Introduction: Crab Bot, Sidestepping Robot

Ok, the title might be a little deceiving, the robot does not actually have claws or does it walk sideways.
But this robot is designed to turn on a dime and be able to move sideways apart from the usual four wheel powered platforms maneuvering.

For this ible i will be assuming that you are familiar with Lego NXT sets and i am just sharing with you what i have learned in making this robot. Mainly some pictures of the mechanisms i use, guidelines and tips

The objective of this project was to build a robot that has as many degrees of freedom as possible on the floor with the minimal amount of motors and NXT(s) used.
You could of cause get better results with omni wheels like mecanum wheels. but this is what i have. 

Step 1: First Up, Some Videos

Just a video of it in action


A little narration to show you how the controls are linked to the robot
 


And the underside

Step 2: Powering Your Wheels

Basically you need the turntable for this to allow your wheels to swivel while having your motors fixed
the pictures below will show a break down of the assemble

It is VERY important that nothing moves except the gears. This is because your gears will be subjected to very high torque (by NXT standards) and if any of the supports come loose, the gears will slip and it will fail.

the gears i used are not very conventional looking and these gears provide good contact as well as smooth power transmission.
the second third gear was used to reverse the direction of the wheels so that the wheels spin in the direction that will not oppose the swiveling action, its a bit hard to explain but you will get what i mean when you try it out

Step 3: Powering the Swivel

In trying to keep to my plan of having 1 NXT control one side of the robot, I placed the swivel motor in the middle of the robot and use gears to transmit that torque all the way to both ends
the key here is to have the gears turn the turntable

Step 4: The 3 Swivel Angles

Here you can clearly see the 3 different angles the wheels can be swiveled to.
For a sample of the programming i used, send me a PM. (i used NXT-G)

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