IronGoober wrote on Jan 11
th, 2022 at 11:28am:
I think the main issue with going sideways on the pendulum is having a consistent brake. With a normal pendulum, the brake is gravity, so you should always get the same amount of swing for the same momentum transfer, no matter where the hit on the pendulum. But for a sideways pendulum, the dynamic friction of the pendulum rotation may change with differing speeds of rotation, so a hit on the near vs far edge may cause different amounts of rotation for the same momentum transfer (because a hit on the close edge will make it rotate faster than the far edge). Not to mention, even with using the "same" materials, the friction can be different and the local conditions can change friction (i.e. humidity and temperature).
But besides those points, and I emphasize this,
it is still a good idea and will be fun to try. I think that if the results are too close to call between separate people's shots, who cares? just shoot again.
There is definitely a way to make a normal pendulum with your same setup and mark how far it swung. You just have to have a collar that has a one-way catch that the pendulum will only move when it swings one direction, and the collar needs enough friction to stay in place. I haven't built one, but I also know that PVC is not the best choice for slinging targets. It can be brittle and doesn't survive impacts well.
This is from over a decade ago, but I don't think PVC has changed much.
https://youtu.be/fnyQI3pgN8Q?t=96 You make a good point, IronGoober. When built by the individuals, it might allow too much room for too many additional variables from the materials. If I can get a good prototype made and can work out a process to keep the costs down, then I could minimize that variance by using machined components and could produce them for those who would be interested (putting the cart before the horse a bit, but you get the idea).
I am liking what has been commented so far; the next revision will have a smaller disc (probably about 8" or 200 mm) on a much smaller frame to minimize the difference between shots placed on the outer edge of the target versus those places on the inner edge. I'll do the best I can to keep the center of mass as close to the axis of rotation as possible so that any hit has a better chance of generating several turns (the higher the turns, the easier it will be to determine differences in impact power; 8 full turns could be 64 points, 7-1/2 turns would be 60). More than likely, I'll include a bullseye (for aiming, not scoring) toward the other edge as well. I get paid this week too, so I may start building this guy and putting up some build and testing videos on YouTube within a week or two.