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Australia
Asked — Edited

Robot Arms And Hands - Construction Ideas Wanted

Our robot "Bob" is becoming demanding. Now he wants to not just move his arms up and down but be able to grab things. We've been experimenting and searching the internet for ideas but keep getting the large clunky, sit on desk, rotational arm clones. It appears in this area innovation has almost dried up. If anyone has anything that can be not just be an arm on a desk but part of a robot - please let us know. Simple is best. I'm trying things with just 2 servos and parts of plastic bottles and household junk but nothing worth showing just yet.

Spain
#2  
Hazbot : In my first robot ROBOT
arms mg995 servos work with 15kg of force, the arm measures 30cm long, and can lift objects at most 150 grams in weight (weight of an apple), to give you an idea of ??the strength and measures that a servo can handle 15kg. The servo is cheap and is in abay
www.ebay.es/itm/2-x-MG995-Hi-Speed-Torque-Metal-Gear-RC-Servo-Horns-/170509088807?pt=FR_YO_Jeux_RadioComRobots_VehiculesRadiocommandes&hash=item27b3223827

I have heard that in Australia use the metric system, if not so correct me please. I also think using bottles trimmed to arms but to do a cover of what is real or arm skeleton, well painted and tastefully chosen can give a pleasing result. regards
Australia
#4  
"Bob has arms and claws but now he's having seiziers !!!!

Ok, Rgordon and R2D2 - weight seems to be a common problem - for this I've used an upside down J design where counterweight can be used opposite ends to balance the weight of the claw (metal) .
I've begun with a servo for shoulder (no elbow) with the arm extending to the claw - again, no elbow.

It begins to work fine but after scripting a few grabs, the robot gets the jitters, almost like having a seizier - then he starts moving and twitching like he has a life of his own - any ideas guys...?
Australia
#5  
Added a pc fan above the board (thanks for the tip Richie) no brownouts so far and Bob seems to be behaving as per this video
#6  
Here is the arm design I have done up for my B9. Maybe it can give you some ideas.
Spain
#7  
Hazbot: very good balances at the shoulders to the weight of the clamp, great!
and bret.tallent good job!
Australia
#8  
Hey Bret, I really like the application of servos on those joints - simple and effective. I might have a go at something like that. Yes R2D2, I had to counter the weight of those metal claws and decided to avoid springs and use a simple counterweight (old plastic wheels of an RC Car). I'm getting stronger servos for the arms and will have a go at adding servos for wrist turning so Bob can grasp both vertically and horizontally.
Spain
#9  
Hazbot: you could replace the wheels of the counterweight by a servo for rotation of the wrist with a carbon fiber rod (light and strong) to transmit the rotation of the wrist, so you would have a similar weight in the counterweight with more movement. It's an idea, I have mounted the servo gripper opening in the shoulder so that acts of contapeso.:)
Australia
#11  
R2D2 - That's a fantastic idea and I will use it... You guys have so much great ideas and info - Now I'm still hanging for that Tank base for his treads to get around... Should arrive soon. Thanks again..