I redesigned the pulley for the double action birdcage pull that I made yesterday. The main difference is that it’s slightly larger and the hole on the non pulley side has been moved 90 degrees.
Here’s a side by side comparison with the one that I made yesterday. The old one is on the left and the new design is on the right with the strings on it.
I foreseeing possibly making it wider with the ends flaring out, so that it doesn’t roll inside the jacket and twist the line. We’ll see if that actually ends up being a problem, or if tension alone will straighten out or keep the lines straight. I’ll play with it a bit and see what happens.
If you’re curious about this style of pull, I think I first read about it in Jim Steinmeyer‘s book The Magic of Alan Wakeling. In that book it’s used to vanish a fan, however I think using a pulley on a wrist to wrist pull is much older than Wakeling using it.
For some reason I’ve been thinking of the “double action” birdcage pull lately. I’ve used one a long time ago, and never really felt it contributed much to the vanish. Essentially what a double action pull does is give you more pulling power with less motion. It converts your motion 2 to 1, so you move one inch and the line moves two inches! It’s a great way to reduce arm motion for the vanishing birdcage, but adds complexity to the setup. Every bit of complexity you add, it’s another thing that can potentially go wrong. This may be the issue I have with it, the gain of having reduced motion isn’t worth the risk.
I haven’t used one in 15+years. Tonight I decided to make one, so I designed this one to be 3d printed:
Here’s what the insides look like:
There’s not really too much to it, it was a simple design and a quick print. Here’s the printed version:
There are a couple of things I want to change after printing the first one. The big change is that I want it just a little bit larger, so that I can fit a bearing inside for the pulley.
I’ll do a new design later today and hopefully I’ll nail it the second time!