Wednesday, November 14, 2018

Making bamboo rings

I've had a steady stream of custom orders for bamboo rings. The first step is to establish the ring size with a closely-match twist drill. I find that if I get the drill press speed and feed rate correct, I can get a very clean bore that requires only light sanding.

There is not a very good agreement between standard drill sizes and standard ring sizes, but in this case, close seems to work just fine. This is the reference chart that I use:

Ring size on wikipedia

So for example, to turn a size 8 ring I need a drill that is 0.714 inches. The closest drill is 23/32", which is more like size 8 1/8. An 8 1/8 ring is indistinguishable from a size 8 ring for most practical purposes, but the imprecision bothers me. ;-)

To make a chuck of sorts for these rings, I rip a 2x4 in half and throw a length on the lathe between centres. As I turn a slight cone at the right side for the rings, I end up using more and more of the scrap wood until I have to start over. But the goal is to slightly undersize the chuck so that the ring is a firm fit when a small piece of fine sandpaper is wrapped around the wood. Without sandpaper, the ring just spins and burns.

I've found the bamboo plywood scraps that I use challenging to turn in the past. The bamboo and adhesive tend to dull tools, and using a gouge risks a catch that tears the work in half along a glueline. So I stick with a square scraper to round and then gently roll the outside form of the ring.

All of my small pieces are shipped in a handmade, recycled card box. This one is made from an empty tissue carton.

The rings are worth the trouble. I love the bands of bamboo fibre bundles sliced at different angles.

Tuesday, May 10, 2011

Building a cut-down bike scooter, part 4

The scooter frame was complete and had been brushed free of grime, finish, and weld slag. All it needed was a deck to stand on. I started by experimenting with a skateboard-style wooden deck, but it seemed visually wrong and probably too prone to wear and breakage.

I liked and so didn't remove the Iron Horse crest from the steering tube.

I decided that what I really wanted was freewheel sprockets on the deck. I played with positioning some and liked how they looked, and liked that they articulated the theme of a cut-down bicycle.

My client was justifiably concerned about the sharp and jagged teeth of the sprockets chewing up the rider's ankles, though, and I had to find a way around that. But I decided to commit to the gears and welded them in place.

After some thought, I decided to cut sections out of a wheel rim and weld them in place on either side of the deck to define its edges and protect the rider from the sprockets. If I had arrived at that plan before welding on the sprockets, I would have placed the largest gear in the centre, at the widest part of the deck. But sometimes I have to make a stand and resolve the remaining problems later to move forward.

With everything welded down, the scooter was complete. The deck was wide, comfortable, and stable.

This is the completed commission. I was very happy with it and rode it around the neighbourhood for a while before giving it up to my client.

Nice ride!

Friday, April 1, 2011

Building a cut-down bike scooter, part 3

With the down tube wrapped around the front wheel and the top tube inverted and moved to the deck, the next step was to find a way to attach a rear wheel. I removed the front wheel from an abandoned child's bike, installed it in the rear dropouts, and positioned it to see how it would look.

I was pleased with the possibilities, and committed to it by cutting off the bottom bracket and what was left of the seat tube.

Positioned this way, it started to have a dragster sort of feel to it, which I liked. To get the chain stays level with the deck, I decided to bend them just at the edge of the wheel.

Again, I cut wedges out of the tubes so that they would bend easily and precisely. I had previously removed material from the dropouts so that I would be able to bend the seat stays down toward the deck, and you can see the missing sections here.

I placed the stays back into position for a final check before bending the stay assemblies closed.

I heated the dropouts where I wanted them to bend, to just shy of their melting point, and then gently closed the triangles.

With those assemblies completed, the whole frame was ready to weld together. The seat stays are inserted inside the top tube, and the chain stays spread outside it.

Here's the completed frame, with the tack welds completed and the rear triangles welded closed.

It was ridable in this state, and my hopes were realized -- it was way too much fun to ride. I did have to lock out the travel in the front shocks, though. Every time I gave a good kick the deck hit the ground. I drilled through the shocks and brazed in a section of bolt to keep them from compressing. The final steps were to brush the frame free of finish, complete the deck, and apply a few coats of wax to slow the rusting. At this stage, I still hadn't figured out how to make a deck to stand on.

Wednesday, March 9, 2011

Building a cut-down bike scooter, part 2

I decided that the deck of the scooter would be built on the top tube of the bicycle. Flipped upside down, the seat tube could extend upward to meet the down tube, which had been wrapped around the front wheel but didn't come close enough to the ground to meet the deck.

So, I separated the seat stays from the top tube.

The seat post sleeve and gusset would drag on the ground, so I removed them also.

Then, with some trial-and-error fitting, I decided where to cut the seat tube and separated it from the stays. The photo below shows the two sections of the bike that remained.

To join the inverted seat tube stub to the now-plumb end of the down tube, I decided to run the seat post through the seat tube and up into the down tube. I brushed the finish off the seat tube and drilled holes to allow for rosette welds, which would help join the seat post and tubes.

With the seat tube installed (forcibly, with a mallet) it was ready to weld.

It was a fussy business getting the alignment right, so that the deck was level and the correct height off the ground. When I was satisfied with it, I tack-welded it all together.

The remaining challenge was to modify the stays to hold a smaller wheel from a child's bike and tack the whole thing together, which I'll show in the next post.

Wednesday, September 29, 2010

Building a cut-down bike scooter, part 1

I had a very exciting commission this summer. My client had seen kids in Cuba riding kick scooters cut down from broken bicycles, and wanted one made. We didn't have any photos to work from, so I got to develop my own design.

This is what I ended up building. It is lots of fun to ride! The deck is made of sprocket gears and sections of wheel rim, and the rear dropouts hold a wheel from a kids' bike.

I watched for discarded mountain bikes with sturdy frames, and picked up a bike with partially rectangular tubes and front shocks, but no front wheel. I pulled a decent wheel from another bike and swapped in a set of cruiser handlebars.

I use a cutting disc in an angle grinder to cut bikes apart. To start, I separated the top tube from the head tube, and the down tube from the bottom bracket. That left the pieces seen above: the front shocks, head tube, and angled down tube, and the rest of the bike.

The plan was to wrap the down tube around the wheel so that it is ultimately plumb, straight up and down. I opted to cut out wedges and cold-bend the tubing before welding the bends shut again.

In the photo above, I've marked the wedge that I intend to remove with soapstone.

After cutting out the wedge, I was able to bend the remaining tube like a hinge, closing the wedge to a weldable line.

Here's a close-up.

I removed a similar wedge at the second bend in the down tube, so that the last segment will be plumb. Then I removed the finish in the area of the welds and tack-welded the bends closed.

The plumb section of down tube did not come nearly close enough to the ground to support the deck, so the next step was to find a way to extend it (and hold the rest of the scooter up).

Thursday, September 23, 2010

Turning a bark-edged bangle

I prepared a stack of bangle blanks a while ago. This time I chose the interesting bark-edged one on top.

It's always best, but I find that to avoid knocking bits of bark off as I turn, I have to keep the gouge very sharp and the cuts shallow. The bark itself dulls the gouge quickly, so there's more sharpening involved. But it's worth it.

Once the shape is developed and the exterior rough-sanded on the lathe, I remove the core with the same hole saw that I used to mark it initially.

After some careful sanding and a walnut oil finish, here's the bangle! It sold quickly.

Tuesday, September 14, 2010

Forging sturdy toggle clasps

I've had trouble recently with storebought clasps breaking, especially on my bicycle chain bracelets. The standard lobster clasps are difficult to operate at best, but they are also too brittle and easily snapped. Toggle clasps (rod-and-loop) are easier to use but aren't any stronger. So I decided to try making my own.

I don't have an actual coal forge, and my anvil is tiny, but the torch is up to the heating job and I don't need much of an anvil table for this work. I get a finish nail up to workable temperature, just red-hot, and then hammer the centre section flat.

In the photo above you can see an unmolested finish nail at right. The rest have been heated, hammered, and quenched in a little tub of cold water.

After grinding and filing the ends smooth and dull, I drill out the centre to take a small lead of cord.

The loops of the toggle clasps are made of heavy wire. I use standard jeweler's wire-bending tools to create one large loop.

Then, a smaller tool to make a smaller loop in a figure 8. It takes some oomph to bend the heavy wire in a tight radius like this.

Then I use a hacksaw to cut the loops free of the wire bale. Side cutters or snips would deform the circles too much.

The free ends are on opposite sides of the loop.

For these, I heat them closer to the melting point. After red, the metal turns orange and then bright yellow, which is where I want it for forge-welding the free ends closed. When it's hot enough, I lay it on the anvil and hammer the overlaps into each other so that the whole loop lies flat.

This is what the finished clasp looks like on a choker. More fun than shopping for findings, much stronger than commercial clasps, and appropriately grungy and rough in appearance. And easy to close and remove.