Gymnastics Rings Are Being Sanded (part 2)

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As previously posted in part 1 I’m making wooden gymnastics rings from 1/8″ layers of laser cut baltic birch plywood. Of many possible methods my friends have suggested for sanding them, while keeping their circular profile, I’m starting off the first one with the most low-tech solution. I’m hand sanding them.

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It is a lot of work. So far, the 60 grit paper is working great at removing the stepped profile and getting a nice, consistent curve.

I joked yesterday that sanding the rings is a better workout than using the rings.

BuEMjkDCEAA5yL2.jpg-largeI’ll move down to finer grits on this one, and then may take a shot at using a power sander and jig or some other higher-tech method for the second ring.

 

Rings Are Being Lasered (part 1)

Today, I began making 1.25″ wooden gymnastics rings. I had designed them in Rhino when I wrote this post for Make: and since then I received a box of 1/8″ baltic birch plywood. I cut the cross sections and guides.

 

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Next, I glued and clamped them. These were the easy parts — stay tuned for the sanding. Not sure exactly how I’m going to approach that yet. PART 2

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Laser Cut Wood Gymnastics Rings

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Gymnastic rings are excellent equipment for bodyweight fitness training. Anything from push-ups, dips, and pull-ups to advanced moves such as muscle-ups and the fabled Iron Cross can be done on a pair of gymnastic rings to improve core and upper-body strength and stability. Plus, as my kids can attest, it’s really fun to swing from them. Here is a great guide to getting started with the rings, and a fundamental rings workout routine.

You can purchase good, commercially made rings, such as these. But how about making your own rings instead? There are several examples online of DIY rings made from either plywood or PVC pipe.

 

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You can create these wooden rings by laminating two pieces of 3/4″ plywood, cutting with a jigsaw, and then sanding.

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These rings are made by filling PVC pipe with a length of rope and sand and then heating them in the oven to soften the plastic, and then form.

I have a set of commercial wooden rings (wood is the preferred material as it absorbs sweat, helping with your grip), but I’ve decided I’d like to make a second set with a slightly larger grip diameter (my current set is the 1.1” international size). I’d rather not use the jigsaw-cut cylinder method and the ensuing difficulty of sanding down straight walls to a perfect circle. My plan is to begin by laser cutting ten thin, stepped layers out of baltic birch, so that when stacked they are closer to the final profile. This approach should make it easier to sand them down to the proper circular profile after gluing.

Starting from from standard dimensions (1-1/4” diameter profile, 7” inside diameter) I drafted the design in Rhinocerous, a NURBS modeling tool I use for precise 3D modeling and laser cutter CAD drafting. (You could do the same in most any CAD or 3D modeling package.)

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I then sliced my final design model into 1/8” cuts with a stepped square profile to mimic the laser cut materials I’d be assembling. This gave me ten circular slices to laser cut and assemble.

Since I’ll be stacking and gluing ten rings of varying size together, I replicated the profile curve of my stacked pieces and used this as a guide to create a laser-cut stacking/gluing jig. I’ll cut four of these into which to lay my ring slices for gluing and clamping.

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I’ve ordered the baltic birch plywood, and am gearing up for laser cutting — and lots of sanding. If all goes well, I’ll get them super smooth, like my current set. (Because, otherwise, splinters. Which is bad.)

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Also, a note on safety: make sure you rig your rings carefully from something that can support the load. You may buy buckled straps online made for rings, or, do as I have and use rock climbing web straps and carabiners to attach them to the backyard swing set.

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If you’d like to get going and build your own gymnastics rings, you can download my design files here, on Thingiverse. Have fun, and please share your results.

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iPhone Case Back Project

iPhone Case Back Project

I’m laser cutting a wood veneer to apply to the back of my slightly cracked iPhone back. The starting point for me is the dimension drawings from Apple. You can get them here.

Rather conveniently, the drawing pdf imports into Rhino (the NURBS modeling/drafting application I use) as curves, so I don’t need to trace and redraw the dimensions.

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I’m only using the inner curve from the camera back and the camera keep out guide, which recommends the distance from camera lens and flash hole to avoid vignetting or tinting your photos.

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Next step was to apply 3M adhesive to a sheet of wood veneer.

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This is the back of my phone — notice the hairline cracks in the glass from dropping it a couple of weeks ago.
Always use a wrench to weigh down your wood veneer sheet.

Always use a wrench to weigh down your wood veneer sheet in the laser cutter bed.

I decided not to etch an image on this first try, so I only vector cut the veneer and adhesive. On an Epilog Zing 16 this is 80% speed, 40% power.

I decided not to etch an image on this first try, so I only vector cut the veneer and adhesive. On an Epilog Zing 16 this is 80% speed, 40% power.

Once it's been cut out, I peeled off the backing.

Once cut out, I peeled off the backing.

I think I'll adjust the camera/flash cutout in a little bit, this is crazy thin at the edge.

I think I’ll adjust the camera/flash cutout in a little bit, this is crazy thin at the edge (due to kerf). This is the adhesive side, not sure what that straight line is all about, it’s not in the wood.

Applied to the phone back.

Applied to the phone back.

Very stylish self portrait of my iPhone with its new wooden back.

Very stylish self portrait of my iPhone with its new wooden back.