Has anyone tested a cell shooter with topspin instead of backspin

We are wondering what happens to a cell shot into the upper goal with topspin and don’t have a way to test it. We’re wondering if it will be more likely to bounce out than one with backspin. Also wondering why there have been no prototypes revealed of topspin shooters. Is it a bad idea for other reasons? We feel like we are missing something basic.

Just throw a ball at the wall with topspin, backspin, and no spin. You’ll see pretty quickly why you want backspin.


Homework: https://en.wikipedia.org/wiki/Magnus_effect

Backspin creates lift resulting in a straighter shot with a longer effective range, topspin creates negative lift resulting in a shorter range with more arc.


A@Ri3D did made a wheel over ball shooter.

In 2016 we did a wheel over ball shooter. It decently lead to balls “rolling” into the tower if they hit the lower edge. But it wasn’t too pronounced of an effect.


I think how it influences bounce might be more important.

That depends on where the shot is being made from. I do not disagree that bounce is important, but the target window is effectively bigger with a flatter shot trajectory, and backspin adds critical range for longer shots.

Packaging is also important here.

A backspin shooter has a higher release point in a given robot envelope than a topspin shooter, and higher than most implementations of a two-side-wheel shooter. A backspin shooter puts the shooter wheel/motor/flywheel lower in the robot than any other solution for a given release height.


We actually tried to throw the ball with top spin but it was a rather silly looking throw.

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The scientific replies have already been made, but think practically. The carnival game mindset should help you understand that a shot into the upper goal that doesn’t make it through the inner port is more likely to bounce out and not score with top spin than with back spin.

Another disadvantage that we (3322) found in prototyping is that topspin causes a significantly higher percentage of the balls to rebound completely out of the goal


I’m definitely advocating for backspin as the appropriate design choice in the vast majority of applications. Maximizing the horizontal width of your shot’s vertical “sweet spot” means more shots go in, fewer miss, and backspin helps with that as well as with whether or not the ball will bounce out of the goal.

I could see a hypothetical place for a topspin-shooter for a robot that scores in the high goal from the protected zone. I’ve no idea if this is a viable strategy in practice, but the idea is sound.

Our plan is to shoot from the close end of the trench (and back up to the far end if capability allows), and all of our analysis has pointed us toward backspin = good, topspin = bad.

What are you seeing that we’re not?

By “protected zone,” I mean the triangle right in front of the low goal.

Oh, sure. Ignore me. :slight_smile:

When demonstrating how spin impacts a ball (everytime we have a shooting game!), I use the same basic motion to throw it. Stand near the wall hold the ball with the fingers of both hands near my stomach, and use my fingers to apply spin while my arms apply forward motion. Works every time, and you can get plenty of spin to demonstrate how it works for bounce! Doesn’t do so well for demonstrating how spin impacts the projectile motion, but that’s another discussion all together :slight_smile:

We had a theoretical reason why we chose topspin, but sadly we really can’t speak with much authority here as we didn’t test both spins. I know team 3322 did some testing both ways, so you could reach out to them?

Could someone please explain backspin/topspin and how these effects are created.

We tried adding topspin to our double flywheel shooter with a range of 40ft. Without topspin, and some slight backspin we were making the shots at a fast rate, but they were bouncing out. We then added backspin (I believe 27% delta in speed between top and bottom with bottom going faster) and we were much more consistent in keeping shots in as well as straightening our trajectory. We then tried adding topspin just to see if it helped with keeping the balls in the upper goal. It ended up being pretty bad, the trajectory was extremely arced, and the initial launch angle was significantly increased. The arc was too steep to consistently hit the inner port, and it was much harder to get a shot in the upper goal in general. It was pretty fun to watch a ball launch high and suddenly sink to the floor though!

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Watch volleyball. There are two serves that are the most effective.

  • Topspin causes the ball to drop and a good topspin serve can drop sharply ad hit the floor mid-court as the backline players dive to try to get under it.

  • No spin causes a knuckle ball effect where the ball will weave unpredictably in the air. It tends to float more but it is the lateral movement that makes it diffcult for the other team to recieve and return.

Both of these effects are bad for shooting. Topspin will reduce your range and no spin will reduce your accuracy. Backspin adds range and produces a predictable stable arcing shot.

FTFY. I could see top spin being useful for a team that’s shooting from inside the TARGET ZONE, right up against the wall. The shot would be almost vertical, and the top spin could help arc it forward into the goal. Would need some testing to verify how useful it is, of course. Pretty much anything else, where you’re going more horizontal than vertical, backspin is the preferred option.

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