Elevators

[mr.engineering]

hi guys...can anyone help me with my robot,i need to have an arm that lifts objects up and down
but i thought to make it like a real elevator,can anyone help me with that,tell me about types i can use,what circuits do i need,give a link to read about it,any type of help

 

[dknguyen]

You mean you want want an crane rather than an arm? A crane is good if it's just lifting stuff up and down and moving it side to side because then you need to fight neither the lever action caused by the load at the end of the arm nor the lever action caused by the weight of the arm itself. You can jsut use cables wound around pulleys with very small radii which lets you reduce the lever arm and put out lots of force.

For a crane you need three motors- the pan motor to rotate the base of the crane, a crank motor to wind the cable, and a motor to open and close of the claw at the end of the crane's cable. Just look at the giant tower cranes used in construction sites. The mechanics aren't overly complicated and the motor circuitry is fairly basic. You need limited rotation servo motors (one for the claw, and one for the base). The crank motor needs to be continuous rotation to wind up all the cable but you need to be able to stop it and lock it into position so a stepper motor is probably good for that.

I suppose if you wanted to be able to move the hanging point towards and away fromt he base's center of rotation you would need a 4rth motor and a pulley or belt system of some kind.
https://science.howstuffworks.com/tower-crane.htm

It's pretty hard to find articles on the mechanics of cranes I found. Sorry.

You might want to some tension cables that travel away from the front of crane and bolt to the back of the robot to provide structural support for the crane when the load pulls the crane down-forwards. It would let you make the crane lighter than if you bulked up the rigidy of the structure to hold itself up. You'd probably stick the crank motor at the base of the crane and use a pulley on the crane's elbow to route the cable up and to the end of the crane. I think it's simpler if you do it like this than if you made it like an elevator. That would involve sticking the crank motor on the claw or at the tip of the crane.