After some four years of prototypes, including Bertha 1 and Bertha 2, Luna has indeed landed. With precision.
It's amazing what we have learned from building and using ovens - both woodfired and 'on the grid'. If I had a dollar for every time I cursed Bertha (and then rapidly retracted my curse, as I knew she'd kick me where it hurts when I wasn't looking later on), I'd have built another ten ovens by now with the proceeds.
Essentially, both Berthas started life in a state of deeply confused creativity.
Bertha 1 was a swiss army knife - a cafe cooker and a baker's oven. She had a useless bottom deck, and arrived without any insulation. She burnt the hairs on our chef's legs so many times they had to wear long trousers, even in midsummer. She burned out the exhaust system, and melted herself out three times in three different places. Despite all this, I managed to tune her effectively enough to pump out a couple of hundred awesome loaves every Saturday morning - and she handled her cooktop duties well, after lots of tweaking. She really was a comedy of errors, though, and the best learning facility a baker and a boilermaker could ever have.
Bertha 2 was more focussed - a purpose built baker's oven from the getgo. She still managed to burn out her first firebox inside 6 weeks, but when we replaced much of it with stainless steel, she ran like a trojan. Then I almost destroyed the bottom deck by accidentally setting a fire inside it (seriously!). But, she was made of stern stuff, and survived nonetheless, with more brick being added in there. Bertha 2's big problem was that she was designed for 7 day a week service, but in the end she only got to be used for two or three days (have a look at the stories concerning Denison Street for more about this). However, as a result of her reduced role, her unsuitedness to short baking shifts really became a major issue. She weighed almost 4 tonnes when fully tuned, and it took a full day to get those bricks hot. In addition, her insulation and flue design needed major work, in order for her to heat both decks within a reasonable time frame evenly.
Again, so much was learned. On to oven number three - a make or break proposition for me, as both Berthas had cost me so much time and lost product due to their many design and application faults, I simply couldn't afford another 'crash test dummy' scenario playing out.
This time, Craig Miller and I spent a whole lot more time on the design and the assembly - almost twelve months in fact.
The brief was very specific, as I wanted to build a mobile bakery and the oven was to be the centrepiece. It was:
- Make a lightweight woodfired oven that can be towed by a vehicle - less than one tonne in weight if possible
- Design it to heat up in an hour from cold
- Design it to heat evenly, top, bottom, sides and back, so that it will be easy to use
- It must be super fuel efficient so we dont have to lug lots of wood around
- It must be very clean, so public places don't fill up with smoke when it's used
- It must be capable of baking 250 loaves in 5 hours
- It must be able to accessed internally easily, and should be able to be fixed with a screwdriver, a drill, a hammer and a crowbar.
Well, now it's built. We called her Luna, because she looks like a lunar landing craft. How did we go, against the brief?
Well, not too bad so far - but some things only time will answer, and I've only baked with her half a dozen times so far. But I'm finally very happy with our oven.
She weighs about 1.5 tonnes - so she's a bit heavy. I'm not sure if it's possible to answer the capacity question with a lighter oven though. And 1.5 tonnes can be towed.
It heats up in two hours from cold. But in two hours, she's VERY hot.
Once she is hot, she is very even. And she heats up evenly too.
She is super fuel efficient - she runs mainly on sticks, with a bit of lumber for holding coals. She uses half of Bertha's fuel, and burns almost without ash.
Smoke only happens at the beginning of the burn, and when a large log is used for a few minutes. The rest of the time, she is smoke free.
She can do more than 250 loaves in 5 hours - though how much more I don't know yet. Let's just say she's very fast. I do hope she's fast enough, though!
Most parts internally can be easily accessed - though now she's on the trailer some of them are not as accessible as they were. And she can be fixed with our third world tools too.
So, Craig and I believe we have answered most of the brief very well. Indeed, only time will tell - we still have to finish the rest of the mobile bakery, so we won't know how good she is until she's been towed around a bit and used in the field. But early indications are very encouraging.
I have to say that I already think she's the best oven I've ever owned.
Stay tuned for the technical stuff!