Flag Force


#1

Is there any estimate about how much force it takes to move a flag.

I realize it varies depending on what part of the flag you hit but a range would be useful.


#2

Can you explain what you mean by force? What launcher are you using?


#3

He is using a flywheel


#4

I saw @tabor473 saying this in his ri3d Reveal…

Original Link

But I think you will have to adjust depending on friction etc.


#5

Hi there! The flags have quite a bit of resistance, but they can definitely be toggled with a decent launcher. During my testing, I’ve found the most important thing is actually the shot angle. A shot from right below the flags will just bounce off, but a shot from 4-6 feet back will easily flip the flags even if the shot has some arc to it. Good luck!


#6

I don’t have any to test. But the force will vary both based on how far out you hit the flag from its axis and at what angle you hit the flag, because it’s the torque that matters. How far off from center the hit is vertically wouldn’t matter ideally, but it probably will as well because of resulting in unwanted sheer.

However, I will suggest to you that you don’t really want to work with the force. The reason is that you then have to figure out how much force the balls cause on impact, which adds a whole extra layer of complexity. What will be a lot easier to work with will be the angular momentum of a striking ball. It still won’t be perfect, but more helpful. While theoretically that would still require the same sort of calculations if you come from the resistance end. But try coming from another side of things. Doing it experimentally, launch balls so they strike the flags nearly on center horizontally. Take video of the balls against a nearby background you can use for measuring. Using just a few frames before the collision, how fast is the ball traveling horizontally when it’s going the slowest and is successful? Once you have that, you’re set. The incoming angular momentum is then rmv, r being the distance from the axis to the flag’s center, m being the ball’s mass, and v being its speed. m isn’t going to vary, so we don’t care. r could be slightly lower, so go with a more worst-case scenario. An angle may well have to be dealt with. That leaves you with rmv=r_badmv_yourssin(ø), or rv=r_badv_yourssin(ø). Once you know what you consider your typical worst-case radius and striking angle (ø), you can calculate your needed striking speed. Noting the ball will slow down as it flies, you might try to go a little higher than this. But don’t go extreme with the bad radius and bad angle. Would you really ever shoot down the line of the wall the flags are on, for example? If you’re that far off target radially, would you consider it a miss instead of a slightly off hit? So be reasonable about these (again, video can help with ø) and you’ll know how fast you want to launch to not worry about it.


#7

You should also consider that the flags are very flexible, if you just clip the edges of the flags chances are the plastic will just flex and the flag won’t actually toggle.


#8

Yeah I’ve seen that in the reveals so far


#9

If you were to hit the middle of the flag, then in order to turn it the ball would have to be traveling at about 4 m/s. I know that’s not a force as in newtons, but at least it’s something


#10

You’re right, it’s not a force, but it’s really a lot better for everyone’s purposes. That’s extremely helpful. At the moment I’m assuming that’s the speed traveling normal to the flag’s face when striking the flag. Is that right?