Differential Drive, Servo, RC lol what?

[Janizary]

Hi, I am planning to make my first robot with 4 servos and 4 wheels obviously. I plan to have differential drive and this sumo bot is explicitly RC ONLY no microcontrollers or any of the such but it leads me to the question how can I have differential drive with this kind of robot. Any type of help will be appreciated.

[VegaObscura]

Do your rear wheels have to have servos attached to them?  Its a lot easier if you put servos on only your front two wheels, and use swivel castors as your rear wheels.

[Janizary]

Do your rear wheels have to have servos attached to them?  Its a lot easier if you put servos on only your front two wheels, and use swivel castors as your rear wheels.

I could do that as I did not actually construct the robot yet

[VegaObscura]

Well then it should be extremely easy.  Just attach 2 servos to your RC receiver and put wheels on them.  When you send the command for the left wheel to go forward and the right wheel to go backward, you get a right turn.  Same goes for left turns.  Just remember the close your servos are mounted to the front of the body, the more you will be swinging the back around.  If you want tight turns, mount your servos closer to the center.  If you aren't worried about getting the back end caught on walls our out of the ring when turning, mounting them towards the front will help with stability.

[Janizary]

Thanks for your help, if anyone else has any suggestions/help please do tell

[Conscripted]

Four wheel will give you more pushing power. You could use a cable like this one http://www.e-clec-tech.com/seyspca.html. Then you can run two servos on the left side of your vehicle and two servos on the right. With that cable two servos get the same commands.  Remember you can only push as hard as your wheels have traction so put some consideration into getting the best wheel possible.

If you don't want to use servos you can use something like this http://www.dimensionengineering.com/Sabertooth2X5RC.htm. It will allow you to use regular motors and still control it with the RC radio. A nice bonus is the mixing that allows you to drive the robot from one stick.

Conscripted.