One year ago today: June 27, 2013, alligator watching.
Five years ago today: June 27, 2009, the patio.
Ten years ago today: June 27, 2004 happy birthday,
National No-Call-List!
This is the project chosen by the Nova group last evening. I flinched at first due to my preference for vehicle-like robots, my dislike of anthropoidal robots, and my experience which says don’t start anything too complicated. And my experience vastly supersedes anyone else in the group. I took an hour and examined this robotic hand and have since concluded we can do it. Here are my observations.
If you look closely, starting from the fingertips, this hand can only contract under power. Why? Because of the limited number of control cables visible at the knuckles. Thusforth, there must be a spring mechanism to straighten the fingers out when tension on the cables is released. This spring would not have to be very strong.
That tension must come from wires in the forearm cavity, tugging on the cables which the literature says is fishing line, but obviously is not in this picture. That that implies four servos to “tug” the finger “tendons”. The fifth motor is likely that odd looking thumb cable. Inside the hand, it appear four more motors in two pairs, when seems overkill. You can’t stop them with your fingers like a spinning toy motor. How difficult is this project? Well, consider this. Here is the link to the Thingiverse blueprints where the author (he was not joking) says he had difficulty photographing the object because he had to hold the camera in one hand, work the cables with another, so he needed a third hand. Gee, can anyone help this guy? You know, give him a hand?
Hmmm, an email just arrived. It seems the next meeting has officially had its name changed to “Building a Humanoid Robot”. This Nova meetup is beginning to have our signature written all over it, Agt. M. Right now I see the challenge as the 3D printing of the hand. I count 19 “finger” joints and six palm plates. Fortunately, the hinges (metacarpophelangeal joints) are in collinear and the “knuckles” are all spaced evenly. The motion is limited to contraction and extension only, that is no flexion or abduction. The thumb appears to have a single position of opposition, perpendicular to the palm. Also, finger rotation (to curl the fingers inward to the palm) seems identical at each.
The challenge will not be the mechanics, so this project now seems more reasonable than first glance. Plainly, to make it do anything impressive other than squeezing, some adept Arduino programming is in order. If anyone wants a head start on that, contact me, and the time is now.
NOON
Instead, it requires a special disk which must be finalized before the files can be transferred, meaning they are use-once. And they cost $20(?) each. In other words, if you want your videos now, you lose any remaining free space on the disk. That alone instantly turns this camera into junk. The SD card insert is for still pictures only, that’s a super-duh! Panasonic, go jump in the lake.
Here’s my mockup from PVC pipe where I learned the difficulties of using cylinders of the same diameter. The other dude didn’t mention it, a step so difficult that I find that a strange thing to omit.
Further, no manner of bolts or screws made suitable joint pins, I finally resorted to using the super-hard slide rail from a surplus DVD player. This chromed bar ruined a hacksaw blade, but can be pushed snugly into a slightly smaller pilot hole and stay put, as you see here. The “finger” is self-straightening due to an internal rib made from the trimmed end of a large cable tie.
The joint shapes themselves were challenging, as the position of the hinge at dead center may not be the most efficient choice. The bottom photo shows how the joints finally come into contact and restrict the maximum amount of bend possible.
When I look at the slick design of the other robot hand, you can see why I have my doubts that the guy is telling the whole story. It is human nature some of us to only reveal the finished product, but in this case, major parts of the process are being glossed over. My joint here required three intense hours just to get the cutting angles right without weakening the contact points.
Later the club met up for a discussion of these finger-like joints. To make it work, we need one of three. Different diameter pipes, solid hemispherical interior joints, or exterior joints like on a bicycle chain. This is tough brain work for a Friday, so we went over to the Romanian Church for supper. But nobody said it was teen day, so we were the oldest guys in the room. And it was pizza and chicken. And pistachio ice cream. It was the hall behind the Church. Teens with no music, that’s new to me.
EVENING
You know that missing ink cartridge that got lost? When I rewired the stereo speakers, I found it. All over my hands, shirt, and second best pair of pants. This, folks, is the destiny of retirement, could go anywhere, but home alone on Friday getting printer ink all over my fingertips the day before the big gig of the month. Maybe I’ll go out for coffee, but not much else. It was another broiler.
Don’t knock it, I’ve stayed in side during many a blizzard and I’ll take the sunshine, thank you. I learned how to hang blankets over the doorways to heat only one room of the house when it was forty below, and now I do much the same to cool one room when it is a hundred above.
By mid-afternoon it is broiling, I can feel see the heat waves off the main road. They can see me too, I often fall asleep reading, which means the light is on, but it does not mean drop in to see me at 11:00AM at night.
And boy, did I get a nasty e-mail from, well, never mind who it is from, they don't know me. But I will say this to the party. I am fully aware the fact that to a deadbeat ignoramus who doesn’t know what truth sounds like, I suppose most everything anybody like me says must necessarily sound like hooey. You obviously have limited exposure to anything but your own kind and yes, the world is passing you by.
But no need to be so nasty just because you live in a hole with no exposure to productive people.
Come to think of it, if I met somebody like that in the places you go, I wouldn’t believe a word of it either.
ADDENDUM
Cancel the coffee. I drove to Dania Beach to get north of the light pollution on this moonless night, but found I could not take any readings. I left it too late and the horizon went dark on me. By the way, that is why almanacs (which I don’t have) list the hours of morning and evening twilight. Those are the only times you can shoot the brighter stars and still see the horizon. Since I have no almanac, I planned ahead wrong. Must I launch a crusade to find an Almanac?
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