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“A wise robot once said to me through Serial.println- that robots teach us about ourselves.”

Frog Feet Experiment

We have a weird idea for a new robot, one that has frog feet that spin! We’re not even sure if this will work. The main reason for making this robot is that it will just be cool.

First task is to create the frog feet. The idea of the feet is that there will be something rigid that will strike the ground when the motor spins it around. This piece will also extend upwards so that it can be mounted to the bot. There will be flexible balls on the toes to help grip, and webbing between them to keep the toes attached to the main foot body.

Here is the bottom piece of the mould:


Here is the foot bone:


The prints were fairly large, taking a long time to print them. The anticipation is crazy, because we have to wait for each of the pieces and also wait for the mould to set!


Here is how the mould turned out:


The foot is attached to some old print fails using hot glue. This then is attached onto the motor. The motor is mounted on a cardboard body for testing. Here it is moving!

This setup is using a motor from Pololu (can’t remember exactly which), and an Adafruit motor shield. In the process we burnt out one of the L293Ds. For some reason the voltage wasn’t working right from the Arduino, and also our multi-meter is broken, so applying 11.1V wasn’t the right idea. Oops. Later on the voltage from the Arduino worked fine- loose connection possibly.

Oh yeah, if you were tuned in to the castAR Kickstarter countdown video stream party, we Skyped in and showed this off! That was pretty cool. :)

There were some issues that needed to be fixed for the next re-design of the frog foot. The bone was too close to the edge of the flexible material. The balls on the feet are not exactly 3-dimensional, instead of extruded circles they should be spheres. There was too much excess material on the top of the foot.


Time to design try #2, with the fixes mentioned above.

Here is the bottom piece of the mould:


The foot bone doesn’t have the long ‘toes’:


Finally the prints are ready and it is time to mould it!


Here is the result:


The balls on the toes look nicer than imagined. The webbing worked out well. However, the bottom of the foot didn’t have enough material, so the bone is very close to the edge.


At this point we’re pretty much disappointed with this and the entire idea. Decided to give it another try anyway.

Now for designing try #3. This one will be simpler and smaller.

Here is what the bottom mould looks like:


Inside there is supposed to be little bones:


The ‘smaller’ aspect of this redesign didn’t exactly fare well. The result was an interesting print fail:


Instead of re-designing it all, we resized it 2x in ReplicatorG. Now this is try #3.5!

Here it is being moulded (blurry photo, hard to hold phone with messy fingers):


Here is the result:


It’s still not exactly as we imagined. It doesn’t bend or stay sturdy in the right places. Some things that did work out though was the bone size, the ratio of bone to toe width, the revolved ellipses instead of spheres. The webbing is thicker than it should be. The heel doesn’t have the bone popping out of it, that’s good news.

Some additional tinkering will be necessary to make the frog foot as envisioned. We want something that is flexible but also sturdy in areas so that it isn’t flopping around. Might give it a few tries more to see if we can make it.


Time to re-think and re-design for try #4.

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