Spinal's Londinium Build

[petec]

wow, looks great spinal,

makes my build look tiny though ! How wide is your oven hearth ?

Great stuff

Cheers
Pete

[spinal]

41" internal diameter of the oven - the bricks are being cut to a 40.5" circle; leaving .25" on either side for expansion. I'll put some toilet paper or cardboard here to keep the gap until the fire's going.

The base is about 1.5m wide by 1.8m deep.

M.

[bookemdanno]

Nice work Spinal. Why not add some crushed glass to your polished concrete idea?
Its all the rage across the pond on the other forum!!

A pair of old Levis...tywrap the ankles, fill with bottles and smash them up. Tip out crushed glass and sprinkle into freshly laid concrete, then tamp down. Grind and polish.

I'd them throw the Levis away!

[cannyfradock]

Spinal

Great progress. Love the herringbone hearth. I laid a herringbone floor but laid it straight not diagonal.....I was just trying to avoid too much cutting, but I don't think it made much difference...I regret it now.

Terry

[spinal]

I was going to post one update at the end of today... but I'm being dragged climbing in the afternoon, so I don't know how much progress I can make.... grumble.

Anyhow, I woke up a bit early (for a Sunday) and started around 9:00. Including setup and clear-up time, I finished cutting the base in one and a half hour, which I'm pretty impressed by. I even "saved" 3-4 bricks by using offcuts and cutting those.



Now I plan to have some breakfast; clean up the dust from the living soom that crept in (before she wakes up), and then start marking up the bricks that are cut.

The intention is to move all the bricks off the platform, clean them properly to remove any rough edges (maybe even give some edges a pass with the grinding disk) and then screen the insulating board with a sand/grog/fireclay (2:1:1) mix. Then I can replace the bricks on top, and adjust to ensure that all the edges line up nice and smooth.

I'm half tempted to put a ratchet strap around them to keep them close... but I can't figure out how to deal with the front... so I guess I'll just have to keep them in nice and tight by hand.

Regarding the diagonal herringbone - to be totally honest, I didn't plan it I started on one of the sides, which is cut at 45-degrees when bringing the bricks from the driveway to the back, and then though "that doesn't look too bad, let's keep it that way"

Some of the cuts were a pain - the two small "shards" (both on the right - you can kind of see them) snapped in two - so are actually cracked underneath... but as long as the top is intact, I don't care too much!

M.

[h12rpo]

Re the expansion gap.........do firebricks expand? I didnt think they did

[cannyfradock]

Looks spot on to me.

Not sure on keeping the entrance in place while building the dome? Even though we all use the same or similar principle in building our ovens there are so many different permutations in getting there. i.e...I used a notched trowel and laid my fire-brick hearth directly on thermolite blocks using HB. On a clay oven I used flexible tile adhesive, lime and sand in the same fashion.

You said in a previous post you want to keep the outer joint free for expansion by temporarily plugging the gap with paper. I filled mine in with the dried left-over HB from laying the first ring, but others have also gone down the same route as yourself by filling that gap with ash......which will hold everything in place but still will "give" when expansion/contraction happens.

......Happy climbing

Terry

[spinal]

I've put the entrace in place as that'll all be attached to the dome (well - most of it). The expansion gap for the front/floor wont be until almost "outside" the oven as I don't want a little groove for the dough to get trapped in!

Re: the expansion gap - how thick did you make it? I was planning on going 2-3mm; but I'm starting to doubt it this is enough...

Since the last post, I've marked up the bricks, removed them. Then, I placed a thermocouple in the center of the oven just under the middle of what will be the hearth.

Laid a screen of fireclay/grog/sand over it all, and then placed the bricks. Running my hand over them there's only 2 edges I'm not happy with (about 1mm height difference) - but they won't go down any more... So once I have the first ring of bricks in place I'll proabably smooth out the edges with some sandpaper....

M.

[cannyfradock]

H12

Good question......They've already been fired in a kiln to 1800 degrees c or something like that. If they do expand it would be very minimal.......and would it be enough to affect the dome....Mmmmm
...good question!!

Terry

[petec]

Great info all this....

I'm hoping that they don't expand much as my hearh is pretty tight fitting inside the ring at a few places. ( less so at others !! )

Cheers
Pete

[spinal]

H12 - they do expand. How much depends on the bricks; some manufacturers will supply a sheet with the thermal expansion co-efficient...

Alumina for example expands at 0.005mm per meter for every degree Kelvin. As the bricks I use are 42% alumina, I'm using that. 1000K is about 725C - so the alumina alone will expand by about 5mm in normal use with a 1m hearth. This isn't massive, but if the dome has no give, the floor will push out the dome by 5mm, which is enough to cause a (small) crack. Nothing serious, you can just patch it up and keep cooking

Based on that, I'm thinking a 3mm gap is sufficient, as 5mm would be 2.5mm on each side... hmmm... maybe I'll make it thicker

M.

[spinal]

It's been a busy day!

Testing the floor/dome/door for size.


I tried assembling the arch separately based on some advice I got online. TBH, not a big fan of this technique as I'm not patient enough to wait for it to cure before I continue the build!


After some grinding, this is the first joint with the arch. Not the prettiest, but it works.


This is the start to my thermal break. I've kept it thin in the floor so that tools/pans don't abrade it too much. I plan on making an arch out of insulating bricks for the flue.


Finally, I got asked to what tools I'm using. This is what's under the hood:

Cheap (£25) PowerTools Mitre Saw with a £5 erbauer diamond disk. It's the first disk (I have a set of even cheaper 2 for £5 disks for when this wears out). Note that I had to remove the finger guard to get it to cut deeper:


This is my angle grinder with the disk replaced with a diamond abrading disk. Had to remove the guard here as well to fit the disk:


Finally, this is what I do to the edges of my bricks before mortaring them. I'm hoping the etches give the mortar more to hold on to...


The plan is to put two more rows tomorrow if I can work it around a lunch I need to go to. I'm leaving large gaps between all the bricks - these will be filled with a slurry when all the bricks are up. I'll try to get a picture of the inside tomorrow...

Finally, the end of the day:

M.

[faz]

Looks like a tidy dome.

One quick question - are you going to add any further buttressing to the arch, as with it sitting outside of the dome there is nothing providing horizontal force to the uprights to counter the forces from the arch.

Also - do you know how you will do the transition, as with the arch sitting in front of the dome you will have a bigger gap between the dome and top of the arch - you should think about how to bridge that gap. It is worth thinking about this now before you go much higher.

Oh - and be careful now you've taken the guards off your tools - especially the chopsaw. It will be difficult to finish the oven off if you're missing a few fingers!

[spinal]

One quick question - are you going to add any further buttressing to the arch, as with it sitting outside of the dome there is nothing providing horizontal force to the uprights to counter the forces from the arch.
I'm planning on coating the entire outer dome/arch in mortar... Then I may put some triangular buttresses in vermicrete beyond that... but I'm not sure yet... haven't thought that far

Also - do you know how you will do the transition, as with the arch sitting in front of the dome you will have a bigger gap between the dome and top of the arch - you should think about how to bridge that gap. It is worth thinking about this now before you go much higher.
Plan is to grind down the arch by 35-45 degrees or so, then with the next ring of half bricks, I'll mortar them onto the top of the arch.

Oh - and be careful now you've taken the guards off your tools - especially the chopsaw. It will be difficult to finish the oven off if you're missing a few fingers!
You should see the scars I have from the other stupid things I've done in the past... I may share a horror story or two one day...
M

[spinal]

Quick update - I'm now stuck.

My angle grinder decided that working conditions were too much like the ones at an Apple manufacturing plant, and decided to kill itself. Need to find a new one pronto!

m.