Category: Metalworking

Alaric’s projects for this year

This year's going to be pretty busy with settling into the new home, but I have a few projects.

  1. Finish the ring casting I nearly finished before the move. That's a priority.
  2. Resurrect my aluminium foundry. In particular, it's our bronze wedding anniversary, so Sarah's going to design a pattern for a sundial, which I will cast in Aluminium bronze, a nice alloy that I can make myself from my scrap aluminium and bits of old plumbing...
  3. Continue with minor stuff on Ugarit, but as a milestone, build the distributed storage backend, which will rock.
  4. Work on my wearable computer project. No specific milestone for this, as it's currently a long drawn out research/prototyping phase as I sort out many details.

Wish me luck... I usually suffer from "all my weekends getting eaten up", but as my New Year's Resolution has been to spend at least one day every two weeks doing something fun with my children, I'm going to be booking weekend days in my calendar in advance through the year for that and my own projects. Before they get filled up!

Ring casting

A friend has asked me to cast her some silver wedding rings. So I am adapting my aluminium casting experience to silver...

The thing to use for silver moulds is cuttlefish bone, which is soft enough to easily carve into shapes, but can withstand the heat of molten silver. For a single pour, at any rate.

In order to get a repeatably round shape of the correct diameters for the two rings, and so I can quickly carve new moulds if my pouring fails so I can try again, I decided to make boring tools that carve ring shapes of the correct diameters.

The boring tools

As you can see, they're made from nails, hard soldered together, and ground to a cutting tooth at the end. The central spike goes down a guide hole I drill in the cuttlefish in advance.

The tool needs to come down exactly perpendicular to the flat surface of the cuttlefish (made by sawing one side off and then sanding it flat), so I made a special jig to hold them:

Cuttlefish bone in the jig ready to be bored

Then it's just a matter of fitting the tool in a chuck and bringing it down. I first tried rotating the tool by hand, but the result was a bit rubbish, so I bit the bullet and just turned the Dremel motor on, which produce a quite perfect circle.

Cuttlefish bone in the jig ready to be bored

The cutting jig

Pour two mould in the cutting jig

I made a couple of moulds, each with a matched flat cuttlefish to go on the other side. I had to carve channels for the silver to flow in by hand, using a screwdriver for rough gouging and a craft knife for the finer parts.

The silver was heated by blowtorch, in a refactory cup called a scorifier:

Preparing for pour one

But first I had to prepare the silver I was given - in the form of a coin, which I felt a bit bad about sawing in half:

The silver (back)The silver (back)

Sawing the silver into two piecesThe silver, cut in half

I melted half of the silver and poured it into the first (roughest!) mould:

Pour one

When I cracked it open, it seemed I'd not used enough silver, but everything had otherwise gone well:

Pour one mould opened - not enough silver

So I pulled the incomplete casting out, crushed it up, and added the other half of the silver, and gave the second mould a go. Here's a picture of it with the channels cut, before I clamped it:

Pour two mould

I put it all together and got ready for some melting:

Preparing for pour two

But this time, as soon as I started pouring, the silver suddenly froze on me, so hardly anything went into the mould:

Pour two failed due to insufficient temperature

It seems that the larger mass of silver wasn't heated up quite as far as the first pour had. I need to rearrange my firebricks to make a better forge to heat the silver in, so heat loss is slower, I suspect...

Wearable computers

One of my too many projects is to make a wearable computer.

Lots of people are interested in making wearables, but nobody's yet come up with one that hits a "sweet spot" of decent functionality along with it being unobtrusive enough to not be a pain.

Well, I'm a nerd, so I'm far happier to put up with obtrusiveness to get my pervasive cognitive-assistance fix... I've been fascinated by pervasive computers since I was a kid; I read about Steve Roberts' recumbent bicycle as a youngster, as well as plenty of fiction about brain implants and the like.

Read more »

Heating an old house

Sarah feels the cold keenly, while I can usually just put on some more warm clothes to deal with British winters. But even I was finding it hard to work in my home office when the temperature went below ten Celcius; fingerless gloves still let me type, but numb fingers increase my error rate, and the pain is distracting.

Part of the problem was that our house is draughty. There were a lot of gaps in the window and door frames, through which daylight could be seen; when it was windy and rainy at the same time, the wind blew rain in through the frame of the large window in my office.

So step one was to fix these. The large office window, it turns out, is somewhat curved, so when my brother in law was visiting, we screwed extra handles to it, pulled it properly closed with levers wedged in the handles, then did up the bolts at top and bottom to force it to stay in shape, which fixed a large source of draughts.

Then I want around a few other choice places, adding draught excluder strips where I could.

Next challenge was to increase the heat. We had only one real source of heat in the house, a wood/coal burning stove at one end of the house. Since it's a long thin house, this was little help for me in my office, right at the opposite end - but it didn't even make enough heat to keep Sarah happy sitting next to it, so she would often use the expensive electric fan heater to keep her temperature up, much to my concern (for if we can't pay the electricity bill, things will quickly become rather unpleasant).

Now, the grate in this fire was rather small compared to the size of the fire itself. The grate had only sides and a front, so had to be pushed back against the firebricks in order to not spill coal out. This meant that air coming in through the vents would tend to rise over the fire and up the chimney, taking heat away without imparting much oxygen to it. Even then, it would slowly wriggle forwards over time, spilling ash and coal down behind, until it came too far forwards for the ash shovel to be pushed underneath it, meaning the fire would choke itself. But as it moved forward, the effective volume fire increased, with a notable improvement in the heat output - even though the fire at the back would be starved of air from beneath, as it sat on a bed of ashes.

While rummaging through piles of random bits of metal lurking about the place from when we moved in, though, I found an iron grating that I suspected might be able to fit in behind the existing grate, enlarging it. Sure enough, it did - and it fitted so perfectly well that I suspect it was actually meant for it. Suddenly it was possible to have a large bed of coal in the fire, with air coming in through the vents from underneath it and being drawn up through; this led to an awesome increase in heat. However, it led back to the same old problem - we now didn't have room to get the ash shovel in underneath to take ash away. And so the fire would slowly choke itself with ash.

So I ordered two metres of 25mm square hot-rolled mild steel from Hindleys, my favourite home-engineering supply house. When it arrived I used my angle grinder to chop off two lengths of the stuff, then used them as spacers on either side of the grate to lift it up an extra inch.

And now the fire's awesome. I can easily get it so hot that it becomes mildly terrifying, an angry yellow glow emanating from the air vents as it roars away, the radiated heat unpleasant to be too near. A few days ago, it actually melted the plastic crates we store our newspaper and kindling in, purely by radiation.

But it's still rather cold in my office.

So we decided to spend some money on the problem, as it was in danger of harming my work. I went down to John Stayte Services, a local purveyor of awesome things. We buy our coal from them, but they also sell propane, butane, related accessories such as heaters and Sievert torches, workwear, and animal feed. To my delight, they had a deal on; a shipment of gas heaters had been damaged due to the shipping container being broken into by illegal immigrants who built a home on top of them for the duration of the voyage... so they were selling a slightly dented heater, along with a cylinder of butane, for £89 when normally a heater alone would cost more than that (and a gas cylinder £50 or so as an initial outlay).

I set it up in my office, lit it... and over the next few hours, the temperature rose from ten degrees to about twenty, with me correspondingly shedding layers of clothing. Since then I've been running the heater on low power, and the temperature's stayed around seventeen degrees; with the stones of the building having been warmed up, it's now not taking much heat to keep it nice and warm.

And so, I can proudly state, for the first time since we moved in, it's actually warm enough at home that we are turning down heat sources so as not to be too hot!

The workshop’s getting there

My good friend and colleague Andy came over to stay for a while, which meant I had 'entertaining a guest' as an excuse to do some of the fun stuff I've wanted to do for ages.

So we finished making the welding bench! I'd made the top and gotten part way through cutting the legs to length, so we finished cutting them and welded them in place, then welded extra flat strips around the bottom to make it reasonably rigid. It's all just tack welds, and it'll almost certainly need some diagonal struts added, but it stands upright and is surprisingly sturdy; I'm going to experiment with it a bit to see just how many more struts it needs. I'd also like to drill holes so I can mount my vice on it, too.

Then we cleared a space and moved my electronics workbench down into the workshop! This is great news, as it clears up space in the office (albeit revealing the piles of junk that were lurking beneath the bench), means all my tools are in one place (which is most convenient, as things were always in the wrong places), and creates more storage space in the little garage, meaning less stuff on the floor.

I've since reincarnated my power distribution rail, which I had when we lived in Ealing, but haven't used since; the idea being that it'd be good to do my electronics experiments on the end of a dedicated RCD so I don't trip the one in the house. It also splits the output into four circuits, each with a six amp circuit breaker (the smallest I could obtain easily).

I still need to get rid of a lot of waste cardboard that's sitting around, and we're still looking after Seth's motorbike, and there's still junk to be sorted - many things need to be elsewhere; the little garage isn't a place to store things we only use a few times a year, as we have the Big Yellow for that!

Although the lighting's not really good enough when I'm explaining the power rail, here's a quick video tour:

For my next trick, I'll stop procrastinating by building infrastructure, and get on with actually making myself a digital watch with an embedded ARM processor and colour dot-matrix LCD. Watch this space.

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