Blog.OhBowz

I put together the Ice Tube Clock kit today.

It was a great Xmas gift!  You can buy them HERE

This test tells me I need greater resolution and strength on my joints.
There is a lot of wobbling, and creaking going on.
If the AX-12 servos can be made continuous rotation, I could gear up.

I will post more progress on this, eventually.

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I have not forgotten about you.

Though I have been spending less time on my robot lately (I blame my new Cintiq), I have been slowly working towards a more stable design.  I want it to stand freely when the power is off.

It’s getting heavier on top, a lot of pressure is focused on one servos connection to the aluminum beam, I’m going to add support to certain areas so my custom brackets don’t snap.

When everything “seems” stable to me, I will begin programming the movements.

Excuse the mess

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M Q Schmidt

Check out the blog of figure drawing studies by the artists at Dreamworks Animation.

http://dreamworksdrawings.blogspot.com/

For those who are interested in where I found the parts to build my biped legs.

I’ve used a combination of Lynx Motion Servo Erector set parts, MicroRax aluminum beams, screws and washers from OSH, and the Dynamixel AX-12 servos.  There is a bit of improvising to get everything to fit together.  If you try to screw down the Servo Horn Bracket into the MicroRax Aluminum beam, there will be a small but significant gap, so a washer to fill that gap is necessary to keep everything tight and snug.  I also had to make a custom part to fit the servos to the aluminum beam.  Some may say that is overkill, and prefer to drill into the existing servo brackets. I found my approach more precise and neat, even though its more expensive.

Parts list:

Aluminum Interconnect / Servo Horn Bracket

Ball Bearing Hub Kit

Aluminum “C” Servo Bracket with Ball Bearings

Aluminum Robot Foot (Pair) (Brushed)

Shocks – 3.5″ (Pair)

Threaded Rod – 12″ x 4-40

Ball Link Set – 4-40

All MicroRax Parts

And I just found more here

Ax-12 Servos  (These make the project expensive)

And I’m using the Arbotix Micro Controller as the brain for now.  (More info on using this controller)

The shocks you see on the knees and ankles are there mostly for stability, the amount of resistance they offer will probably be an issue, and I might have to remove the spring itself.   I really just need some friction.

That’s the quick list of details, without getting into quantities.  My background is in Arts and Animation, that is my approach to this project.  I’m not thinking things through like an engineer would, which means I am probably making many errors, and this design is very inefficient.  I welcome all feedback on how I’m doing it wrong.  Take my advice with a grain of salt!

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More details in my next post!

Two Legs

If your ready for some good Sci-Fi, check out the Fighter King, now on Amazon

For your Kindle

If you want the whole saga, I recommend Vow to Sophia, Star Marine, Fighter Queen

This is the first step in making my own bipedal robot.  If I’m satisfied with this leg, I will build another and some hips.  I want this leg to operate using Inverse Kinematics .  I currently have no idea how to do this, so if anyone wants to give me some advice please email me! ohbowz@gmail.com

I am using a combination of the Lynxmotion servo erector set, and MicroRax to build the frame.  I chose to mix these two because I like the aesthetic achieved with MicroRax and the function that the Lynxmotion parts provided.

Dynamixel AX-12 servos are moving the thing, special parts were made to get these to fit the MicroRax.

The brain is an Arbotix Robot Controller, which is like an Arduino, with more beef.

AX-12 servo mounted to MicroRAX

I’ve been playing around with the Dynamixel AX-12 servo. It’s a nice little servo that has a variety of attachment brackets that allow you to build many cool things.  The problem is I want to mount the servo onto a frame built from MicroRAX. The brackets that come with the servo are too small for this, when it comes to screw hole size.

Original Bracket - No fit

Luckily we live in a day and age where a solution to this problem has an easy fix.  Since the cad file for these brackets are freely available online, I was able to remodel the screw holes to the size I want, then I sent it off to Shapeways.com where it will be fabricated in a 3D printer and shipped to me.

Shapeways Materials

I ordered it in three different materials to see which works the best.  The results are very satisfying, the bracket fits on the servo perfectly and mounts nice and tight on the MicroRAX beam.

Shapeways Bracket, and Original Bracket

Problem solved!  If anyone has a similar need, here are the resources.

Order the bracket at Shapeways.com

Dynamixel Servos

MircoRAX

OBJ File of Bracket  (Right Click and Save)

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