Nice Bot, Do you have details/pictures of the building of the claw? Where did you get the gears? I’m interested in creating a claw too, and am debating some of the variables. For example, I have a toy claw.
The joints are pretty nice, they'll keep the fingers parallel with one another through the whole grip. I do like your solution too - especially the re-purposing printer-ink parts !
I found this thing in the garbage (who would have thrown it away!) and will begin dissecting it for interfacing with a servo.
That’s a really nice toy claw. I’ve got a couple toy claws I would like to use, but they don’t have that parallel jaw feature. I’ll have to look for a couple like that. I could really use that for Robot Leader (poor guy still has no hands!).
GRAB-E’s grabber is dead simple. I had a set of plastic gears lying around. I think I ordered them from the Electronic Goldmine. I just superglued the ink cartridge parts to the gears. One gear is mounted right where the servo horn goes and attached with a screw.
The second claw is a little tougher. I banged together a bracket from some scrap metal. It wraps around the servo, but has a little space near the top where the other claw is. A machine screw is inserted upwards through a hole in the bracket. Then I slide the bracket and screw assembly onto the servo. The other gear-claw assembly is mounted on the machine screw and attached with a small nut. I had to set the bracket carefully for the gears to mesh. It is only held on with hot glue.
Honestly, it was one of those temporary prototyping ideas that never got made into a nicer finished product. I may find that the gears slip and that I need to make a better bracket. Now that I have some experience with polymorph, I may refabricate the bracket for a cleaner, more precise result. That probably won’t happen unless the current one misbehaves. I’m lazy that way. ; j
I plan to. His programming right now is such complete crap as far as his claw is concerned. The challenge is just what I need to program him for a focused task.
Im currently building my first robot and im using a tamiya dual gearbox with the tracks as well. When mine arrived, one of the pinion gears was all mushed and I have the same problem as you with a gear that has a real wobble with it. When testing the gearbox and motors it would make a horrible noise. I have managed to silence it a bit with lube. The other side appears to be perfect (no wobbly gears) and doesnt make any horrible noise.
The Tamiya gear set it notoriously noisey. I don’t think my set wobbled when it was new, and if you received a mangled pinion gear as well, you should contact the seller for a replacement.
The set should come with lubrication, and the instruction manual indicates that you should lubricate the gears during assembly.
What is the servo on the front of GRAB-E in the video you posted. I have noticed that a number of people on this site add a swivel point to a servo opposite the horn to provide strength and prevent the torquing that might result from only attaching to one side of a wider leg or other object. I was wondering if servos come with either a swivel point built in opposite the axis or with the axis extending from both sides of the motor. You seem to be using such a servo in GRAB-E.
It is actually just a normal servo. I fabricated a simple bracket by bending some sheet metal around the body of the servo. The bracket runs along the top, back and front, with some overhang on each end in front of the servo. It is crudely hot glued in place.
I have heard of people who will open up their servo, and drill out a hole in the case opposite the axis of the servo horn. Then they use this to mount a shaft of some kind to support that back side of the servo.
I have indeed thought about some sort of feedback on the grabber. I may use a method similar to the one you describe, or use some conductive foam to make a tensile sensor.
