Pleat Swing Physics?

[tyger]

Anyway, I still think the movement of the pleats has a lot to do with the slight springy-ness of the fabric.

You must be correct. If the fabric were infinitely not springy (therefore, totally rigid), wouldn't swing be affected? Likewise, if the fabric were infinitely springy (therefore, totally 'plastic', not elastic), wouldn't swing be affected?

[george7]

I'm sorry to say that it is not that simple (though it may be very close). The problem is that each pleat is coupled to another on each side. What you will need to do is find (one of) the natural frequencies to find maximum swing. This will depend on the number of pleats. Also it will depend on the size of your seat. Because your curvature will ensure that they are not swinging in the same direction. That is, they will want to swing left & right in back as you look at it straight on, but they will want to swing back & forth on the sides as you look at it straight on (albeit a much smaller swing). I imagine that things such as the weight of the wool will not matter much if you can make a generality.

I think I just found something to procrastinate with today.

Connecting the pleats and assuming that they swing in different directions doesn't change the resonance, just the dampening. The period of a pendulum tied to another pendulum of equal length will result in a system of pendulums with the same frequency. If you weave them together, they'll dampen each other, but it won't change the frequency they prefer.

[Bugbear]

I haven't gotten back to working on the acrylic kilt, I was working on the wool StillWater, but I did see some promising results with a strip of light weight hair canvas interfacing the pleats from the inside part of the fold. Just a strip of hair canvas, slightly wider than the pleat reviel, hanging there and attached at the top where the fell steeking would be.

I am guessing that the kilt would need to be lined or the hair canvas strips lined, at least. Also that a very loose stitch be put in the canvas to the pleat to keep it from moving too far out of place.

If the kilt were being hemmed a bit, it would take care of some of that I think, but the canvas strip has to be free to move a little. The pleat has to be able to float over the canvas a bit, though the canvas does grab the fabric just a little.

The hair canvas along the leading edge of the pleat seems to help the acrylic behave more like wool, so...