I have not had a chance to test this outdoor properly yet - as it is still raining. But we did have 20 minutes break in the rain - long enough to take this picture:
This is our first version of a NXT Amphibious vehicle. We tried to make it so that it can crawl over rocks like the Packbot [iRobot] / LNE [Brian Davis] / SCAT [222Doc] and also can track through 3" of water by raising its head and NXT using the two side arms while moving. We also want to add some buoyancy in the middle so that it can float and use the arms to 'swim' through the water and when it reaches the water edge, start climbing walking with the flippers and when it reaches flat ground use the flippers and tracks to move really fast.
We also have plans to make it so that the long tail will be pivoted at multiple places so that the tracks move like a snake and will aid with the motion. But it is a bit hard to do that - as the tracks allow very little lateral bending and not designed to be flexible from side to side!
I will post the detailed instructions in NXTLog shortly. It has some really clever stuff to do with using the Differentials in a new way - driving three tracks with two motors.
The question is - will it really work outdoors in the mud / rain ? Can it really go over rocks and climb mountains?
While I wait for the rain to stop to test this out doors, tell us what you think?
Thanks Brian for the comments. I have posted some detailed pictures on NXTLog which shows the inner working in more detail.