40" corner build in canada: underway

[semlin]

well i have finally made enough progress to start a build thread. it a tight fitting corner build. you will see i am using insulating bricks underneath as the price was better than i could cf board. i ordered 60 bricks and used 58 with very little waste, so that worked out.

[semlin]

i have gotten my indispensible tool done but still lots to work out.

for example, i am planning an integrated arch but still not clear on where it emerges. i think that the second red horizontal line from the bottom (the one below the screw) on this photo will give me a minimum 1.25" arch emerging from the oven. this is important because i want to put a heat break in the floor.

[semlin]

for the or heat break i am planning to break up the herring bone pattern with a single perpendicular brick line crossing at the outer edge of the oven arch. this will be a split/half height firebrick with a half height insulating brick underneath. the leading edge of the half firebrick will then be cut at a 30 degree angle except for a 1/2" vertical face. the 1/2" vertical will form the surface and butt against the oven floor. i am hoping this will not conduct too much heat and will give some strength to the floor.

here are some photos of the corner unit hearth process. it worked out great but i overdid the corner cut so i wouldn't need to cut any cinderblocks and i later realized this made my original plan of a 42" oven impossible. so it will be 40". it's build on a garage slab for a garage we moved when we bought the house so we could enjoy our view! we are converting it to a patio.

[semlin]

i am fortunate that this corner of the old garage is where power came from the house and we left the old conduit so it was easy to pull wire from the house under the driveway and i can have a gfci power outlet in the wall of the hearth. of course, "while i was there" it made sense to run power out to my wife's garden shed, so a trench was duly dug all around the garage slab and wiring is in place ready. now if i can just persuade the electrician to come by and connect it all.

the hearth and oven will be surrounded with recycled brick, which i have been grabbing off craigslist whenever i can for a while now. i am also on my third cheap craigslist power washer since this project started. two consecutive $20 small electric washers lasted a day each proving you get what you pay for. so i bought a honda engined unit with a blown pump (priced accordingly) and ordered a new decent pump online. i think my wife is skeptical this is a legit project related expense but i am not buying another cheap pressure washer and i don't know how else to clean these old bricks..

[UtahBeehiver]

Nice jog on the IT, this is a great example of having the pivot point at floor level, the IT adjustable, etc. When you do a tapered inner arch you will start out with a full size brick, not half bricks. This allows you to have the arch project from the dome with the Top Dead Center arch brick being the longest of the bricks. If you have not seen already, here is pic of what the profile of the tapered arch bricks look like, Remember they are all different, as determined by where they sit on the arch. The second pic is how the IT determines the various cuts on the arch bricks. The arch placement is right on.

Also, make sure the centerline of the IT rod and L bracket are at the centerline of the brick face.

[JRPizza]

Russell's right - nice job on the IT. That design will give you lots of flexibility in terms of attachments, like different width brackets or drawing instruments. What type of arch are you going with - hemispherical or a flatter one? This is a good time to make your arch form, then you can place it where you think it should go and verify by putting a brick at TDC and using your IT to check the distance.

[semlin]

thanks guys. i think the it will work pretty well.

for the arch form, i was thinking i would do a perfect arch top at 63% of dome height or 12.6" for a 20" dome. so with a 20" arch opening i think i need about a 2.6" section of vertical wall in the opening under the arch to make this work which i will then cheat to 2.5" so i can just use a single brick on either side of the arch for the vertical wall.

i also decided last night that i should vary my soldier height to match this exactly and then the arch wall will hopefully more easily blend into the dome. i will check the spreadsheet tonight because i know changing soldier height changes dome height, but i will guess my soldiers will be little guys only 5" high total.

[JRPizza]

Don't forget your mortar thickness. It is pretty easy to get a tenth of an inch of mortar, so that plus a brick would be your 2.6"

[daveskis]

Great work Semlin......love Canada

[semlin]

made some reasonable progress today but ran into all kinds of things i didn't think through properly. lots of learning.

my soldiers ended up being 5.5" vertical for a 3 1/8" reveal (allowing 1/8" for mortar as jr pizza suggested). that will allow me to trace a perfect 10" radius arch for the correct 13 1/8" height for my dome height.

i got the arch base walls built and the floor done flush to the oven opening. the soldiers were more of a challenge

the trouble started when i cut some soldier side angles initially using the deejayoh spreadsheet before i realized the spreadsheet assumes 4.5" wide soldiers when mine are turned sideways so only 2.5" wide. way too much angle. then i cut some again calculating the angle using the spreadsheet formula with the correct brick width and allowing 1/8" for mortar but that was still too much angle and yielded large gaps in the oven wall. i ended up allowing for 1/8" mortar on the outside edge but turning the 1/8" mortar allowance on the inside edge into more brick width which has the effect of reducing the angle of the side cut. kind of a weird calculation but it worked pretty well and the soldiers fit tight together on the oven wall. i realize afterwards a better way which i will try and illustrate with a photo tomorrow.

i also used many more soldiers than i planned for due to using the wrong width when i initially calculated. i am going to use the 3.5" shorts i cut off the soldiers for a course at some point so hopefully that will put me back in the black.

finally the mr chipster jig i made was too thick for my 10" saw. i used a 2x6 for the top and bottom and it ended up being too thick for the blade at max height. i will need to make it again out of much thinner wood to be useful. someone here warned me that chipster had a 14" saw but i missed the significance of the warning!

once i got into the cuts they went fine. i found that to utilize the blade width available i needed to make a very slim jig for each angle on my table saw. basically i am cutting wedges to suit.

also i need some thicker popsicle sticks!

but overall a decent day of learning with tangible progress. i am getting the feel for the saw and how best to do production work. my last round of soldiers took a lot less than the first round.

[semlin]

slow steady progress. i am pouring a second half of the concrete slab tomorrow am. plan is to pour a level 2.5" slab even with the insulating brick bringing total slab thickness to 5.5". i will also shape a 3/4" high drainage collar slope right around the brick.

biggest doubt for me is whether to pour the gap in front where the decorative outer arch will be. i want to do it for rebar strength and containment, but am a little worried about heat transfer since there will be firebrick directly on top of concrete..

also wondered whether if i do seal the front i should include a small drain/weephole at the front in case at some point water gets into the oven. leaning towards doing that but again worried about heat transfer.

very interested on whether anyone has views on this,.

[semlin]

also got my thermometers. these are military surplus remote dial capillary thermometers off ebay. big (4.5 or 6" dial face) but i think very cool and 3 cost less than a single oven remote t-mometer new. i tested them with the bbq and they work very well.

the plan is 200-1000 in the oven floor dead centre, 400-1200 in the ceiling poking into the oven and the 50-750 either half way into the oven wall somewhere or maybe in the chimney.