Mindstorms Questions

[dandexter]

I'm currently designing up my next MOC, I decided to combine to things I'v always wanted to make/use. First being the NXT Mindstorms, i'v have a fair bit of experience from years with the RCX 2.0, however I'v never used a NXT etc. So naturally I want to check a few things before I start designing to make sure my idea will work.

I'm designing a large Abrams M1 Battle Tank, i'v always wanted to make one. Basic dimensions will be 100cm long (123cm to end of gun barrel), 48 wide, 30cm high.

So to my questions. Clearly I will require several NXT to run all the motors (i'm thinking 8 to drive and 1 to operate the gun turret). Would it be possible to connect a sound sensor to each one, so I can give them a verbal command which each NXT hears then runs the program. So they'll all work together?

The Servo Motor, according to the lego website it can be programmed to produce different RPM's. Does this mean at lower RPM's its geared down hence higher torque? Or is it just drawing less power, hence less RPM?

Thanks

[SNIPE]

To change the RPM the 'voltage' or 'power' as it is written in the software is changed.

The motor has reduction gears inside of it which always spin with the output shaft of the motor or in this case the axle hole thing on the end.

other lego motors don't have or have different reduction gears some motors are much faster the motor in the nxt is quite slow but for a tank gun it is realistic speed wise.

The other motors are compatible with the NXT using the motor ports you might just need a converter cable for the different connector it requires.

Edited May 13, 2012 by SNIPE

[dandexter]

Thanks, I had a feeling it was only un-volted not geared down. However I thought I should check, just on the off chance.

[SNIPE]

Using gears changes the torque unless its a 1;1 ratio where they are the same size.

[dandexter]

Another question, not related to mindstorms, but is about my project. I'v never built anything with tracks before (only the Lego Bull Dozer) and I can't figure out how to make tracks/driving gears for the tracks that are big enough for this project. I want to use the same/similar method as the below model...

http://www.brickshelf.com/cgi-bin/gallery.cgi?i=4556132

I understand how the track is made, but I can't find any pictures or videos on the driving gear for the track. Can someone post pictures/videos or something to help me design/make one. I know the theory behind how it works, just not how to make it out of Lego yet.

[le60head]

Hey there!

I think the answer of your question lies within that picture:

If i understand correctly, the friction from the rubber tire is used to drive the "chains"

[dandexter]

Thank you very much, I hadn't noticed that picture before. It would be so much easier if I can just use that method.

[le60head]

You're welcome ;)

I wouldn't have thought about using a tire to drive chains, so i was surprised to see that too!