The Ball Sculpture
As the base of the project I created a set of rules. I had these rules in mind when I built the whole sculpture.
As the base of the project I created a set of rules. I had these rules in mind when I built the whole sculpture.
I started the design of the sculpture in August 2012. The designing part took about 100 hours in Google SketchUp. I draw everything from my head so the slope of the tracks where all estimates. Basically I just made everything slope about 1 degree. In retrospect this was too much, but at the time I had no idea how to calculate this (still don't :). The design picture was the end result of all my design work.
Now after this, I had to start somewhere so I decided to start with the elevator. More specific the actual screw that is going to push the ball upward when the elevator pipe turns. I did not really have a clue how to do this so I just used a pipe that was just the right diameter and basically bent the brass rod around it until I had a spring with enough turns. Then I pulled every turn apart until it felt good. :) Then it was on to the pipe that holds the spring in place. I had decided to only use two track holders on each turn. Each turn then needs two holes. So lots of filing had to be done...
When the two pieces where done, it was on to the actual track holders. It turns out there are quite a lot of angles to keep in mind when creating these. The slope, the turn and the bend of the screw. Then of course the holder itself can not be in the way of the ball. I did not want to use any glue or screws to attach either the track nor the holder so a "snap in place" had to be the only solution. Because of the nature of FDM 3D-Printing one side of the part must be flat on the print-bed for the part to stick when printing. That's kind of a challenge when designing. :) I don't remember how many versions I made before it was perfect. But it was a lot. :)
Same principal goes for the rest of the track holders. No glue, no screws only friction. I wanted to use as few "pillars" as I possible could. This meant that I needed different lengths of the holders for the tracks to stay where I wanted. It turned out to be 8 different ones (10 really, but I only used 8 in the end). You can see number two in closeup and then all of them printed (plus some extra ones)... The print time for all these holder where about 30 hours. All parts are printed with 0.2mm layers.
Now it was time to start with the actual tracks. I calculated that I would need about 40 meters of 3mm brass rod. So that's what I ordered. It is about 20 meters of tracks in total in the sculpture. Turned out that I was about 2 meters short in the end and had to do another order... If you take a closer look at the sculpture you may notice that it is actually only two types of curves on the track. One wide and one narrow. I wanted the sculpture to look "clean" so that's why I kept it to only tow types. This also meant that I only needed 4 curve templates. :)
As you can see, the templates are very simple but they worked well. Sure, it was lot of work bending it all manually, but that was one of the challenges with this sculpture. Now, to be able to bend the tracks exactly as needed I had to get the track parts out on paper to use as templates. It turned out to be 67 papers with tracks...
I would say it's about 5 moths in between the pictures. Remember, I could only work on evenings with this. :)
Now when all parts of the track were done I had to learn how to gas weld. I asked around a bit but it seems that not so many think that it is a good idea to weld 3mm brass rod end to end. In fact, I heard a lot that it would be very hard... A challenge! :) So, I started to learn... It turns out it IS pretty hard, not impossible but you have to be really careful with both temperature, the amount of flux and silver solder. I had the idea to not needing to file so much after the weld was done. After about 100 tries, I was skilled enough to start on the tracks. :) The welds in the second weld picture has not been filed, only polished with emery cloth. Here you can see the technique I used for the testing / learning. In the clip I'm applying too much heat that's why its not a perfect weld. I learned this eventually. :)
I was ready to start on the real stuff!
There where 67 track templates each holding 2 rails of track. That makes it 134 welds... :) The printed black and white track spacers you see in the pictures are just there to hold the tracks in place when moving them and working with the welding. You can also see my temporary welding bench. :)
Now on to the base platform. I needed to make sure the whole sculpture was always in level, for this I found a small round spirit. The total size of the board is 1000mm x 220mm.
I had decided that I wanted a glass-box to cover the whole thing when it was done. For the glass-box to stay in place I made a groove on the edges of the top board. Again I had to learn something new. :) I had never used a over hand cutter before...
I also had to fit the motor underneath the board and I needed some way to be able to adjust the feet of the sculpture to keep it horizontal. For this I designed a special corner part. This part also made sure the sides of the base stayed together neatly.
The corner part has a prolonged "pipe" that sits against the top board to lead the weight of the sculpture from the feet up on to the top boards underside instead of letting the corner part hold all of it. With the glass box and everything, the whole sculpture is quite heavy. :)
One more thing about the corner part, I did not want any visible screws on the outside of the base of course. :) Now I just needed to get the base top board attached to the base frame. For this another part was needed...
Base done. :) The holes you see on the top board are for the pillars, elevator, elevator counter holders and drive gear. Now adding the motor...
The motor is a 230volt Crouzet that runs 1 RPM. I'm using small parts of rubber to isolate the vibrations form the motor. I also made a small adapter in aluminum. This gets the gear just in the right place. And of course the small drive gear is also printed. Unfortunately I forgot to take a photo of them, but here is the SketchUp designs of both the aluminum adapter and the gear.
The adapter goes on the motor shaft and a small screw holds it in place, then the gear goes on top of the adapter with a snug fit and protrudes up trough the hole in the top board.
Now it was time to start with the pillars to hold the tracks. I use the same 3mm brass rod as pillars. Except for the elevator counter support. I wanted to make sure the balls stayed in place so I used 5mm brass rod on those two pillars.
Ok, time to put the parts together... All the small black and white track spacers you see will now be removed. Time to add the track holders and start adjusting the levels... I started from the lowest level to set the slope, the problem is that I don't know what speed the ball will have when it arrives at the level... You can see on the picture above that I use cardboard parts to protect the base from falling balls. :) Also I still have to figure out the load and unload of the balls in the elevator.
Now loading and unloading works. :) It turns out that one of the hardest parts of the project was to adjust the levels of the tracks. It is very important that the balls are the same weight and size. And its very hard to lower the speed when it has accelerated. The amount of slope I used in the design is WAY to much and I had to lower the tracks considerably to even come close. This meant that I had to shorten the elevator as well. The balls are now rolling all the way, but the speed is a bit high. It works and all, but in my mind I imagined them to go slower. I will continue to adjust the levels for a while.
Here it is, the design and the real thing. :)
And some fancy shots... :)
You can watch a video of the sculpture in "action" here. It's a very dull and slow video. If you do not like RBS:es. This is nothing for you. This video was shot before the glass cover had arrived...
Total design time in Google SketchUp: About 100 hours.
Total building time: About 300 hours.
Total printing time: About 50 hours.
All printed parts are printed on a: RepRapPro Huxley (Beta) 3D-Printer.
There are six 16mm glass balls in total in the sculpture.
Only one ball at a time rolls on the track.
The motor turns 1 rpm, then it's geared down a bit more so one turn on the elevator takes about 5 mins and 32 secs.
The ride for the ball from start to end takes about 1 min and 30 secs.
This means that most of the time nothing happens except the elevator slowly pushing the balls upwards.
This was one of the key elements of the sculpture. It shall not disturb you, but when you watch it, you will be impressed. :)
You can find all the STL-files for all printed parts on Thingiverse.
Mark Bischof - Most beautiful and impressive rolling ball sculptures I have ever seen.
Eddie's Mind - Where Creativity and Engineering Meet.
