Mechanarchy Solar Cookers - Cook Your Food Free, From The Sun
This was the very first Solar Cooker that I built. Some 4 years down the track and it's still going strong, and, because there are no working parts to fail, I suspect that it will see out my lifetime.

It is made from an old Truck Tool Box, with a fabricated inner lining, with insulation between it, and the outer box. The mirrors are off old wardrobe doors. The frame holding the mirrors, I made from scrap pine wood that I had lying around, and scrap plasterboard battens, to hold the mirrors in place.

The lid is Double Glazed, Vacuum Sealed, Toughened (heatproof) Glass. I had no idea just how well it was going to work when I built it, but you can see from the photo's below, the exceptional results. The Solar Cookers I make these days, are smaller and a lot more refined. You can see the new design Mechanarchy Solar Cooker in the photo's below. (Coming Soon)

Home
If you want to skip this introduction to Solar Cooking and jump to the step by step of how I build them, click here. For Solar Cooker Recipies, click here.
Chilli Red Kidney Beans, Rice and a Barm Brack Cake, all cooked in less than a day......
Chocolate Chip Cookies, Golden Brown.......
Zucchini, Tomato, Herb and Cheese Bake.........
Chocolate, Apple and Cinnamon Bread.........
Setting up your meals for the day couldn't be easier. Everything just goes in the pot in the morning, you stick it in the Solar Cooker and 3 - 4 Hours later, you are ready to eat.

No stirring, no temperature to turn up or down, no worries about burning, just very slow cooked, highly nutritious food, all cooked free from the Sun........

The Step by Step, on How to Build Your Own Solar Cooker
One of the easiest ways to get the 'inner' part of your solar cooker, is to get your hands on an old laundry tub. You can sometimes find these at the local tip, but they are often damaged or too rusty to use.

I picked these two up at a local second hand store for AUS$35.00 each, they are in good condition and will last for a very long time.

The main aim here is to locate a tub that isn't damaged or rusty, that way, you'll ensure that the cooker you build will still be around and working fine in 20 plus years time.

Solar Cookers develop a lot of moisture during the cooking process when compared to electric or gas cookers, so we don't want any existing rust to develop further.

These two still have remnants of tiles, tile glue and silicone on them, from when they were ripped out of their previous life, and they still have the drain plug holes in place and, the one on the left, some overflow holes and piping.

If you can find a tub without the overflow holes, it will make life easier, as these need to be covered to prevent heat from escaping, an extra task.

The first job is to remove all the remnants. I use an old hacksaw blade, broken down to about 150 mm, and sharpened like a chisel, on my hand grinding wheel.

Most laundry tubs have tile / tile grout / silicone and paint splatters on them (the latter from people washing down their paint brushes), and all this needs to be thoroughly removed.

Next, I use a good quality cloth backed sandpaper, to rub down the tub, both inside and out. It's important here not to go overboard, we just want to create a slightly roughened surface for the etch undercoat to stick to.

Paint? Yes, the tubs need to be painted in a matt black heatproof paint, we're talking 200 Deg C here. A shiny stainless steel tub will reflect, rather than absorb heat.

These instructions cover the full manufacturing process for a professionally made solar cooker. You can make a solar cooker from just about anything, including a cardboard box and aluminium foil. But following a number of years of research, I have come to the conclusion that there are a lot of claims out there in Interenet land, many of which result in less than satisfactory results. A lot depends on where you live, the amount of sun hours you get, and the amount of wind (which can cool the cooker), and, the materials used to make it. The cookers below are not cheap to make, but the aim is to produce a cooker that not only lasts for at least 20 plus years, but also one that works to maximum efficiency in various conditions.
Most laundry tubs are made with a 'lip' which sits under the tiles to prevent water from washing down behind the tub and onto the wall. This lip is not needed on the solar cooker, in fact, it gets in the way of the glass lid.

Whilst it could be bent 180 degrees from where it normally sits, this is no easy task with stainless steel. So instead, I bend it down (carefully) to around 90 degrees from its original position, before cutting it off.

To bend it, I simply place a piece of wood under the tub, clamp it, and then very carefully bend the lip using an adjustable spanner.

This takes a bit of time, we don't want to 'kink' the metal on the top face of the tub, as this is where our glass lid seal is going to sit. Take it slow, a centimeter or so at a time.

Some tubs have a thin lip, and others a thick one. The thin lips can be cut using a pair of tin-snips, the thicker ones, an angle grinder if you are careful.

You need a good quality pair of tinsnips to cut stainless steel, so don't skimp and buy the cheap ones. It's important not to cut to the 'end' of the tin-snip blades, as this will create a notch in the steel.

Every centimeter or so, get a pair of pliers and 'curl' the steel that you have cut, away from where you are going to cut next. This makes life a little easier.

As you go, you should end up with a nice 'curl' like the one to the left.

If you keep your tin-snips straight, you should also have a nice straight edge, that has no 'jagged' protrusions.

Once finished, I file the edge on both sides to remove any small 'burrs', and smooth out any sharp edges.

Next, we need to cut out the seal for the the drain hole in the tub. I am using some scrap 1.6 mm aluminium plate which I have lying around, but any steel sheet will do fine. If and when I can get my hands on an old washing machine, it often provides much of the steel sheet for an entire outer solar cooker build. I am going to use aluminium in many parts of this build however, because of its superior heat retention when painted black.

I use an old 'borax' container as a template, as it it the perfect size.

I mark around it with a pencil before cutting it out.

To cut out the metal seal, I use a jigsaw with an aluminium cutting blade, set to 3 - 4 on the speed variation, and 1 on blade orbit.

Make sure you clamp your work-piece and that you wear safety goggles, aluminium plate throws off a lot of particles when it is being cut and they go in all directions, including towards your eyes.

Take the cut slow, and make sure you move your body around the work-piece instead of trying to move only your arm. If this means stopping, in order to re-position your feet, do it, it will make for a far neater cut.

Once finished, use a file to remove any burrs and smooth out your circle.

We're looking for a fit something like this. If it is a bit rougher, don't be too concerned. This aluminium plate will be siliconed before being pop-riveted into position, meaning that it does not have to be a perfect fit in order to seal off the old drain hole.

The main aim is to stop any moisture (during the cooking process) from getting in underneath this plate, as this will only deteriorate the aluminium and possibly rust the laundry tub.

Once this work is completed, it's time to put the first coat of etch primer onto the outside of the tub.

Make sure you wash the tub down first in hot water and detergent, then wipe it over with a clean rag dipped in some methylated spirits to remove any residues.

It is important to paint the 'underside' of the cooker, black, as any reflective material, anywhere in the cooker, will simply reflect heat away, which totally defeats the purpose.

If we think about house insulation, it often has a reflective foil component that is always placed facing the 'inside' of the house, this is because it works more efficiently to reflect radiant heat when it is placed this way.

So in the solar cooker, to gain maximum heat retention, we do not want any reflective surfaces (apart from the mirrors, that reflect heat 'in') that reflect heat away from the cooker.

Whilst the first layer of undercoat is drying, I make up the plates to seal off the washing machine spin dry hose outlets in the tub. Not all laundry tubs have these, so it isn't always necessary.

I considered placing a temperature gauge in one of the holes, as it would be the perfect spot, but in this build, time is against me sourcing one that's the perfect size. Instead, the gauge will sit where it normally does, on the top inside surface of the oven.

I am fitting the seal plates (seen here placed on the left and right holes) underneath the tub, this makes for a far neater look from above.

Once again, I simply cut these out to shape with the jigsaw.

Next, I begin cutting out the outer skin plates. I have two sheets of 1.6 mm aluminium plate for the three builds I am doing. I would much rather get hold of second hand aluminium but it is extremely hard to find. Aluminium is incredibly resource excessive during its manufacture, sucking up huge amounts of electricity.

But its also the most efficient material to use on solar cookers, so I figure if it's going to last for way more than 20 years, without consuming one more watt of human produced energy, that's pretty damned good!

After cutting out each of the outer skin side plates, they need to be painted in etch primer, 2 coats, before adding two coats of 'Pot Belly Black' Heat Resistant paint. At this stage, I am only painting the inside faces of the outer skins, the outside surfaces will be painted once all the engineering work is completed.

There are some very ordinary versions of Heat Resistant Paints available, that are thin and take numerous coats to get a good finish. I use an Australian Made variety, produced by 'White Knight'.

It's self priming, but with the Etch Primer Undercoat, adds a very thick layer of paint to the surfaces, and requires far less coats than the thinner cheaper varieties on the market.

Whilst the paint is drying, I cut up the corner pieces of aluminium angle. These are 20 mm x 20 mm x 1.6 mm, and will be attached by Pop Rivets to the side plates.

Try and get these cut to exactly the same lengths, it will save a lot of time and effort if you can.

Make sure that you file off all the burrs after cutting them, it will make for a better seal against the side plates.

Next, I begin the process of covering up the Spin Dry holes in one of the Laundry Tubs. This will not be necessary on all tubs, simply because not all have them.

Firstly, I put the aluminium plate that I have previously cut out, over the hole and drill it in two places.

Then I use a good wad of silicone around the hole, before putting the plate in place and use Pop Rivets to secure it in place.

This helps to ensure that no heat is lost from inside the Solar Cooker.

The aluminium plate that I previously cut out, is positioned over the silicone and Pop Rivets are used to secure it in position.

These will also be painted in Etch Primer and Pot Belly Black, as we do not want any 'reflective' surfaces removing heat from the inside of the Solar Cooker Box.

I've also added extra silicone around the edges of this plate, to ensure that the seal remains in place for years to come.

The Etch Primer and Pot Belly Black will only cover silicone that is paintable, so make sure you get the right variety.

To attach the side plates with approximately 5 mm protruding above the laundry tub top, I use some scrap aluminium channel (10 mm), cut down to about 5 mm as shown here.

This can be placed under the tub (when it is upside down), allowing the side plates to sit on it at the correct position before I Pop Rivet them into place.

You can see the aluminium channel protruding just slightly from the side plate that is sitting on them.

I use Vice Grips to hold the plate in place, before marking out the drill holes, at approximately 100 mm spacing.

You'll need to make sure that you get your drill speed right, as you will be drilling through aluminium first, and then Stainless Steel second.

Aluminium drills far better at a slightly faster speed, and the steel, with a good sharp drill bit, cuts better at a slower speed.

Once the top Pop Rivets are in place on two sides, I attach the 20 mm aluminium channel on the corner, with Vice Grips, mark out the drill centres at 100 mm spacing and drill through.

Sometimes when drilling through aluminium, you will get a small burr on the other side, which will prevent the Pop Rivet from 'pulling in' sufficiently enough to close any gaps.

Make sure you remove this with a file, it will help create a better seal.

Once the three side panels are all in place, it's time to drill the aluminium round plate to seal off the old drain hole.

First I drill through both the plate and the stainless steel of the laundry tub, this ensures that no drilling swarf gets mixed up in the silicone.

Then I simply put some silicone around the area to be sealed, before using Pop Rivets to secure the plate in place. Use a liberal amount of silicone to get the best seal.

The plate in position and secured. Once dry, make sure that you remove any excess silicone from around the sealed area, this will help the Etch Primer bond to the Stainless Steel.

This is easily achieved using a hacksaw blade scraper or similar.

Check the underside of the hole to make sure that the silicone has sealed off correctly.

Because I removed the 'lip' from the old laundry tub (because it was too high and would have interfered with the lid seal), I need to put something in place to secure the rear side panel.

I am using some aluminium channel, which I have clamped with Vice Grips, before drilling through the top of the laundry tub.

Because the channel that houses the Glass Lid seal will sit above this, I dont want to fix it permanently at this stage. Both channels will eventually be fixed together through the stainless steel.

For the moment, I simply want to drill it and temporarily secure it in order to fix the rear side panel.

Once drilled, I temporarily secure it in place with self tapping screws.

This will enable me to drill and secure the rear side panel in the correct position.

When the rear side panel is in its correct place, I drill through it and the channel pictured here, and secure it with Pop Rivets at the same 100 mm spacing.

Then I simply add the last two 20 mm aluminium angle to the corners.

I leave the base plate off at this stage, because there is still much work to be done, attaching handles, mirror brackets and other bits and pieces. Once that's complete, the underside gets stuffed with insulation, to make sure that the heat stays where it is needed, inside the Solar Cooker.
Two Solar Cookers starting to take shape.

Whilst the silicone is drying in cooker number two, I wash the other one down and then paint the inside and outside of with its first coat of Etch Primer.

Once dried, I then paint the inside of the cooker with two coats of pot belly black.

The Double Glazed, Vacuum Sealed, Argon Gas Filled Lids will be arriving this week, as well as the Silicone Coated Fibreglass Braid Seals, and the insulation, so I can soon start the lid construction.

Next I fit the aluminium channel that will hold the lid seal. I am using some channel from an old computer frame, it has an inside channel measurement of around 8.5 mm. I put it in place, drill through it at 100 mm spacings, and slightly mark the stainless steel beneath it with the tip of the drill bit.

I remove the channel, centre punch the marks and then drill through the stainless steel. After cleaning all the drill swarf from the area, I then run a bead of silicone along the corner to help create a better seal and help prevent the edge of the Tub from collecting moisture and rusting.

Then, after removing the burrs form the channel that the drilling caused, I replace the channel and pop rivet it in place. If you are using channel that's about 8 mm deep, you'll need a pop rivet gun with an extended nozzle, so that it can reach down.

Because I am using aluminium channel from an old computer frame, it isn't exactly the right length (as you can see top left of this photo), so I will cut another short piece to finish off the length.

The reddish brown strip on the right, is one of the silicone coated, woven fiberglass braid lid seals already in place.

It's approximately 10 mm in width and needs to be slightly compressed to get it into the channel, but this helps keep it in position.

This braid can withstand temperatures of up to 300 degrees celsius, in excess of what we need, but it will last a long time. I've tried sourcing natural materials for this seal (like cork) but not surprisingly, most natural products (ouside of rocks) are rarely subjected to this kind of intense heat and deteriorate rapidly.

Whilst I am drilling all the holes for the aluminium channel, I mark out the two sides of the solar cooker where the handles will sit.

These are the shortest length sides of the cooker.

I don't attach them until the external surfaces of the cooker are painted with two coats of pot belly black paint.

When drilling through the sides, make sure that you are extremely careful not to push too hard, otherwise, when the drill goes through the outer plate, you can easily hit the outside surface of the stainless steel tub, scratch off the paint and possibly break your drill bit.

Following the drilling, I paint the outside of the cooker with its first coat.

Once dried, I continue on with the installation of the lid seal aluminium channel.

I've mentioned before, just how important it is to make sure that you de-burr all the aluminium after you have drilled through it.

If you dont, it will create a gap, by lodging between the two surfaces you are trying to bring together when using pop rivets.

We are looking for the best seal possible without any gaps. If you do it right first time, you'll cut down on the amount of silicone sealant you need to use.

The lid completed. In this construction, I've used two pieces of 20 mm aluminium angle to form a channel as I had some spare around the workshop. To make life easier, you can simply use extruded aluminium channel of the right size to fit around the glass. The glass is toughened, vacuum sealed, argon gas filled, double glazed. Each piece of glass is 4 mm thick and there is a 12 mm gap between them, 20 mm in total. The 12 mm gap is the optimum for heat retention. You can get these made up to any size you like at a good glazier.
As you can see here, I've extended the glass frame beyond the back of the cooker, to provide a hinging point. To add extra support to the hinge, I've placed some 19 mm aluminium box tube inside the channel (from where the glass ends) and pop rivetted it in place. I then mark out where I want the hinge bolt, and drill through. The easiest way to get this centred, is to use a wood dowelling jig. For the hinges, I've used some left over checker-plate aluminium. I buy this for some of the bicycle trailers I make and keep every bit of offcut for other projects. I've cut them out with a curve to contrast with the overall square box shape. I use pop rivets to secure them to the side of the cooker. I then put a black plastic plug in the end of the box tube to finish it off.
In between the hinge plate and glass lid frame, I have used a spacer that came from an old BBQ. It's heat resistant and provides a perfect amount of movement without binding. If you can't locate any of these, a good thick fibre washer will suffice.

Next I attach the hinges for the rear highly polished stainless steel reflector, to the 19 mm box aluminium that I also placed at the rear of the glass lid frame.

Once the lid is secured, I turn the cooker upside down, (making sure I've got something soft underneath the glass), to begin fitting the base plate. I've left this off until now, just in case I needed to get to anything inside the housing, and to clean out any drill swarf.

Here I've attached some small pieces of aluminium angle that came from an old computer frame. These will help keep the base plate in position whilst I attach the 20 mm aluminium angle around the edges.

Once again, these are simply pop rivetted in place.

I quickly paint the underside of the plug hole in Pot Belly Black, before starting to put the insulation in place.

Insulation? Thanks to the incompetence of the Australain Government, there are simply truck loads of this stuff going out at bargain basement prices in 2011.

It's not often that one can take advantage of the massive waste that governments perpetuate through their inane pursuit of 'economic growth'.

Don't you just love the labelling? 'Green Batts'. No doubt some Canberra based totally unimaginative marketing bureaucrat came up with this one.......

But I digress. I cut up the appropriate sized pieces using a pair of scissors, whilst wearing gloves and breathing apparatus.

The safety gear is essential as these fibres are very fine and diperse everywhere. It's also a good idea to have a shower after completing this step, because no matter how carefully you cover up, these itchy fibres tend to get inside your clothing and irritate you.

Then I simply push them down the sides of the cooker, before finally fitting in the bottom layer.

If you want to bypass using this kind of insulation, you can buy a wool based version, but it will add considerable cost to your build. Unfortunately, most (not all) customers want heir cookers at the lowest possible price.

I've already cut out and painted the inside surface of the base plate with undercoat and Pot Belly Black. I sit this on top of the supports that I previously fixed inside the cooker box.

Then I cut up the 20 mm aluminium angle with 45 Degree angles at the corners.

Once in place, I drill through each surface and fix them in place with Pop Rivets.

Then I paint the underside with undercoat, wait for it to dry before adding two coats of Pot Belly Black.

I will fix four rubber feet to the underside once this has dried.

This method of hinging allows the lid to swing 'over centre' and prevents abrasion of the seal.

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