Adventures with Lego Mindstorms: NXT

Tuesday, February 20, 2007


Well, I was hoping to regale you all with tales of code churned out by the Megabyte, but allas.. it is not to be. There was code written and I was very excited to show you all, but when I came to work and inserted my USB drive, the entire thing was corrupted. Lost everything on it, including the code I had just created for this project, and the updated flowcharts as well. Not fun.

Well.. things happen and it looks like I will have a chance to improve on what I had written! In the mean time I have done some modifications on our Test Bed robot. Recently my LEGO Crane (8288) arrived and after completing the main model and then disassembling the entire thing I decided to give the wonderful tracks that come with the set a go. The results have been beyond my expectations! I would like to present to the world....

Mikey v3.0b!

As you can see the big addition is the treads. However, the chassis design is such that you could also use my previous skid steer configuration easily. Both setups connect to the chassis in the same fashion using a long 15 hole Lift arm with the drive gear towards the back. The only change necessary would be to move the drive gear so that it meshes with the motor gear forward of it's current position.

This version of Mikey addresses some issues I was having with the overall sturdiness of the model. The back end of the robot has always been uncomfortably loose for my liking, and it is very hard to stiffen it up. You can see in this version of Mikey that I have added some stiffening bars to the back and a frame that comes down between the motors giving the rear of the drive assembly a place to connect. The loose rear end of the robot was causing some shaking during turns converting energy that could be used for movement into vibration. Stiffing up the rear end of the model has helped out considerably.

I have completed a LDraw file of the basic chassis and will be posting it up just as soon as I learn how to do so. Hopefully I will be able to make up some step-by-step building instructions as well. There are some things with the LDraw file to keep in mind!
  • First off, I had some issues with connecting the treads to the chassis in MLCad. The entire drive assembly actually drops one hole from it's start position to give the gears room to mesh. In the LDraw file it appears that the rear axle connects one hole up from where it actually is supposed to go.
  • The returns on the treads can be in any configuration you would like. There is one set up on in the LDraw file and another you can see in the pictures. Just fool around until you get it to all fit together.
  • I have attached the weight from the crane set to the back of the chassis to give the robot some balance. The tSensor apparatus and the weight of the NXT cause the robot to be unbalance forward unless it is there. One solution would be to turn the NXT brick around so it faces the rear (like with Mike v2.0). It is a good solution if you don't have the weights, but would require a rethinking of the chassis.
With that in mind, comments? Suggestions? Rude remarks? All are welcome, post away!


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