Using End-Feed Shuttles
I recently purchased two end-feed shuttles in an attempt to improve my selvedges. Can you tell me if there are yarns that would make using an end-feed shuttle difficult? Are there times when an end-feed shuttle would be inappropriate to use?
An end-feed shuttle operates with a pirn instead of a rotating bobbin. The problem with a rotating bobbin is that when the bobbin is full, it rotates fewer times than when it is empty to unload the same length of yarn. More rotations put more drag on the yarn, so the bobbin pulls more on the edge threads as it empties.
A pirn is stationary, and the yarn is pulled off the tip of it the way it is pulled from a cone. The tension on edge threads is applied by passing the yarn through a tensioner on the shuttle, which can be adjusted so that just the right amount of drag is placed on the selvedge threads as the shuttle is thrown.
There is a slight difference in the drag between one edge and the other, however (for one thing, the distance between the tensioner and the edge is greater, since you don't turn the shuttle as you throw it back and forth). Usually, you adjust the tensioner so one edge is an eeeeeeense tight and the other edge an eeeeeeeense loose.
Winding the pirn has to be done in a very specific way. You wind the base first, and then move in sections toward the point, going back and forth and lapping over as each successive section is filled. You need to wind with tight tension or sections of yarn will pull off the pirn as you weave instead of just the outside strand.
For this reason, it could be that both very sticky yarns (mohair) and very slippery yarns could be a problem (the first not wanting to pull off, the second not wanting to stay on as needed).
Also, when a yarn is pulled off a prin, a twist is added to it, in the same way as when it's pulled off a cone. If the twist that's added untwists a loosely spun yarn or adds twist to an overspun yarn, that could also be a problem.
Really, though, for most situations, an end-feed shuttle is a wonderful tool. I don't use them only because, truth be told, I love the sound of a rotating bobbin and the feel of a boat shuttle.