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.....

Monday, 13 May 2013

May update

Well, here we are in May already, another month and some more new stuff occurring.

First, a progress report on the Whizzcopter.  The early flight experiences, all quite a long way south of 'good', have resulted in a number of changes to the design.  The original frame was a fine engineering piece, immensly strong, but quite heavy as it was made mostly from aluminium, although I was pleased to see that the motors and props were quite happy to hoist its considerable weight into the air with ease.  My plan was to practice in the garden to aquire at least some rudimentary skills before heading for the airfield, but this didn't work out too well.  For starters, what seems like quite a big open space suddenly shrinks when the 'copter starts swerving about, and then there are all sorts of obstacles that it seems to find as if with a magnet - flowers, trees, fences, houses, people - and most of these result in broken propellers. I struggled on, but soon began to see the real problem with the weight - not with lifting it up in the air, but instead with the considerable impact when it hit the ground and the resulting damage to the metal frame.  Slowly but surely, the alloy arms became bent; the motors started to lean in different directions and the rudder became less and less useful, all of which made it more and more erratic and hard to fly.  Eventually a very substantial prang onto the tail boom trashed the steering servo, and it was back to the workshop for repairs.

Bent alloy arms
Only when I had it in pieces did I realise how much of a hammering it had taken, and it was clear that a reduction in weight was necessary.  Off to that nice Mr Ebay, and a couple of days later some lengths of 10mm square carbon fibre tube arrived.  Easy enough to make some new arms, mounted the motors directly to them instead of using the metal mounting plates, ordered a new servo (mounted above the arm and out of impact range) and we're back to the garden.  Flying skills still much the same, but the much reduced weight means that the crashes no longer woke sleeping children in the next village, so off we went to the playing field just down the lane.

Broken carbon arm :-(
With more space to work with, things were a lot better, although of course the higher you fly the more the wind affects it and the harder it hits the ground when it comes down:  however, the carbon fibre arms took the punishment pretty well until one of them snapped off at the root.  I had some spare material, so replaced the arm but a few flights later the steering servo sheared all the teeth off one of its gears and it was back to the workshop again.

Sergei ready for taking off

As an aside, we did try a couple of flights with Sergei the meerkat strapped to the top.  His extra bulk made the copter very unhappy in the brisk breeze, and he didn't enjoy the landing much so we let him get off.

Close examination of the arms showed an interesting thing.  The carbon tube is immensly strong across its section - ie, left/right and up/down - but the landings rarely hit the ground straight on, and instead the impacts apply a twisting motion to the arms.  The tube is 'pulltruded', which means the fibres are arranged longitudinally, and twisting the tube makes the fibres crack apart. This then makes the arms very rubbery, and as the craft swings wildly around the sky the force of the propellers twist the arms which then confuses the flight controller board  and results in even more wild gyrations and the eventual crash.  Hmm, unless I can guarantee to only land in a controlled manner (unlikely any time soon), I need to modify things a bit.

Revised steering servo mounting
More carbon tubing duly arrived, as well as some alloy tubing of the exact diameter of the hole in the carbon tube, and I epoxy glued the alloy tube inside.  It adds a bit of weight, but not a great deal, and the arms are now much more rigid and twist resistant. I also replaced the servo, deciding that the cause of the gears stripping was probably the weight of the motor jerking to the side when crashing and applying considerable force to the servo gears.  I've re-made the motor mounting and the steering pivot to make the whole thing smaller and mounted lower, and fitted an old 'servo-saver' that I had in the old RC car racing junk box - these devices are intended to absorb the shock of car wheels hitting a rock or a kerb, so I'm guessing they should work here as well - if not, I also have some model shock absorbers in the junk as well, so I can fit one of these to the motor mount.

I've only had a quick test flight, but the inevitable heavy landings don't seem to have had any effect on the arms, even though one of the crashes was hard enough to jerk the motor connectors apart.

The other thing which will almost certainly help matters is an upgrade to the firmware on the flight controller board.  All the experts on the web tell me that the automatic levelling is much improved, and I have to say that the early test flights are much more stable and predictable.  Woo hoo, if the weather improves from today's wind and rain I'll be off to the field to try it out proper like.  Watch this space

'Copter battery charger PSU
The 'copter needs batteries, so I bought a cheap charger which only runs off 12 volts DC - ideal when on an airfield where you can charge from the car battery, but no use in the house.  So I knocked up a simple power supply using a transformer, some capacitors and a 12v voltage regulator all mounted in an old metal case and it works a treat.  Solved the problem, and reduced the quantity of unused spare parts in the workshop, good result.

While playing with this I tried to use an old PC power supply, but although it supplies the required 12 volts, it couldn't handle the current and kept tripping out.  I tried a second one in case the PSU was faulty, and that one was worse.  Presumably the charger is asking for more juice than the PSU can provide without getting upset. This does present another opportunity though, as these PSUs supply well regulated 12v and 5v outputs, which are very useful for a whole host of things, so I plan to modify it slightly to give it proper plugs and sockets, and then mount it underneath the top cupboards and above the bench in the workshop.  Another triumph of turning junk into something usable, hooray!

Now for something more simple, a windshield for the camping stove.  This little stove has been invaluable for brewing tea, coffee, soup and other stuff on karting weekends and out other travels.  However, it suffers badly from wind (stop giggling at the back) so I decided to make a simple folding windshield.

The windshield under test
I unearthed some stainless steel sheet left over from the chimney of the hob extractor fan unit and cut it into four equal squares with the jigsaw, then carefully rounded the corners and took off all the sharp edges with a file.  I need the thing to fold up, so I drilled the side edges of all four sides and hooked them together using some strong wire split links (made from an old coat hanger, wound round an 8 mm rod and split with a Dremel).

... and folded flat
The end result is pretty good, I think.  Its heavy enough to stand solidly on its own, but not so heavy that it will be a pain to cart around, and it folds up into a neat flat arrangement that will be easy to stow.  Another triumph of turning junk into useful stuff, so another hooray.

Next up, the deck table - no, not a deck chair, a table.  This is a simple design that I've been thinking about for some time, so I fetched the timber a couple of days ago and yesterday decided to start preparing it.  Before I knew it, around 4 hours later, and the thing was finished and in position on the poop deck at the back of the house.

This is a Serious Table.  The top is made from four 6 inch x 4 inch sleepers, and the legs cut from another one, with various chunky bits screwed up underneath to hold it all together. I've left a gap down the centre to fit a pair of plastic planting troughs which will eventually be packed with exotic blooms (or pansies if the exotic stuff fails to grow). The sleepers weigh around 25Kg each, so the whole thing weighs in at around 140 Kg:  the wind that's been tossing our garden chairs all over the village for the past couple of weeks is going to have a bit of a struggle moving this puppy.

Last, there's the happy story of the cows on the wall. Before we moved into the village, an elderly gent who lived in a cottage at the far end decided to paint the side wall of his house with pictures of cows.  He may have been slightly deranged, but he painted huge cows and flowers in the style of a five year old all over the wall and although the traditionalists probably recoiled in horror, I liked it.  He was a nice enough chap, if slightly eccentric, but unfortunately he died a couple of years ago and the house was sold.

A few weeks ago I drove past the house and a local decorator was up a ladder repairing and re-painting the wall:  a bit sad, I thought, the old boy had been a bit of a character and the cows were a bit of fun.  Ah well.

Fast forward a few more days, and hooray! - the decorator is also an accomplished water colour artist and here he is painting a new set of cows on the wall.  Not the cartoon ones of the original, this is a proper true to life painting, it looks absolutely great and its also a nice tribute to the old boy who originally lived there.

And finally, an update on my medical situation which is looking much rosier, I'm pleased to say.  I'm well under way with the 3 months hormone injections for the prostate, and expecting the radio therapy to start probably sometime in June or July.  The lymphoma is apparently a very slow growing type, and may end up being treated with chemo or just left alone and closely monitored - I'm having a bone marrow sample taken tomorrow which will provide some more information and seeing the specialist again next week to work out what happens next.  I've stopped tae kwon do training while we work out what is going on, so I need to start a regular excercise programme to keep me fit until I return to the dojang.
Must go, the workshop is waiting....