View Full Version : Want to build a backhoe or a crane ARM

07-06-2011, 04:20 PM
I would like to build a backhoe robot arm. It could also be something like a crane, where it's not just a bucket at the end, but more like a claw, or a hand.

I have a question as to what parts I should use for the "joints." I have started down the path of using motors, with phidget motorControl boards, but I am realizing that I may want to use servos instead.

The goal is to have a robotic arm that can play and dig in a sandbox. If you can picture that.

Has anyone built something similiar? Do you have a link to something similar? Do you have suggestions on parts, like should I use servos, or can I get by with motors?

Thanks in advance for your input!
The Space Cowboy

07-06-2011, 10:51 PM
So a couple of questions before I think we can give you much help. Servos is probably the route you will end up going, but I am concerned that you are going to be pretty disappointed. The problem is, most of the hobby scale robot arms (kits and scratch built) don't have a very high payload capacity so if you want to "play in the sand" with it, you are looking at playing on a very small scale unless you want to build a very expensive arm.

You could go with linear servos which would increase your payload by a lot, but would also come at a cost of about $145 per joint by the time your done, which all said and done may end up on the relative low end...

I would also think you will need to be careful not to have sand bunging everything up.

Hope this helps


07-08-2011, 08:39 AM
here's a pic of one i made (http://forums.trossenrobotics.com/showthread.php?t=4902&highlight=quad) it took five Dynamixel AX-12A's and it worked great adn it was just attached with a few of the regular bioloid frame parts :happy:

07-14-2011, 10:30 AM
Hey darkback2, thanks for the link you sent. Looks very helpful to examine the mechanics of the arm.

I'm going to go through this and see what I come up with. My first stab is going to be with a motor / winch type of system and see how that pans out. It also seems that most backhoes in real live use some sort of pole-type actuator, where it extends and retracts.

Good point about the sand too. I will have to think about that.

07-14-2011, 11:57 AM
Real life backhoes use rams with hydrolics.


07-14-2011, 01:42 PM
"Rams." Yea, I guess that's what you would call it. A "ram actuator." Perhaps that is the right way to go long term. Where can I get one of these types of actuators?

Meccano Jay
08-01-2011, 11:50 PM
I have seen some amazing creations with motors. Do a little digging into the meccano shows and see some of the scale replicas they bring to life via motors and metal gears as well as pulley systems. Ive often added phidgets into meccano projects to control motion. I would think with motors you may want to utilize a few pots for positional report back to the program. As for framework i would suggest aluminum over the plastic bioloid pieces for digging in the sand. The metal will give a more authentic look also.

Just my 2 cents, might not be worth that ... lol

Meccano Jay
08-01-2011, 11:55 PM
Crane with claw