Six legged walker with strong joints!

http://www.instructables.com/id/Hexabot_Build_a_heavy_duty_six_legged_robot/

The above linked instructable is awesome. It's cool, and the joints it uses (holes drilled in box tube) will egg out very quickly and degrade with time.

So, I decided to beef it up, so mine wouldn't end up crippled. I followed the instructable pretty well, but used different motor mount configuration, used the wheelchair's motor controller, and made my eccentric drive plate out of steel (free) instead of aluminum.

The theory in my telescoping sleeve bearings is that there is strong steel in the middle (bolt), and less strong steel on the outside (pipe/box tube), with brass and grease inbetween. This brass/grease will decrease wear on the steel components, and take up the slop.

This is a work in progress, to be updated as progress comes along. 

Step 1 Measure your bolts.

Get a micrometer and measure your bolts. The issue here involving the micrometer is that often the threads are slightly wider than your bolt size, or slightly smaller. For instance, my 1/2 inch bolts have .495 or so diameter on the bolt, and .485 on the threads. this is all basically meaning "use 1/2 and pack with grease". The measureing of everything comes more important later.

Your top end bolts will probably be smaller, I used 3/8th up top, and 1/2 for main drive.

Comments

[r570sv]

I like!  I'm planning on sometime similar in size this summer.  Can't wait to see what you end up with.

Did you use the standard diminesisons for your plans or did you modify them?  To get the increasing the length of the legs makes the body waaaay to big for a standard sized garage. 

[seraphus]

 Hey... So I've been not updating this, because I've basically come to the conclusion that my design was fundamentally flawed. No matter what I do, the sleeve bearings are being consumed, my motors are mismatched (one side is much stronger), and it has a tendancy to shatter the cast urethane feet I made for it.

That being that, I'm storing it until fall, when I will participate in a robot show, and most likely, one of justin grey's robots will destroy, then burn my robot. 

[rpantaleo]

Hey, I just found your instructable today; awesome! Glad you're trying to improve the design, mine was built on limited time and budget (and a bit of inexperience). I definitely cut a few corners. 

Yeah, I wonder what's up with the sleeve bearings getting eaten up. The original hexabot maybe has about 10 hours of loaded operation on it, and it hasn't had any problems with things getting really worn out. There's more slop in the joints than when it was first built, but nothing too terrible. Only thing that immediately jumps to mind is an over-constraint problem. Maybe if the tube inserts in welded into the legs and linkages have some angular misalingment, combined with the tight fit of the brass sleeve, there could be excessive wear? Or maybe the brass sleeve is just too thin? This is a puzzling problem.

[r570sv]

Interesting about the motors.  Lots of people have used those in battlebots without issue (at least they look like NPC motors).  How are you controlling them? 

How much does this thing weigh?

[rimar2000]

Will continue?  I am anxious...

[seraphus]

 Yeah, I spend about 3 5 hour days a week working on this specific project. I've got a little more lathe work to do, so I might get some detailed pictures and details on that process. If not, it'll skip to Relay control!