Introducing to you today, the Quadbeest, the next evolutionary step in the Strandbeest genealogy. It seemed to be about time for Strandbeests to evolve to take over the air, so I made it happen. Able to be controlled over a kilometre in the air, land (result not guaranteed) and walk serenely/lumber in any direction (taking advantages of the rudder of the quadcopter) to the final-destination. The Quadbeest truly adds new dimensional freedom to what previously has always been a land creature. And that was just unfair.
Quadcopter + Strandbeest = QuadBeest
Over a hundred 3D printed parts later this my dream has become a reality. I hope the creator of Strandbeest himself, Theodorus Gerardus Jozef Jansen, will be proud. To be fair though his creations are wind-powered whereas my creation creates a lot of wind so he may have qualms there. See below to see the Quadbeest fly and jump onto his website to get a great understanding of previous generations of Strandbeests and the Jansen’s linkage.
Here it is Walking and Here it is Flying (Albiet it Briefly!)
So here is the process I took to make the Quadbeest.
The overall feeling of this build was attempting to maintain methodical zen regarding the printing, post-processing, construction, refinement, piloting and repairing. If you dig linkages this is a project for you. I have truly put linkages on linkages on linkages. Then I even stacked the linkages.
The emotional rollercoaster of not knowing for sure if it will fly matched with the joy of seeing it absolutely pound the air into submission and ascend made this whole project worth it. As a note, Strandbeests are prone to breaking when quickly decelerated from speed to a standstill. Depending on how they are constructed and what broke it can require some invasive time-consuming surgery and reprinting of parts. This I learned after the maiden flight. Footage found here.
The contents of the Quadbeest project can be seen below.
- Parts Required for the Quadbeest
If you want to build your own Quadbeest or want to ask questions we are always available to answer questions and queries. Also, if you have ideas to add please let us know your thoughts!
Parts Required for the Quadbeest
Below is the part list used for the final design.
- 3D Printing Filament to produce Strandbeest Components (STL CAD files I used to create the Quadbeest can be found attached at the bottom)
- Zip-Ties
- Deans Connectors
- LiPo Batteries. 2C and 3C
- LiPo Battery Charger and Balancer
- Arduino UNO
- Pololu DC Motor
- DC Motor Controller
- Jumper Wires
- Powerful Quadcopter (I jive with Armattan and their lifetime warranty on their carbon fibre frames but so long as you can take a payload with your quadcopter you can build a Quadbeest in your own Makerverse)
- Spare Propellers
Tools Used
Below is a list of the tools I utilised to make this project a reality.
- 3D printer (Ultimaker S5 utilised)
- Sandpaper
- Grit
- Plyers
- Craft Knife
- Scalpel
- Soldering Iron
- Solder
- Heat Shrink tubing, multiple sizes
- Allen Keys
- Anatomical Precision Kelly Forceps Locking Tweezers Clamp (one of my oldest and most favourite tools, observe them in action on the right)
- Power Drill and Drill bits
- LiPo Charger
- Superglue x6
- Double-sided tape
- Metal Wire (Thin Diameter)
- Silicon Grease
Project Build
The project build will be separated into two major components the quadcopter and Strandbeest. This seems natural and is also the order in which I made them. Then I will talk about combining these two sections.
1. Starting off I would recommend more modern technology in regards to the quadcopter if you were going to build your own Quadbeest. For example with the advances in transmission technology, like Crossfire, you can get an amazing 30+km range.
My quadcopter required the carbon frame to be built up with mainly M3 screws and bolts and the motors to be screwed to it. Linked here is a YouTube video on doing exactly this for my CF 355 frame.
Whip out some soldering skills to connect the four motors each to their own ESC (electronic speed controller) then these ESC are all connected to the brainbox (in this case a vintage KK2.1.5 board). As this process was occurring all of them were strapped with zip ties on the frame and shrink wrapped. Part of the frame is an integrated power management board plate that gets soldered directly to the ESC components and then to the KK2.1.5 board. Then the Spektrum receiver was plugged into the KK2.1.5 board and attached to the frame. This was all the electronics and hardware connected except for the propellors and battery. The link here is a youtube video for the soldering process to build a very similar quadcopter doing exactly what I’m talking about. The Strandbeest is heavy duty so a serious amount of lift is needed. The four 8 inch propellers powered by 1800KV Armattan brushless T motors gave enough Oomph to spring the Quadbeest off the ground. God bless them. The LiPo battery for the flying is a 3S 3600 Lithium Polymer Battery.
Always take a safety check and a moment for some thoughtful consideration before ever attaching propellers to any quadcopter. Particularly when using Carbon Fibre Propellers you end up with a very mean razor blade lawnmower with no protection totally liable of flying into yourself or your closest family and friends. A quadcopter by itself can be quite a liability even before it has a Strandbeest attached to it.
Without the propellors installed I charged up my lipo and spent some time tinkering with the PID settings of the system. This can be all done directly on the KK2.1.5 Board. This was done with the consideration of it becoming a powerful flying work mule. Stability and maximum power going to the voltage were the two main criteria. In a previous life, the sole purpose of this quadcopter was to do loop-de-loops and sharp flips so the PID was set at an incredibly unstable twitchy amount so I was really happy I remember to alter this. Can also confirm this quadcopter in a previous life has done quad flips and crashed spectacularly many many times. It has even crashed straight onto concrete from all kinds of orientations. Quick nerd out PID (proportional–integral–derivative) is a control loop mechanism found in all kinds of industrial control systems from suspension to cruise control to your smart air-conditioner maintaining room temperature.
So with that little bit of tinkering with the PID controller, this quad becomes very capable of carrying the weight and a stable platform in the air. I then paired the KK2.1.5 board to my Spektrum Transmitter and flight was possible. So now its time to sort the Strandbeest. See below for an image of the quadcopter and it on top of the Strandbeest.
2. The largest part of the build is the Strandbeest. Now I have found some great parametric CAD files that I based my Strandbeest from and altered to best serve my purposes as the platform for the Quadcopter. The best that I found was made by Alex Matulich (link to the article on his website) who even has a write up on the actual creation of the Strandbeest legs and drive mechanism. Furthermore, there is a fantastic PDF step-by-step process of building up the linkages with his design. I would highly recommend printing the PDF out if you are using this Strandbeest design as it is so good for understanding. Alex rules with these Parametric files for the Strandbeest design. He also has the files on Thingiverse. Working with parametric files in CAD programs do require some finesse, if you remove certain sections from one linkage it can affect another seemingly unconnected linkage. So be careful when altering them. Parametric files differ from the more common direct modelling.
There ended up over 100+ individual parts to make these Strandbeests legs and power input so it was time to crack on and start printing. I 3D printed the leg linkages all 140% larger than the original CAD model. It was going to move a very large quadcopter after all.
This design by Alex however is not driven by any kind of motor. For that, I would need to create several other parts. These parts would attach the end of the leg mechanisms and act to get motion into the drive train. A large gear and a pinon were designed up in CAD to migrate the rotational force from a motor. These were printed from Nylon. Initially, it was a small brushless quadcopter motor but quickly it was realised that it spun too fast and did not have enough torque. A new faceplate was designed and CPE+ was the material chosen to create it. CPE+ has great material properties in terms of toughness. This faceplate would hold a Pololu DC motor and a similar design was used to attach it to the rest of the walking mechanism. Overall design aesthetics and consistency. Another faceplate was made for the other side (made from ABS) and the two faceplates acted to lay the quadcopter frame on top of the Strandbeest. See below for the CAD files of these.
Now I know the Strandbeest section looks all black but, in the end, five different filament materials were utilised. Ultimaker Nylon for the legs with flexible connectors and the gears. Ultimaker PLA and Tough PLA for the legs that are snap-fit into, Ultimaker ABS for one of the faceplates and Ultimaker CPE+ for the drive train. These materials all have different properties, so for situations where a little flexibility was desired Nylon was used and sections, where strength was essential CPE+, were used. Alex's Strandbeest design has a fantastic click into place system however it is crucial that the right materials are used for the purpose. For example, for sections that would not need to flex much, I used Tough PLA and PLA, for sections that did need to flex to click into place I used Nylon.
The printers used for this task was an Ultimaker S5. See below for an image of a sheet of linkages being printed from Nylon. I was having issues with adhesion when using Nylon so had resorted to using a raft. I would also use a gluestick to improve adhesion. A dialled in 3D printer will definitely save time particularly when it comes to post-processing as I did then need to remove all these parts from the sheet.
Once all the pieces were printed it became assembly time. It is important that the parts run smoothly across each other and each part locked in together correctly so it became necessary for me to make certain holes larger with a drill. This enabled less friction between the linkages (too much and the whole system becomes quite unstable, however). Also, silicon grease was used on all wearing components as this was determined to be the best way to minimise the force required for the mechanism to function. When building it take the time to constantly double-check that all the moving parts are free to move. Take a moment to appreciate that workbench below and see below for images from the Strandbeest leg assembly process. Once all connected and rotating freely and legs walking a small amount of super glue was used to connect the layers of legs together.
Electronics of the Strandbeest section involve a Pololu DC motor, with encoder, controlled by an Arduino UNO with a DC motor driver in between. Right here is a guide made by Aiden to do so without a Motor Driver and here is the process I used to do so with a motor driver. Crucially make sure to run the DC motor slowly and build up the speed only when you feel comfortable that the Strandbeest can take it without self-combusting. See below for the images of it all connected together.
Having set this all together it needed a faceplate to sit all comfy and nice which I designed in Fusion 360. The DC Pololu motor connects directly to the pinion gear which rotates the spur gear which is directly connected to the drive train of the Strandbeest see below for images of this. Also, note the faceplate connects directly to the Strandbeests X components. The Pololu motor is press-fit into the faceplate and the wiring is made tidy.
3. Combining the Strandbeest to the Quadcopter. The lithium polymer batteries act as a kind of suspension between the two systems (with all locked together with my motif of zip-ties) which is a bit red hot but so far the majority of landings have been okay. The zip ties and wires thread through the gaps in the quadcopter frame and then around the holes in the faceplates of the Strandbeest. Firmly held together but not choking the pieces together. Below you can see I have loosened some of the wires on the left and kept the wires on the right tight and how they should be. Oh and you noticed those extra LiPo batteries and wondering what the go. I personally think of them as ballast.
And with that, you will have a completed Quadbeest!
Acknowledgements
Massive thanks to Theo Jansen. He said ‘ The walls between art and engineering exist only in our minds’ and I dig it. See below for one of his creations. Big shout out to all the support I have from everyone around me. Another massive shout out to Alex Matulich for creating excellent CAD files for building a Strandbeest.
Where to Now
The next step is evaluating potential re-designs of the Quadbeest. More legs, thicker legs, legs stacks arranged in rows. All of these potential ideas are to improve the Quadbeest's capacity to travel across different surfaces. Instead of wearing parts perhaps a bunch of bearings (likely the ones in skateboards) could also be incorperated. As Jansen's sculptures are constantly being improved so will the Quadbeest. Personally, I feel like it would only be natural for it to breathe fire, I will need to put some high-temperature Polycarbonate filament into a 3D printer. Or maybe, Strandbeest to the moon! Until then, keep your eyes to the skies.
