geometry or pool forum?
Colin,
The pivot point is an artificial sticking point that has been created by a few people. Almost everyone reading this is aware of the basics of pivot points so most understand there is more to the story.
Lets ignore your field of expertise and move into mine for a minute and look at a variable pivot point. Consider a two foot roller fixed into position. Now add a 4"x4"x16' beam laying across the rounded surface of the roller. Where is the fixed pivot point when the beam is rocked across the roller. Damn! Look at that, a continuously variable pivot point. I thought we all knew there could only be one pivot point on a fixed line and I think we all agree that the beam is as much of a fixed line as the cue stick is. Of course rocking a cue stick over a drinking glass gives the same result. Seems that we can be wrong when we take theory out into the real world.
We may or may not be wrong concerning CTE pivoting, we have yet to get enough information to know. Bogging down over this geometry issue in a pool thread is off topic and a waste of time. Once the technique is understood I suspect all of the arguing over a fixed pivot point will turn out to have been a false trail. I have watched more than one design meeting get bogged down in a meaningless technical argument over how something worked that was totally fringe to the matter at hand. I think we are doing the same here.
I want to know how to make Ron V's system work. I already understand fixed and floating pivot points, years in mechanical design will do that for you.
Hu
Colin,
The pivot point is an artificial sticking point that has been created by a few people. Almost everyone reading this is aware of the basics of pivot points so most understand there is more to the story.
Lets ignore your field of expertise and move into mine for a minute and look at a variable pivot point. Consider a two foot roller fixed into position. Now add a 4"x4"x16' beam laying across the rounded surface of the roller. Where is the fixed pivot point when the beam is rocked across the roller. Damn! Look at that, a continuously variable pivot point. I thought we all knew there could only be one pivot point on a fixed line and I think we all agree that the beam is as much of a fixed line as the cue stick is. Of course rocking a cue stick over a drinking glass gives the same result. Seems that we can be wrong when we take theory out into the real world.
We may or may not be wrong concerning CTE pivoting, we have yet to get enough information to know. Bogging down over this geometry issue in a pool thread is off topic and a waste of time. Once the technique is understood I suspect all of the arguing over a fixed pivot point will turn out to have been a false trail. I have watched more than one design meeting get bogged down in a meaningless technical argument over how something worked that was totally fringe to the matter at hand. I think we are doing the same here.
I want to know how to make Ron V's system work. I already understand fixed and floating pivot points, years in mechanical design will do that for you.
Hu
Colin Colenso said:Chuck,
For those of us who have spent quite a bit of time studying the nature of the geometry of pivoting we all pretty much agree that if the bridge doesn't move then it is THE pivot point.
So until we get past that sticking point, whether there are any adjustments and how they are implemented is a bit like asking which way we are driving while still looking for the car keys.
In all the posts here, from those familiar with 90/90, I don't recall anyone mentioning adjustments. Seems Ron and others are pretty firm on the idea that all you need to do is align 90/90, then hip pivot to center of the cue. It was suggested that the system does not work well under 2 feet of separation.
I could suggest a table of adjustments that would make this work, but that is jumping in front of where most of the audience of this thread is at. Let's wait for the video to see if anyone can make these shots aligning 90/90 without moving the bridge for shots over 50 inches.
I suspect close up video will show us bridge movements which will be pretty close to exactly what amounts that PJ's math suggested. That would mean we are seeing a shifting pivot point.
If people agreed that a shifting pivot point was the mechanism, then we could suggest a systematic approach to how this pivot shift changes with shot distance, bridge length and pot angle. Personally I think it would be too complex to be particularly useful, but it might be used as a guide for 'feeling' new line to the center CB.
Hope my response is along the lines of your query.
Colin
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