Rolling Ball Sculpture #3

See also Rolling Ball Sculpture #1

The Smaller, Friendlier RBS
The first two RBS's that I made were huge and I really could find no place to put them in the house, so the third one was supposed to be a smaller one. The inspiration for this one came from seeing Jeffrey Zachmann at the Austin Art Fair in April '04 again and seeing his pieces. (His web site is http://www.jeffreyzachmann.com).

I have decided to switch exclusively to stainless steel. Granted, it is harder to work with, but the tracks are lot sturdier, cleaning it is easier and no painting it in clear lacquer afterwards is required. I went to the local metal supply house and got the stainless steel 3/8" tubing for the frame and a couple of dozen 6' lengths of 1/8 stainless steel rod for the tracks. It is more expensive than the hanger wire I used before, but as you will see in the results, a better choice.
The Lift
The motor is a small AC gearmotor that runs at 40 RPM or so. It is mounted on a thick plate welded to the bottom right of the frame.

The chain that I used here and will probably continue using from now on is so-called "ladder chain" (thanks to Jeffrey Zachmann for showing it to me). The only place to buy it on the Net that I found is at SDP-SI - look under "chains - ladder". It is much less heavy-looking than any bycicle chain, can be bought made from stainless steel and is not very expensive.

The sprockets for the lift came from SDP-SI as well - the plastic ones are inexpensive and work very well.

The hooks on the chain I made from the 1/8" stainless rod that I also use for tracks. That was not the best choice, but I didn't have thinner material when I was doing it. Next time I will use 3/32" wire for the hooks - the hooks require quite a bit of tweaking, and bending short pieces of 1/8" thick stainless steel wire is not easy. Welding them to the ladder chain was fairly awkward - the best way I found was to take one link off the chain, unbend the two ends of it, seat the link on the edge of a thick (1/4") metal plate and weld each half of the hook to the link while clamping it to the plate. After you weld both sides of the hook to the ends of the link you place the link back on the chain and carefully bend it back in place.

The pickup of the lift is a triple fork with the hook sliding in between the prongs of the fork. This has to be carefully tweaked for each hook. I also made a mistake of making the pickup on the wrong side the sprocket - so the pickup is done at the acute angle side. This makes the hooks push the marbles back while picking up the end marble, which causes problems. It works now, but next time I will make the pickup on the obtuse angle side.

The top takeoff is also a triple fork with the hook sliding inbetween the prongs. The fork has to come fairly close to the chain so that the marble does not fall off - but not close enough to catch the chain or the hook. Again, careful tweaking is needed.
The Track
Tracks are made from 12 gauge (1/8" diameter) stainless steel wire. It is smoother than the hanger wire that I used before, and is a lot stiffer - so the tracks hold shape better.

The track width is approx 1/2" for the 3/4" marbles that I used. I use two-wire tracks for both straight parts and the turns (as opposed to Zachmann's 3-wire tracks on turns) so some banking is required - the steeper/faster the turn the more the bank.

The track spacers and supports are made from the same wire that is used for the tracks. It is stiff enough that the supports hold very well. In critical spots I use stainless steel 3/16" wire for supports.

The sections of the track are butt-brazed together.

(The track is hard to photograph because the camera insists on focusing beyond it on the background.)


Design Elements
Spiral
It is made from one piece of wire rolled into the spiral. I bend the wire by hand with the help of some PVS plumbing pipe pieces of various diameters. The best way to do these, of course, is to get hold of a solid metal (preferably) cone - but I still have not figured out where I can get one of those.
The Through-Drop
Decided to do something different here and instead of a cup made it a pipe. The marble rolls in, is stopped by the wire support on the other side of the end-piece, the drop tips down onto the lower track where the ball rolls out on the other side of the pipe because the wire support ends and is not holding it in anymore.
The Come-Back
The murble roll over the tip bridge, onto a rising curving track, stops at the end of it, then comes back and drops into the opening below the bridge.
The Capacitor
The marble rolls onto this element and is caught because the marble's weight is not enough to tip it. When the second marble comes, it tips the thing over and both marbles roll down the lower track together.
Final Spiral
The two marbles from the Capacitor come to this one and roll in it together. It is pretty steep, and the two marbles twirl there for a while to slow down.
The RBS
And here is the final product in its natural habitat - a shelf in the library. I painted a few things in primary colors - yellow, red and blue - to add a little life to the steel gleam. Works pretty well.
Videos
Running13,363KB
The Ball Path5,558KB
Lift Pickup5,519KB
Lift Takeoff4,011KB
Through-Drop5,613KB
Spiral1,675KB
Come-Back4,465KB
Capacitor4,761KB
Whole Video25,872KB
Some Tips on Cleaning Stainless Steel Welds

I found a great way to clean stainless steel after welding. The method is called Electropolishing. What you need is a DC source - 20 to 40 Volts, 10 to 50 Amps (the higher the amperage the better). I used a 24V/10A source to clean this RBS but am looking for a more powerful one. You will also need an electrolyte - I used CitriSurf 9002 from Stellar Solutions - because it is very mild compared to the usual solutions of nitric or hydrochloric acid. You hook the negative electrode to the RBS and fashion a "wand" out of the positive end - and put some absorbent resilient non-conductive substance on the end of the wand (I used either denim or fiberglass cloth). Turn the DC source on, dip the wand into the electrolyte, then rub the black oxide stains on the RBS with the wand - they get removed like magic.
If you want to know more, ask questions, or exchange information about RBSs, contact me at mike@medved.net