joe greiner
7th November 2009, 02:07 PM
I thought it would be interesting to make a set of tumble rings (aka magic chain or drop chain illusion) of wood in lieu of metal. It turned out to be more interesting than I wanted. I'd made a set from split metal rings about 30 years ago, and saved the instructions. But after moving from Long Beach CA to Seattle, and then from Seattle to Tallahassee, and then once within Tallahassee, both the rings and the instructions were hard to find. It was easier to start over, with assistance from Google. And I came upon a video with an elegant assembly procedure to make things even better. The only hiccup in the searches is that "tumble rings" and "magic chain" can refer to other devices.
I initially intended to make a set with only 8 rings, because that would be sufficient to illustrate the mechanism. But before assembling them, I decided to make another batch. With an extra ring to allow for mistakes, and an initial test ring, the total became 18. I took some WIP photos of the second batch, including the assembly process.
The timber is mahogany, a roadside orphan salvaged from a neighbour's billiard table. It had been damaged by basement flooding during last year's hurricane Fay. Most of the upper frame was in good condition, and it's been stored in my timber cache. It was likely originally kiln-dried, and it's very stable now.
I turned the outsides of the rings on a faceplate. I mounted them on my large Longworth chuck to turn the insides, re-mounted to turn their other faces; and used the same process for sanding the insides. And again for polishing with EEE, as well as for applying and buffing paste wax. On the first batch, I hogged out the insides, the same as for turning a bowl; for most of the second batch, I got the brilliant idea of coring them to retrieve the cores for later projects. This worked reasonably well. The brightly-coloured mason's twine on the template is an aid to recovering the template from piles of shavings.
I mounted the rings on my small Longworth chuck to polish and wax the outsides. I found that in expansion mode, the buttons didn't need to be tightened, because centrifugal force (or centripetal, if you must) is adequate for the task at hand; I won't rely on that for finishing bowl bottoms, though.
Only half of the rings need to be broken for assembly. I labelled the broken rings to preserve the mating relationships. I assembled the whole set, using masking tape as temporary bandages, to verify proper construction and operation. I glued each broken ring with CA, while maintaining the assembly. The makeshift bridge assisted in holding the parts. I abandoned the food wrap and the proctologist's gloves, probably too soon. I used masking tape to clamp the glued joints, and that was also not a perfect solution; some of the glue extruded from the joints, and had to be cleaned afterwards.
I replaced the labels with burnt dots, similar to pips on a die, in case of future breakage. When the glue has finally cured, and breakage is unlikely, I'll address re-finishing those regions.
To the best of my knowledge, this is the only execution of tumble rings made of wood. Each ring is 5-1/2" OD, with 5/8" diameter body. The overall assembly is about 6" wide x 42" high. In operation, they're slightly louder than conventional sets made of metal.
I suppose they could have been made from dowels, steamed and bent, but that would have been a PITA itself.
The first picture is a stereo pair, with exaggerated baseline of about 5" vs. 2-1/2" normal eyeball separation. It can be free-viewed by aiming each eye on the separate images. If the images on your monitor are more than 2-1/2" apart, you should adjust your monitor's resolution for best results. I've included clues to how I combined the images into a single picture.
Cheers,
Joe
I initially intended to make a set with only 8 rings, because that would be sufficient to illustrate the mechanism. But before assembling them, I decided to make another batch. With an extra ring to allow for mistakes, and an initial test ring, the total became 18. I took some WIP photos of the second batch, including the assembly process.
The timber is mahogany, a roadside orphan salvaged from a neighbour's billiard table. It had been damaged by basement flooding during last year's hurricane Fay. Most of the upper frame was in good condition, and it's been stored in my timber cache. It was likely originally kiln-dried, and it's very stable now.
I turned the outsides of the rings on a faceplate. I mounted them on my large Longworth chuck to turn the insides, re-mounted to turn their other faces; and used the same process for sanding the insides. And again for polishing with EEE, as well as for applying and buffing paste wax. On the first batch, I hogged out the insides, the same as for turning a bowl; for most of the second batch, I got the brilliant idea of coring them to retrieve the cores for later projects. This worked reasonably well. The brightly-coloured mason's twine on the template is an aid to recovering the template from piles of shavings.
I mounted the rings on my small Longworth chuck to polish and wax the outsides. I found that in expansion mode, the buttons didn't need to be tightened, because centrifugal force (or centripetal, if you must) is adequate for the task at hand; I won't rely on that for finishing bowl bottoms, though.
Only half of the rings need to be broken for assembly. I labelled the broken rings to preserve the mating relationships. I assembled the whole set, using masking tape as temporary bandages, to verify proper construction and operation. I glued each broken ring with CA, while maintaining the assembly. The makeshift bridge assisted in holding the parts. I abandoned the food wrap and the proctologist's gloves, probably too soon. I used masking tape to clamp the glued joints, and that was also not a perfect solution; some of the glue extruded from the joints, and had to be cleaned afterwards.
I replaced the labels with burnt dots, similar to pips on a die, in case of future breakage. When the glue has finally cured, and breakage is unlikely, I'll address re-finishing those regions.
To the best of my knowledge, this is the only execution of tumble rings made of wood. Each ring is 5-1/2" OD, with 5/8" diameter body. The overall assembly is about 6" wide x 42" high. In operation, they're slightly louder than conventional sets made of metal.
I suppose they could have been made from dowels, steamed and bent, but that would have been a PITA itself.
The first picture is a stereo pair, with exaggerated baseline of about 5" vs. 2-1/2" normal eyeball separation. It can be free-viewed by aiming each eye on the separate images. If the images on your monitor are more than 2-1/2" apart, you should adjust your monitor's resolution for best results. I've included clues to how I combined the images into a single picture.
Cheers,
Joe