Monthly Archives: February 2015

Build and test of the new design

Today I finished the new design for the body. I began to use iDraw for this project, and until now it has been a very positive aquaintance. I used to be a competent Illustrator user, but jumped of the Adobe wagon some years ago. iDraw fells very familiar and stay out off my way.

You can download the pattern here: FelixBodyPattern.svg

To test the dimensions and the range of movements, I cut the pieces from 4mm plywood using the pattern as a template, then put it all together using bolts and washers.The servos are fastened with 3mm. bolts and the knee with 2mm. Below you can se af video of the assembly process.

NodeBots & Johnny-Five

I run a bit out of steam while tinkering with the gaits. The write/compile/upload/test cycle on the Arduino took some of the fun out of it.  For the new leg I have to rewrite the IK and control to accommodate the new servo’s setup. So instead of doing this as Arduino sketches, I decided to give NodeBots (  and Johnny-Five ( a try.

This days most of my (professional) projects include NodeJS and Angular, so JavaScript is part of my “mindset”. If a have some spare time during the day I don’t need to “shift-gears” in order to write sketches.

Furthermore Johnny-Five have an Animation module ( that looks like a perfect fit for managing Felix’s walking cycles.

Felix second wind

Lately I have had some time to revisit Felix’s leg design. I wanted to experiment with a simplified version without linkages to increase movement precision. A positive side effect of this, is that by moving half the servos closer to ground I can rely on less powerful servos (HiTEC HS-422).

Another step to increase precision (and repeatability) is to move from an aluminium (hand made) based hardware to laser-cut acrylic. I’ll be posting SVG files of the design as I move along.

I don’t have a Laser Cutter at home, the leg on the picture was made with my scroll-saw to test the geometri and basic movement. Once I’m happy with it, I’ll borrow one at my local Fablab (