About Me

I've been taking things to bits, and making things ever since I can remember, starting with dismantling knackered alarm clocks and watches and helping my dad fix the car. Now I have a well-equipped workshop and have aquired lots of new skills, so I can make better stuff. When they first appeared, I became involved with personal computers, and these and developments in electronics have increased the scope of the things that I can do. Just recently retired, so O yes, now I can make all sorts of stuff.....

Wednesday, 4 September 2013

Late August update

As usual, the work of the retired person is never done, and there's been lots occurring this month.  Lets look at some of it:-

First, a bit of a rebuild of my ancient air compressor.  I originally built this the best part of 30 years ago from an old compressor unit from a scrap fridge and an air tank off a lorry, and even had the build featured in one of the Model Engineer type magazines.  Given that the compressor unit is probably around 40 - 50 years old, its done sterling service - it blows up the tyres; blows dust and gunk off; and has done a huge number of spray painting jobs (including a set of kitchen cupboard doors; large parts of the old Morris van, and a complete Vauxhall Astra).  After all these years, its leaking a bit and the pressure switch - made from various junk including a piece of an old truck inner tube - was looking a bit sad. Time for a freshen up.

The main reason for looking at the compressor was because I have also ordered myself a new airbrush (yes, from China) and I will need a decent adjustable air supply for that.

It quickly became apparent that a new pressure switch sourced from the UK was going to cost £30 plus, so off to China to buy the same item for around £6 including postage.  Inspired by this find, I also ordered a new moisture trap for the princely sum of around four quid.

New moisture trap
Delivery was around 3 weeks, so in the meantime I set to work dismantling the old girl. For those that don't know, the back heavy lump in the bottom of a fridge is a steel bottle containing a motor driving one or two pistons.  Air is drawn into the space inside the bottle through a pipe, and is then sucked into the cylinders, compressed, and forced out through a narrow pipe. The bottle also contains a small amount of oil which lubricates the pistons via a crude pump arrangement, but unfortunately this also produces a fine mist of oil which gets sucked in with the air and which is guaranteed to ruin any freshly applied paintwork unless its removed first.

The rebuilt compressor
I took the top off the bottle by sawing through the weld seam with a hacksaw - if you choose the right spot, no metal filings will find their way into the innards.  My plan was to run the intake of the compressor directly to the outside of the bottle, thus stopping the oil from being sucked in with the air, but the contraption of pipes that I had to create to do this made the air intake much smaller than before and the compressor ran massively hot after only a few minutes, and it was clearly struggling to suck the air in fast enough.  So I reverted to the original design and will deal with the oil mist by means of the new moisture trap.  Topped up the oil a bit and tack welded the lid back on the bottle.  A bit of a tip here if you do this - after tack welding, make sure that you cover the joint around the bottle with tape or silicone sealer, if you don't the air gets drawn in through the joint instead of through the filter, and the noise it makes resembles the sound of a thousand centipedes farting.
.. and from the front, the string operates the drain valve on the tank

Earlier than expected, the new pressure switch arrived, a bit of hacking about of the pipework and its up and running.  Unlike the old home made switch, the new one is adjustable and also has an unloader valve which releases the pressure in the compressor itself when it switches off so that when it turns back on there is no pressure in the cylinders - a good idea to save wear on the compressor, and a very satisfying blast of air every time it switches off.

I plan to use the new airbrush on the bench, so I will need to run a long hose from the compressor and mount the moisture trap on the wall above the bench.  The moisture trap also has a pressure regulator, so it needs to be close to where I'm working.  Pacing up and down now waiting for  the postie to deliver the airbrush, and from then on anything remotely flat that stands still long enough will end up with an assortment of flames, skulls, dragons and flags.  Can't wait to get stuck in, though there is a lot of dark muttering from the kitchen every time I mention it.

Next, I've finally finished the water alarms.  When we built the house, I planned for these to be installed in both the utility room and the kitchen, as a water leak in a timber frame house with solid wood flooring would be a complete disaster. Over the years we've had occasional explosions in washing machines and I've become a bit paranoid about them, so a couple of weeks ago when the washing machine stared leaking and it turned out that the rubber seal on the door had a tear it prompted me to finish off the alarms.

The rubber seal was fairly easy to replace - you need to remove the top and the front of the machine and its pretty easy after that - although the genuine Miele spare cost the thick end of £90 plus postage.  Gulp.

Indicator panel in utility room
as well as the blow-your-head-off siren
The alarm is a simple Velleman kit which I installed inside a standard double wall box, with a trailing wire to connect the sensor - two stainless steel plates held around 3mm apart with a block of plastic and laid on the floor under the machine.  In the utility room, the box is in the wall behind the washing machine and connects to an adjacent CAT5 wiring point with a short patch lead, as well as a second lead that goes up inside the wall to emerge in a single wall box above the worktop.  This box contains a set of indicator LEDs and a fly cable to a siren mounted underneath the high level cupboards, as well as a kill switch for the siren and a test button. The test button has already given me endless entertainment at the expense of unwary visitors :-)
The unit in the kitchen

The CAT5 connection provides 12 volt power for the sensor, LEDs and siren, and also has a feed back to the Arduino to tell it when an alarm is triggered. I plan to rig up another central siren fed from the Arduino to kick off not only when the water alarms go off but also when any other alarming event occurs - for example, if the back door should open after 1 am.
The alarm unit in the kitchen is set up in much the same way, although its mounted in a cupboard which unfortunately muffles the siren a bit, but its still loud enough to trigger a change of underwear when it goes off unexpectedly.

Then there's the brass clock. Since last month, I've stopped drooling over it and made a ring face from 3mm thick aluminium sheet, mounted on to a satin black steel carrier plate and a small bracket for mounting.  I plan to mount it to a seriously chunky block of timber, then encase the clock proper in a glass-panelled shallow box - hard to explain, but you'll understand when I post some pictures hopefully next month. In the meantime, its been running more or less continuously, driven by the Raspberry Pi for now, although it will be eventually driven from another Arduino hidden inside the timber chunk. 

I've started writing the software, a bit tricky as the clock will need to know what the real time is without any feedback from the mechanism, and if there's a power failure it will need to automatically adjust its own hands to bring it back to the correct time. The plan is for it to continuously count the number of pulses it has delivered since 00:00 and convert that into time which it will compare with its own internal real-time clock. 

The glass panels will all be engraved with some suitable text, and I'm going to try edge-lighting the glass with high brightness LEDs in the hopes that it makes it look as if the lettering is hanging in mid air. Its gonna be a pointless beast, but a beautiful one

Last month I attempted to play chess with my grandson, OB, but failed as I had a set of pieces but realised we didn't have a chessboard. So this month I made one, and when OB and Charlotte came to stay last weekend we tried it out a few times.
As usual, its made from scraps, starting with a square of 18mm MDF.  I already had some offcuts of yew and some left over maple from the flooring, so I cut these into strips and planed them down to around 3mm thick.  Trimmed the strips to the correct width on the radial arm saw, and then set up a stop on the same saw to cut 32 squares of each colour.  I also had some left over strips of dark imbuia which I planed to around 3mm thick. 

Starting from the centre, I glued the first square and let the glue dry, then added a strip of imbuia and the next square pressed against the first.  Long strips of imbuia in one direction, and short bits the other and fairly quickly I had a board.  A final strip of imbuia all around the four edges, a strip of light wood salvaged from some venetian blind slats glued on all four sides, and we're done.  It took some fairly brutal work to sand the top flat - first took off the big sticky-up bits with the angle grinder, then the big plate sander with 80 grit paper, and finally the small plate sander with 240 grit wet and dry (much better than sandpaper, o yes). Three coats of danish oil, final rub down with a fine scotch pad, a good whack of beeswax and some serious elbow grease polishing with one of those micro-fibre dusters, a set of stick-on felt feet and it looks pretty good.

I'm pleased to report as well that the kart race in August went a lot better than the previous month.  The weather was perfect, warm but not too hot, and spending the money on a new set of tyres made a massive difference.  (Note to self: replace tyres every two or three races in future, instead of trying to make a set last all year.) I ended up having a couple of close runs with one of the many guys who are always faster than me, went quicker than him on two of the four races but never managed to pass him.The new tyres helped, of course, but I was a lot better at braking a bit later and not as much, as well as trying to resist the inevitable elbowing in the first few corners.  All in all, a good days racing.

Some movement on the medical front this month at last as well.  Rather than just opt for the standard radio therapy treatment from the local hospital to fix my prostate, I wanted to explore whatever other treatments might be available as well, so I persuaded my GP into referring me to the Royal Marsden in London.  This is a world-renowned cancer centre and one of only five hospitals in the UK to have a Cyberknife machine.

Standard radio treatment bombards the tumour with low power beams over a period of around seven weeks - it takes this long because the beams can damage healthy tissue, so the dose has to be strictly limited.  The Cyberknife (great name, eh?) fires multiple beams at the target from all different angles, so the tumour gets the full dose, but the surrounding pipes don't get damaged.  It was originally developed for use on brain tumours where surgery was not possible and standard radio therapy would cause too much damage.  The machine is very accurate, and automatically adjusts for the body moving as you breathe.

Well, we saw the Marsden last week, with good and not so good news.  The less-good news is that the Cyberknife treatments are only being done as a series of strictly controlled clinical trials and I don't qualify because of my previous colon cancer and my ongoing lymphoma.  The good news is that although they have a variety of more conventional radio treatments available, the one they recommend happens to be exactly the same as the one that is provided at the local hospital.  No point in trekking to London for that, so I've started the wheels moving here with the expectation of radio treatment starting late September and finishing around 8 weeks later, some time in November.

And finally:  busy flying the whizzcopter the other day down on the playing field when I was approached by a lad of maybe 10.  "Cor" says he, " that's great, can I have a go?"  "No" says I, "its too dangerous".  Lad thinks for a moment, then says "did you make it?", and when I told him 'yes' he says "Are you a scientist?".  "No", I says, "I'm a genius".  "Oh, right" he says and tootled off home, presumably to tell his mum that he'd just met the village idiot.

And next month?  If the airbrush arrives there will be lots on that, plus I should be well under way with the clock.  Vroom, vroom