As some of you know: One potentially deadly problem that skateboards have is called “death wobble” (or speed wobble / tank slapper / etc.). It is a phenomenon that only occurs when a given riding speed has been reached where riding vibrations resonate with the skateboard’s natural frequency. When resonation occurs these vibrations will produce forces on the skateboard which will make it wobble.
When this occurs your body will try to correct these wobbles instinctively, but it will inevitably overcorrect the wobbles making matters only worse. The usual thing to do is to not panic and stiffen up your ankles while concentrating on your movement and looking in front of you.
On an electric skateboard you might try to break but you might lose your balance, in that case you just have to let yourself coast while doing the above. You also won’t have to concentrate on the brake that way.
There are a few ways to get around death wobble such as tightening your trucks or having them at an angle. What this effectively does is it changes the skateboard system’s natural frequency. Death wobble will stop occuring at the speed you were riding at before but it will occur at a different, higher speed. At a higher speed the vibrations will have a higher frequency (= more vibrations), the wobble will be faster and thus will be harder to correct. The skateboard system behaves much like a damped oscillator. When a force is applied it will start oscillating (= wobbling) like a harmonic oscillator and will not stop unless a counteracting force is applied. The counteracting force by default is your body/ankles and the friction caused by tight trucks.
However, you can only tighten up your trucks so much and tightening them will make turning harder. This is where the implementation of an adjustable steering damper becomes interesting.
This is my implementation of a steering damper that can be bought on AliExpress. It cost me €29.29 and even though it’s cheap it’s well made in my opinion. You can find it in all sorts of funky colors. It also has a knob to adjust the damping force. It’s all CNC and the knob is clicky, it feels nice in general.
Without this upgrade wobble would start occurring in my build around the 25 km/h mark. Unless I tightened the trucks of course. The damper has been mounted in such a way that the adjustment knob is accessible whire riding. When I want to go 40 km/h I just turn the knob and off I go.
A possible upgrade would be attaching a servo motor to the knob and controlling the servo motor with a custom app with the VESC. That way the ERPM could be interfaced to the servo motor and in turn the damper could be adjusted without human intervention while riding. But I haven’t had the need to do that as I am not THAT lazy.