Now that I have a bunch of the mk2 servos set and ready to go, a new leg design, a new power distribution board to power them, and a raspberry pi3 hat to communicate with them, I built a new quadruped!  I’m calling this the mjbots quad A1, since basically everything is upgraded.

After I initially assembled the new legs onto the chassis, I realized I had the geometry slightly off and there was some interference through part of the shoulder rotation.  I made up new printed parts and replaced everything in front of the camera.  Thus, watch some high speed robot surgery:

To build a second demonstration quadruped and to generate some development kits, I’ve built up a set of 20 of the mk2 servo.  The production process is working out fairly well, in fact slightly better than I had predicted for overall cycle time.  The servos so far are coming out great, moving smoothly with full power.

I’m planning on building up a set of mk2 servos to test them on a quadruped and make some development kits.  As of now, I’ve got all the materials in house for the build and many things partially assembled!

As mentioned previously, I’m releasing moteus controller development kits to a few lucky beta testers.  Building these wasn’t too hard, but was my first foray into low-volume production for someone who wasn’t myself.  Here are a few pictures of the build:

While gearing up to make some dev-kits followed by a pre-production run of the moteus servo mk2, I recently received a bunch of frameless rotors and stators.

As with the other custom items, I’ve got some spares of these for sale at shop.mjbots.com if you’re building along with me!  [UPDATE no longer!]

Now it’s time to start building some servos!

Now that I have at least one functioning version of each of the pieces made for the moteus servo mk2 (planet input, outer housing, front housing, and back housing), I integrated all of them together into a functional prototype.

Some time ago I put in orders for all the long lead time items on a second version of the moteus servo.  This is primarily aimed at improving the manufacturability and reliability, along with some minor performance improvements.  I’ve now got at least samples of all the long lead time parts in house!

In the last post in this series, I conducted a fit test on the new chassis.  After my ignominious belly-flop, I now had a more urgent need to complete the switch.

The chassis cracked in the corner, completely separating.  Doing anything more with this chassis was likely to result in many more things breaking very quickly.

Build process

So, here are the photos as I put everything together.

The next step in (re-)building the quadruped with a full rotation leg was getting all the motors ready.  I had to first install reinforcing rings on 6 of the motors:

Then, I needed to lengthen the power leads on 3 of the motors to serve as the lower leg joint.

To switch to the full rotation gear design, I needed to get all my gearbox motors, some bearings, and a lot of other bits and pieces disassembled and ready for re-use.

Taking everything apart took a surprising amount of time, nearly a full day.  Each leg resulted in quite a collection of fasteners.  Seeing them all in one place made me realize how complex this has become!