[widgitmaster]

On many a post here on the Zone, I have read where someone had made an "Impulse Buy" on eBay or other stores.

Well, while surfing through eBay I noticed a seller that had large chrome steel precision balls. 2.5000 +-.0002" to be exact! Now most people would just keep surfing, but I bought FIVE of them (chair) So for the next few evenings I stepped away from my current projects and started designing a HUGH "Newton's Cradle" using these large balls! It took me a little while to make everything proportionate, and I have to say that I must be totally NUTZ

The base plate is 1" thick aluminum, 11.375 wide, 15.125 long! The over all height of this widgit is 13.938" Not sure what the total weight is, but each ball weighs 2.7 Lbs! The material has been ordered, and the balls arrived today! The swing arms are aluminum, and have steel double sealed bearings pressed in. The pivot point at the center of the ball is to be a 1/4" hardened dowel pin, so each ball will need to have a hole drilled & reamed through the center. The balls will spin freely on the dowel pins, and the ends of the pins will be pressed into the swing arm fork!

The last FUN project I've done was the large Turner's Cubes, I hope this project is as rewarding!

Here is a picture of the 5-balls, and a full scale sketch on graph paper!

[CalG]

Neat project

Not to spread rain on a great plan, but......

The action will continue longer (if that is important) if you get rid of the sealed bearings and use a line contact pivot. (like a beam balance might show in example)

Soo.....Soo much less friction.

Waiting to see the video!

CalG

[widgitmaster]

Actually, I'm too worried about the level of friction, or the actual run times! The idea of making one so big is the selling point for me

I will make the prints available to anyone with an equal level of eccentricity and skills!

Eric

[CalG]

Anyone know a source for cannon balls?

This man is on a mission.

"Go big, or go home!" ;-)

CalG

[BobWarfield]

Heh, heh, I knew you had big balls, but so round too!

Cheers,

BW

[Geof]

I am not interested in prints, if you make something that works and keeps going for a long time I will buy one provided the price is not astronomical.

I have always dreamed of making one of these using balls about two feet in diameter hung from about twenty feet high. The period would be several seconds and if it was built correctly would run for a longggggg time.

P.S. The Turner's Cube sits in a 'Tunneller's' beer mug above my desk at home.

And if anyone tells me exactly what a Tunneller's beer mug is, and PMs their address, I will send them a money order to buy themselves a few beers or donate to their favorite charity, their choice.

[martinw]

Anyone know a source for cannon balls?

This man is on a mission.

"Go big, or go home!" ;-)

CalG

Dear CalG,

That had me falling about! Thank-you.

Best wishes,

Martin

[bill south]

This is just sooo coooool!
Bill

[universalfab]

This is just sooo coooool!
Bill

Your strong sarcasm is agreed with...

[widgitmaster]

Thanks Guys!
Wow, and I haven't even starting cutting metal yet

For those who are interested, the prints are now finished and available!
Just send me a PM!
Eric

[widgitmaster]

The remainder of the material arrived today, along with all the carbide tooling needed to drill holes through the balls!

It looks like I will be starting this project on Monday 10/05/09, not a day too soon either

Eric

[widgitmaster]

I started working on this project at 10:00 AM, and everything is going just fine!

First I mounted a flat 12" round steel plate on top of my little 8" rotary table, milled the top nice and true using a 3" face mill.

Then I cleaned up one of the large aluminum plates, filing off any burrs & hi-spots. Then I washed it with Acetone, and put three strips of double sided tape on the aluminum plate. Then I marked the center of the plate with an sharpie, and centered it on the round steel plate.

Next I used a large fly-cutter with a sharp carbide bit, and set the tool so the point was in the center of the plate. With the spindle running at 350 RPM, I slowly raised the knee until the cutter made contact. Now I slowly rotated the plate under the cutter, until I had as flat and smooth a surface as possible! The aluminum plate was .03" oversize, and I removed .015" from the 1st side.

Then I used 4x screw jacks to lift the plate off the tape, and repeated the process on the 2nd side! The plate now measures 1.000" on all four corners, and has a slight hollow in the center. The only straight edge I have thats long enough is my 18" vernier caliper!

A DIY Blanchard Grinder!

So I now proceeded to repeat the process on the 2nd plate! They will look really nice after anodizing!

[jalessi]

Eric,

How much did all of the aluminum plate for this cost?

Cant wait to see it finished.

Jeff...

[widgitmaster]

Hopefully when its finished, I can get all the aluminum anodized, Burgundy would look nice!

[martinw]

Dear widgitmaster,

What a fun project, and thank-you for posting.

I worry about the bearings. Friction could be your undoing Could you perhaps try a mockup to get an idea of how the bearings perform, maybe just one swinging ball in the chosen geometry, and see how long it swings for?

MVVHO,

Best wishes,

Martin

[widgitmaster]

Dear widgitmaster,

What a fun project, and thank-you for posting.

I worry about the bearings. Friction could be your undoing Could you perhaps try a mockup to get an idea of how the bearings perform, maybe just one swinging ball in the chosen geometry, and see how long it swings for?

MVVHO,

Best wishes,

Martin

Thanks Martin!
Your concerns are noted, but I can't think of any substitute for a ball bearing that will support a 1040G (2lb 4.8oz) steel ball! A string or wire tether is not easy to work with, and makes it impossible to align the balls.

I believe the force of impact resonating throughout the entire frame will be better controlled by a solid pendulum supported by precision pre-lubricated steel bearings. Also, the ability for the big balls to spin reduces the wear by offering a full 360 deg. of possible surface area for contact!

If you have a valid alternative, I will consider it!
Eric

[jalessi]

Eric,

Check these out.

http://tinyurl.com/yc5qztl


http://tinyurl.com/y922eaa

Jeff...

[widgitmaster]

Eric,

Check these out.

http://tinyurl.com/yc5qztl


http://tinyurl.com/y922eaa

Jeff...

I rest my case!

Although they have bigger balls, the cables are too flexible and ALL the energy is lost due to poor alignment! The first one only worked 5-times, and all the balls separated upon impact, causing the returning ball to make multiple impacts. It even looked like the one in the middle bounced up upon impact! I do not think plastic would be a good choice either!

When working properly, the balls in the middle should be totally motionless, and all the energy should be transferred through each ball to the outer ball! Thus causing it to react with equal and opposite force! Thus Newton's Law!

In my honest opinion, my design will gain tremendous efficiency due to perfect alignment, and any friction caused by using ball bearings at the pivot point will be negligible! Gravity causes the friction, but Gravity also perpetuates the motion!

Eric

[martinw]

Dear Eric,

I think you are absolutely right to go for a rigid pendulum instead of "string", but maybe CalG's suggestion of a line pivot might be worth considering instead of ball bearings.

Good luck, and please keep posting.

Best wishes,

Martin

[Geof]

.....In my honest opinion, my design will gain tremendous efficiency due to perfect alignment, and any friction caused by using ball bearings at the pivot point will be negligible! Gravity causes the friction, but Gravity also perpetuates the motion!

Eric

Come on Eric, nobody is perfect.

But I do think you come closer to it than most people when it comes to machine work.

On source of friction that may remain in your design is the lubricant in the bearings and the seals. Have you considered open bearings running dry; they are going to be very lightly loaded.