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Saturday, 4 January 2014

Building a wood fired bread and Pizza Oven - Fabricating the arch supports

It's been a few days since I had chance to work on the wood fired oven project.  The temperatures are forecast to be above zero for a few days, so I had to make progress today.  Even though this is Poland in January, I was able to work all day in just a shirt.  The goal for the day was to fabricate the steel strapping that is designed to prevent the weight of the arch from pushing the supporting brickwork outwards.

Before staring on the steel work, I decided to mock up the soldier bricks that will support the roof dome.  I also rendered the cast lintel with refractory mortar to give the surface a harder wearing outer layer and to fill any voids.  This was a great suggestion made by Terry on The UKWoodFiredOvenForum.  If anyone is planning on building their own oven, would recommend signing up to this forum and discuss you plans with the other members.

Soldier bricks mocked up

For my steel arch strapping, I have chosen to use this 'C' section, I was not entirely sure what size to use, without going into engineering calculations, so instead I used the largest size I could get.  My oven design has a low, parabolic arch which will produce a substantial outward force on the soldier bricks, so it is very important that my strapping is ridged enough.
steel section chosen for bracing arch supports
 The steel frame is first cut to size using a cutting disk on a hand held grinder, then the vertical angle pieces and flat section, lower perimeter pieces and carefully positioned to be in the correct alignment before two small tack welds done on each joint.  The tack welds are small enough to make the frame ridged enough, without pulling the frame out of shape as the weld cools.  My welding skills at beginner level, but I really enjoy doing this bit.
Lower perimeter and vertices tack welded 
 In order to reach the framer on the wall side of the oven, I had to remove the plastic sheet siding.  Once the oven is finished we will build some proper walls.

Welding the oven strapping
 In order to weld the larger arch support pieces in place, which weigh about 60 Kg each, a support block at each end at the correct height made this part of the job very easy.  In this picture you can clearly see the two little tack welds.
Temporary support block while tack welding
 The same technique was used to position the tension strap above the oven door and at the rear of the oven.
Above door tension strap


 Once all the tack welds are in place the frame is already very ridged and has no noticeable flex.
Tack welds completed
 Finally each joint is re-welded with a proper full length weld making sure that the weld penetrates fully to give maximum strength.  With the oven strapping now completed, the next step will be to set the soldier bricks.
Oven strapping now completed