Just a brief note to let you all know that Lisa, Steve Monahan, and I
finished welding the aluminum orb last night and brought it to the Box
Shop for testing. There, Erik, Lee, Jon and I got it running and put
it through it’s paces. I’m pleased to report the test was a success!
I am confident that the current design with 1/8″ 5052-H32 aluminum is
structurally sound and rolls acceptably smoothly.
Special thanks are due to Jack Schroll, Steve Monahan, and Germ
Travis, who went out of their way to help us out in our hour of need!
Otherwise, a couple modifications were made to try to improve steering
performance, based on the feedback from many people to make it the orb
easier to roll straight and avoid a high point at the equator.
One was to cut into the equator rings (annuli) to keep them from
sticking out further than the ribs. I think this is successful, and
its my intention to move forward with this design feature.
The other was to make a elliptical cutout on all the elements near the
equator so that there is a kind of flat spot in the middle to provide
a slight centering force. The consensus last night was that at 0.2
inches of the radius, this was too extreme a cut. This self centering
tendency resulted in a significant trade off with turning ability,
logically enough. My feeling is to move forward with a more subtle
cut; I will be experimenting with the geometry to see if there is any
way to make sense of deciding the optimal balance of self-centering
and steering capability.
And a little supplement from Lee
We put in a late night Wednesday night…
– The orbs look great :-)… like something made by NASA or a benevolent alien race come to destr^H^H^H^H greet us. Clear anodizing at the Tech Shop could keep them looking like that for a long time.
– they didn’t bend or buckle or nuffum :-) :-)
– they were designed to be a little flat at the equator to help stabilize them…. maybe they were too flat… we’re still thinking on that
– it’s pretty hard drive around smoothly. It sometimes rocks around uncontrollably…. solutions to that are forthcoming…
– some PID feedback loops have to be tweaked a little
– maybe the length of the steering motor throw has to be increased
– we didn’t try it on soft ground. Only in the shop.
That’s the most of it. I’m off to install the TIG welder :-)
Our latest toy arrive yesterday. It’s a Lincoln Electric Precision TIG 225. This will help us get the orbs together and enrich the Box Shop for years to come. After getting it installed in the Box Shop, Michael and I got some play-time (IE practice time) and all I have to say is “Weeeeee!”