I made this small Van de Graaff generator for my English class ( they all do physics ) The sphere is 15cm diameter ( 6" ) and made from stainless steel. It is hand-cranked to show that no other source of electricity is needed to produce a spark. The top roller is PTFE and it will  give a 2 cm spark with a few rotations of the handle. It goes much better with a motor driving the belt ! 

I estimate the maximum voltage at 100 Kv

I had the stainless-steel parts welded in Phnom Penh. The re-entrant shape was produced by welding in a toroid.


My baby ( 15 cm ) Van de Graaff charging a 700pF capacitor

The audio compression on the camera makes the motor sound much noisier than it actually is - and the sparks from the discharging capacitor are quite loud and fierce - you would not want to touch it !

I was cutting up a big plastic bag and had a brainwave - why not try a loop of polythene from a plastic bag ? The latex rubber I used before was no good - after a few months it turns into a sticky, gooey mess and falls apart. The polythene would not need glueing into a loop either. The loop would be bigger, so the supports would need to be longer.

The original supports were made from acrylic rulers glued together - and did NOT look very good [ In those days I did not know where to buy perspex in Phnom Penh ]

I therefore I did a design in Sketchup and had them cut from 5mm acrylic [ perspex ] sheet by laser. Two longer supports for $5 - much better than the original ! 


At the laser-cutting shop [ street 105 Phnom Penh ] I made this video :

If you have never seen laser cutting before, it is amazing, but otherwise it can be quite boring ! It took 5 minutes to cut out the two supports.



However, a polythene belt did not work with top roller PTFE and lower roller nylon. [ opposite polarity rollers give charge-doubling ] It did work with the lower roller aluminium - no charge-doubling. Until I find the best combination of rollers, a polythene belt cannot be used.

The recommended belt material is neoprene and McMaster-Carr sells 'Food-Grade' white neoprene sheet 36" wide X 12" X 1/64" and 1/32" [ perfect ] but cannot post to Cambodia because of export regulations ! I did not know that rubber sheet would compromise National Security ? They sent me the following email :

Hi John,

The US Department of Commerce has extensive regulations covering the sale and documentation of products exported from the US. Those regulations apply whether the products are shipped directly outside the US or somewhere within the US for later transport. The Department of Commerce classifies both kinds of transactions as exports and imposes the same requirements for documentation and review.


We will not accept your orders, and I apologize for not helping you further.


So that was that ! The US doesn't want to export anything now ? 

If I cannot get white neoprene, I will try and find surgical rubber tube and spice a strip of it. [ I could not find surgical rubber tube in Phnom Penh ]

This one is bigger with a 20 cm dia. sphere.


 It has an external latex belt, PTFE top roller and nylon bottom roller. Also matching lower casing to increase capacitance.

My bigger Van de Graaff has a 20 cm diameter sphere ( 8" ) – the Baby VDG has a 15 cm sphere ( 6" ). The theoretical maximum voltages that spheres of those sizes can be charged up to before discharging to air is 225 KV and 300 KV respectively.

This uses the formula 'radius in cms times 30 KV ' as 30 KV per centimetre is a standard breakdown voltage for air between large ( > 5cms ) spheres.

On the first test run the big VDG comfortably produced 6 cm sparks between the 20 cm VDG sphere and a 15 cm grounded sphere. That is easily 180KV which is 60% of theoretical maximum. If the gap is increased, there is audible corona discharge from somewhere – I will check it at night - so there is considerable room for improvement.

It is estimated that not having a high polish reduces the Vmax by 1% but the biggest reduction occurs at the opening – around 14% loss – therefore 15% can be immediately deducted from theoretical maxima to give :
15 cm diameter VDG 191KV
20 cm diameter VDG 255 KV
These are more realistic figures and now a 180 KV spark becomes 70% of maximum – not bad for a first test !

I made two different spheres for the big VDG – the first one has a very generous re-entrant opening which also means the size of the opening is a bit small ( 5.5 cms ) and the second one has a 9 cm diameter opening but not such a good re-entrant profile. There was an obvious discharge between the belt and the inner rim of the sphere with the first one as a 4cm wide belt gets close to the rim. In fact, without a plastic insulating collar, it hardly works. I decided that having more insulation between the belt and the opening is more important than a perfect re-entrant shape but too small an opening. Many of the commercial VDGs I have seen have a minimum of re-entrant shape. The first one was made by TIG welding four 90º elbows together to make a torus and then welding the torus inside a sphere with a section cut off it. The elbows are made from 5cm diameter tube giving 5.5 cm inside dia. and 15.5cm outside dia.
The bigger sphere has a commercial torus welded in with 9 cm inside dia. and 12 cm outside dia.
The height of both truncated spheres is 18 cm. so surface area and capacitance of the active regions should be the same.

This photo shows the difference in re-entrant hole size between the two spheres. The widest possible belt is needed for maximum charging current - and enough distance between the belt and opening - so number 2 is better.

Thid diagram shows the difference between the two re-entrant openings - the 15mm torus works better !
The perfect shape might be an Archimedes spiral – the best transition between a hole and a sphere ? My spheres are both with a linear transition.
I have polythene insulation around the opening of the larger sphere, but most probably not enough. This is just visible in the photo.

Instead of using a belt to charge the sphere, if a microwave beam was used ( I think this could be possible ! ) then the re-entrant hole could be very small with very generous radius of curvature and little corona loss from the opening. Of course, it is sometimes easier to just make the sphere 15% bigger ! The biggest stainless-steel spheres I can get in Phnom Penh are 20 cms dia. This is not counting the monster 1 metre diameter ball that they won't sell me !!!

It is so large that a selfie with it was very difficult.

The largest sphere on eBay is 42 cms dia. from Germany, but this one is higher quality :

40cm Premium Quality Grade 304 Stainless Steel Contemporary Ornamental Sphere £49.00 from direct-global-trading-ltd (41047)

Should be good for 535 KV !





Sometimes I need a quick spark (!) and Van de Graaffs take some setting up - they don't like latex belts installed and under tension for long periods of inactivity - the belts stretch and the join breaks - so I made this friction electrostatic generator.

The drum is a PET bottle with PTFE sheet glued on. Initially I copied a design from YouTube ( Friction Generator 2 )

The PET bottle gave very poor performance in Cambodia's humid conditions so I glued on 0.3mm PTFE sheet. Yes, you can glue PTFE very well - if you use Polyolefin Activator first - I used this ( expensive ) kit from eBay

4ml + 4g Adhesive Glue Gel For PP Polypropylene PE Polyethylene PTFE Silicone ( from The-Tuning-Shop )

The friction is from a nylon cloth pad and the charge is collected with a spiky comb and conducted to a 4 1/2" ( 11.4 cm ) diameter stainless-steel ball. Plastic gears give rapid rotation and a few turns produce a 1 cm spark to the knuckle. Friction generators are reliable, but don't make very high voltage - the voltage is not limited by the size of the stainless ball : 4 1/2" is good for 170KV ! No need for a hole so less loss than a VDG. 

For a sphere of 4.5 inches diameter in free-space, the capacitance is 4.5 * 1.412 = 6.35 pF - which is not very much !

I have since made three modifications to the generator : 

1 ) Idler gear and flywheel - originally the small crank had to be turned anti-clockwise so the heavy flywheel and extra gear enable normal clockwise rotation with much less effort and a smoother action.

2 ) Adjustable spark gap - usually set at 1 cm.

3 ) 'Leyden Jar ' Capacitor - uses HDPE dielectric from a Vietnemese washing-up liquid bottle - measured at 322 pF.

Energy stored in the capacitor = 1/2 CV2 Joules

322pF @ 30kV = 0.15 Joules - gives a satisfying spark and you would not want to touch it !

 Rear view showing capacitor ( covered by a PE bottle )

It takes longer to charge the capacitor - 5 to 10 seconds

It works even in damp weather when it is raining outside !

This electrostatic machine was originally produced by Louis Bonetti, an instrument maker of Paris ( France ) in 1894. The design had been proposed earlier in 1869 by Holtz and Poggendorff. It is basically a sector-less Wimshurst machine. 

The project started when I saw PTFE discs on eBay. I now have a pair of 30cm diameter discs, 5mm thick - expensive !  I have never seen anyone using PTFE - usually they use acrylic, G4 fibreglass or delrin ( polyacetal ) so I am expecting good performance.

My very expensive PTFE discs as arrived from the UK.


The big problem, for me, was making the hubs to securely mount the discs. Delrin is recommended - but expensive - so I decided to cast them in polyester resin. I made this crude lathe to square-up the castings.

The baseplate is steel and heavy ( 11 kgs ) I used my X - Y cross-slide to mount the toolpost and the tailstock has double ball-bearings.


With rough casting mounted - ready for turning.

This will be a long project !


Turned to size ready for polishing - I now have a good selection of lathe tools from the Russian Market.



Completed hubs. Holes tapped M5 to mount disc with nylon bolts.



Facing-up the hubs

New lathe set-up to face the hubs. 

I used the actual ( empty ) motor frames, with ball-bearings fitted, and brand-new shafts cross-drilled to take the hubs. This worked very well and gave a good finish. Previously I had used 8mm studding as a mandrel to turn the hubs - and less-than-perfect bearings. It wasn't so good and needed re-work. The hubs are a good fit on the new shafts and required turning to get them concentric. On the left of the grinder motor is a diamond wheel for sharpening the cutting tools. The grinder is a bit too fast for turning the outer surface, so I used a variable-speed drill. It worked very well.


Two neutralizers made from 6mm and 7mm diameter stainless steel - bent with my home-made bending jig and TIG welded locally.


Encapsulated in polyester resin and fitted with nylon screws and polythene sleeving :



I was given two big pieces of a local hardwood called S'Grom - still with the bark on ! Too large to cut by myself, I went to a sawmill at a nearby Vietnamese village.

The boss is sharpening the bandsaw blade on a grinding jig - he does this regularly - some of the hardwoods are really hard !

Here he is cutting a big block of wood - LOTS of dust in the shop.

The woodwork is now complete - it kept me busy for a long time. The uprights consist of two pieces glued together - they have a hollow central channel for the motor wiring and one has a slot for the charge-collector support.

I had planned on making my own 3-phase induction motors from Vietnamese fan motors - converting them from single phase to three phase. However, it would be quite a long project in itself and there is a good chance of the inverter getting blown up by the high-voltage sparks. I had already installed ball-bearings in the motor frame - so I bought these new stators in Phnom Penh [ I used old, dead motors for 50¢ each as frames and rotors ] for $3.25 each. Sure saves a lot of work !



Sanding the PTFE Discs.

This is the sanding jig I used to true-up the edges of the discs and make them concentric. The two PTFE discs are sandwiched between two pieces of 12mm plywood. Below them is a Vietnamese chopping block. The base-plate is 6mm steel. I found the plywood - for free - in Phnom Penh.

I could not decide on what type of motor to use for the Bonetti machine ; there are so many choices :

  •  Permanent-magnet brushed DC motor
  •  Brushless DC motor - a 3-phase synchnonous motor with magnets
  •  Single phase 220Volt capacitor-run induction motor
  •  Stepper motor (!)
  •  12 volt 3-phase induction motor 

It needs a 50mm long shaft - preferably 8mm diameter. 12 volt operation would be nice ! I could not find anything suitable on eBay, so I decided to modify Vietnamese fan motors. Upon further thought, the high-voltage sparks would probably destroy the inverter electronics - a single-phase 220Volt induction motor would be better. Therefore I am continuing the 3-phase motor as a seperate project - not for the Bonetti machine.


 Typical Vietnamese fan motor - I can buy burnt-out motors for 50 cents ! The copper wire alone is probably worth that ?


The laminations have 16 slots for single-phase, capacitor run

( single split-phase ) I need 12 slots ( or multiple of 3 anyway ) for re-winding as 3-phase. 18 slots would be best, but more work !



I designed a new pattern with Sketchup and had a sample laser-cut in Phnom Penh. The shop have a CNC plasma cutter and a CNC router as well as the laser cutter. They usually do huge advertising signs. Their prefered file format is Corel Draw - which I don't have - but they will import the Sketchup file into Corel Draw, check the dimensions and clean it up if necessary - while-you-wait and free-of-charge ! Cutting costs $1.

However, they only cut stainless steel on the laser cutter - ordinary mild steel does not cut well ( the edges melt and lose definition ) . The stainless is non-magnetic - no use for a motor !  The laser is argon-shielded. They also cut perspex ( acrylic ) on the laser cutter ! It cuts beautifully with polished edges.

I am using transformer laminations as raw material (Silicon Iron) so I bought a complete set of laminations for a BIG transformer ( 80mm center leg ) - they will not sell it by the kilo.  More than I need so - if it works - I might have some spare motors.  I can get two motor laminations out of one transformer lamination    

The laminations are size 215 as they measure 215mm across the longest dimension - they are sold by the 'lump' (!) maybe we would say bundle ? They weigh 16 kgs and @ $2 a kilo cost $32  

 I have now punched out the holes on 36 laminations - a lot of work !

The laminations are now cut to size. They now need de-burring ( although burrs are very small because holes were punched out ) and flattening. 


On the left : hand-cut laminations

On the right : factory stampings

The central hole was bored to size on a lathe so they need more de-burring.

If you are not sure about how an induction motor works, here is an entertaining old video tutorial.

[ Check out the Jeff Quitney channel on YouTube if you like old documentaries ]


Winding detail



Wound stator

This is connected in Delta. Windings not yet laced up.



. . . and its backside . . .

Measured inductance of windings @ 200kHz - 7 strands 0.3mm copper in parallel  ≈ 36 turns :

RED        164 μH


BLUE      165 μH

It was a pain counting turns, so I used equal lengths of wire. It came to 36 - 40 turns and ended up quite closely matched.

. . . and the completed motor . . . I was so surprised when it worked !




This is the circuit I am using. I tried using an HIP 4086 driver and discreet mosfets, but I could not get it to work. This also works with a HDD motor.

Induction motors are non-synchronous - there must always be SLIP - the rotor rotates slower than the magnetic field. This is not really a problem and these motors are simple and robust. 

Permanent-magnet brushless 3-phase motors [  they are called BLDC - Brush-Less Direct Current - motors, but do not run on DC - they need a 3-phase inverter or ESC - electronic speed control ] are also called Permanent-Magnet Synchronous motors. They will run with a sensorless controller or with Hall-effect sensors.

This maker has it all under control . . . 

This is his website :

Other new and interesting motors :

The Focused Magnetics Inc website is in 'Stealth Mode' - very useful - good luck trying to find it. 

These motors are very compact  . . .

For a good tutorial  . . . 

. . . and their advert . . .

As BLDC motors and induction motors with VSD [ variable-speed drives ] all use high-frequency inverters, the windings are usually many turns in parallel [ LITZ wire ] for small motors.  This is because of the 'Skin-Effect' of high-frequency currents and reduces losses. Litz wire does not seem to be used in the larger motors [ why not ? ]

When winding with Litz wire, it is more convenient to twist the wires together to keep them as one unit and stop them getting in a tangled mess. I have the following questions :

  • What % improvement is Litz wire over single-strand copper wire ?
  • Is it really OK to twist the wires together ?
  • How much twisting is OK ?
  • Would solid silver wire or silver-plated wire be a worthwhile improvement ?

The silicon-steel laminations should be very thin so that a high-frequency inverter can be used. Frequencies used are 25kHz or more - a conventional AC motor runs at 50 or 60Hz. For example, NO-02 material (0.2mm thickness) or M235-35A ( 0.35mm thick ) 

My questions :

  • Why not use ferrite like in switched-mode power supplies ? A solid ferrite stator would be easier to make than stamping out laminations.
  • Can ferrite be 3-D printed ?

If ferrite stators work, what is the highest practical frequency ? Small SMPS use up to 5MHz switching frequency these days. There are PWM Class-D transmitters, so power electronics exist at VHF and UHF. It seems motor technology with soft-iron laminations is still using the old 50 or 60 Hz transformer idea and has not graduated to ferrites. 

Batteries for electric cars are usually single-supply. They could easily be ± supplies as in audio amplifiers - for example ± 500 Volts. My questions :

What output topology could be used with ± supplies ?

Would there be any benefit ?


This motor is a 9N6P ( 9 stator poles, 6 magnets )
The winding pattern is called an ABC wind – ABCABCABC as you go around the stator – it works for any brushless motor with 9 stator poles and 6 magnets. It will not work with the very common 12N14P motors.
It is Delta connected – the most common system for small hobby motors.
Delta spins 1.7 times faster than a WYE configuration.
Wye has 1.7 times more torque than Delta.
WYE may be more efficient (?)


Other winding patterns ( lower-case letters indicate winding in the reverse direction ) :



9N8P AaABbBCcC ( very rare )

12N14P AabBCcaABbcC or AaACBbBACcCB ( this winding may be easier )

Winding a motor can be complicated (!)




The students at Kratie High School learn Chemistry and Physics, but don't have a lab - so I thought I could do some electrolysis as an English lesson ! I built this electrolysis set up and use water with a little sodium hydroxide as electrolyte. The electrodes are stainless-steel perforated plate. The base is a Vietnamese chopping board with recessed holes. In the picture it is drawing 8.14 Amps at 2.68 Volts - limited by my power supply - on a good 5 Volt power supply it will draw 30 Amps !


The original plan was to blow bubbles and ignite them, but Cambodian bubble mixture is very weak and I cannot get glycerine locally to make my own. The weak bubbles expand quite quickly and then burst - they don't float away. So I am filling small (!) plastic bags with hydrogen and oxygen and then igniting them with a candle flame at a safe distance. They explode with a satisfying bang !  


I upgraded my power supply and here it is drawing 11.1 amps - much better ! - The device in series with the positive ( red ) wire is a resistor block to limit the current. It seems that the explosion is much sharper - and louder - with more current ? Sometimes, even with a quite small plastic bag full of gas, it surprises me. The students really love this demonstration !

Induction-heated Essential Oil Pipe

There are two main problems with Essential Oil in a wooden pipe : firstly when it is hot enough to vaporize, it runs through the holes at the bottom of the bowl and is lost. Secondly, using a flame to heat it, gives poor control of temperature and can burn the wood. My new Pyramid Induction heater solves these problems.

 Instead of the usual bowl, a stainless-steel capsule is used. This unscrews and the lower half has a stainless-steel tube to allow the vapor to escape while preventing the liquid oil dripping into the pipe.

With capsule unscrewed - The short section of stainless-steel tube was silver-soldered in using the induction heater ! This forms a well into which the Essential Oil is placed and the tube allows the vapor to escape while preventing the liquid oil from dripping out into the pipe.

 The pipe was made of Gro-ngoong ( Pa-yoong in Thai )

  • The Pyramid is made with the same angles as the Great Pyramid in Egypt - I don't know if this helps (?) but it was worth a try !
  • Lithium battery powered - re-charged with 12 Volt charger
  • Arduino computer-controlled
  • Individual cell and total voltage display in base with low-battery warning alarm
  • RGB LED for status - cycles through the rainbow on standby, green when object is in range and red when heating
  • Infra-red sensor to detect when pipe is in range
  • Current sensor to detect when heating
  • High Power output - heats capsule quickly and uniformly

My NEW 12 Volt Travel Vaporizer



  • ARDUINO computer-controlled temperature
  • Stainless Steel construction
  • Sterling Silver bowl - hallmarked 92.5% pure
  • 12 Volt Lithium Polymer Nanotech Power
  • Red - Green - Blue Status LED
  • Ambient to 190 degrees C in 2 minutes 30 seconds
  • Low battery warning and shutdown
  • PTFE insulated wires
  • PTFE and silicon Aerogel thermal insulation
  • Uses standard 12 Volt charger
  • Plays a tune when ready !                                                                                                                                                                                                             

With tube and mouthpiece fitted




With lid removed showing silver bowl

I made a box for it out of  'T'nong ' wood - the second-best hardwood in Cambodia. This luxury wood is restricted, difficult to obtain and expensive, however I was given a big block of it for free ! The box houses the charger and a stainless-steel funnel for easy filling.                                                                                                                

Small-scale aluminium-melting furnace made from cooking stoves - used for melting discarded aluminium beer cans - and there are a LOT of them in Cambodia !


With lid removed


Centrifugal blower fitted to my grinder motor

The galvanised-steel sheet I used to make the housing came from a sheet-metal workshop run by a Vietnamese-Khmer husband and wife team. The woman cut it to size for me and gave me it for free - absolutely would not accept any payment !

I later bought a sheet for the outer furnace-jacket for $2 from her husband. 

If I made another, I would use commercial Chinese furnace-blowers

These three were on sale near the Russian Market - the smallest one was $28

Cylindrical stove found thrown-away in Phnom Penh

Dimensions were perfect - except for the air-hole and the bottom. A plain fire-brick tube would have been ideal, but equally hard to obtain.

 With bottom removed ( upside-down view )

I used the piece cut from the bottom to block the air hole. Cement used was investment-casting refractory plaster - Plaster-of-Paris and Silica  -  $3 for 2 kilos 


Now made into a tube, the liner was used to extend the height of a regular cooking stove. The gap was filled with a 50/50 mix of plaster and crushed-up fire brick.

Charcoal is sold everywhere here and I used an old steel aerosol can as a crucible.

 With blower going full blast there are lots of sparks flying


However, the can was much too thin and soon melted (!) there is plenty of heat with this furnace.


I then used an oil-filter cannister from a truck - thicker steel - this was OK


 I did not have a mould prepared as this was just the first experimental firing - the end result was these two lumps of aluminium - maybe a kilo ?


New melting pot

This pot is 12 cms diameter, 16 cms deep with a 3mm wall. It is very easy to buy small amounts of steel and get it welded in Cambodia - and cheap also.

Using my new pot

Note the high standards of safety and foot protection in Cambodia !

Finished ingots

This is at least 1½ kilos of aluminium - I'm not sure what to cast from it ?


This project was inspired by the following videos from YouTube

Deep Hole Drilling Jig

This jig is for drilling the hole in pipe stems - the electric drill slides on aluminium guide rails and the wood blank is mounted between two ball bearings. It is mounted eccentrically and the drill bit used is 5mm diameter by 350mm long. A router will be fitted on top to reduce the diameter to the final pipe-stem size. A Chinese wood-lathe seems to be difficult to find in Laos - there is nothing in Pakse anyway - so I decided to make my own router lathe.

 Router fitted on top

Improvements - two 1/2" stainless-steel tubes used as slide rails

The router bit used was 1/2 "diameter ball-end tungsten carbide 

The wood used is called "Pa-koon" wood in Lao ( Pa-Yoong in Thai ) and is very rare, expensive and highly valued : it does have a beautiful grain and is nice to work with. I recently found out that this wood is regulated as an endangered species : it is illegal to export as logs, but a manufactured article is OK. It is extremely rare now – all the trees have been cut down long ago, but most Lao seem to have some pieces on display and a few sacks of it stashed away under the house. It only grows in Cambodia, Laos, Thailand and Vietnam and only Cambodia has trees left in the forest – and they are rapidly being sold to China and Thailand. In China the wood is exclusively used to make furniture for the Emperor's Palace and possession of it in Thailand is illegal. The Lao don't know what to do with it – they just keep it in case a buyer turns up which is unlikely in such a remote area as this. I decided it is better to make something with it and have bought up pieces that are usable – most are not ( too small or damaged ) – so far I could only get a dozen usable pieces which shows how rare it is !

Dalbergia cochinchinensis Pierre 
Although beautiful and venerated as a true rosewood in the Dalbergiagenus, Siamese Rosewood has been one of the central species in illegal logging in Asia.

To help put it in perspective, as of 2013, the largest remaining Dalbergia cochinchinensis tree in Thailand is currently guarded day and night by an entire platoon of Thai soldiers.

 Siamese Rosewood may fairly be called a blood wood, and sadly, the label has nothing to do with the colour of the wood  ( Wikipedia )


As cut to the rough shape and ready for finishing


The Finished Pipe in its Case

The case is bamboo - The pipe is Pa-yoong  13.5 inches overall length - The bowl is antique Sterling Silver about 1895 Hallmarked    


My first attempt at wood carving - luckily the pipe is a bit out of focus !!! .... Actually it's not too bad .... 13.5" long - Pa-yoong wood 


Had a few disasters when the hole went off-center : this only becomes apparent when turning the blank down to nearly final size and the hole breaks through the side – an “ oh, no !  WTF “ moment. At first I put this down to the drill-bit flexing – the final drill-bit is 350mm long by 5mm dia. A friend kindly donated a set of “ flat-bits “ for wood and the smallest is 6mm which I think is as big as you would ever need. This did not improve matters however ( they are much stronger being mostly a solid rod, but need clearing very often ) so it must be the guide-rails for the power drill. It is just hand-planed wood so not at all properly flat to start with (!) and the only straight parts are the lengths of aluminium extrusion – a very thin-and-twisty finishing strip. It hardly glides with any precision, but by sheer luck the first two pipes turned out fine ( the drill must have been wandering in the opposite direction to the off-set of the guide-rails ! ) so I thought it good enough. The blank work-piece was fixed between ball-bearings and I didn't rotate the blank because the power drill was not perfectly centred – it was not too bad, but not good – and I didn't want to drill a cone-shaped hole !

Then three failures in a row. The next one I tried a completely new approach : I drilled the hole as best I could – without fixing the blank between ball-bearings - just clamped down - and then removed it from the jig ( normally I would procede with turning at this stage ) Then I inserted a ground-steel rod ( 5mm by 305mm silver steel ) - it is a firm fit – and gripped it in the drill-press chuck so that the blank was hanging vertically downwards.



I had previously suspended a plumb bob from the drill chuck and positioned a 3mm twist drill held in a machine vice so that it centered on the tip of the plumb bob.


I next lowered the blank – a drill-press is very handy for this – until it just rests on the 3mm drill bit. By carefully rotating the blank ( by hand ! ) and backing-off and then lowering it again a number of times, the locus of points becomes apparent and the drilled-hole is very likely to be pointing at the center of the locus.


Locus of Points


The silver-steel rod is removed, ends of the blank cut to fit the ball-bearings and back to the turning part. It remains to be seen whether this is a cure …. It seems to be : I made 14 usable blanks using this method and most were accurate to within a couple of millimetres over a length of 350mm !

The next two successful pipes using the new drilling method

Monster Pipe

Length 34 cms ( 13.5 " )


 The Joker

Made from a particularly fine piece of Pa-yoong wood - length 36 cms ( 14 " )    






This a very long term project, but it has started ! 

When I was casting polyester resin for the Bonetti machine, I decided to cast the coil former for the secondary of a Tesla coil at the same time. It is 18" high ( 45cm ) and 3.9" diameter ( 9.9cm ) to give an aspect ratio of 4.5. I used six polyester rods to give an open-frame construction for higher Q. I did not want to use PVC pipe as it is very lossy at high frequencies.


With toroid top-load in place


The toroid has a free-space capacitance of 10pF and was made by TIG welding four 3" 90degree stainless-steel elbows. I bought the elbows in Laos and had the welding done in Phnom Penh. 

The secondary former will be wound with 0.5mm dia copper wire ( approx. 24 AWG ) and with the top-load capacitance should have a resonant frequency of 337 kHz




Electronic design with Kicad - The original plan was for Gerber files to be emailed to Bangkok for PCB production, but the setup cost is too expensive so they will be made in-house. Printed circuits will be made using silk-screened resist as thermal transfer and photoresist systems are not easily available here.


  My design of Silk-Screen Stretcher. The four side pieces are blocked up so that the hinges are at 90 degrees i.e. the top surface is flat. The piece of silk-screen is placed on top and the top slats are put on top of the screen. The clamps are fitted and tightened. The blocks are removed and the weight bottles hung on. The bottles are each 1.5 Litres and put the screen under tension. It is best to avoid silk-screens with creases, although I have never tried ironing it ?? White latex glue is spread onto the silk above the frame and left overnight to dry. Two rows of staggered staples fix the screen as well. Finally it is cut out with a sharp knife.

Two-part Diazo photo-sensitive emulsion is applied with a squeegee ( plastic spreader ) and left in a dark box to harden overnight.

First usable silk-screen - the design is a high-end headphone amplifier


 My first finished PCB   -   silk-screened here , ready for assembly

I need a bigger soldering-iron for solder tinning.




Silk-screen printing is involving a lot of trial and error : I have never used this technique before and watching professionals doing it on YouTube is one thing, but doing it yourself is quite another. The photosensitive-emulsion came from Thailand with no guidelines as to exposure time. Their website is completely hopeless – no use whatsoever. OK, I know exposure time depends on the UV intensity and wavelength, but most Thais will be using sunlight exposure, like I do, so the frequency is more-or-less fixed ( full spectrum ) and at noon it can't vary by more than 50% through-out the year, can it ? So they could give you an idea of the time it takes in Thailand ( and you can usually count on a plenty of sun all the year – here it is better from November until the rains come ) I only saw one video on YouTube about sun exposure and that was from Hong Kong – 3 minutes exposure on a sunny day. So I tried 3 minutes with my first screen, but didn't reasise how much water-pressure it takes to “ wash out “ a screen after exposure. It might have been a good screen, but I didn't blast it long enough to find out. Later another video suggested 2 bar water-pressure with their brand of emulsion. What does 2 bar of water feel like ? They had a huge shower-rose blasting the whole screen with 30 psi water.  I use a 1 Watt red LED ( 635 nanometres ) which gives enough light to easily see what I am doing. I am worried that using too much pressure will blast off the hardened emulsion. I did a bracketed exposure test with sections exposed in 30 second increments – it seemed that 2 minutes was best. My next shock was in the acid-etching of a PCB with screen-printed resist ink ( again Thai ink – black “ rubber-based ink !” - says it has excellent adhesion to fabrics so it is not a proper acid-resist ink ) anyway, half-way through etching the screen-printed ink started to lift off and float to the surface ! I use equal amounts concentrated hydrochloric acid / 6% hydrogen peroxide. However, the pattern was still there and not getting etched any more so an invisible layer – the lacquer in the ink – was doing its job. After solder-tinning you could not tell where the ink had lifted. I was also standing the screens vertically to let the emulsion dry in a dark cupboard and now I rest them horizontally to give a more even coat. The major problem is the contrast of the positive. Originally I was to use clear acetate film in the laser printer – this does not work : the first one came through the printer with low contrast – after that none of them came through – they all got jammed and I don't want to ruin the machine. Internet searches suggested using ink-jet printers – they said a colour ink-jet prints a more opaque black than a laser can. There are special machines only for printing transparencies, but out here I only have a laser printer.  Therefore I bought some tracing paper in Phnom Penh and am using two sheets on top of each other to double-up the image and get the blacks a bit blacker – it seems opaque, but is it opaque to UV ? I have to hand-feed the paper if I want to pass it through the machine a number of times and I think the registration will suffer – my machine doesn't have a paper tray. ( I have managed two passes with good registration, but not three ) I think this is my biggest problem – lack of a good black and this conveniently brings us to a rather lengthy lecture about the solution to this problem in the olden days when I was working at Space-Age Electronics ( around 1972 (?) to 1976 )


I had my own darkroom there and used “ lith “ film which has an ASA rating of about 5 ! - the clear areas come out crystal clear and the blacks like the blackest night. Nanoparticles of silver make it black so UV is no problem. Resolution is excellent. Most designs were done as “ tape-ups “ then : using pre-cut lines and pads on clear acetate-film. The tapes were quite thick and totally opaque so the image came out perfectly on the lith film from a contact print. I had a copying-camera in the darkroom with two photo-floods ( 275 Watts each ) It was home-made ( don't know by who ) with a beautiful bellows, ground-glass focussing screen, rack-and-pinion adjustment. I could enlarge or reduce and tape-ups were often done twice-size and reduced to sharpen the image. There was a box of 100 sheets of 10” by 8” Kodak lith film, two part “ A & B “ developer, wash trays and fixer ( sodium thiosulphate ) I could turn out artwork with ease – I did all the artwork for the echo-sounder myself. I did not use the usual tape-ups – I use “ mechanorma “ which is like “ lettraset “ - a rub-down plastic stencil of fonts, symbols, lines and pads. Of course, gone the way of the Dodo these days, but we did not have laser or ink-jet printers back then. Because the original positives were so good, and lith film so forgiving, the negatives and subsequent contact-prints came out excellently. My friend, Peter Hull, even hand-drew a design on tracing paper with black Rotring ink and that transferred to lith film without a problem. I have not seen Rotring pens much lately (?) but they were very popular then – a capillary tube as the “ nib “ - sizes down to 0.1 mm, I believe ? Rotring ink is very black ( the Thais use it for tattooing ! ) and they used to make an “ etching ink “ used with funnel-pens to lay down a very tough acid-resist ( although concentrated nitric acid might be pushing it !! ) Lith film was available very cheaply as surplus or out-of-expiry-date and it worked OK – so basically the artwork side was taken care of. I used photo-resist to make PCBs : there was a gallon of Kodak stuff in the darkroom and it was applied to blank PCB with a “ Whirler “ - the board was stuck to a motor and spun while dropping the photo-resist onto the center. It was centrifugally coated and lots of it sprayed off everywhere, but it gave a good coating. To expose I used a “ Boots SunRay Lamp “ which was a UV ( mercury ? ) discharge tube with tungsten ballast all in the same envelope – about 300 Watts. Can't remember the exposure time – 20 to 40 minutes ? - the resist was very “ slow “ and could be whirled in the daylight. Later a sales “ rep “ sold me ( anything I wanted was on account – the company paid ) a German dip-coating photoresist : very expensive, but totally different to the old Kodak stuff. It was green – a quick dip and then it dried very fast to give a thin and even film. Exposure was also fast and results good. Much later, when I had “ Silicon Systems Ltd “ I did not bother with lith – I took my artwork to a printed-circuit factory in Letchworth and they churned out the PCBs at a very reasonable price. When I wanted a one-off PCB at home I had a can of spray photo-resist which was OK, but messy, and pre-coated photo-resist PCB which was not too expensive and easy to get. 


Electronic design prizes :


June 2018 ( $ 50 )


Special Use items in Stainless Steel 

                                Example : Vaporizer MK 1



 Example : Pantograph 

Example :   Balance  with ceramic/knife-edge bearing






The latest version of the Vaporizer has a polarised thermocouple plug and socket fitted for easy removal of the upper part when re-charging - not that you have to re-charge often : it's big enough for a generous amount of bud.  Two units for sale are being constructed - the metalwork is finished already. They incorporate improvements derived from months of rigourous testing (!) 

                                                                                                                                                                                                                 Vaporizers are not a new idea - they were popular in Victorian times in a crude form : a basin of very hot water with variations on the theme of Menthol, Eucalyptus and Camphor added and a towel over the head to inhale the vapours. If Aromatherapy is considered a gentle allopathic use of vapours , then the Vaporizer can deliver a good dose for acute conditions and recreation . The Stainless Steel Vaporizer is the modern evolution with accurate temperature control and has proved most effective in use.  

  • All Stainless Steel Construction
  • Thermocouple temperature sensor
  • Power stirrer
  • Temperature set range 175 - 195 C
  • Sintered Bronze air-inlet filter
  • Holds a good load
  • Optional Gas bubbler - no silly plastic bags !
  • Easy to open and re-charge
  • PTFE and Silicone polymers used
  • Precision Scientific Instrument
  • All parts connected to ground wire
  • Polished and Ultrasonically cleaned
  • Looks nice in the dark
                                                                                                  I made these Magdeburg hemispheres for my High-School English class - they also do physics. They read about this experiment, but do not have the equipment to do a practical.

I saw the two stainless-steel bowls in a Phnom Penh supermarket @ $1 each. The handles are from a stainless ring, cut in half. All TIG welded locally. The vacuum pump is Chinese - I ordered it to bleed the brakes on my car. An O-ring and silicone grease makes a good seal. The brass fittings are from the Russian Market.


 This demonstration was first performed on 8 May 1654 by Guericke - and thirty horses, in two teams of fifteen, could not separate the hemispheres until the valve was opened to equalize the air pressure. My version is smaller and my hand gets tired of pumping after 400mm Hg - even at half-vacuum, it is not possible for me to pull them apart.




                          GRAVITY PUZZLE


The center nail is fixed - The object is to balance all 14 nails on the head of the center nail. They must not touch the wood. The outer 14 nails are a loose fit in the wooden base. Is it possible ? - and no, I'm not going to show you the solution here ... !


My students at Kratie High School trying the gravity puzzle - Khmer teacher in background - I took the photo





Can you remove the metal ring from its cage .... and then replace it ? Is it possible ? ( answer is yes ! )


                            Chinese Puzzle


This is a 3-D Chinese wooden Puzzle - Can you separate the pieces and then re-assemble it ? I used T'nong wood and milled the parts to shape.


                                 Spinning Top


I made this spinning top - the flywheel was cast from melted beer cans and the handle is Pa-yoong ( Gror-ngung in Khmer ) The handle makes it very easy to spin the top up to speed.


With handle removed. As I don't have a lathe, I had the blank machined in Phnom Penh. There are small gas bubbles in the aluminium, but it is not a problem for this application. It spins very well.




I made this gyroscope - the flywheel is from a VHS video head and the support ring I cast from beer cans. Fittings are stainless steel.

I now have my old amplifier that I made in Thailand - and a 15"  subwoofer. 


Inside view

The amp is rated at 350W R.M.S. continuous sine-wave drive

( 480 W music power ) into 4Ω - more into the 2Ω of the dual voice-coils in parallel.

Also 5 channels of 50W each for the surround sound.


 I designed and constructed this active filter unit

It has a bandpass filter for the Bass -  10Hz high-pass to remove subsonics and 150 Hz low-pass to remove mid-range and treble.

Also there are three channels of 150 Hz high-pass filters for the Left, Right and Center  -  to remove low bass.







In its box

 I used a stainless-steel surgical box fron Phnom Penh. They are cheap ( $2 ) and come in a variety of sizes.

Usually when you think of a sound system, you imagine a matching pair of rectangular wooden boxes with identical bass, midrange and treble drive units. The drive units share the amplifier's power – maybe with a passive crossover network.

I have been making sound systems for over 50 years and now am convinced that this is not the most cost-effective way to go. ( This article is not for Audiophile Purists who only listen to classical music from vinyl with valve amps ! )

Most bass is not directional and one big mono bass speaker performs better than two smaller ones. There is little to be gained from stereo bass.

One BIG bass amplifier is better than two medium-power ones.

Wood speaker boxes are very expensive and not structurally stiff – much better and cheaper is a single large concrete enclosure.

Rectangular speaker boxes give off resonances from the flat parallel walls which colours the sound. It is basically the wrong shape.

Most distortion in a sound system is from the speakers, very little from the amplifiers.

Most of the power in music is from the bass. You do not need the same power to drive the midrange and tweeters.

If all the speakers share the same box, the bass modulates the other drivers and causes distortion.

Speakers for midrange and treble can therefore be small and sealed – no large cone excursions or bass to handle. Any-shape wooden boxes are OK as there is no bass power. Use similar units for Left, Right and Center. Left Rear and Right Rear can be driven from the Left and Right outputs. Volume controls for the Rear speakers are not necessary – they can be moved nearer or further away.

Most music will be from YouTube and phones, computers and media players usually have equalizers built-in with profiles for techno, rock, trance, house, pop, jazz etc.

Tone controls should not be necessary – only the bass level needs cranking up and down depending on the music.

A 10 Hz subsonic high-pass filter is necessary to prevent subwoofer damage.
The bass amplifier only needs a 10-150 Hz power bandwidth – ideal for a class D switching amp.
2,3 or 5 smaller amplifiers can drive the Left, Right, Center ( and Left Rear, Right Rear ) speakers. These can be ' bookshelf ' speakers. These amplifiers need a 150-20kHz power bandwidth – a good choice is the LM 3886 50W module.

The bass amp could be the ' Studio 350 ' ( 350 W into 4 Ω January 2004 ) or the ' Classic D ' ( 250 W into 4Ω November 2012 ) or preferably something more powerful. The 'Classic D' cannot drive 2Ω loads - so you would need two : one for each voice coil.

The Loudspeaker Protector should be used ( October 2011 Silicon Chip  )

The Subwoofer Controller ( August 2007 ) is unsuitable – it is overcomplicated, can barely drive a Classic – D ( it has maximum output signal of 2.4V RMS and the Classic – D needs 2.2V RMS for 8Ω loads so no headroom. It has the Low Pass filter before the High Pass – everyone else designs bandpass filters with High Pass before Low Pass which seems more logical )

Multi-Function Active Filter Module ( July 2009 ) was the basis for my circuit using these design aids : ( High-pass filters ) ( Low-pass filters )

The prototype used a single-sided PCB with many links ! A double-sided PCB would be much neater. The case was a stainless-steel surgical box.

The Bass and Center channels are mono. Left and Right are stereo. This is not intended for 5.1 or 7.1 Dolby encoding – most music will not have this feature.

This is all you need. It works extremely well. Try it !


15 inch Bass Speaker


It is ZULEX brand with dual 4Ω voice-coils. Very heavy - 25 kgs ? Maybe rated at about 1000 Watts ?

Speaker bolts are fitted to fix it to the concrete - the speaker can be removed later if necessary.


A strip of steel sheet is used as a temporary mold and pop-riveted together. The concrete should just cover the top of the bolts and washers. A steel ring could be welded to the top of the bolts to prevent them turning.

The only place for the speaker would be up on the roof ...


Casting concrete base

It is one metre diameter with a 40 cm hole for the speaker. It is placed next to the 5000 litre water tank on the roof - on the same supporting beam.  If the water tank is 5000kgs then an extra 500 kgs should not be any problem. Portland cement is cheap here - $5 for a 50 kg bag - $3 in bulk. Much better and cheaper than wood. In all, I used about 1½ bags ( 50kg bags ) of cement, 200 kgs of pebbles and 200 kgs of sand ( estimated ! )

I had to do it surreptitiously as I didn't want the owner of the building to know - until it was completely finished. He would not approve of concrete work, thinking I would make a mess or maybe I was breaking down walls and modyfying his apartment.

After 24 hours I tried lifting it - no way ! - it would not move, not even a little bit. Must be over 100 kgs ? What to do ? Off to Phnom Penh to buy a ratchet strap winch.

 Winch details

I bought a $5 Chinese strap winch and it effortlessly lifts the base and speaker. I was very impressed with the winch - I have never used one before ( I have never mixed concrete before either ! )

With rubber feet 


I used Chinese solid-rubber tyres, cut into three sections, as feet for the base so that it is about 10cm off the ground. The rubber decouples vibrations from the floor ( a bit ! ) and the speaker should be loaded correctly (?) 

The correct distance from the speaker face to the floor should be ¼ to 1/3 of the cone diameter for proper loading. I used two tyres - one stacked on top of the other one and screwed together to prevent sliding. They must be solid rubber or they will collapse under the weight.  




Small-size Chicken cage as inner mould.


Large size chicken cage - as outer mould ( 1 metre diameter )

With the first layer of cardboard


With the second layer of cardboard


The cardboard is necessary to bulk up the size of the inner cage - it is a bit too small - and reduce the amount of concrete needed. It also maximizes the volume of the enclosure.  


 Inside view


Last layer

It is now cemented to the base. Wires for the two voice-coils can be seen.

The next stage is fitting the outer mold and pouring concrete

 It all went to plan until this last stage – the concrete pour. I could not mix up the concrete fast enough to feed it and I put in too much on one side. I use a big washing-up bowl to mix it in – so as not to make a mess on the floor.

The outer mold shifted a bit due to the weight of concrete and now it is lopsided. I should have fixed the outer mold more securely to the base so it could not move – maybe drilling the concrete and fixing screws ( I do not have a percussion drill ) It fits the base OK, but was only held on with tape. Not a big problem – I will slit open the mold after a day and re-position it. It needs a lot more concrete to finish – maybe another sack of cement ? The concrete base worked out really well – the concrete is hard with no cracks !

The owner of the building was not happy about the position ( and weight ! ) of the speaker and suggested a better place for it would be in the corner by the attic door. 

There was the small problem of shifting the 300 kilo lump into the corner. I had originally decided to buy castors or wheels and glue them on. However, I thought it better to do it like the ancients moved heavy objects – with rollers. 

I bought a metre of steel tube – 12 cm diameter and about 1mm wall – and had it cut into 10 cm sections. These ten sections were the rollers – five each side – and it was an easy job to move it.  It was heavy because some of the tubes went oval quite quickly, but it worked a treat without marking the floor.

A car jack and the ratchet strap winch came in handy !

( It would move with just a push )


 In its new place

You can see the two ports for tuning.

Now it needs the packing removed, the top to close it and final finishing ...

With packing removed. This is the last view inside before the lid goes on.

 Ready for the lid

With lid on

Now it just needs cosmetic finishing - and testing.

I couldn't resist adding a nose !

Maybe needs a mouth ?


Plan of the speaker box

The volume is about 0.28 m3 or 280 litres - smaller than I would have liked, but OK. The ports should tune it to about 10Hz resonance (?) I have not checked this yet.


Covered in aluminium tape, it is finished and sounds magnificent !

Here is the complete story of the concrete speaker  :

Concrete Speaker Saga
I am retired and living in Cambodia on the top floor of an apartment building. My apartment is at the back – not the sunny side – and above it there is a large flat roof where the water tank lives. There is only one other apartment, next to mine, that has access to the roof space so I thought it would be an ideal place for a sound system without disturbing anyone else with the volume. ( If you have a patio, that would be equally as good. ) This sort of sound system is not intended for the average living room which is generally too small for the bass frequencies to reach their full potential : it is better in a large fairly open space such as a rooftop or patio where you can have a party and play dance music or watch a movie in the evening. The owner of the building very rarely comes up there and I didn't think he would mind, however I had to do it surreptitiously as I didn't want him to know - until it was completely finished.

With a wooden speaker box there is not a problem as to the construction, but I am dissatisfied with the muddy bass, resonances and booming – or 'toothpaste bass ( because it sounds like the bass is being squeezed out ) of a too-small box. Previously I made a concrete speaker box in Thailand of 337 litres capacity and, although it was of standard rectangular proportions, it sounded good with an average 15 inch bass speaker and a 'Studio 350' amp driving it. Therefore, for me, concrete is the way to go – but the owner would not approve of concrete work, thinking that maybe I was breaking down walls and modifying his apartment (?)

A long time before I had asked him if I could buy some cement – there was building work going on in the underground car park so there was always plenty of cement, sand and pebbles. I only wanted to make some concrete exercise weights that time and he was not into it. He told me in Khmer ' No ! Don't mix concrete upstairs – do it in the car park and take it upstairs when it has set.' ( He obviously thinks I will make a mess mixing cement. ) This may be OK for exercise weights, but not for a 500KG speaker ! Being a foreigner in Cambodia I can always claim that I misunderstood – however I knew that asking permission was out – he would refuse for sure – but he might not complain if it was already there when he next visited the roof. He had seen the bench press with sand-filled weights I made up on the roof and made no comment – only smiled - so he was basically good natured, however I could not start by carrying a 50 KG sack of cement upstairs – he was sure to see me and ask questions. ( This apartment block is more like a hotel and you can imagine the reaction of a hotel owner if a guest started bringing cement and sand into the hotel ! ) You can buy cement in 5 kilo bags here – which can be smuggled up slowly – and sand and gravel I could bring upstairs by the bucketful at night ! It might work ?

I was originally going to make a concrete pyramid as an enclosure for the subwoofer and thought the proportions of the Great Pyramid would do. ( I don't like the typical rectangular speaker box because of reflections and resonances - and a pyramid would look cool ) To get a reasonable volume of about 0.5 m3 the base would be too big and it is a bit squat with the 52º angles. I could have made a taller, more spiky, pyramid, but it would lose the classic proportions and the flat sides would still give reflections. I decided on an ovoid dome structure – should be about 0.5 m3 and the curved sides will lessen reflections. This time I wanted to make it 'down-firing' which gives a more omni-directional bass so placement is not critical. It would be quite a project in itself and take some time, but was doable. In Cambodia, Thailand and Laos they like to keep the roosters in wire cages for some reason – to stop them fighting maybe ? ( Maybe you can't get these cages ? If not, wickerwork baskets or an inflatable inner mold like a weather balloon might do ? ) I bought two of these chicken cages – one big one and a smaller one. They are a flattened dome-shape and certainly big enough for a bass box even if the biggest size available will not be 0.5m3. They would be the framework for the molds and could be covered in cardboard and plastic.

Casting the concrete base
The first thing to do would be to cast the base in situ - one metre diameter with a 40 cm hole for the speaker. I would place it next to the 5000 litre water tank on the roof - on the same supporting beam. If the water tank is 5000kgs then an extra 500 kgs should not be any problem (?) I used steel strip as molding – pop riveted together. The speaker was protected by double plastic bags. The M6 speaker bolts poke out of the plastic bags so that the heads of the bolts are covered in concrete and secured in position. The bolts are long enough for 5 cm thickness of concrete. The nylock nuts are on the lower side which makes it possible to remove the speaker afterwards if you blow it up ! With this system the bolts are set in the concrete perfectly aligned for easy speaker replacement. Two ' U' bolts with a strap attached – like a car exhaust clamp – serve as lifting points.

Portland cement is cheap here - $5 for a 50 kg bag - $3 in bulk. ( Much better and cheaper than wood. ) In all, I used about 1½ bags ( 50kg bags ) of cement, 200 kgs of pebbles and 200 kgs of sand ( estimated ! ) The concrete base worked out really well – the concrete is hard with no cracks !

After 24 hours I removed the molds and tried lifting it - no way ! - it would not move, not even a little bit. Must be over 100 kgs ? What to do ? Off to buy a ratchet strap winch. I bought a $5 Chinese strap winch and it effortlessly lifts the base and speaker. I was very impressed with the winch - I have never used one before. I could now place the three rubber feet in position. As the inner cage is a bit too small, cardboard is necessary to bulk up the size of the inner mold and reduce the amount of concrete needed. It also maximizes the volume of the enclosure. The finished inner mold was cemented in position so it could not move. The outer mold was only held in position by tape – a mistake – I had underestimated the weight of a concrete pour.

Lopsided ?
It all went to plan until this last stage – the concrete pour. I could not mix up the concrete fast enough to feed it and I put in too much on one side. I use a big washing-up bowl to mix it in – so as not to make a mess on the tiled floor. The outer mold shifted a bit due to the weight of concrete and made it lopsided. I should have fixed the outer mold more securely to the base so it could not move – maybe drilling the concrete and fixing screws (I do not have a percussion drill) It fits the base OK, but was only held on with scotch tape. Not a big problem – I slit open the mold after a day and re-positioned it. With more repositioning and rework it became even all round – maybe a bit thick near the base @ almost 10 cm wall thickness where I had planned on a 5 cm wall thickness. More is better with concrete speakers – don't worry about the weight – the heavier the better. The inner and outer wire-and-cardboard molds were still in position and the casting was covered with a tarpaulin while the concrete set. The next step would be removing the molds and fitting the lid.

A blessing in disguise
It was Wednesday the 13th - about 11pm and I was about to go to bed. The bed and mosquito net were already set up on the roof – I usually sleep up there when it is not raining because you can't beat sleeping under the stars on a warm tropical night. Then, suddenly, I heard the balcony doors being unlocked and someone going up the stairs to the roof. It could only be the owner of the building – nobody else goes up there besides me, and he very rarely goes up there – only if there is a problem. ( I thought 'Oh, no ! He will see the speaker' )
Most unusual for him to go up there at such a late hour, so I hurried up there after him to see what he wanted. There was a problem ! The 5000 litre water tank was overflowing ( again ) and he had noticed water dripping downstairs. I had only set up my bed about an hour before and it was all dry then. The plastic ball-cock had broken – and this was the second time within a few months. The last time I was sleeping and woke up in a wet, soggy bed at about 4am. I turned the inlet tap off myself and informed him the next morning. He didn't have a spare that time, but I had previously noticed a ball-cock in the attic and gave it to him. The plastic is low quality – from Thailand or Vietnam – and they only last a few months before the ball snaps off and floats around on its own.

There was a difference this time – I had started making my concrete speaker, without permission as I knew if I asked him he would refuse – so I planned to finish it as quickly as possible and it would be a fait accompli and – I hoped – harder for him to refuse. Although it was dark and covered with the tarpaulin he noticed it immediately ( hard not to notice a 1m diameter lump and nearly a metre high ) I said it was only a speaker and, despite the poor light, he also noticed it was concrete. That bought an instant reaction of " No, No, No. No, No, No! – rising up and down in tone ! " ( He does not have much English – he calls me 'mister' and apart from that, the only word he says to me in English is ' No ! ' )

There wasn't any mess, but he was worried about the weight. I had positioned it exactly over the main concrete lintel that also supports the 5000 litre water tank. I said to him in Khmer that it was mostly cardboard covered in a thin layer of concrete and only about 100 kilos. If it was strong enough to support 5000 kilos + the weight of the tank ( 120 kgs ), then an extra 100 kilos shouldn't matter – it's only the weight of two people. ( small people ) Actually, it's more like 400 or 500 kilos – the concrete is at least 5 or 6 cm thick ! The base alone is about 100 kilos with the speaker and I used 70 kilos of cement total. Without the lid and cosmetic finishing, it was still heavy and I had invested a lot of work into it so I was hoping he wouldn't tell me to break it up and throw it away. He said nothing else that night.

The next morning I awoke at dawn and started work on it. I removed the outer mold and cut open the inner mold so it could clearly be seen to be hollow – and not a solid lump of concrete which would be heavy ! I had everything tidied up by the time he came to fit a new ( plastic ) ball-cock at about 7.30. He was in a better mood and seemed to believe that it was only about 100 kilos. He actually suggested that a better position for it would be in the corner by the attic door. So, in saying that, he had given permission without me asking for it !

I was complaining about my bed getting soaked and said he should get a stainless-steel ball-cock and not the Thai plastic rubbish ( thinking that, if I was indignant, it would take his mind off the concrete speaker ) He agreed and said that stainless-steel ball-cocks are not available locally. I replied there are loads in Phnom Penh and he asked me to get him one the next time I was in Phnom Penh and he would pay for it. ( My bed was not very wet and soon dried out )

A plan was forming in my mind, maybe the situation could be turned around ? – I would need wheels or castors to move it and maybe more rope so I could get them in Phnom Penh the same day. By 9am I was ready and at the bus station. I got a stainless-steel ball-cock set for $12 and presented it to him the next afternoon for free. That way I had done him a favour and the concrete speaker episode was not mentioned. I also got him a Chinese synthetic Chamois Leather for cleaning his car. They are less than $1 and amazing. So it didn't end up with me being in the dog house for disobeying him – it ended up with indirect permission and him and his wife thanking me !

There was the small problem of shifting the 300 kilo lump into the corner. I had originally decided to buy castors or wheels and glue them on. However, I thought it better to do it like the ancients moved heavy objects – with rollers.

I bought a metre of steel tube – 12 cm diameter and about 1mm wall – and had it cut into 10 cm sections. These ten sections were the rollers – five each side – and it was an easy job to move it. It was heavy because some of the tubes went oval quite quickly, but it worked a treat without marking the floor and it would move with just a push.. A car jack and the ratchet strap winch came in handy ! I had it re-positioned by the time I gave him the stainless ball-cock.

Another morning, after heavy rain in the night, I finished off the speaker by wrapping it in aluminium tape. Just as I was rubbing it down with a rag – everything clean and tidy – the owner came up to the roof to check on rain-water leakage in the attic. He saw the shiny speaker in its new position and only said '100 kilos, OK ?' I said it was not too heavy as I was able to move it on my own ! He was very friendly and the speaker is obviously no problem now. Phew ! Relief !

I have been enjoying my roof-top sound system whenever the rain allows – which is not very often in the rainy season – and adjusting the settings. I listened for a total of about three hours, spread over various days, and got it quite loud sometimes ! No problems so far. The next day I turned it on and – nothing from the bass speaker. Not even a click or a puff of smoke – just silence. One of the dual voice coils had gone open circuit and, as they were wired in series for 8Ω, it stopped working. I used it with just the other voice coil for 4Ω – tested it at increasing volume. The power of the bass was impressive and then, just as I was nearing maximum volume on the media-player remote, there was an ominous click and silence again. I guessed it was the other voice coil and was dreading having to repair it. Big voice coils are easy to buy in Phnom Penh and I have rebuilt a 15 inch speaker before, but it is still a big job. I jacked up the speaker dome and unbolted the bass driver. ( Use a car scissor jack ) It was OK – the wires from the voice-coil connectors to the outside junction box had broken off ! It was cheap Chinese 'Jumbo' flat-twin speaker cable. It was quite hefty cable, but was not copper ! It would not solder and was a dull colour. It was either vibration or the cable rotted through, but it's bad when a cable breaks after 3 hours. I was most relieved and replaced the speaker using some good copper cable. It is a fiddly job removing and replacing the speaker – but not too difficult.

I tested it and was not disappointed. The bass is solid and tight. I only have the two voice-coils in series – 8Ω – so power is limited to 250 Watts and, as the filter unit is unity gain, I cannot drive the amps to their full output. Even so, it is very loud and music I know well sounds quite different with proper bass. I adjusted the gain of the system and wired it for 2Ω ( It was used in Thailand driving 2Ω with no problems – the amp has 5 fans and does not over-heat )

When playing techno dance music, the bass has real authority – no booming or bleating and a bass drum sounds and feels like a bass drum. Action movies sound great too. It amazes me how low bass notes will go and how powerful they can be ( the system has a 10 Hz cutoff ) There are plenty of 'Bass-Boosted' music tracks on YouTube for impressing others with your car subwoofers – and they will not destroy a concrete speaker ! The speaker cone is well loaded from below and from above and does not flap around. A wooly mat or carpet can be placed underneath the speaker for more damping if thought necessary. When not in use, plug the ports with plastic tubs and cover with a tarpaulin. ( Half-kilo yoghurt tubs fit perfectly )

We should not forget the importance of dance – it is something ancient and tribal in our subconscious and often neglected these days. Aerobics with dumb-bells is also more fun with dance music. Whatever you listen to, you will be satisfied with the clean, tight bass that only a concrete speaker can give. ( An even better speaker would be granite if you have the skills, money and time to make it )

Cultivation of Essential Oil Plants and perfume oils

Extraction by steam-distillation .

 Ethyl Alcohol 90  ( A cotton bud dipped into it will ignite easily so it must be 90%  )  is available @ $2.5 for 500ml and is from a pharmaceutical company so it is colourless not " purple meths " - I am hoping the other 10% is just methanol. However, steam is easier ...

So steam it will be for now !

 This is the prototype, small Essential Oil Still built entirely of stainless steel - TIG welded . It has an electric heating element and phase-shift controller, thermometer, and water replenishment system.


An immersion water pump circulates cooling water. Now waiting for white jasmine which is grown in Cambodia.  I have tried mango and mint, but not very successful. Inside view of tank with 1500 Watt heater and silicone gasket. Four extra bolts and wing-nuts now added for better sealing.


A wide variety of fragrant plants can be grown in Cambodia

Amplifier and speakers made in Cambodia


After having a reasonable sound system in Thailand and Laos, I really missed not having one in Cambodia - so this was made from Chinese packing crates and scrap wood - hence the slight mis-match in sizes ! The drive units have double magnets and sound quite good - better than expected !  The amp has an internal 60Watt switching power supply or will run off a 12 volt battery during a power cut. I have since used these speakers for the rooftop sound system.

The first amp I repaired in Laos had one channel not working and I made this quick and nasty signal generator to fault-find it with. ( I didn't have much test equipment then ) - I now have a dual-channel USB 'scope, dummy load and much more equipment.

This is my room in Laos : an audio amplifier is under test - the small black box with 3 knobs on top is my new Wien-Bridge signal generator ( much better than the first sig gen ), dual-channel USB scope and 8 ohm dummy loads. The computer can display on two screens which is most convenient.

Most TVs in Laos are ancient CRT jobs and usually Chinese or Korean as they are much cheaper than LCD ones ( the Chinese ones have spare parts easily available ) - after 10 years or so the cathodes are losing emission and the colours are weak or non-existent ! I built this TV re-juvenator to strip the surface of the cathodes and give the tubes a new lease of life : It gives the heater a 50% boost and briefly applies 300 Volts to the first grid until it will conduct 50 mA or so. If 300 Volts is insufficient it can be increased up to 1300 Volts ! It was most successful restoring red and blue to an old TV that had only a green picture and the picture is still good so far.......

Liquid butane is a very good non-polar solvent and will extract essential oil without extracting chlorophyll - it does, however, extract undesirable waxes but these can be removed with an ethanol separation if necessary. The procedure must be performed outside as butane is highly inflammable !!! No flames or electrical equipment nearby.


 All stainless steel construction TIG welded with PTFE and silicone seals. Needle valve control. Korean butane. Packed column and butane kept in the freezer for at least two hours before extraction. Excess butane boiled off after extraction by hot-water bath - leaving the essential oil in the Pyrex dish.

Extraction in progress - column gets even colder and covered in ice. One can of butane used for each packed column.  

Uses a ( donated ) Tec 12706 Peltier-effect solid-state cooler

The ambient temperature was nearly 40 C and so it had trouble getting to freezing - but it immediately gets cold enough to chill a finger ! It draws 4.3 Amps @ 12.9 Volts from my newly constructed power supply.

Hot-side uses an old Pentium Heat-Pipe cooler ( Must have been a hot and inefficient  beast of a computer ! )

What do I mean by "Less = More " - well the basic idea goes like this :
Our life force – that which separates a clearly living biological entity from an otherwise identical but dead one – is maximum at the time of birth and slowly decreases during our life span until our death. ( compare the energy of a 5 year-old with that of some-one soon to die ) What about the time of conception you might ask ? That is the time of first combination of genetic material but is not the time of first life as the egg and sperm ( or ovary and pollen as the case may be ) must by definition be already alive because conception has not yet been observed in dead ones ! During the time between conception and birth we are alive but in state where consciousness is suspended but vigorous growth occurs. It is the time of birth when breathing starts and marks the transition between an entity completely dependent upon its host and an individual entity – albeit dependent upon milk in the case of mammals. There is a sort of parallel between an animal birth and a seed bursting open into the world - so eating germinating seeds should give the most charge. Birth can be regarded as the first ticking of our "life-span clock" or in other words our " life-force clock" running in reverse. This force is used up at a rate corresponding with our well being – a serious illness will completely deplete our life force resulting in premature death. So if you accept that we are fully-charged at birth and discharged by death , where does our re-charging occur? I am using the example of a battery to imply that it is a FORCE that is being re-charged and not the other more-tangible nutrients from food. If our food is cooked until dead and has no remaining life force it is sustaining us physically but not topping up our special battery. Eating living food must give us the opportunity of ingesting this force and having it inside us until the moment of the food's death inside our mouth or stomach – whether we are able to retain it to re-charge depends upon our ability to receive subtle energies : sensitive people like mediums and dowsers should do well on a raw-food diet – and I believe eating the maximum possible amount of living food will get our body accustomed to and gradually more able to make use of it. There is also an exact parallel between the Big Bang Theory of the Universe evolving from a microscopically-small singularity and the first life on Earth from which all of us evolved ( It must have been a pretty tough group of extremeophiles to survive the vacuum of space ). If you accept that the singularity was very energetic (!) then it is reasonable to assume that the first life on Earth was also quite potent compared to an entity's life force now. ( In the case of Panspermia, or the first life on Earth arriving here on incoming space debris , The originator of all life in the Universe must have been REALLY powerful. ) The object of Zen is to miss out all the intermediate stages and go straight to the source but that is a very severe practise – too hard for me. I am trying to absorb living energy from plants that have already processed it from the Sun by photosynthesis and have it in a ready-to-go form rather than do a Zen-like direct attack at the source. I do not believe that plants mind me eating them and killing them inside me as in my present state of consciousness I am linked with my physical body which needs food and have not transcended into a state of not needing to eat , drink or metabolize any more – if such a state exists apart from death? It is reasonable to assume that life was more vigorous in pre-historic times : compare the huge size of many dinosaurs and insects to today's creatures - I doubt if Gravity was weaker then? – and wild animals are more vigorous than domesticated ones and modern humans. Wild animals in their natural habitat survive mostly on raw and living food – if you are not vegetarian you should eat Sushi ! Is life force quantised – does it vary smoothly or in discrete jumps ( Is the life force concentrated in each individual cell or does it seamlessly permeate the physical space occupied by the entity? ) - Is there more or better life force in a newly sprouted seed rather than a cabbage – Is quantity more important than quality – When a creature dies, does its life force just stop or does it go somewhere? - If there was an extinction event and all life force on the planet was extinguished, would it spontaneously re-generate or would it need to be "seeded" -These are difficult questions to answer so I don't bother with them too much ! I have decided to live off fruit which includes nuts and beans and is entirely suited to a life in the Tropics. It was difficult stopping bread, tofu and humus – but like when I stopped coffee and tea it becomes easier with time. I tried raw mushrooms in Thailand but they gave me severe diarrhoea for a couple of days ! There are other means of life-force charging like Chi Gong and meditation . Do not underestimate the value of Dance - there is something very tribal and necessary in free-expression dance : it is an element of all ancient cultures, but has been forgotten in the West - or replaced by over-stylized ball-room dancing and Waltzs etc. Raves are a deep part of our heritage and connect with our tribal past. So, dont forget Music and Dance.

Hence Less=More.


The Elixir of Life

Seriously ! I am conducting a personal project to try and live 20 years longer than normal - Not a mad Scientist but LESS = MORE