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 Robotics / NXT / 835
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Subject: 
A Better Robo-Arm With Mindstorms Old And New
Newsgroups: 
lugnet.robotics.nxt
Date: 
Mon, 30 Jul 2007 16:22:53 GMT
Viewed: 
22070 times
  
Hello everyone. Here is my better robo-arm. It's meant to be an improvement on
the "56-C" arm which is on the official NXT CD.

A movie of the BetterArm (I hope it works)...

http://profile.imageshack.us/user/patrickslego/videos/detail/#532/betterarmgh1.flv

Another view (click on Quick Pic)

http://patricks-lego.mysite.orange.co.uk/

What's wrong with the official Lego arm?

* It's unbalanced
* It's jerky
* The bevel gears slip
* The reaching motion is coupled to the slewing so the grabber changes height as
it slews
* The reaching motion is not horizontal anyway, which makes it useless for 2-D
searching

After I unpacked NXC and built a couple of designs, I got out my old Mindstorms
2.0 kit and put all the parts in the 2.0 box. So, my BetterArm needs parts from
one (1) "old" Mindstorms kit and one (1) "new" NXT kit.

It also needs a few M4 steel screw parts (50mm screws, nuts, washers and spring
washers).

Why build my BetterArm?

* It's balanced
* It's counterweighted
* The reaching motion is horizontal
* It's stiff and sturdy
* The reaching (or radius) motion is endstopped

So, it can do a 2-D search (as shown in the movie).

Photo-documentation for the construction starts here. NB, because of the way
Imageshack works, you have to go backwards from this, which is pic 89, to pic
2... If image seems washed out, try a refresh

http://profile.imageshack.us/user/patrickslego/images/detail/#98/ba088py1.jpg

NXC code to drive it (click on Code)...

http://patricks-lego.mysite.orange.co.uk/

I hope this is of interest. I am not sure all the links will work. If they
don't, please reply on this forum and I will try to find a better way.

Best wishes, Patrick



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