Not a physicist, so can’t explain it like you’re five – sorry.
The best I can do is that it seems to be a factor of geometry (front head angle, rake, and trail in particular – although no doubt length spindle to spindle, swingarm length, etc. play into it), the weight of the bike, the the weight distribution / centre of gravity of the bike, the speed, and the acceleration or deceleration it’s undergoing. It’s also worth understanding the idea of counter steering, which in itself is a product of many of the above factors, and I believe contributes greatly to what you describe. (How hard someone grips the bars can even contribute!)
Generally a steeper head angle is twitchier, and this can be mitigated with a steering damper, but that won’t completely solve a tankslapper if it arises.
The best I can offer is that all of the factors above have a complex relationship, and the right (or wrong) mixture can likely set up a harmonic resonance within the steering. I don’t have mathematical proof, however – and I don’t know whether anyone has bothered to find any.
Not a physicist, so can’t explain it like you’re five – sorry.
The best I can do is that it seems to be a factor of geometry (front head angle, rake, and trail in particular – although no doubt length spindle to spindle, swingarm length, etc. play into it), the weight of the bike, the the weight distribution / centre of gravity of the bike, the speed, and the acceleration or deceleration it’s undergoing. It’s also worth understanding the idea of counter steering, which in itself is a product of many of the above factors, and I believe contributes greatly to what you describe. (How hard someone grips the bars can even contribute!)
Generally a steeper head angle is twitchier, and this can be mitigated with a steering damper, but that won’t completely solve a tankslapper if it arises.
The best I can offer is that all of the factors above have a complex relationship, and the right (or wrong) mixture can likely set up a harmonic resonance within the steering. I don’t have mathematical proof, however – and I don’t know whether anyone has bothered to find any.