Barrel Oven Build Part 1 - External Metal Parts

So quite some time ago we decided to build a barrel oven, all the better to feed ourselves with whilst building which had become more of a challenge as more people got involved. I found it quite difficult to find anything approaching a detailed account of how to build a barrel oven. Lots of stories, very light on the specifics. I have the barrel ovens book from Firespeaking, which is quite thorough on how to do the brickwork, and found a few blog posts about the interwebs that helped. Most useful is probably this one, but it doesn't mention measurements or anything. There wasn't anywhere that could tell us in detail how to do the metalwork (mostly people just say "give some pictures to your local backyard welder dude" but since that's us we had to work it out), so we just sort of went for it, trying to think it through logically and come up with something that looked like it would work pretty good. We figured we might as well document what we did so that someone else can follow this for some tips and not have to work it out from scratch like we did.

I sketched up the parts based mostly on these two images:

 

Then I worked out the measurements based on a 55 gallon drum we bought at the tip, as everything had to fit around that. The front of the barrel will be flush with the front of the whole oven, and the front of the ash grate will be too, we want the outside of the ash grate to be about the same length as the barrel.

For the width, I figure it's best to judge this from the size of the bricks we're likely to be able to use to build the oven and make that + a mortar gap equivalent to the inside edge of the ash grate so that it can rest on the brickwork. This presents us with a problem as we haven't got them yet but would still like to begin the metalwork. Apparently the length of a standard brick is 22.5mm (again, trusty Wikipedia), and since the consequences of getting this bit wrong are that we'll spend a bit of extra time cutting bricks to size or getting creative with how we lay them it seems fair enough to run with that number.

I put these measurements together with my sketches and produced a cut list for Kyle and Baz (our handy blacksmith friend who's also good with a welder).

We ended up buying new metal as it was a lot quicker than accumulating tip shop offcuts and we had a long weekend we wanted to get it all done in. Cost us about $250 all up, and we had all the welding gear already between the three of us. The metal shop could have done most of the cutting for us, but they were a bit busy so it would have taken them three days and we wanted to get it done over the weekend. And so commenced the Long Weekend Weldathon of 2018.

Starting with the Ash Drawer we added a couple of little bits of angle iron in the corners to stabilise the structure as we were only using 2mm plate. All the welds went on the inside so it would sit flush against the brickwork. The welder was new (well, new to us) so there was a fair bit of trial and error and complaints about dodgy welds before they were happy with it.

  

We left a 10mm lip around the edge of the front of the drawer, and Baz is going to use his Mad Blacksmithy Skillz to make a handle out of offcuts a bit later on. I don't think the boys welded all the way along, just tacked down an inch or so every so at regular intervals along the edges. The drawer took maybe 3 hours all up, including all the setup, cutting and finishing.

Next came the Ash Grate, dimensions of which are based entirely on the drawer (the idea is that ash will drop through the grate into the drawer, but the burning wood stays on top). We had many extensive discussions about how far apart the bars should be and eventually settled on 10mm rod with 20mm between, after consulting many internet images and painstakingly counting how many bars they had. The grate took about 2 hours, and most of that was cutting and getting it all square.

   

Next came the Firebox Door, slightly more complicated but still pretty straight forward. We did an angle iron frame for the door frame, then a smaller angle iron frame around the edge of the door itself, and a strip of flat bar for the latch mechanism. The boys did something fancy (well, they thought it was fancy) with the hinges to get it all to open and close smoothly, but I was out getting insulation at the time they worked that out so I'm not entirely sure how it all worked.

   

Again, handle and latch from random offcuts a bit later on. One thing I noticed in some of the pictures I found was that there's a small piece of metal rod at a diagonal connecting the firebox door and the ash grate, to hold the door frame in place. This seemed like a pretty good idea to us, but for ease of storage in the mean time we'll only add that when we go to actually build the thing. That way we can also adjust bits as needed while we set the bricks around each part.

We tackled the Shelves next. I figured the mesurements after messing around with a tapemeasure up against the end of the barrel for a while and seeing what looked about right. After finding it almost impossible to find steel mesh that wasn't either painted or galvanised we went with the lesser of two evils and then vinegar-washed the galv off. We couldn't find a wash tray big enough so I made one with duct tape and corflute and lined it with a sheet of clear plastic so it wouldn't leak. I think we added a bit of hydrochloric acid at one point too because we got tired of waiting for the vinegar to work and didn't have time to leave it all night.

We strengthened the mesh with 10mm steel rod all around the edges, and another across the middle, so the shelves would stay flat rather than sagging over time.

The Racking for the shelves was the only part where measurements became a bit more important, in the sense that every other part once we cut things to length it just had to all go together, whereas with the racking we had to weld it at a particular spot. This is so that when the oven is eventually built the shelves sit perfectly level and our cakes don't end up wonky or spilling out. This was pretty fiddly, and was achieved mostly through meticulous use of calipers and squares. The distance between each of the uprights was determined by the rippling on the edge of the barrel, so anyone using a slightly different barrel to ours will have very different m

   

Finally, cleaning the barrel out was the topic of many discussions and an awful lot of messiness. We did search high and low for a place that would sell us a fresh new one, but the conclusion was that unless we wanted 1000 of them no one would even talk to us, so we had to clean out a used one we found at the tip. Eventually we cut off the end (with a chisel, a bit like a can opener) and Kyle scrubbed it several times with methylated spirts, then several more times with warm water that had super concentrated detergent in it. Kyle had to kind of climb inside it with each rinse (strongly recommend very good breathing equipment for this part, even the detergent stage). It seemed to work pretty well, but we'll be very careful the first time we fire the whole thing up anyway.

We bolted the racking to the inside of the barrel, which was the other part of the whole operation that really had to be totally meticulously perfect (to achieve level shelves) then done! Levelling the racking was a multiple-person job involving several spirit levels and a lot of swearing. I don't have good tips for this because I'm pretty convinced the way we did it wasn't very effective, though if you're in the mood it did occur to us later on that if we'd sat the barrel up vertically we could have done it off a plumb level rather than tried to hold the whole thing flat.

The last part of welding was the Oven Door, which we did last because we weren't quite sure how it was all going to work. This bit took quite a while to work out, so deserves a post all of its own, in Part 2.

Soap!

Given that our house won't be connected to any grid services, and we won't have a septic tank (and also we're not completely silly) we'll end up with a greywater system feeding into the garden. This raised questions for us about sodium build-up in the soil over time from soaps, to which the obvious solution seems to be potassium-based soaps instead.

(long story short, soap is made by combining a strong base with oils or fats, usually sodium hydroxide is used as the base but alternatively potassium hydroxide can be used and the potassium is friendlier to plants than the sodium).

After a bit of a search it seems it is possible to buy potassium soaps in Australia but they're either quite pricey or have loads of perfumes in them (which sets off Kyle's asthma). Ordering from overseas is again possible, but postage adds up.

Now, one of my majors at Uni was chemistry, and I spent 5 years as a science teacher. So I'm not particularly worried by the thought of making it all myself. But it was pretty easy.

I started with the Castille soap recipe here, with the aid of more detailed instructions here.

It doesn't look very exciting yet.

The soap paste turned out a little more fluid than I thought it would, but I suspect that's because my attempt at making distilled water in my kitchen resulted in nothing but burns and swearing so I had to use filtered water instead, which is not as good. I'm going to try and source some proper glassware for next time (lots of high schools don't do distillation anymore but have heaps of the kits and occasionally get rid of them).

I'll experiment with different dilution, maybe some colours and essential oils, and then a few different liquid soap recipes. I've also seen recipes that claim success in making a hard potassium based soap by using animal fats (as is traditional for sodium based soap), but accounts vary so I think I'll experiment when I have more time (and easy access to animal fat).

The power of the wind

We turned up at the site today to find that the site shed (a good 12m long, weighing in at somewhere around 3t) had shifted about half a meter at one end, and toppled off it's concrete blocks.

After much discussion, Dad and I spent about half a day very carefully jacking up the structure again and removing the blocks before re-stacking them. We cut out the soil underneath to tilt the blocks inwards, and Kyle shaped a block of hardwood to fit in the triangular gap to provide a flat surface for the joists to sit on, and a little shelf cut out so it couldn't shift side to side.

What we think happened is that in the strong gusting winds the end of the shed had shifted, milimeters at a time, and eventually ended up on the edge of the previous stack which caused it to topple over and move the whole thing such a substantial amount. We're hoping that the angle of the blocks here prevents that incremental movement in future so it can't get to the point of toppling again.

But, to be sure, we dug a hole about 45cm deep and used some leftover concrete we're glad we had lying around to sink half a sleeper right up against one of the main struts. Currently we only have one, as it was an awkward hole to dig (half under the structure) and so took us a long time. The aim was to get the building to a point that was stable and safe first, before ensuring it stayed that way longer term.

We're going to add another couple of these posts (we've got loads of sleepers leftover) until we have a few on each side, though the prevailing wind is strongly from the northwest so this first post went on the northeast end (the end that shifted).

The other possibility that occurred to us was that the building could roll. The wind is very strong, and it's close to side-on (we wanted a cross breeze in summer). We're not really sure how much of a risk this is, and have no way of knowing. My assumption is that the shed is bottom heavy (there are two very large steel girders, with substantial steel joists across, that make the base of the structure, whereas the wall joists are smaller and I think aluminium). However, while the chance of it tipping may be low the consequences if it did so would be catastrophic - I doubt the structure would survive, nor potentially would we if we were inside at the time. We'd certainly have no way of righting it again ourselves.

A few suggestions were made, everything from angle iron braces on either side, and guy wires. Eventually our favourite suggestion so far came up - webbing and ratchets (substantial ones) attached to hooks concreted into the ground on either side, strapped over the whole structure at solid points. We're still figuring out the details that will make it work, and may yet do something different. We have most of the stuff for this strategy already, and it would be fairly quick to implement, whereas any other way would require us to go buy a bunch of materials.

For the moment, crisis averted. But we'll watch this space very carefully for signs of movement.

Let there be light!

My Dad kindly offered to design and put together a custom solar electrical system for us. Always nice to have bored retired engineers floating around when you need them. He was planning on replacing the solar panels on the roof of his camper van anyway (upgrading to make better use of the space) and we got the (still perfectly functional) old ones.

Batteries arrived a few days after Dad did, having been off to the coast for a few weeks. Lithium, 8 cells in total to achieve 24V.

He had a friend help him switch them on the roof of the camper van, as he had some better equipment than we did. They also welded up some frames for us for the old panels.

The framing is designed to be as simple as possible, able to stand up to strong winds, and potentially mobile in case we ever want to shift the panels closer to the eventual main house. There are 4 uprights of heavy angle iron (50mm) pounded into the ground at the corners. Then a rectangular frame of lighter angle iron (25mm) to hold the panels. Finally, two pieces at the southern corners to raise the frame at an angle.

We had to add an extra upright in the middle of the wider section of panels, as they sagged a bit which bowed the frame and made it prone to swaying in the wind. An extra piece of angle iron and a bolt fixed that.

The angled pieces on the southern end are fixed with bolts and wingnuts, and though they're current set to a steep angle as it's coming in to winter there's another hole drilled in the right spot for a shallower summer angle. The extra effort involved in changing the panel angle twice a year is well worth the gain in power.

Dad keeps joking that we'll have to stage some kind of ceremony twice a year on the equinox to change the angle of the panels. I'm not sure what the appropriate attire would be for blending science and druids - I have mental images of a group of people in long flowing lab coats chanting Monty Python songs while switching the bolts.

Dad spent a few hours testing the wiring in the site shed, which we were surprised to find seemed to check out.

Kyle and I spent two days building a weather proof box to house the batteries, inverter, and so on. A wooden frame, with cross pieces positioned in specific places to allow for attachment of various parts.

Then galv sheets over the outside to clad, and a corrugated iron roof. We made one side out of leftover perspex we had lying around, as one of the parts inside the box has a display to do with battery cell balancing. I thought about doing a window, but the whole side was just easier.

Dad spent the next week while we were at work setting up all the parts and cabling. At some stage I'll get him to do a post about why he picked each particular part, and how it all went together. It'll be like an entire thesis, I'm sure. He keeps talking about first principles of battery charging, but the system he's designed is a highly customised set-and-forget. Either way, he wired up everything into our box nicely.

Then, we turned up the next weekend, and most of the wiring in the site shed just worked!

We have a dozen or so power points, several internal lights, and an external light. Over the coming few years the idea is to expand the system as needs arise, but currently we have panels that add up to about 600W, batteries at Ah, and a 3kW inverter. That translates to enough power to run most things we need for day to day living, though there's not so much extra that we won't have to watch it a bit.

After all of this was hooked up Dad and I ran cabling into the building for an inverter on/off switch and a battery level gauge, but I forgot to take photographs of that part. Which is a shame, as passing the cabling up through the walls required some amusing gymnastics. I'll take a photo next time I'm out there as we have a few bits to add to it yet.

Site Shed

Time pressure on self-builds is a funny thing. It makes everyone mad and stressed. Most people try and make it go away by having a temporary house while they build the main one, to avoid paying rent and building at the same time. Often a caravan, or garage that's been converted, that kind of thing.

We'd had it in the back of our heads for a while, even tracked down a mining company that was selling off a bunch of temporary accommodation blocks a few months back, but we had trouble finding something with more than one window that was within a reasonable distance. Then we found this on GumTree:

It needed a fair bit of fixing up, but was very cheap, so we figured we didn't mind. Getting it to the site was a whole day, then it took us three weekends worth of work to get it completely weather proof. One day of silicone and caulking guns on the outer walls, about half a day for Kyle on the roof (we went over all the screws as the seals had perished, and up under the edge of the rim just in case).u

There were 3 big rectangular holes in the wall, one in each of the 3 rooms, that had had air conditioners in them. Kyle tidied them up a bit, then screwed a sheet of perspex over two of them. We sealed up the outside, then Kyle plastered up the edges and put frames around them to make them look like windows.

The third one, though, still had the metal frame that had held the air conditioner itself. We decided to leave that in, and make a little hidey hole for our cats with it. I cut away the vent screens with an angle grinder, and gave the whole thing a good clean. Kyle put perspex over each of the gaps and sealed it up with silicone.

I'm going to make a full height scratching post for our two cats to climb up to get to their sunroom. But first, we had to make the rest of the place liveable.

Pulling up the old vinyl flooring took a lot longer than I thought it would, and it was a hard job. The old vinyl was very brittle, so you couldn't just get a big patch then pull, it came off in tiny little pieces more often than not. Eventually my Dad had the bright idea of hooking Mum's hair dryer to a long extension cable plugged into their camper van, which softened the glue enough to help.

At this stage, the walls are sealed (inside and out), the old floor is out, we've bought new flooring, and will likely put it in sometime in the next week or two. We did spend the night in the end room one weekend, and it was bitterly cold, so we're exploring our options for adding to the ceiling insulation, and I'm going to make some thermal curtains for all the windows. We'll look into diesel heaters as well. Given this is a temporary home we don't want to spend too much time on it - we'll get it comfortable, but our focus is still on the main house.

Birdwatching

My Dad is a very keen birdwatcher. By very keen, I mean that he has well over 5000 pictures of birds that he's taken and loaded onto his computer, and has been known to abandon cups of tea, chocolate biscuits, even entire bowls of dessert in order to leap for his camera and capture some rare feathered example. There was one moment, building the outdoor kitchen block, in which he almost made a leap from the top of a ladder because he forgot he couldn't just grab his camera from there. I think he's made it his mission in life, lately, to single-handedly undertake a survey of the local bird populations around our property.

This particular bird (you may have to zoom in above to see that I've taken a photo of him taking a photo of a bird in flight) had been hovering just outside the range of his lens for a few weeks. Apparently this was most frustrating, as it prevented him identifying whether it was a Nankeen Kestral or a Black-Shouldered Kite.

Luckily, a day or so later it seemed to have gotten used to him enough that when he approached the tree it was perched in it just looked disdainfully in another direction rather than acknowledge Dad's presence by actually flying off.

Which is how we know that we have a small family of Black-Shouldered Kites in the area, in addition to the vast numbers of crows, cockotoos, galahs, wrens, some kind of swallow relative we've yet to identify, and the occasional Wedge-Tailed Eagle.

Places in the garden

Kyle and I are both firmly of the opinion that you need a certain amount of 'silly' when embarking on a project like ours. So, as stories emerge of our exploits on the property we give names to the places they happen.

For example, my sister Rachael came with us when we first bought the place and we went to explore the creek. She's a bit more concerned than we are about getting muddy and wet, so when we jumped across the creek she said she'd find a better spot further upstream. We told her that was as good as it would get, but she stuck to it, so 500m further upstream she was stuck on the other side from us. Thus, this section of the creek is dubbed 'Rachael's Folly'.

Which, of course, necessitates putting up an artfully rustic sign...

... and taking selfies underneath it...

... to forever commemorate this event, and remind Rachael in future that she should cross there after all...

... we're not really sure how Rachael feels about this. But, now that I've posted it here I guess we'll find out!