draw string bag perhaps witha solid
ring to make the "draw string" and provide suspension points.


Tie wraps and a tie gun. Tighten the ties gradually and in a sequence to
keep tension balanced on the rings. The wraps will lie *fairly* flat after
the use of a gun and no-one will be nicking the balls (unless they cut the
wraps).

I'm thinking metal curtain rings to match the balls might be a low effort
method. I'm sure there would be some rings that would suit billiard balls or
similar.

--
Tim Watts

Managers, politicians and environmentalists: Nature's carbon buffer.

Newton's cradle
 

Grimly Curmudgeon wrote:

Sack? I use a wheelbarrow.

That sounds unfeasible.

You might want to read up on Elephantiasis. but _not_ if you are squeamish.

Andy

Newton's cradle
 

In message
,
Owain writes
On 4 July, 19:56, Andy Champ wrote:
You might want to read up on Elephantiasis. *but _not_ if you are squeamish.

"Daddy wouldn't buy me a spacehopper"
http://elephantiasis.freeyellow.com/eleph-fiji.gif

Now, if you could just find another 5 sufferers ...

--
geoff

Newton's cradle
 

In message
,
Owain writes
On 4 July, 21:14, geoff wrote:
"Daddy wouldn't buy me a spacehopper"
Now, if you could just find another 5 sufferers ...

... there's be enough for a freakshow edition of Come Dine With Me.

Apparently it's possible to D-I-Y with sterile saline injection.

And we have a new invention

Laydeez 'n gentilmin, I give you ...


Newton's Crotch



--
geoff

Newton's cradle
 

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Andy Champ
saying something like:

Grimly Curmudgeon wrote:

Sack? I use a wheelbarrow.

That sounds unfeasible.

You might want to read up on Elephantiasis. but _not_ if you are squeamish.

That'd be a whoosh, then.
http://en.wikipedia.org/wiki/Buster_Gonad

Newton's cradle
 

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Owain
saying something like:

"Daddy wouldn't buy me a spacehopper"
http://elephantiasis.freeyellow.com/eleph-fiji.gif

Jeez, there's a bloke in his bollock.

Newton's cradle
 

On Jul 4, 8:42 pm, Mike Barnes wrote:
http://www.jubileeclips.co.uk/pdfs/L...uperclamps.pdf

(you could DIY a slightly neater looking version I'm sure)

or these if the crimp marks could be concealed:

http://www.jubileeclips.co.uk/pdfs/L...0O%20Clips.pdf

In any event clips would be good for quick non-destructive testing of
the dynamic properties of various ball materials.

I think I could make some neat clips out of strips of sheetmetal and
roll the join together.

Nobody had mentioned duct tape. I have some clear duct tape!
I have now bought the billiard balls (new) for almost nothing.

Newton's cradle
 

Matty F wrote:
On Jul 4, 11:55 am, Roger Dewhurst wrote:

Forget the billiard balls and go looking for the largest ball bearing
available. They might come from some very heavy machinery, not
necessarily with wheels! Steel is much more elastic than billiard ball
material. I mean elastic in the physical sense not like rubber.

I've already considered steel balls. If they were the size of billiard
balls or bigger, they would be very heavy and would squash the fingers
of the unwary and OSH would be nasty to me.
I have considered steel rods in wooden balls. I may go back to that
seeing as the billiard balls are going to be more expensive than I
thought.

This thing works because and only because of the elastic property of steel.

R

Newton's cradle
 

geoff wrote:
In message , Gib Bogle
writes
geoff wrote:
In message
,
Matty F writes
OK I've decided to use billiard balls for my Newton's cradle.
But I would rather not drill into the balls or try to glue things on
them.
How can I hold the balls in position?
Large scrotal sack

Sack? I use a wheelbarrow.

That might explain your sexual problems

Elephantiasis of the testicles is no joke!

R

Newton's cradle
 

On Jul 5, 12:47 pm, Roger Dewhurst wrote:
Matty F wrote:
On Jul 4, 11:55 am, Roger Dewhurst wrote:

Forget the billiard balls and go looking for the largest ball bearing
available. They might come from some very heavy machinery, not
necessarily with wheels! Steel is much more elastic than billiard ball
material. I mean elastic in the physical sense not like rubber.

I've already considered steel balls. If they were the size of billiard
balls or bigger, they would be very heavy and would squash the fingers
of the unwary and OSH would be nasty to me.
I have considered steel rods in wooden balls. I may go back to that
seeing as the billiard balls are going to be more expensive than I
thought.

This thing works because and only because of the elastic property of steel.

Where were you when I last discussed this? You mean my billiard balls
won't work now that I bought them? :)
However I just tested them. They seem to work fine!