Bram Cohen ([info]bramcohen) wrote,
@ 2008-05-13 03:21:00
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Three-saw
I had an idea the other day. A see-saw has two seats, each of which is offset from the other one by 180 degrees. A more complicated linkage could create a three-saw which had three seats each of which was offset from the next by 120 degrees.

Why? Because.

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[info]theducks
2008-05-13 10:29 am UTC (link)
I'm not sure about a threesaw, but there was a park near my place with a four-saw when I was a kid. Same basic idea, instead of just one axis of travel, each seat has two (up/down, yaw left/right)

Edited at 2008-05-13 10:29 am UTC

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[info]bramcohen
2008-05-13 07:19 pm UTC (link)
What you describe has extra movement, but not extra seats, which is what should really define a four-saw, unless I understood incorrectly.

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[info]theducks
2008-05-13 11:48 pm UTC (link)
Yes, I think I neglected to mention that the platform was + shaped, with the pivot in the middle

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[info]bramcohen
2008-05-14 12:02 am UTC (link)
Neat! That's quite an elegant mechanism, although I can see how with a bunch of kids on it it would tend to move kind of haywire with no coherence. If the people on it were working in unison then the energy losses from the springs would be reasonably small, and the whole arrangement would look like a coin which had been spun and was in the process of winding down.

Adding a third see-saw to make it hexagonal would make it a lot less chaotic, but also require a lot more coordination to move at all.

Edited at 2008-05-14 12:03 am UTC

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[info]rolphus
2008-05-13 01:44 pm UTC (link)
The "more complicated linkage" you suggest is generally served by a strong spring in the four-saw. I can't see why that wouldn't work for the three-saw as well. Of course, I'm an idiot, so I'm probably missing something.

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[info]stigant
2008-05-13 05:18 pm UTC (link)
The last time I was on a foursaw, there was a lot of lateral jiggling back and forth but not much movement in the vertical direction other than jiggles as well. This is in contrast to a see-saw in which the movement is smooth and graceful as each person goes up and down. Their heights can be modeled by sine-waves which are 180 degrees out of phase with each other. Ideally (at least in my vision), on a 3-saw each person's height would be modeled by a sine wave which was 120 and 240 degrees out of phase with the other two, and the graceful up and down movement would be accompanied by minimal lateral movement. I don't think this can be accomplished with a strong spring, but perhaps it could be accomplished with some other linkage which constrained lateral motion, but allowed slight lateral rotation.

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[info]tobylane.pip.verisignlabs.com
2008-10-24 01:57 pm UTC (link)
I think the springs, under the three seats, should be on a rail.

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