# How a live catch works (slo-mo)

I never really understood how live catches work, and I recently stumbled upon a great slo-mo video that sheds some light on that mystery (sorry if this has been posted before, I haven’t been very active lately).

The usual handwavy explanation is that somehow the flipper stopping at the exact moment it makes contact with the ball somehow “deadens the momentum”, which sounds like hogwash, because where does the energy go, and how is this different from the ball bouncing into an already stopped flipper.

Here’s how it actually seems to work, based on the video:

1. If a ball comes down to the flipper and you flip it away, the flipper makes contact with the ball not once but twice: On first contact, the ball presses the flipper down a bit, thus losing contact. At this point the ball has lost a lot of its momentum and may even stand still on the playfield. Its kinetic energy has gone into pressing the flipper down against an electromagnetic force moving it up. After that energy has been absorbed, the flipper continues to go up and hits the now more or less motionless ball a second time, thus flipping it away.
2. If this happens near the end of the flipper movement, when the second contact happens the flipper isn’t moving up anymore, because it doesn’t go that far.
3. Something that may or may not play a big part in this is the fact that on each flip the rubber completely separates from the flipper, and on a live catch sort of envelops the bottom part of the ball.

If someone’s feeling adventurous and wants to help science, you could glue the rubber to a flipper and tell me whether live catches still work.

Here’s the video, the flipper stuff starts about 10 minutes in: https://www.youtube.com/watch?v=Tmg5WOvPKpU

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To quote Mr. Spock, “fascinating.”

The “failed” live catch looks a bit like a semi-loop pass.

Interesting how the rubber motion was all up-flipper from the point of ball impact in the first one, then split about 70-30 up-flipper and tip-ward in the second one. Dissipation energy direction depends on proximity to the flipper tip.

There’s a chance that if you glued the rubber to the flipper surface, the flipper plastic would break after a significant amount of play since the cushioning effect would be greatly reduced.

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I get that there are a lot of complicated factors involved, but isn’t the “handwavy explanation” essentially a simplified explanation of what is happening though? It does appear that the energy from the flipper (and everything involved) IS cancelling out the energy of the ball to bring it to a stop.

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Well, yes, otherwise it wouldn’t work, and we know that it does work. Maybe I didn’t say that right, my point was just that I’ve never heard a good explanation of how exactly that momentum is canceled. Could be I was just asking the wrong people, but until watching that video I didn’t realize how much give an upwards moving flipper actually has, so it’s almost a little bit like a drop catch.

So, yeah, saying the flipper somehow cancels the ball’s momentum is observably accurate, but at least for me not very satisfactory. I would never have imagined either the huge rubber movement or the fact that a flip against an oncoming ball always hits it twice.

I’d also love to see a slo-mo of a ball hitting an already extended flipper to figure out the difference to a live catch—does the flipper have less give in that state or is it because of the missing rubber movement? Does it also push down the flipper and then bounces away only after getting hit a second time by the flipper moving back up?

Yeah, I’d love to see a super slo-mo video of pretty much every way the flipper and ball interact: dead bounce, drop catch, shooting an incoming ball, shooting from a trapped ball, etc.

I’m also curious if a black flipper rubber pulls away from the flipper in a similar way as a red one? Or how non-rubber (ie. silicone and others) flipper rings react.

Now I just need to start a GoFundme to buy one of those super expensive cameras!

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That lens looks like it costs more than my house. Haha

now i know how a replay knocker works

I have always assumed the transition to hold power was in play in the livecatch. Does disabling the EOS (on era just used EOS for this purpose) impact the ability to perform the livecatch.

i have aluminum flipper bats on my STTNG, and i’ve noticed i cannot live-catch on it. I’m not sure if it’s the extra rigidity or the higher mass, but it’s the only game in my collection i can’t live-catch on. (i also have super bands on it, but i doubt that’s the reason)

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Modern games don’t use the EOS to transition between strong and hold, it is all timing based. The EOS is used to refire is the flipper is pushed down.

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It is used for refiring, but starting with later versions of LOTR, whitestar absolutely used it for transitioning. JJP games use it for transitioning too. Pretty sure SAM did/does also.

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