This project is a collaboration between Victor Leung, Tobias Klein and Jane Prophet. This is one of the exhibit in the Blood Exhibition in The Science Gallery Melbourne in 2017. Official project description written by Tobias and Jane:
Blood Work is a biologically inspired kinetic sculpture. A glass sculpture, filled with blue and red liquids, is suspended in a two axis gimbal. The organic glass sculpture symbolizes the closed cardiovascular systems of living things. Blue and red liquids represent copper-rich and iron-rich blood.
The outer gimbal ring is suspended from the ceiling and connected to a motor fixed to the floor. A timing belt mechanism transmits the motion to the outer ring which in turn tumbles the freely-rotating inner ring and the suspended sculpture.
Victor designed and constructed the delicate mechanical parts of the sculpture, the suspension details, the electronics and the motor assembly. The glass sculpture is made by Tobias Klein and Jane Prophet.
You get the idea. Tobias and Jane made a cool looking glass sculpture and I made the frame that holds it up and spins it around. My part is to suspend this sculpture in mid-air and provide some mechanical energy to spin the sculpture.
Now, before we get into the specifics, let me declare that this is not a 2 DOF mechanized gumball. A true 2 DOF gumball is awesome and I’m sure someday I’ll get to make one. Here, we have two circular frame, the sculpture is attached with metal cables to the inner ring, that ring is pivoting freely within the outer ring. The outer ring is suspended with two hangers with bearings, above and below the ring.
The top hanger’s bearings are free to rotate, but the bottom hanger is driven by a belt. That belt is driven by a motor assembly on the ground. Below is the motorized hanger: You can see the thick belt that goes to the ground. And two smaller belts that transfer motions to the bearings. The outer circular frame has a T shaped profile and the bearings ride on that edge.
Most of my previous works are made with planar cut metal plates but this time the complex profile made it rather difficult. This is the first time I had to contact a CNC milling fabricator to produce this piece. My research assistant Wang Xiao Tong helped me a lot in sourcing the right manufacturer on TaoBao and producing drawings for fabrication.
One major screw-up is our lack of experience in communicating the tolerance requirements to the fabricator. They did most of the guess work correctly, except the mini shafts are too tight to fit the bearings. Those were re-made. Below are some of the parts during test assembly and before anodized.
I also detailed the connections that goes with the crimped metal cables so that it hides within the thickness of the inner frame. I later realized this detail is totally wrong and insecure and is prone to loosening due to vibrations. I relied on the tension of the cable to tension the bolts, which is very unreliable. (Good lesson for myself)
Final assembly with the anodization and black dye. So many miniature bearings were used in this hanger, luckily they are cheap in China.
You can see the assembled hinge between the two rings. Inside the packing, there is a ball thrust bearing and a deep grove ball bearing. This is also the first time I use a thrust bearing, despite it being very very small.
Rubber O-Rings were used as a complaint bearing surface between the hanger bearings and the T-profile ring. It works out rather fine.
The motor assembly is highly compact. The stepper motor, driver, power supply and an Arduino Micro all housed within a aluminium tube frame. Exposing only the hole for the belt to come up.
I am pretty proud of the compactness of the design, although no one actually see the guts of it. (That’s why I had to put an image of it here) I had to discard the casing of the stepper driver and re-solder the plugs to face up for it to fit. I fitted a mini fan that I found in Huaqiangbei for cooling.
This was a rather fun project for me and the feedback turns out the be rather positive.