Most of the time I just keep notes in a simple text editor on my computer — one file per prototype or experiment. I’ve ended up with hundreds of them, but it’s faster and more convenient than keeping a journal. It’s easy to scan through folders, find what I need, and add something quickly. I only record videos when I need to check something fast-moving in slow motion (240 fps on an iPhone works well). Sometimes I take a few photos before disassembling a prototype, just for my records.

@Bryan StClair With three masses it does work, but visually it seems to be of low efficiency, because the impulse amplitude is very low and the wheel axles must have extremely low friction for it to start moving. I also tested versions with two masses and with one, and the strongest impulses were in the version with a single mass. The reason the three-mass version did not work in your case is probably because your device is very heavy and the friction is too high, even if you are using rollers or balls as I saw in your videos. Even small surface irregularities act like a kind of “pit” that the wheel falls into, and with such low impulse amplitudes the device cannot get out of this “pit.” My device is very light, and for my wheels I used thin chrome-plated axles about 1 mm in diameter (well-lubricated), so the friction was minimized to the point where I could gently blow on the device and it would start moving. I observed this problem not only with the PIE replica, but also in dozens of other devices with small impulse amplitudes that I have built. So the issue is not the number of masses, but the reduction in motion amplitude as the number of masses increases. I think it would even be possible to make a version with four masses, but the amplitude would decrease even further, while the impulse frequency would increase. You once mentioned that you were able to move your car using the PIE device, but that it could move slowly and only when the tires were heavily overinflated. However, if you built an inertial drive with an amplitude of, for example, half a meter, your car would move very well even with normally inflated tires. Although perhaps I’m just stating things that are already obvious and trivial to you 🙂

@Bryan StClair Yes, I did not use a speed differential control in this version, but I have done that in other systems so I can try to make another version of the PIE with this modification. Thanks for the suggestion!