Electric Double Pendulum

note this project will be more of a log than a build guide.

anyway so this project started 4 weeks ago when I found out about a double pendulum I thought I might be cool to build one but I saw that most were very large. so I decided to design my own and to make it the second ever electric double pendulum!(more on that later)

ok so the physics are pretty simple the basis is when it has a large movement it is a chaotic, a chaotic system is one where the movements are random and unpredictable. this causes erratic and crazy motions such as in the image but with small movements it acts as a normal predictable pendulum (boring) now you can read more into the physics here: https://en.wikipedia.org/wiki/Double_pendulum. ok, so I have explained the physics behind a non-powered one but for an electric one I would need a way to add energy to the system without making it predictable in the end decided to move the whole pendulum with a servo, a servo is a precise motor. so by moving it back and forth like in the video it still stays random but now added energy from moving back and forth quickly. now like I said at the beginning this is not the first electric double pendulum from my knowledge one other person has built on the major downside to it is because it uses a piston it is very fast and does not show the effect that well.

because the design required many variables to be accounted for I designed it in fusion 360 though my main goal was to get the 3 arms designed right for the rest I just added a base and didn't bother to add in the servo. the main variables in the design where one the arm ratio 2 the weight ratio between the 2 moving arms and 3 the degrees of movement the servo that would move the pendulum. to calculate the arm length I got height I wanted them to be then divided it by 2 then added length to each up compared to the overlap they had, then for the main arm design I got the height I wanted for it and added space for the bearing. to calculate weight I just added small weights in the back to get a good amount (about 9g each). for the degrees of movement I started by moving my hand back and forth to get the right amount (after I built it) which I then measured with a protractor and after coding it to move those degrees that part was done.

the electronics were fairly simple I thought about using a transistor to control the servo but opted instead for my lap bench power supply and an Arduino UNO the wiring was just all grounds to ground lap bench positive pin to servo positive pin and servo signal pin to pin 11 on the Arduino UNO and the Arduino was powered by usb.

so for the final assemble I cut all the wood pieces out of poplar wood using a dremel. then I sanded and used a staining pen on them after that I used pcb standoffs, m4 screws and bolts, 2 bearings, a drill, and some superglue to attach the bearings into the wood and then the screws into the bearings with spacers in between the arms the for the final step I drilled some holes on the bottom and attached the servo to the pendulum then glued the servo to a block of wood. and the assembly was done!

so how did I think this project went well I think it went ok it was not my starting vision but it was a ton of fun and I learned a lot but now for the best part of it the long exposure images.

thanks for reading