Originally shared by Brandon Heller
https://www.youtube.com/watch?v=lnp1Pmki3lI&feature=autoshare
+1 for trying out something new! But i do have doubts about the mechanical stiffness of the construction, especially since you’re involving rubber bands. Can you deflect the effector by hand when the strings are fixed?
While the rubber bands make for a necessary evil at this point, I could see them replaced with line and counterweights (at 1/3 the effector weight) that’s a very interesting design! (Be warned, it probably won’t t work very well in zero-G. 
)
How about no rubber bands or counterweights? Use continuous lines instead. That’s what I thought it was at first glance.
@Ben_Malcheski i don’t think you’d be able to create a loop from the strings and springs that would stay a constant length.
If you can make the legs shorter, the slack has to go somewhere…I’m also thinking the skycams you see in football (and presumably other sports, I’m not a sports guy), seems to move rapidly, without a lot of shake…so the theories are sound.
I could also see rubber bands wearing out in time.
I was thinking more along the lines of making the currently “sprung” lines integrated with the motor driven lines. I’m not sure if the current geometry would allow for it as I’m guessing the spring lines have different speeds than the lower lines.
It’s possible you could use Springs and a block and tackle solution, I’d have to give it a little thought… The mechanics of elevators and garage doors are coming to mind.
If you can figure out a way to do continuous lines, let me know! I don’t think it’s possible. The rubber bands were from a first prototype and I’ve since purchased other springs that do better: surgical tubing, spring steel extension springs, and CF springs.
This design is on hold while I print GUS Red, but then I’d like to go back to it.
Can you create a closed loop using two spools linked together by gearing the two together so that when one spool unwinds, the second spool then winds in the slack at the same speed keeping the tension in the string…
Just a thought.
It looks really cool! I have a little question that how do you make sure the strings not interfering the object you’re printing?
This is a downside of the design; you need to leave some space around the envelope to avoid string interferences.
Very interesting design ! First we need to clear the build site below. Because printing pyramids is boring. Use position cables from above. then we need to push the hot head down from on top and stabilize the angle of the hot head. Perhaps a Gyroscope can keep the hot head vertical. We need some pressure from above(the ceiling) a weight would increase inertia so forget using raw mass. Perhaps some type of expanding spring from above pushing down on the hothead. The spring doubles as a conduit to feed the filament, perhaps the spring is anchored to some type of ceiling trolley to keep the spring vertical. voila, no more pyramids. The ceiling trolley for the spring is passively tracking the hot head or actively positioned by its own position cables.
I am thinking about a tensegrity design. the hot head pulled up by dynamic cables in tension from the sides and the hothead pushed down by a rod or spring or piston in compression from on top center.
Now it would be fun to mount the drive cables on rails in three corners of a room. then we can build really big things. With slight geometry change to a right triangle build space. Now half of any room becomes a delta bot.